GULF RESEARCH REPORTS Vol. 7, No. 1 December 1981 ISSN: 0072—9027 Published by the GULF COAST RESEARCH LABORATORY Ocean Springs, Mississippi Gulf Research Reports Volume 7 | Issue 1 January 1981 Morphometries of the Burrowing Clam Diplothyra smithii Tryon Alfred P. Chestnut Gulf Coast Research Laboratory DOI: 10.18785/grr.0701.01 Follow this and additional works at: http:/ / aquila.usm.edu/ gcr Part of the Marine Biology Commons Recommended Citation Chestnut, A. P. 1981. Morphometries of the Burrowing Clam Diplothyra smithii Tryon. Gulf Research Reports 7 (l): 1-11. Retrieved from http://aquila.usm.edu/gcr/vol7/issl/l This Article is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf and Caribbean Research by an authorized editor of The Aquila Digital Community. For more information, please contact Joshua.Cromwell(S>usm.edu. Gulf Research Reports, Vol. 7, No. 1,1-11, 1981. MORPHOMETRICS OF THE BURROWING CLAM DIPLOTHYRA SMITHII TRYON 1 ALFRED P. CHESTNUT 2 Gulf Coast Research Laboratory, Ocean Springs, Mississippi 39564 ABSTRACT Diplothyra smithii Tryon, a small bivalve mollusk, is a common inhabitant of the calcareous shell material of the American oyster, Crassostrea virginica Gmelin. Large populations of this clam are found on commercial oyster reefs in the western portion of Mississippi Sound. Several aspects of the population of D. smithii in Mississippi Sound were examined. On the Pass Marianne Reef, 71% of the live oysters and 44% of the dead shells were infested with D , smithii. The mean number of clams removed from valves of live oysters was 22.1 ±1.7 (range, 1-109; N = 146). Infested dead shells had a mean number of 23.7 ± 2.6 (range, 1-103; N - 75) clams per shell. Clams from live and dead shells indicated monthly variations in morphological stages. During January through April, clams were predominantly immature, In late spring and early summer, clams matured morphologically. In May and June, the majority of clams were mature. Immature clams from early and midsummer spawnings appeared in July and August. Mean lengths and heights of clams with and without a callum and the monthly changes in those dimensions were deter- mined for clams from live and dead shells. All clams from live oysters had greater mean dimensions and size ranges than clams from dead shells. Female clams were significantly larger than nonfemale clams from live oyster shells; females from dead shells were significantly larger than nonfemale clams in length only. INTRODUCTION Information on population dynamics of invertebrate organisms is essential to adequately appraise the role of specific organisms within an estuarine ecosystem. Although numerous population studies have been conducted on burrowing bivalve species from sand or mud substrata (Fraser 1967, Moore and Lopez 1969, Holland and Dean 1 977), few have been conducted on rock- or shell-burrowing bivalves. Diplothyra smithii Tryon is a small bivalve mollusk specialized for burrowing into calcareous shell material, particularly the American oyster, Crassostrea virginica Gmelin. Despite the high incidence of D. smithii in oysters on the northern coast of the Gulf of Mexico, very little information concerning the percentage of shells infested, the density of clams per shell, or the morphology, size, or sex of those clams is available. Collier ([unpublished] cited by Hopkins 1949) attempted to survey the D. smithii population in Texas; however, only a few unpublished reports were available. Most surveys have reported only the prevalence of D. smithii and have made observations on oyster-shell damage (Moore 1899, Cary 1906, Galtsoff et al. 1935. Higgins 1940, Federighi and Collier [unpublished] cited by Hopkins 1949). Higgins (1940), Menzel (1950), Galtsoff (1964), and Harry (1976) reported densities of D smithii within single oyster valves. Information on the size of D . smithii can be found in the original description (Tryon 1862), in taxonomic monographs (Bartsch and Rehder 1945, Turner 1955), and in numerous guides to marine mollusks (Abbott 1974, 1 This paper is part of a dissertation submitted to the Graduate School of the University of Southern Mississippi. 2 Present address: Department of Biology, Belhaven College, Jackson, Mississippi 39202. Manuscript received July 30, 1980; accepted October 15, 1980. Andrews 1977). None of those reports presented series of measurements. Diplothyra smithii is characterized by a change in shell morphology as it develops from an immature to a mature form. Turner (1954) described the morphological stages and their characteristic behavioral, structural, and functional patterns for pholads in general. Specific information on the morphological stages of D. smithii has not been reported. The objective of this study was to obtain information on the oyster shell as a substratum inhabited by D. smithii, the percentage of shells infested (prevalence), densities of clams within oyster shells, and information on the morphological stages, sizes, and sex of D. smithii . MATERIALS AND METHODS Field Sampling Samples of live and dead oyster shells containing D. smithii were dredged monthly from January through August 1976, and infrequently during 1975, 1977, and 1978, from Pass Marianne Reef. This reef is located 2 miles due south of Pass Christian, Mississippi, in the vicinity of navigation marker 7M in Mississippi Sound. Surface salinity and tem- perature were also recorded on each sampling date. Laboratory Procedures ; Percentages of Shells Infested The percentage of live and dead oyster shells infested with D . smithii was determined by placing individual live oysters and dead shells in a large fiberglass trough of sea water which was heated to approximately 30°C to drive off oxygen. This forced the clams to extend their siphons and facilitated identification of infested shells. Oyster Shell Measurements To adequately describe the substrata inhabited by 1 2 Chestnut D. smithii, live and dead shells were examined. Ten live oysters were arbitrarily selected and shucked. Measurements were made with vernier calipers of left and right valves for height and length (to the nearest 1.0 mm), and thickness in the umbo region and at the ventral margin (to the nearest 0.1 mm). Heights and lengths of ten dead shells also were measured. Because of the eroded nature of dead shells, only a single measurement of thickness was made midway between the dorsal and ventral margins. Number of Diplothyra smithii per Oyster Valve From the infested shells, ten live oysters and ten dead shells were arbitrarily selected to determine the densities of burrowing clams within the shells. The numbers of siphon holes in a given dead valve were counted, Each valve of live shells was divided into four quadrants through the dorso- ventral and anterio-posterior midpoints, and the number of siphon holes within each quadrant was counted. Quadrant densities were examined to relate the number of clams to thickness, i.e., age, of the shell. The procedure that was followed and the orientation of the quadrants were basically those described by Galtsoff (1964). Cross products of shell heights and lengths were used to compute relative shell areas which were correlated with the number of clams present. This was determined to be the most feasible method for computing area, since the actual shell areas were not calculated prior to destruction of shell valves to obtain D. smithii. Burrowing clams were collected from oyster shells cracked open with a hammer. All clams visible to the naked eye were removed by successively breaking and picking through the shell fragments. Morphological Stages of Diplothyra smithii Clams were separated into three stages of morphological maturity based on callum development to determine rela- tionships between the season and the stage of maturity. Clams without a callum were morphologically immature and in the active burrowing stage. These were characterized by the presence of a wide pedal gape through which the foot protruded, unprotected by a shell covering. Clams with a partial callum varied from those with a thin shell just beginning to grow over the pedal gape to those having a thin, pliahle callum almost completed but still allowing valve articulation about the umbonal-ventral axis. The mature stage was characterized by a complete callum. At that stage, the pedal gape was completely covered by shell material with no valve articulation. Sizes of Diplothyra smithii Lengths and heights of all clams were measured to relate size to substratum, to morphological stage, and to sex. Length was the greatest anterior-posterior dimension of the shell. Height was the length of the umbonal-ventral sulcus, a line from the umbo to the ventral shell margin (Evans 1968). Clams were measured to the nearest 0.1 mm using an ocular micrometer and a steroscopic binocular microscope .To deter- mine the monthly population structure, length-frequencies for all clams from a given month were plotted to indicate the percentage of clams within 2 mm size classes. Sex; Mature Females Numbers and sizes of mature females in each monthly sample were compared with numbers and sizes of all other clams. Only ovigerous females were recorded because they were recognized easily by the presence of pink gonadal material. Statistical Notation Numerical and size measurements in text and tables herein are represented as mean ± one standard error of the mean. The sample size is given in parentheses. All tests of significance were done using Analysis of Variance (ANOVA). Only probability levels exceeding 95% were reported. RESULTS Oyster Shell Measurements From live shells, the mean height of left valves, 83 ± 1.5 mm (73), was significantly larger than the mean height of right valves, 77 ± 1.4 mm (73). The mean length of left valves, 64 ± 1.1 mm (73). also was significantly larger than the mean length of right valves, 59 ± 1.0 mm (73), There was no significant difference between the thickness of left valves, umbo: 8.9 ± 0.2 mm (73), mid-ventral: 2.6 ± 0,1 mm (73); and right valves, umbo: 8.8 ± 0.3 mm (71), mid- ventral: 2.6 ± 0.1 mm (71). Dead shells had a mean height of 82 ± 2.5 mm (76), a mean length of 49 ± 1 .0 mm (76), and a mean shell thickness of 5.7 ±0.2 mm (75). Percentage of Shells Infested with Diplothyra smithii Seventy-one percent of the live oysters and 44% of the dead shells were infested with D. smithii (Table 1). Density of Diplothyra smithii per Infested Oyster Valve There was no significant difference between the mean densities of clams in the left and right valves of live oysters, left: 22,6 ± 2.5 mm (73); right: 21.6 ± 2,2 mm (73); combined: 22.1 ± 1.7 mm (146). The maximum density was 109 clams per shell. Fifty-seven percent of the live shells examined contained between 1 and 20 clams. There were significantly greater numbers of clams near the umbo in the dorsal quadrants of live shells. Anterior quadrants had mean densities of 9 clams per quadrant compared with mean densities of 2 clams per quadrant in the ventral quadrants (Table 2). Dead shells had a mean density of 23.7 ± 2.6 clams per valve, and a maximum number of 103 clams per valve. Fifty-one percent of the dead shells had between 1 and 20 clams present. Morphometrics of the Burrowing Clam 3 TABLE 1. Numbers and percentages of live oysters and dead shells infested with Diplothyro smithii from Pass Marianne Reef, 1976 and 1977. Month Live Oysters Dead Shells With D. smithii Without D. smithii Total With D. smithii Without D. smithii Total February 1976 140 13 153 _ - April 45 22 67 77 98 175 May - - - 38 148 186 June 9 46 55 - - - July - - 39 118 146 264 August - - 43 82 62 144 September - - 22 149 86 235 February 1977 15 6 21 53 108 161 Total 209 87 400 517 648 1165 Mean 52 22 57 86 108 194 Range 9-140 6-46 21-153 38-149 62-148 148- 264 Percentage 71 29 - 44 56 - TABLE 2. Number of Diplothyro smithii located within each of four quadrants of live oyster shells from Pass Marianne Reef. Quadrant Mean Number Removed (N) Range Dorsal Anterior 9.3 ±0.8 (136) 0-53 Dorsal Posterior 8.9 ±0.7 (136) 0-41 Ventral Anterior 2.2 ±0.3 (136) 0-20 Ventral Posterior 2.2 ±0.2 (136) 0-11 The mean densities of clams per infested valve were similar for both live and dead shells, and the proportion of valves containing equivalent numbers of clams also was similar for both live and dead shells. There was a positive correlation between the number of clams and the size of the shell for both live shells (r 2 =0.1084; N= 146) (Figure 1), and for dead shells (r 2 = 0.2215; N = 75) (Figure 2). Morphological Stages of Diplothyro smithii Monthly frequencies for the presence of morphological stages of D. smithii were similar from both live and dead shells except during July and August (Figures 3 and 4). During the First four months of 1976, 60 to 90% of the clams were present in the immature stage in both live and dead shells. Live shells had 10 to 20% more immature clams than dead shells. In April, there was an increase in the number of mature clams in both live and dead shells, and in May and June, 70 to 90% of the clams examined had a callum. In July and August, differences were found between the morphological stages present in live and dead shells. In live shells 70% of the clams had a callum present; however, in dead shells 80% were without a callum. Sizes of Diplothyro smithii Clams from live shells were larger than clams from dead shells (Tables 3—6). Clams from live shells also had wider ranges for both length and height measurements. Mean lengths for clams with a callum were larger than the mean lengths for clams without a callum from both shell types (Figures 5 and 6). Mean lengths and heights for each morphological stage are given for each month (January through August 1976) in Tables 3 and 4 for clams removed from live shells, and in Tables 5 and 6 for clams removed from dead shells. Clams removed from live shells had a total mean length of 6.8 ± 0.4 mm (1,567) for clams with a callum, and a total mean length of 3.9 ± 0.0 mm (1,451) for clams without a callum (Table 3). Clams removed from dead shells had a total mean length of 5.5 ± 0.1 mm (724) for clams with a callum, and a total mean length of 3.0 ± 0.0 mm (917) for clams with- out a callum (Table 5). The greatest recorded length was 1 1.4 mm (Table 5). Diplothyro smithii: Length-Frequencies Changes in length-frequencies of the sample population of D. smithii throughout an 8-month period from live and dead shells are shown in Figures 7 and 8. There was a pro- gressive shift in increasing length of clams from January through June for clams from both live and dead shells. With recruitment of young individuals during July and August, an increase in the percentage of clams was observed in the smaller length intervals. Changes in length-frequency were more pronounced for clams removed from dead shells than for clams removed from live shells. Sex: Mature Females Means and ranges for lengths and heights of females from live and dead shells, both with and without a callum, Chestnut RELATIVE SHELL AREA (mm 1 ) 496.133 1194.120 2884-373 4674.626 6264.880 7966,13 RELATIVE SHELL AREA (mm' ) Figure 1. Relative area (length X height) of live shells compared Figure 2. Relative area (length X height) of dead shells compared with the number of D. smithii removed from the shells. with the number of D. srnithli removed from the shells. Without callum ^° o ° 0 °] With partial callum $$$ With callum LIVE SHELL JAN FEB MAR APR MAY JUN JUL AUG MONTH Figure 3. Percentage of clams present in each of three morphological stages for clams examined monthly, January -August 1976, from live shells. Without callum k° 0 o ° o °1 With partial callum With callum ; DEAD SHELL Figure 4. Percentage of clams present in each of three morphological stages for clams examined monthly, January-August 1976, from dead shells. Morphometrics of the Burrowing Clam 5 TABLE 3. Mean lengths for each of three morphological stages of Diplothyra smithii removed from live shells monthly, January- August 1976. Month With Callum With Partial Callum Without Callum January 6.3 ±0.2 (3.2- 9.5) 40* 0 3.8 ±0.1 (1.4- 9.2) 249 February 5.7 ±0.3 (1.2-11.0) 57 6.5 ±0.2 (3.1— 8.7) 62 3.9 ±0.1 (1 .2-9.7) 207 March 6.2 ±0.3 (2.9- 8.7) 29 6,5 ± 0.5 (4.0-8.7) 9 4.4 +0.1 (1.4-8. 7) 310 April 6.0 ±0.1 (2.4- 9.7) 150 6.1 ±0.2 <3.5 8.7) 56 4.1 ±0.1 (1.4-8. 8) 210 May 6.5 ±0.1 (3.2-10.5) 292 5.7 ±0.9 (3. 8-8.0) 4 4.0 ±0.1 (1. 6-8.0) 107 June 7.0 ±0.1 (3.1-10.7) 299 6.1 ±0,2 (3.9-9. 1) 43 4.8 ±0.1 (2-7 -9.2) 77 July 6.7 ±0.1 (2.9 11.0) 276 6.8 ±1.0 (3,9-8.6) 4 2.7 ± 0.2 (0.8-7. 1) 103 August 7.3 ±0.1 (3.2-11.0) 424 8.1 ±0.4 (6. 6-8.9) 6 3.0 ±0.1 (1.0 8.4) 194 Total 6.8 ±0.0 (1.2-11.0) 1567 6.3 ±0.1 (3.1-9. 1) 184 3.9 ± 0.0 (0.8— 9.7) 1457 ♦Mean (mm) ± 1 standard error (range), N. TABLE 4. Mean heights for each of three morphological stages of Diplothyra smithii removed from live shells monthly, January-August 1976. Month With Callum With Partial Callum Without Callum January 4.6 ±0.2 (1. 9-6.8) 40* 0 2.7 ± 0.1 (1. 0-6.6) 249 February 3.9 ±0.2 (1.0- 7.1) 57 4.4 ±0.1 (1.9-6.0) 62 2.8 +0.1 (1 .0—6.7) 207 March 4.1 ±0.2 (2.4 5.9) 29 4.7 ±0.3 (3.0-6. 0) 9 3.4 ±0.1 (1. 0-7.0) 310 April 4.1 ±0.1 (1. 6-6.6) 150 4.3 ±0.1 (2. 3-6.0) 56 3,1 +0.1 (1.2-7.8) 210 May 4.4 ±0.0 (1.8-7. 1) 292 4.1 ±0.5 (3.1 -5.5) 4 3.1 ±0.1 (1.4 -5.3) 107 June 4.5 ±0.0 (2.0-6.6) 299 4.1 ±0.1 (2.1 -5.8) 43 3.7 ±0.1 (1. 7-6.1) 77 July 4.4 ±0.0 (1.9-7. 3) 276 4.4 ±0.5 (3.0-5. 3) 4 2.1 ±0.1 (0.5-5.0) 103 August 4.8 ±0.0 (2.1 — 7.6) 424 5.5 ± 0.2 (5.1 -6.5) 6 2.3 ±0.1 (1. 0-6.3) 194 Total 4.5 ±0.0 (1 .0-7.6) 1567 4.3 ±0.1 (1. 9-6.5) 184 2.9 + 0.0 (0.5 -7.8) 1457 ♦Mean (mm) ± 1 standard error (range), N. TABLES. Mean lengths for each of three morphological stages of Diplothyra smithii removed from dead shells monthly, January-August 1976. Month With Callum With Partial Callum Without Callum January 3.6 ±0.3 (3.3- 3.9) 2* 0 3.7 ±0.2 (1 .9-6.0) 50 February 5.3 ±0.2 (2.0- 9.1) 66 5.5 ±0.2 (2.9— 8.2) 56 3.5 ±0.1 (1. 3-8.4) 110 March 5.0 ± 0.1 (1.9- 7.0) 62 4.5 ±0.4 (2.9-6.9) 11 3.7 ±0.1 (1. 4-9.2) 154 April 5.3 ± 0.1 (2.2— 8.0) 103 4.9 ±0.2 (1. 6-7.4) 40 3.3 ±0.1 (1 .4-7.4) 99 May 5.7 ±0.1 (3.0- 9.4) 221 0 3.7 ±0.3 (1.6-5. 1) 16 June 6.1 ±0.1 (2.3-11.4) 160 0 4.2 ±0.4 (2,0-6. 1) 10 July 4.8 ±0.2 (1.9-10.0) 70 5.4 ±0.0 (5 .4 -5 .4) 1 2.3 ±0.0 (0.8-6.6) 314 August 4.8 ±0.3 (1.9- 8,9) 40 0 2.7 ±0.1 (1. 2-6.2) 164 Total 5.5 ±0.1 (1.9-11.4) 724 5.2 ± 0.1 (1.6-8. 2) 108 3.0 ±0.0 (0.8-9.2) 917 ♦Mean (mm) ± 1 standard error (range), N. 6 CHF.STNUT TABLE 6. Mean heights for each of three morphological stages of Diplothyra smithii removed from dead shells monthly, January -August 1976. Month With Callum With Partial Callum Without Callum January 2.4 ±0.0 (2.4-2.4) 2* 0 2.6 ±0.1 (1,4-43) 50 February 3.6 + 0. 1 (1 .4-6.0) 66 o +1 q (1.9 6.2) 56 2.6 ±0.1 (1.0-5. 2) 110 March 3.2 ±0.1 (1 .4-4.8) 62 2.9 ±0.2 (2.0-3. 9) 11 2.7 ±0.1 (1. 2-6.3) 154 April 3.3 ±0.1 0. 6-6.3) 103 3.2 ±0.1 (1.1 -4.4) 40 2.5 ±0.1 (1.4 -5-6) 99 May 3.7 ±0T (1 .7-6.5) 221 0 2.9 ±0-2 (1.2 4.4) 16 June 3.8 ±0.1 (1. 4-6.8) 160 0 3.0 ±0,3 (1. 3-4.8) 10 July 3.1 ±0.1 (1. 3-6.2) 70 3.7 ±0.0 (3.7 -3.7) 1 1.8 ±0.0 (0.7-4.0) 314 August 3.0 ±0.2 (1 .3-5.6) 40 0 2.1 ±0.0 (0.9-4. 6) 164 Total 3.5 ±0.0 (]. 3-6.8) 724 3.6 ±0.1 (1.1 -6.2) 108 2.2 ±0.0 (0.7- 6.3) 917 *Mean (mm) ± 1 standard error (range), N. 12 11 10 9 8 I 7 X S 6 z LU - 1 5 4 3 2 1 0 Figure 5. Mean length (horizontal line), one standard error of the mean (box), and size range (vertical line) of D. smithii with a callum (open box) and without a callum (solid box) removed from live shells: January-August 1976. WITH CALLUM WITHOUT CALLUM * ♦ H I I I I I 1 I I I JAN FEB MAR APR MAY JUN JUL AUG MONTH E E MONTH Figure 6. Mean length (horizontal line), one standard error of the mean (box)., and size range (vertical line) of D. smithii with a callum (open box) and without a callum (solid box) removed from dead shells: January-August 1976. are given in Tables 7 and 8. Female clams removed from live shells had significantly greater mean lengths and heights than females removed from dead shells, Females removed from live shells had significantly greater mean lengths and heights when compared with mean lengths and heights of nonfeitiales of the same morpholog- ical stages (Table 7). There was a significant difference between the lengths of all females and nonfemales removed from dead shells (Table 8). Also there was a significant dif- ference between the heights of females without a callum and nonfemales without a callum removed from dead shells; however, there was no significant difference between the heights of females with a callum and nonfemales with a callum removed from dead shells (Table 8). DISCUSSION Oyster Shell Measurements Oyster shells are the primary substratum for D. smithii in Mississippi Sound. Several characteristics of oyster shells, including the nature of the shell material (living or dead), the surface area available for setting, and the age and Chestnut TABLE 7. Comparison of lengths (A) and heights (B) of ovigerous female clams with and without a callum, and nonfemale clams with and without a callum, from live shells. Month Ovigerous Females Non female With Callum Without Callum With Callum Without Callum LENGTH (A) April 6.4 ±0.3 (4.9- 7.5) 11* 0 6.0 ±0.1 (2.4- 9.7) 139 4.1 ±0.1 (1.4-8.8) 210 July 7.0 ±0.2 (4.3-10.9) 56 0 6.7 ±0.1 (2.9-11.0) 220 2.7 ±0.2 (0.8 7.1) 103 August 7.3 ±0.1 (3.2—10.6) 161 4.7 ±0.4 (2.1— 8.4) 15 7.2 ±0.1 (3.6-11.0) 262 2.8 ±0.1 (1 .0-7.9) 179 Total 7.2 ±0.1 (3.2-10.9)228 4.7 ±0.4 (2. 1-8.4) 15 6.7 ±0.1 (2.4-11.0) 621 3.4 ±0.1 (0.8-8.8) 492 HEIGHT (B) April 4.2 ±0.2 (3.4- 5.2) 11 0 4.0 ±0.1 (1.6- 6.6) 139 3.1 ±0.1 (1 .2—7.8) 210 July 4,5 ±0,1 (2.3- 7.3) 56 0 4.3 ±0.1 (1.9- 6.4) 220 2.1 ±0.1 (0.5 -5.0) 103 August 4.8 ±0.1 (2.1- 6.7) 161 3.5 ±0.3 (1.4-6.2) 15 4.7 ±0.0 (2.3- 7.6) 262 2.2 ±0.1 (1 .0-6.3) 179 Total 4.7 ±0.1 (2.1- 7.3) 228 3.5 ±0.3 (1. 4-6.2) 15 4.4 ±0.0 (1.6- 7.6) 621 2.6 ±0.0 (0.5-7, 8) 492 •Mean (mm) ± 1 standard error (range), N. TABLE 8. Comparison of lengths(A)and heights (B) of ovigerous female clams with and without a callum, and nonfemale clams with and without a callum, from dead shells. Ovigerous Females Nonfemale Month With Callum Without Callum With Callum Without Callum LENGTH (A) March 5.5 +0.9 (4.6- 6.4) 2* 0 5.0 ±1.4 (1.9- 7.0) 60 3.7 ±0.1 (1.4— 9.2) 154 April 5.6 ±0.2 (3.6- 8.0) 35 5.6 ±0.0 (5 .6-5.6) 1 5.1 ±0.2 (2.2- 7.8) 68 3.3 ±0.1 (1.4— 7-4) 98 May 5.8 ±0.1 (2.0- 5.8) 93 0 5.9 ±0.1 (3.0 9.4) 128 3.7 ±0.3 (1.6-54) 16 July 4.9 ±0.3 (1.9-10.0) 33 3.1 ±0.1 (1. 9-4.6) 46 4.7 ±0.2 (2.4- 7.8) 37 2.1 ±0.0 (0.8 6.6) 268 August 4.4 ±0.4 (2.1- 8.2) 15 4.4 ± 0.2 (3.4-5.5) 9 5.1 ±0.4 (1.9- 8.9) 25 2.6 ±04 (1. 2-6.2) 155 Total 5.5 ±0.1 (1.9-10.0) 178 3.4 ±0.1 (1. 9-5.6) 56 5.2 ±0.1 (1.9- 9.4) 318 2.8 ±0.0 (0.8-9. 2) 691 HEIGHT (B) March 3.2 ±1.0 (2.3- 4.2) 2 0 3.2 ±0.1 (1.4- 4.8) 60 2.7 ±04 (1. 2-6.3) 154 April 3.4 ±0.1 (2.0- 4.5) 35 4.0 ±0.0 (4 .0-4.0) 1 3.3 ±0.1 (1.6- 6.3) 68 2.5 ±0.1 (1.4-5. 6) 98 May 3.8 ±0.1 (2.0- 5.8) 93 0 3.7 ±0.1 (1.7- 6.5) 128 2.9 ±0.2 (1. 2-4.4) 16 July 3.1 ±0.2 (1. 3 6.2) 33 2.4 ±0.1 (1. 2-4.0) 46 3.0 ±0.1 (1.5- 5.6) 37 1.7 ±0.0 (0.7 -3.2) 268 August 2.8 ±0.2 (1.4- 4.6) 15 3.3 ±0.2 (2.7-4. 2) 9 3.2 ±0.2 (1.3- 5.6) 25 2.0 ±0.0 (0.9 -4.6) 155 Total 3.5 ±0.1 (1.3- 6.2) 178 2.6 ±0.1 (1 .2-4.2) 56 3.4 ±0.0 (1.3- 6.5) 318 2.1 ±0.0 (0.7-6. 3) 691 •Mean (mm) ± 1 standard error (range), N. thickness of specific shell regions may affect setting, density of infestation, growth rates, and morphological development of D. smithii. Oyster thickness had the greatest effect on clam size and morphological maturity (see discussion on Morphological Stages and Sizes). Live shells had regions of greater thickness than dead shells. Dead shells varied less in overall thickness because of wear at both the umbo and ventral edges. Shell thickness may be related to the presence of burrowing organisms. Gunter (1953) suggested that the oyster may secrete additional shell material as a response to burrowing organisms. Thick shells may be an adaptive feature which prevents penetration by burrowers. Percentage of Shells Infested At Pass Marianne Reef, 71% of the live shells were infested with D. smithii. The prevalence of infestation in live shells could lead the reader to draw misleading conclusions. Prevalence of infestation does not indicate a preference of clams for live shells, rather it reflects the unsuitability of morphometrics of the burrowing clam 9 dead shells for either initial or continued infestation. Whereas live oysters must be at least partially exposed, dead shells may be either exposed or buried, a factor which would affect initial infestation. Infested shells could be buried by dredge activities which would kill burrowing clams. Constant movement of the substratum by wave action also may pre- vent otherwise suitable dead shells from becoming infested (Gunter 1979). The prevalence of infestation of live shells in this study (Table l) was consistent with high values reported for the northern coast of the Gut*' of Mexico (Galtsoff et al. 1935, Federighi and Collier [unpublished] cited by Hopkins 1949). Varying conditions afreet the population of oysters present from yeaT to year, as well as the numbers o f burrowing clams. During the same time that the prevalence of D. smithii infestation increased on Pass Marianne Reef (1976—1978), the number of live oysters declined (Table 1). If fewer num- bers of oysters were available for setting, a higher percentage may have been infested by the burrowing clam. Density of Diplothyra smithii Density of D. smithii was influenced by shell area and thickness, i.e,, age of the oyster. The number of clams increased with an increase in sheli area for both live and dead oysters (Figures 1 and 2). More clams were found in the dorsal quadrants of live shells than in other regions. Hof- sietter (R. P. Hofstetter, Texas Parks and Wildlife Depart- ment, personal communication) also noted that heavy concentrations of clams were more common near the hinge (dorsal portion). This is the oldest region of the oyster and thus has been available for setting clams longer than other parts. Danglade (1917) noted that burrowing clams were present primarily in larger and older shells. Densities of burrowing clams per oyster shell reported in this study are lower than those reported in previous studies (Higgins 1940, Collier [unpublished] cited by Hopkins 1949, Menzel 1950, Galtsorf 1964). Morphological Stages of Diplothyra smithii The proportion of burrowing clams in each morphological stage followed an annual pattern consistent with seasonal changes in water temperature. Undoubtedly water temper- atures affected the rates of growth and burrowing, and the rate at which substratum limits were reached, at which time metamorphosis occurred and growth stopped. Seasonal changes in morphological stages are shown in Figures 3 and 4, and temperature and salinity changes are recorded in Figure 9. Clams spawned during the summer or fall of 1975 were predominantly immature during the first four months of 1976. Clams remained immature during the months when water temperatures were below 15°C. Clams were found in the transition stage with partial callums from February through April. The presence of a partial callum indicated changes in morphological stage. These changes were most pronounced when water tempera- tures increased in March and April. In May and June, callums had developed in most clams. Along with increased water temperatures, the ratio of immature to mature clams changed dramatically during May when the majority of clams from the 1975 spawning season Figure 9. Surface salinity and temperature measurements from Pass Marianne Reef, August 1975 through July 1978. 10 Chestnut reached substratum limits, metamorphosed, and matured. In July and August, recruitment of juvenile clams resulted in increased numbers of immature clams in dead shells. In live oysters the ratio of immature clams to mature clams remained approximately the same throughout the summer, .Although there were no differences between mean densi- ties for live and dead oysters, there were differences in mor- phological maturation, Clams in thinner, dead shells readied the substratum limits faster than clams in live shells, and metamorphosed at smaller sizes (Tables 3 and 5). The larger percentage of mature clams observed in dead shells throughout 1976 may be related to the thinner valves of dead oysters. Prior to this study, the attainment of a critical size (Evans 1968), crowding (Turner 1954), and substratum thickness (Smith 1969) were the only agents known to influence the production of a callurn in the subfamily Martesiinae. This study indicated that, in addition to those factors, metamorphosis in A smithii is induced also by seasonal temperature changes either directly or indirectly. There was a yearly cycle during which clams set in the sum- mer or early fall and reached morphological maturity during the following spring and summer. Sizes of Diplothyra smithii Since growth ceases at metamorphosis (Turner 1954), factors which affect the onset of metamorphosis directly influence the size reached by A smithii. Hence, mature clams vary in size depending on the thickness of the shell substratum which affects the onset of metamorphosis, and on environmental conditions which affect the rate of growth. The mean lengths of mature clams removed from live and dead shells in this study were below the values reported by Tryon (1862), Turner (1955), Abbott (1974), and Andrews (1977), Although the largest clam from this study was comparable with that reported by Turner (1955), mature clams from Mississippi Sound were shorter than those reported in the literature. The umbonal-ventral sulcus dimensions recorded in this study were not comparable to the height measurements of previous investigators. Although the cJam may be oriented in the oyster shell at almost any angle, the majority of clams burrowed approxi- mately perpendicular to the shell surface. The mean length of mature clams from live oysters (6.8 mm) can be related to the greater shell thickness at the dorsal margin (8.8 mm). The mean length of clams removed from dead shells (5.5 mm) also can be related to the thickness of those shells (5.7 mm). Mean sizes from each month for clams from both live and dead shells (Figures 5 and 6) can be related to the monthly percentage of clams in given morphological stages (Figures 3 and 4). The size increase for clams with a callurn, which began in March in dead shells (Figuie 6) and in April in live shells (Figure 5), and continued through June, is not anindication for growth of mature clams. A callurn indicates that a clam is mature, and has terminated growth (Turner 1954). The increase in size resulted from the larger-sized, immature clams undergoing metamorphosis. The results in Figures 3 and 4 indicate that the number of mature clams increased slightly in April, then sharply in May and June. The change in size of mature clams during the same period (Figures 5 and 6) has been related to the maturation of immature clams. The mean size of immature clams remained fairly con- stant from January through May, as larger, immature clams metamorphosed into mature clams. In July and August, decreases in mean length of immature dams resulLed from summer spawning and the subsequent recruitment of small, postlarval clams in live and dead shells. Also in some dead shells, immature clams burrowed completely out of the shell, thus limiting both the number and size of immature and mature clams. The length-frequency histograms (Figures 7 and 8) suggest a seasonal pattern of mid- to late-summer setting. From March through June, dams in smaller size classes from both shell types gradually decreased in number. With the onset of spawning in June, July, and August, numbers of clams in the 1- to 2*mm size class increased. In August, the numbers in the 3- to 4-mm size class increased, an indica- tion of growth of clams which set during the months of June and July. Dead shells had a much lower frequency of clams in the larger size classes, particularly during July and August, probably related to shell thickness. Sexually Mature Females The size difference noted between females and non- females of D. smithii (Tables 7 and 8) may be evidence of sexual dimorphism. Among mollusks, particularly bivalves, sexual dimorphism is rarely obvious. Galtsoff (1964) found that in Crassostrea virginica , the sexual identity of the organism was influenced by size. He stated that oysters which were larger or were able to respond more quickly to favorable changes in the environment may develop into females first. Several females from both shell types developed sexual maturity without a callurn but developed only a small quantity of gonadal material. The presence of a completed callurn was not a prerequisite for sexual maturity. ACKNOWLEDGMENTS I thank the Gulf Coast Research Laboratory for providing support during this study, and the Computer Section for the statistical analysis of the data. Dr. Edwin W. Cake, Jr., Gulf Coast Research Laboratory, and my graduate committee at the University of Southern Mississippi provided many helpful suggestions and comments. I also thank Dr. A. F. Chestnut, University of North Carolina Institute of Marine Sciences, for his critical review of the manuscript. MORPHOMETRICS OF THE BURROWING CLAM 11 REFERENCES CITED Abbott, R. Tucker. 1974. American Seashells. Van Nostrand Rein- hold Company, New York. 663 pp. Andrews, Jean. 1977. Shells and Shores of Texas. University of Texas Press, Austin, Texas. 365 pp. Bartsch, P. &.H. A. Rehder. 1945. The west Atlantic boring mollusks of the genus Martesia. Smithson. Misc . Collect. 104:1 -16. Cary, L. R. 1906. The conditions for oyster culture in the waters of Vermilion and Iberia parishes, Louisiana. Gulf Biol. Sta. Bull. 4:1 —27. Danglade, Ernest. 1917. Condition and extent of natural oyster beds and barren bottoms in the vicinity of Apalachicola, Florida. U.S. Bur. Fish., Kept. U.S. Comm. Fish. (191.6) App. V:1 68. Evans, John W. 1968. Factors modifying the morphology of the rock-boring clam, Penitella penita (Conrad, 1837). Proc. Malacol. Soc. bond. 38:111-119. Fraser, Thomas H. 1967. Contributions to the biology of Tagelus divisus (Tellinacea: Pelecypoda) in Biscayne Bay, Florida. Bull. Mar.Sci. 17:111-132, Galtsoff, Paul S. 1964. The American oyster, Crassostrea virginica Gmelin. U.S. Fish Wildl. Serv. Fish. Bull. 64:1-480. Galtsoff, P. S., H. F. Prytherch, R. O. Smith & V. Koehring. 1935. Effects of crude oil pollution on oysters in Louisiana waters. U.S. Fish Wildl. Serv. Fish. Bull. 48:143-210. Gunter, Gordon. 1953. The relationship of the Bonnet Carre spillway to oyster beds in Mississippi Sound and the “Louisiana Marsh,” with a report on the 1950 opening. Puhl. Inst. Mar. Scl. Univ. Tex. 3:17-71. . 1979. The grit principle and the morphology of oyster reefs. Proc. Natl. Shellfish. Assoc. 69:1-5. Harry, Harold W. 1976. Correlation of benthic Mollusca with sub- strate composition in lower Galveston Bay, Texas. Veliger 19: 135-152. Higgins, Elmer. 1940. Progress in biological inquiries for 1939. U.S. Bur. Fish., Rept. U.S. Comm. Fish. (1940) App. 1:1-96. Holland, A. F. & J. M. Dean. 1977. The biology of the stout razor clam, Tagelus plebeius: 1. Animal-sediment relationships, feeding mechanism, and community biology. Chesapeake Sci. 18:58—66. Hopkins, Sewell H. 1949. Preliminary survey of the literature on the boring dani,Martesia. Texas A&M Research Foundation Project 9 (mimeo). 16 pp* Menzel, R. W. 1950. Report on oyster studies in Lake Felicity and Bayou Bas Bleu, Terrebonne Parish, Louisiana. Texas A&M Research Foundation Project 9 (mimeo). 69 pp. Moore, II. F. 1899. Report on the oyster beds of Louisiana. U.S. Bur. Fish., Rept. U.S. Comm. Fish , (1898)24:49-100. Moore, H. B. &N. N. Lopez. 1969. The ecology of Chione cancellata. Bull. Mar. Sci. 19:131-148, Smith, E. 1969. Functional morphology of Penitella conradi relative to shell penetration. ^4m. Zool. 9:869-880. Tryon, George W. 1862. Description of a new genus and species of Phoiadidae. Proc Acad . Nat. Sci. Phila. 14 449-450. Turner, R. D. 1954. The family Phoiadidae in the Western Atlantic and Eastern Pacific. 1. Fholadinae .Johnsonia 3:1-63. . 1955. The family Phoiadidae in the Western Atlantic and Eastern Pacific. II Martesiinae, Jouannetiinae, and Xylophaginae. Johnsonia 3:65-160. Gulf Research Reports Volume 7 | Issue 1 January 1981 A Preliminary Checklist of Marine Benthic Diatoms of Mississippi Michael J. Sullivan Mississippi State University DOI: 10.18785/grr.0701.02 Follow this and additional works at: http://aquila.usm.edu/gcr Part of the Marine Biology Commons Recommended Citation Sullivan, M. J. 1 98 1 . A Preliminary Checklist of Marine Benthic Diatoms of Mississippi. Gulf Research Reports 7 (l): 13-18. Retrieved from http://aquila.usm.edu/gcr/vol7/issl/2 This Article is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf and Caribbean Research by an authorized editor of The Aquila Digital Community. For more information, please contact Joshua.Cromwell(S>usm.edu. Gulf Research Reports, Vol. 7, No. 1, 13-18, 1981. A PRELIMINARY CHECKLIST OF MARINE BENTHIC DIATOMS OF MISSISSIPPI MICHAEL J. SULLIVAN Department of Biological Sciences , Mississippi State University, Mississippi State, Mississippi 39762 ABSTRACT A checklist of diatoms collected from various benthic habitats in coastal salt marshes and offshore seagrass beds of Mississippi has been compiled for the first time. The checklist includes 213 taxa (species and their varieties) in 43 genera with 19 of these taxa found only on the leaves of offshore seagrasses. Synedra fasciculata vat. intermedia (Grun.) Sulliv. comb. nov. is proposed to be consistent with the nomenclature of the nominate variety. Future work with this ecologically important group of marine algae should result in many new additions to this preliminary checklist. INTRODUCTION The marine benthic diatom flora of Mississippi remained an unknown entity until the publications of Sullivan (1978, 1979a). This is somewhat surprising in view of the great ecological importance of these organisms as major constitu- ents of the base of food webs in marine coastal ecosystems. Conger et al. (1972) compiled a list of diatoms from the Gulf of Mexico based on reviews of the older literature, and on results of phytoplankton collections in oceanic waters of the Gulf. Despite the broad coverage of their review, a great many species found in Mississippi by this author were not included in their checklist , an up-to-date list of diatoms in Mississippi’s coastal environments was thought to be needed. Furthermore, the present checklist reflects current taxonomic thinking, and restricts itself to a specific com- ponent of the flora (i.e., those forms leading a benthic existence). Other major groups of marine algae in Mississippi have fared little belter than ihe diatoms and only two published studies could be found. Humm and Caylor (1957) surveyed the blue-green, green, red, and brown algae of Mississippi Sound during two consecutive summers. The majority of collections were made around Ship Island, although a few were noted from such localities as Deer Island and a salt marsh near Ocean Springs. Sage and Sullivan (1978) collected blue-green algae from Graveline Bay Marsh over a yearly cycle, and noted the similarity between their Bora and those of Atlantic coastal salt marshes. CHECKLIST COVERAGE Although the geographical limits of the checklist theoret- ically include all benthic habitats of the Mississippi coast and its salt marshes, as well as those of Mississippi Sound and its offshore barrier islands, the number of localities sampled are few and the actual coverage represents a very small percentage of the total area just defined. However, the similarity of the diatom flora from different salt marshes or seagrass beds suggests that the checklist, although pre- Manuscript received June 10, 1980; accepted December 2, 1980. liminary, is representative of the character of the marine benthic diatom flora of Mississippi. This similarity also suggests that the number of additions to the checklist will decrease with each new locality sampled. The present checklist is biased towards the edaphic (sediment-associated) diatom flora of coastal salt marshes. Most of this work has been conducted in Graveline Bay Marsh which is located ca, 11 km southeast of the Gulf Coast Research Laboratory, Ocean Springs, Mississippi. Some of this work has been published (Sullivan 1978); the remaining data have been submitted for publication but without a complete listing of all diatom species encountered. Three different salt marshes in St. Louis Bay, MS, have been sampled, and these unpublished data also have been incorporated into this checklist. In addition, diatoms epiphytic on the red algae Caloglossa leprieurii (Mont.) J. Ag. and Bostrychia radicans Mont, in St. Louis Bay also have been included. Three different seagrass species in beds off the north shore of Horn Island recently were sampled (Sullivan 1979a) and form an important part of the checklist. Therefore, the flora reported herein is of an edaphic or epiphytic nature, and represents both inshore and offshore habitats. CHECKLIST FORMAT For the purposes of this checklist, diatoms are considered to constitute the single class Bacillariophyceae. There is no universal agreement among authorities as to which division diatoms should be assigned, and there is even less agreement on the number and identity of orders and families that should be recognized. Hendcy (1974) provides pertinent comments on the problems involved in arriving at a natural classification of diatoms, and reviews the different classification systems that have been proposed. The most recently proposed classification is that of Simonsen (1979) who recognizes two orders, five suborders, and 21 families. In view of the flux and uncertainty characterizing current thinking con- cerning relationships between higher taxonomic categories, the present checklist is concerned only with genera and species of Bacillariophyceae in marine benthic habitats of Mississippi. Genera are arranged alphabetically, and species 13 14 Sullivan and their varieties are arranged alphabetically within each genus following the format of Hendey’s (1974) checklist of British marine diatoms. Numbers in brackets after a name refer to NOTES which immediately follow the check- list. Species and their varieties collected only from offshore seagrass beds are marked with an asterisk. BACILLARIOPHYCEAE ACHNANTHES Bory, 1822 biasolettiana var. sublinearis Grun. brevipes var. intermedia (Kiitz.) Cl. coarc fata (Br£b.) Grun. curvirostrum Brun hauckiana Grun. lanceolata var. dubia Grun. (15) lemmermanni Hust. temperei M. Perag. AMPHIPRORA Ehrenberg, 1843 gigantea var. decussata (Grun.) Cl. hyalina Eulenstein paludosa W. Sm. var. paludosa var. duplex (Donk.) V.H. pulchra Bailey sim ilis Hust. AMPHORA Ehrenberg, 1831 angusta Greg, var. angusta (1 ) var. oblongella Grun. caroliniana Giffen (2) coffeiformis (Ag.) Kiitz. cymbelloides Grun.* cymbiformis Cl .* exigua Greg. laevis var. perminuta Grun. lib yea Ehr. pediculus (Kiitz.) Grun.* proteus Greg. robusta Greg.* sabyii Salah tenerrima Hust. tenuissima Hust . ANAULVS Ehrenberg, 1844 balticus Siinonsen ANOMOEONEIS Pfitzer, 1871 vitrea (Grun.) Ross (3) BACILLARIA Gmelin, 1778 paxillifer (Mull.) Hendey (4) BERKELEYA Greville, 1827 rutilans (Trent.) Grun. (5) CALONEIS Cleve, 1894 westii (W.Sm.) Hendey CAMPYWSIRA Grunow, 1882 alexandrica Salah cymbelliformis (A.S.) Grun. CAPARTOGRAMMA Kufferath, 1956 crude ula (Grun.) Ross COCCONEIS Ehrenberg, 1838 deperdita Giffen cf. discrepans A.S. disculoides Hust. placenlula var. euglypta (Ehr.) Grun. placentula var. lineata (Ehr.) V.H. scutellum Ehr. var. scutellum var. parva (Grun.) Cl. woodii Reyes-Vasquez* (6) CYCLOTELLA Kiitzing, 1833 caspia Grun. meneghiniana Kiitz. sty lorum Brightwell CYL1NDROTHECA Rabenhorst, 1859 gracilis (Breb.) Grun. C.YMATOSIRA Grunow, 1862 belgica Grun. CYMBELLA Agardh, 1830 pusilla Grun. (7) DENTICULA Kiitzing, 1844 sub tilis Grun. DIMEREGRAMMA Ralfs, 1861 hyalinum Hust. minor (Greg.) Ralfs DIPLONEIS Ehrenberg, 1840 aestuari Hust. elliptica (Kiitz.) Cl. graendleri (A.S.) Cl. mediterranea (Grun.) Cl. obliqua (Brun) Hust.* pseudovalis Hust. puella (Schum.) Cl. smilhii (Brdb.) Cl. EUNOTIA Ehrenberg, 1837 naegelii Migula (8) EUNOTOGRAMMA Weisse, 1854 laevis (laevcj Grun. FRAGILARIA Lyngbye, 1819 atomus Hust. gessneri Hust. hyalina (Kiitz.) Grun.* obtusa Hust. pinnata Ehr. schulzi Brockmann FRUSTULIA Agardh, 1824 asymmetrica (Cl.) Hust. rhomboides var. saxonica (Rabh.) DeToni sim ilis Hust. Marine Benthic Diatoms of Mississippi 15 GRAMMATOPHORA Ehrenberg, 1840 oceanica Ehr.* GYROSIGMA Hassall, 1845 balticum (Ehr.) Rabh. beaufortianum Hust. macrum (W.Sm.) Griff. & Henfr. obliquum (Grun,) Boyer obscunm (W.Sm.) Griff. & Henfr. peisonis (Grun.) Hust. HANTZSCHIA Grunow, 1880 distinctc-punctata Hust. L1CMOPHORA Agardh, 1827 abbreviate Ag.* cf. debilis (Kutz,) Grun.* MASTOGLOIA Thwaites, 1856 exigua Lewis pumila (Grun.) Cl. pusilla Grun.* MELOS1RA Agardh, 1824 dubia Kiitz. lineata (Dillw.) Ag. moniliformis (Mull.) Ag. nummuloides Ag. westii W.Sm. NAVICULA Bory, 1822 abunda Hust. accomoda Hust. aequorea Hust. alpha Cl. ammophila Grun. amphipleuroides Hust.* binodulosa Sulliv, & Reim. (9) capitate var. hungarica (Grun.) Ross circumtexta Meister clamarn Hust. dementis Grun. cocconeiformis Greg. creuzburgensis Krasske digito-radiata (Greg.) Ralfs diserta Hust. fauta Hust. (10) fenestrella Hust. flanatica Grun. florinae Miller gregaria Donkin hanseni Miller hudsonis Grun. (11) incerta Grun . incomposita Hagelstein longirostris Hust. maculate (Bailey) Edwards mendolia VanLand. cf. menisculus Schum. mutica Kutz. (12) nolens Simonsen obsolete Hust. orbiculata Patrick (13) pavillardi Hust.* peregrina (Ehr.) Kiitz. phyllepta Kutz. pseudocrassirostris Hust. pseudony Hust. pusilla W.Sm. radio striata Hust. regularis Hust. rhynchocephala Kiitz. sal inarum Grun. (14) salinicola Hust. (15) schroeteri Meister spicula (Hickie) Cl. subforcipata Hust. subirritans Gif fen taraxa Hohn & Hellerm. (16) tenera Hust. teneroides Hust. tripunctatu (Mull.) Bory (15,17) yarrensis Grun. zostereti Grun. NITZSCHIA Hassall, 1845 (18) angularis W.Sm. apiculata (Greg.) Grun . bilobata var. ambigua Manguin brevissima Grun. (19) calida Grun. closterium (Ehr.) W.Sm. communis var. hyalina Lund constricta (Greg.) Grun.* dissipate (Kiitz.) Grun. dubia W.Sm. dubiformis Hust, epithemoides Grun. fasciculate (Grun.) Grun. filiformis (W.Sm.) Schiitt gandersheimiensis Krasske (20) grana Hohn & Hellerm. granulate Grun. hungarica Grun. hustedtiana Sal ah Icvidensis (W.Sm.) V.H. lorenziana Grun. var. lorenziana var. subtilis Grun. microcephala Grun. minutula Grun. ( 1 5 ,2 1 ) obsidialis Hust. obtusa W.Sm. var. obtusa var. nana Grun. (15) palea (Kiitz.) W.Sm. paleacea Grun.* 16 SULLIVAN panduriformh Greg, var. panduriformis var. continua Grun. perversp Grun. plana W.Sm. pseudoamphioxys Hust. (22) recta Hantz. romana Grun. romanoides Manguin scalaris (Ehr.) W.Sm. sigtrn (Kiitz.) W.Sm. socialis var. massiliensis Grun. suhvitrea Hust. tryblionella Hant/.. visurgis Hust. vitrea var. salinarum Grun. OPEPHORA Petit, 1888 pacifica (Grun.) Petit parva (Grun.) Krasske schwarzii (Grun.) Petit PARALIA Heiberg, 1863 sulcata (Ehr.) Cl. (23) PL A G10GRAMMA Greville, 1859 tenuistriatum Cl. PLEUROSIGMA W. Smith, 1852 delicatulum W.Sm. distinguendum Hust. salinarum (Grun.) Grun. strigosum W.Sm. RHOPALODIA O. Muller, 1895 gibberula (Ehr.) Mull. ST A U RONE IS Ehrenberg, 1843 amphioxys Greg, var. amphioxys var. obtusa Hendey salina W.Sm. STRJATELLA Agardh, 1832 unipunctata (Lyngbye) Ag.* SUR1RELLA Turpin, 1828 atomus Hust. litoralis Hust. ovalis Breb. stria tula Turpin SYNEDRA Ehrenberg, 1830 fasciculata (Ag.) Kiitz. (24) var. fasciculata var. intermedia (Grun.) Sulliv. comb, nov .* (24) THALASSIOSIRA Clove, 1873 eccentrica (Eln.) Cl. (25) TRACHYNE1S Cl eve, 1894 aspera (Ehr.) Cl.* TRACHYSPHENIA Petit, 1877 acuminata Perag.* TROPIDONE1S Cleve, 1891 lepidoptera (Greg.) Cl. vitrea (W.Sm.) Cl. NOTES (1) See Hendey (1974) for differencesbetweenA angusta and A ventricosa Greg. (2) Giffen (1980) examined the type slide of Amphora granulata Greg, and concluded that A. granulate sensu Hustedt (1955) represented a previously undescribed taxon, which he named and described as A. caroliniana after the type locality. (3) Only two valves were found in a St. Louis Bay salt marsh. (4) This taxon is better known as Bacillaria paradoxa Gmelin, but the correct name is B. paxillifer if one recognizes the validity of the genus Bacillaria The former specific epithet apdy describes the paradoxical movements of colonial associations of this organism which have fascinated botanists for almost 200 years. (5) See Cox (1975a,b) for the separation of the genera Berkelya and Amp hip leura Kutzing. (6) Cocconeis woodii differs from C scutellum only by its sigmoid axial area on both valves of the frustule, and perhaps deserves only a varietal rank. In any event, the two entities clearly were separable in collections of epiphytic seagrass diatoms. (7) Cymbella pusilla is perhaps the only true marine member of the genus. (8) Only three valves were found in a St. Louis Bay salt marsh. (9) This taxon originally was described from a Delaware salt marsh by Sullivan and Reimer (1975), and only has been found within the sediments beneath Distichlis spicata (L.) Greene in Mississippi salt marshes. (10) Navicula fauta was first described by Hustedt (1954) from mangrove vegetation on the Pacific Coast of El Salvador, and has not been reported since to the best of my knowledge. (11) Considered to be conspecific with the earlier described taxon N. pygmaea Kiitz. by Simonsen (1975). (12) Includes N. mutica var. cohnii (Hilse) Grun. as des- cribed by Patrick and Reimer (1966), (13) Observed only once in Graveline Bay Marsh. (14) Includes f. minima Kolbe which is likely to be identi- fied by some authorities as N. cryptocephala var. veneta (Kiitz.) Rabh. ( 1 5) One of the most abundant and characteristic salt marsh diatom taxa. (16) Maybe a synonym for N. platyventrisW[Q\$\.et described earlier. MARINE BENTHIC DIATOMS OF MISSISSIPPI 17 (17) Later synonyms are TV. transversa Boiy and N. gracilis Ehr. (Patrick and Reimer 1966). See Cox (1979) for a detailed study of this highly variable and widely dis- tributed taxon. (18) The revisions of Lange Be rtalot (1976), and Lange- Bertalot and Simonsen (1978) were used in identifying taxa belonging to the section Lanceolatae. (1 9) This taxon is identical with Nitzschia parvula Lewis. (20) Most specimens identified as this taxon fit the descrip- tion of Nitz. laevis Hust., which is very likely a syn- onym of Nitz r gander sh eimiensis according to Lange- Bertalot and Simonsen (1978). (21) Those individuals identified as Nitzschia frustulum (Kiitz.) Grun. in Sullivan (1978) belong to this taxon based on interpretations of Lange-Bertalot (1976). GENERAL SUMMARY A total of 213 taxa (species and their varieties) in 43 genera comprise the present checklist. Genera with the largest number of taxa are Navicula and Nitzschia with 53 and 44, respectively. This is not surprising in light of a sampling bias towards forms inhabiting salt marsh sediments where motility would appear to be a distinct advantage. The third most important genus in terms of number of taxa is Amphora , which also possesses a raphe system on both valves of the frustule (unicell). Also well represented are Achnanthes, Cocconeis, and Diploneis with eight taxa each. Exactly 19 taxa were collected only from the leaves of offshore seagrasses in Mississippi Sound. If more collections were made in the seagrass beds, this number certainly would have been much higher. Clearly, the physicochemical char- acteristics of the waters that bathe diatom cells in inshore and offshore habitats aie different as is evidenced by the distribution of diatom genera and taxa (e.g., Grammato- phora, LAcmophora , Striatella, and Trachysphenia are thus far only known from seagrass beds). (22) A very abundant diatom of Graveline Bay Marsh that could be mistaken for Hantzschia amphioxys var. minor Perag. (23) See Crawford (1979) for an excellent description of this taxon and its separation from Melosira. (24) Patrick and Reimer (1966) have determined that Synedra affinis Kiitz. and *$’. tabulata (Ag.) Kiitz. are later synonyms of S. fasciculata (Ag.) Kiitz. Therefore, S. ( affinis var.) intermedia Grun. in Van Heurck is to be properly regarded as a variety of fasciculata . See Sullivan (1979b) for a description of var. intermedia. (25) Based on the frequency of its appearance in salt marsh sediments, Thalassiosira eccentrica may be capable of a benthic as well as a planktonic existence. The present checklist provides important distributional information on an ecologically significant group of organ- isms. Future work along the Mississippi coast and In the Sound should result in many new additions to this preliminary checklist, and hopefully will encourage other workers in the remaining Gulf coastal states to compile similar checklists. ACKNOWLEDGMENTS 1 particularly thank Ruth O’Quinn for her considerable efforts in compiling the present checklist. Any errors or omissions are my responsibility, however. Lionel N. Eleu- terius, of the Gulf Coast Research Laboratory, kindly pro- vided the author with laboratory facilities, and suggested most of the collecting sites. Comments provided by two anonymous referees were helpful in dealing with nomencla- ture. This work was supported in part by funds provided by the Office of Water Research and Technology (Proj, No. A— 099— MISS, A-l 14-MISS, and A-124-M1SS) U.S. Department of the Interior, Washington, D,C M as authorized by the Water Research and Development Act of 1978. REFERENCES CITED Conger, P, S., G. A. Fryxeil & S. Z. El-Sayed. 1972. Diatom species reported from the Gulf of Mexico. Pp. 18-23 in V. C, Bushnell (ed,). Serial Adas of the Marine Environment. American Geo- graphical Society, Folio 22. Cox, E. J. 1975a. A reappraisal of the diatom genus Amphipleura Kiitz. using light and electron microscopy. Br. Phycol. J. 10:1 12. . 1975b Further Studies on the genus Berkelya Grev. Br. PhvcolJ. 10:205-217. . 1979. Taxonomic studies on the diatom genus Navicula Bory: the typification of the genus. Baciltaria 2: 1 37-153. Crawford, R. M. 1979. Taxonomy and frustular structure of the marine centric diatom Parulia sulcata . ./ Phycol. 15:200-210. Giffen, M. H 1980. A checklist of marine lit total diatoms from Mahe, Seychelles Islands. Bacillarta 3:129-159. Hendey, N. I. 1974. A revised check-list of British marine diatoms. J. Mar. Biol. Assoc. V, K. 54:277 300. Humm, II. J & R. L. Caylor. 1957. The summer marine flora of Mississippi Sound. Publ. Inst. Mar. Sci. Univ. Tex. 4.228-264. Hustedt, F. 1954- Neue and wenig bekannte Diatomeen. VI. Ber. Disch. Bot. Ges. 67:269-280. . 1955. Marine lit toral diatoms of Beaufort, North Carolina. Duke l/niv. Mar. Sin. Bull. No, 6:1-67. Lange-Bertalot, H. 1976. Einc Revision zurTaxonomiederNitzschiae Lanceolatae Grunow. Die “klassisehen” bis 1930 beschriebenen Susswasseranen Europas. Nova Hedwtgia 28:253-307. & R. Simonsen. 1978. A taxonomic revision of theNitzschiae lanceolatae Grunow 2. European and related extra-European fresh water and brackish water taxa. Bacillaria 1:11 111. Patrick, R. & C. W. Reimer. 1966. The Diatoms of the United States. Vol. 1. Acad. Nut. Sci. Philadelphia Monograph No. 1.3. 688 pp. Sage, W. W. &. M. J. Sullivan. 1978. Distribution of bluegreen algae in a Mississippi Gulf coast salt marsh, J. Phycol. 14:333-337. Simonsen, R, 1975. The diatoms Navicula pygmaea Kiiiztng and N. hudsonis Grunow Br Phycol J 10:169 — 178. 18 SULLIVAN . 1979. The diatom system: ideas on phytogeny. Bacillaria 2:9-71. Sullivan, M. J. 1978. Diatom community structure: taxonomic and statistical analyses of a Mississippi salt marsh. J. Phycol. 14: 468-475. . 1979a. Epiphytic diatoms of three seagrass species in Mississippi Sound. Bull. Mar. Sci. 29:459-464. . J979b. Taxonomic notes on epiphytic diatoms of Missis- sippi Sound, ll.S.A. Nova Hedwigia , Beih. 64:237-249. & C. W. Reimer. 1975. Some diatoms (Bacillariophyceae) from a Delaware salt marsh -four of which are described as new. Bot. Mar. 18:115 121. Gulf Research Reports Volume 7 | Issue 1 January 1981 Larval Development Under Laboratory Conditions of the Xanthid Mud Crab Eurytium limosum (Say 1818) (Brachyura: Xantbidae) from Georgia Hiroshi Kurata Nansei Regional Fisheries Research Laboratory \ Hiroshima, Japan Richard W Heard Gulf Coast Research Laboratory Joel W Martin University of Southwest Louisiana DOI: 10.18785/grr.0701.03 Follow this and additional works at: http://aquila.usm.edu/gcr Part of the Marine Biology Commons Recommended Citation Kurata, H., R. W. Heard andj. W. Martin. 1981. Larval Development Under Laboratory Conditions of the Xanthid Mud Crab Eurytium limosum (Say, 1818) (Brachyura: Xanthidae) from Georgia. Gulf Research Reports 7 (l): 19-25. Retrieved from http:// aquila.usm.edu/gcr/vol7/iss 1/3 This Article is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf and Caribbean Research by an authorized editor of The Aquila Digital Community. For more information, please contact Joshua. Cromwell(2)usm.edu. Gulf Research Reports, Vol. 7, No. 1, 19-25, 1981. LARVAL DEVELOPMENT UNDER LABORATORY CONDITIONS OF THE XANTHID MUD CRAB EURYTIUM LIMOSUM (SAY, 1818) (BRACHYURA: XANTHIDAE) FROM GEORGIA HIROSHI KURATA, 1 RICHARD W. HEARD, 2 AND JOEL W. MARTIN 3 1 Nansei Regional Fisheries Research Laboratory , Hiroshima, Japan, 2 Gulf Coast Research Laboratory, Ocean Springs, Mississippi 39564, and 3 Biology Department, University of Southwestern Louisiana , Lafayette, Louisiana 70504 ABSTRACT Larvae of the xanthid mud crab Eurytium limosum were reared in the laboratory from hatching to first crab stage. Four zoeal stages and one megalops stage were obtained and are described. Complete larval development required about 15 days under culture conditions of 26.0° to 28.0°C and 25 ppt sea water. A long antenna and short antennal exopods consign E. limosum to the Group 1 xanthid zoeae of Rice (1980). The first stage zoea closely resembles that of Panopeus herbstii and is distinguished by having the dorsal spine strongly recurved at the extremity. Stages 2 to 4 are dis tinguished from Rhi thro panopeus harrisii and Neopanope sayi INTRODUCTION Xanthid larvae have been the subject of more studies than have larvae of any other family within the Brachyura. Wear (1970) in his bibliography of xanthid crab larvae listed 23 references to xanthid larvae, exclusive of the 25 references given by Gurney (1942). More recently. Rice (1980) sum- marized current knowledge of xanthid larvae and listed 15 references not found in Wear (1970) or published since that time. Not listed by Rice (1 980) were the descriptions of larvae belonging to Pilumnoides perlatus by Fagetti and Campodo- nico (1973), and to Neopanope texana by McMahan (1967). Since Rice’s review, the larvae of Micropanope barbadensis have been described by Gore et al. (1981). Xanthids generally are characterized by having four zoeal stages and a megalops stage, although five species have been shown to have less than four zoeal stages (Hale 1931; Wear 1967, 1968; Saba et al. 1978); the five exceptions are from somewhat restricted habitats. Members of the subfamily Menippinae have five and sometimes slx zoeal stages, but there is strong evidence that these crabs constitute a separate family (Scotto 1979). Only one other xanthid crab, Pilum- noides perbtus (Poeppig, 1936), has been shown to have five zoeal stages (Fagetti and Campodonico 1973). The xanthid genus Eurytium Stimpson, 1859 is repre- sented in North America by three species, only one of which occurs on tire eastern coast of North America (Rathbun 1930). Though primarily a tropical species associated with mangrove habitats, the mud crab Eurytium limosum (Say, 1 81 8) is a common member of the Spartina salt marsh fauna of coastal Georgia and southern South Carolina (Teal 1959, Williams 1965), and it is probable that its larvae represent an important part of the estuarine meroplankton in those and other regions. The present study is the first description of larvae within University of Georgia Marine Institute Contribution No. 424. Manuscript received September 2, 1980; accepted October 20, 1980. larvae by having two lateral spines on the telson. the genus Eurytium, and is in part the result of studies conducted at Sapelo Island, Georgia, by Kurata (1970). MATERIALS AND METHODS An ovigerous female captured in a Spartina marsh adja- cent to Sapelo Island, Georgia, on August 16, 1964, was kept at room temperature in a large finger bowl half filled with filtered sea water diluted to 25 ppl until August 21, 1964. when the eggs hatched. Most of the zoeae were placed in three large finger bowls. Later, the first stage zoeae were placed in 10 small 3.5-inch finger bowls in groups of 10 per bowl and maintained at 26.0° to 28.0°C in 25 ppt filtered sea water. Water in the finger bowls was changed daily, and a record was maintained of larval molting and mortality. All zoeal and megalops stages were fed once daily on newly hatched Anemia nauplii. Various stages used for the descrip- tions were removed from the large mass-culture bowls and fixed in 10% formalin; 48 hours later, stages were transferred to 70% ethanol. Drawings were made with the aid of Wild M-5 and M-20 drawing tubes; an ocular micrometer was used for all measurements. Preserved larval stages and the parent currently are in the collection of the senior author. RESULTS Rearing Results of rearing experiments are summarized in Figure 1 . Mortality of larvae was negligible during the zoeal stages, but was considerable in the tnegalops stage. Mean duration of each zoeal stage was 2 to 3 days and that of megalops was about 8 days. Complete larval development required from 8 to 15 days; molting to first crab stage occurred between days 16 and 19. Larval Stages Four zoeal stages (Figures 2 and 3) and one megalops stage (Figure 4A-C) are recognized. No additional zoeal stages were observed. 20 KURATA ET AL. Figure 1. Duration and success of larval stages during development of Eurytium limosum. One hundred newly hatched zoeae were Teared in 10 small finger bowLs at 26.0° to 28.0°C, at 25 ppt. Figures on right hand side of diagram show the total number of larvae successfully reached at each stage. Zoea Carapace with 1 dorsal, 1 rostral, and 2 lateral spines. These are all smooth with the rostral spine long and almost straight. Dorsal spine about 3/4 the carapace length (meas- ured from tip of rostral spine to posterior margin of cara- pace), curving posteriorly at the end. Lateral spines small, about 1 /8 length of dorsal spine. Small anterior and poster- ior protuberances on carapace. Ventral margin of carapace smooth and fringed with up to 10 hairs, increasing in num- ber with the progression of stages. Abdomen (measured from posterior of carapace to tip of telson forks) about 1.1 times longer than carapace, lateral hooks present on segments 2 and 3, those on segment 3 distinctly smaller than those on segment 2. A pair of lateral spines present on segments 3 to 5, these spines all nearly the same size and never reaching the posterior margin of the following segment. Telson with 1 dorsal and 2 lateral spines, second lateral spine quite small, hairlike and seen only in the first stage. First lateral and dorsal spines distinct in all stages, though the former decreases in size in later stages. Telson forks slender, smooth, and curving dorsally at end. Central indentation on posterior margin wide but shallow. Three pairs of internal spines, the third pair (innermost) longest and slightly longer than 1/2 the length of telson fork. Antennae nearly equal to or slightly longer than rostral spine; exopod is vestigial and represented by a small process with a short terminal spine (sometimes wanting) at the base of the spinous process. Spinous process furnished distally with several spinules in stage 1 , but smooth in later stages. Stage 1 (Figures 2 A , K; 3 A , E). Carapace length: 1.13mm. Eyes sessile. No ventral, marginal setae on carapace. Sixth abdominal segment fused with telson. Telson fork length nearly equal to width of telson (measured at the level of the first internal spine). Antennule represented by a simple conical process with single group of terminal aesthetes. No endopod on antenna, mandible with no palp. No outer setae on maxillule. First and second maxillipeds bear 4 swimming setae on each exopod. No third maxillipeds, pereopods, or abdominal appendages. Stage 2 (Figures 2C: 3B, F). Carapace length: 1.43 mm. Eyes stalked and free from carapace. Base of rostral spine slightly expanded laterally just in front of eyes but not produced into distinct spines. Two hairs on inner ventral margin of carapace. Second lateral spine on telson disappears in this stage. Inconspicuous swelling at base of antennal spinous process representing rudimentary endopod. Densely plumose outer setae on maxillule. Six swimming setae on exopod of first maxilliped, 7 setae on exopod of second maxilliped. Third maxilliped and pereopods appear as small buds. Stage 3 (Figures 2D; 3C. G). Carapace length: 1.90 mm. Sixth abdominal segment articulated From telson. A pair of small setae added between innermost pair of internal spines of telson. Length of telson forks about 1 1/4 times longer than width of telson. Endopod of antenna about 1/8 length of spinous process. First and second maxillipeds each bear 8 swimming setae on exopods. First pereopod bilobed. Ple- opods appear as simple conical buds, those on segments 3 and 4 shorter than respective lateral spines of segments. Stage 4 (Figures 2E~J; 3D, 11). Carapace length: 2.17- 2.43 mm. Telson usually with 2 pairs of small internal setae between innermost pair of spines. Antennule greatly swollen at base; outer flagellum segmented from piotopod and bearing 3 groups of aesthetes, inner flagellum appears as a simple process. Mandible (Figure 2F) well calcified with incisor and molar processes distinctly divided, and with small palp. Endopod of maxillule (Figure 2G) consists of 2 segments with a seta on short proximal segment and 6 setae in 3 groups on long distal segment. A simple outer seta present near base of maxillule. Endopod of maxilla (Figure 2H) unsegmented but divided into 3 indistinct inner lobes with 3, 2, and 3 setae on each respective lobe. Endo- pod of first maxilliped has on terminal segment a vestigial, outer seta not reaching distal end of terminal segment (Figure 21). Exopod of first maxilliped with 8 or 9 setae. Larval Development of the Xanthid Mud Crab 21 Figure 2. Eurytium limosum, zoeal stages 1 to 4. Stage 1 zoea: A, lateral view; B f dorsal view of abdomen. Stage 2 zoea: C, lateral view of abdomen. Stage 3 zoea: D, lateral view of abdomen, Stage 4 zoea; E> lateral view; F, mandible; G, maxillule; H, maxilla; I, terminal segment of maxiUiped 1 ; J, endopod of maxilliped 2. (0.1 mm indicated.) 24 KURATA ET AL. Endopod of second maxilliped consists of 3 segments, the second slightly longer than the first, the third (terminal) segment about 1 1/2 times length of combined proximal 2 segments (Figure 2J). Proximal 2 segments bear 1 seta each, terminal segment bears 3 apical, 1 inner, and 1 outer setae. Exopod of second maxilliped with 10 or 11 setae. Pereopod buds exposed from ventral margin of carapace. Carapace fringed with up to 10 setae. Pleopods with rudi- mentary endopods, those on segments 3 and 4 longer than respective lateral spines. Megalops (Figures 4A-C). Carapace length : J ,06 mm. Total length: 2.01 mm Carapace slightly longer than wide, without conspicuous dorsal protuberances. Gastric and cardiac regions distended dorsally. Small process at center of posterior margin, Eyes extend somewhat beyond lateral margin of carapace; cornea not wider than stalk. Rostrum bent obliquely down and terminates as slightly bifid, blunt central process with pair of pointed lateral spines that extend almost horizontally forward, curving inwardly like horns. Abdomen slightly shorter than carapace. Lateral plate of segment 5 nearly reaching posterior end of segment 6. Telson about 2/3 as long as wide and slightly longer than segment 6, with rounded posterior margin. Uropod bears 1 seta on proximal segment (protopod) and 8 or 9 setae on distal segment (exopod). Protopod of antenna with 4 segments and a flagellum of 7 segments. Mandible with 3-segmented palp. Cheliped with large curved hook on ischium. No other spines or hooks present on any pereopod segments, except dactyli of pereopods 2 to 4 which bear 3 short spines. Dactyli of pereopods 2 to 5 about 1 1/2 times longer than their propodi. Fifth pereopod bears 2 short aesthetasc-like hairs on dactyl. First Crab ( Figure 4D). Carapace length: 1.33 mm. Body covered throughout with numerous minute hairs and sparsely with long hairs. Carapace nearly as long as wide, with a slightly bilobed front. Two lateral spines on either side of carapace in hepatic region just posterior to orbit. No hooks on ischium of chelipeds. DISCUSSION The zoea of E. limosum, like other typical xanlhid zoeae, is characterized by a long antenna with a reduced exopod. It is distinguishable from other known xanthid zoeae by stages 2 to 4 having a smooth antennal spinous process and two distinct outer spines on the telson. How- ever, as the first stage zoea of E. limosum has a serrated antennal spinous process and three outer spines (2 lateral, 1 dorsal), it is difficult to distinguish from the first zoea of Fanopeus herbstii Milne-Ed wards, 1834. Only the strongly recurved extremity of the dorsal carapace spine in Eurytium limosum appears to distinguish the first zoeal stages of these two species. Rathbun (1930) reported 18 species of crabs in the family Xanthidae from the coasts of Georgia and the Caro- linas. Williams (1965), and Williams et al. (1968) added 8 more species, and Williams (1974) reported a new genus and species, Allactaea lilhostrota. Thus, 27 species of xanthids belonging to 16 genera are now known to occur along the eastern coast of Georgia and the Carolinas. Larval stages of 12 species belonging to the genera Leptodius, Fanopeus, Neopanop e, Hexapanopeus, Eurypanopeus, Micropanope, Rhithropanopeus, Menippe, Lobopilumnus, Filumnus, and Eurytium are now known from the eastern coast of North America. Larvae of the remaining genera (Glyptoxanthus, Actaea, Domecia, Eriphia, and Allactaea) known from this region remain undescribed. However, information on the larvae of Eriphia is available from other geographical areas (see Gurney 1942). Wear (1970) concluded that the most important character of Lebour (1928) separating xanthid zoeae into recognizable groups was the length of the antennal exopod relative to the length of the protopodite. Scotto (1979) agreed with Wear (1970) in that a well-developed antennal exopod indicated a more primitive condition, and she mentioned the extra zoeal stage and the placement of male and female genital openings on the adults (after Guinot 1977) as evi- dence for the apparent “primitive” placement of (he genus Menippe. If the antennal exopod is indeed a good character for placement within the family Xanthidae. Eurytium limo- sum is an advanced xanthid and is more closely allied to the genera Hexapanopeus , Heteropanope, Neopanope , Lopho- panopeus, and Rhithropanopeus. Aikawa (1937) placed much phylogenetic significance on the antennal exopod and expanded the two xanthid zoeal groupings of Hyman (1925) into three groups. Rice (1980) has separated the known xanthid zoeae into four groups, employing the setation of the mouthpqrts as additional characters. The first of these groups, into which Eurytium limosum falls, contains the most advanced xanthids, with antennal exopods greatly reduced or absent. The antenna of the first stage zoea of E. limosum is furnished distally with several spiuules, but is smooth in later stages. This character, plus the presence of three outer spines on the telson of stage 1 zoea, indicates a not too distant relationship to less advanced xanthids such as Fanopeus herbstii. The first stage zoea is similar to that of Fanopeus herbstii Milne-Edwards, 1834 as described by Costlow and Bookhout (1961), but can be distinguished by the more strongly recurved distal portion of the dorsal carapace spine in E. limosum. The later stages resemble the zoea of Rhithropanopeus harrisii (Gould , 1 84 1 ) as described by Connolly (1925), Chamberlain (1962), and Hood (1962), and the zoea of Neopanope sayi (Smith, 1869) as described by Hyman (1925, after Birge 1883) and Chamberlain (1957, 1961). However, the zoeae of Eurytium limosum have two outer spines on the telson in contrast to the single outer spine on the telson of R. harrisii and N. sayi. Larval development of the xanthid mud Crab 25 Available data indicate that Eurytiwm may have originated from Panopeus stock but advanced along a separate line from those genera that have undergone a reduction in telsonal armature. There is, however, still some doubt as to the phylogenetic significance of many decapod larval characters. For example, according to the scheme of Aikawa (1937) and to the categorization of xanthid larvae by Rice (l 9 S0) y Panopeus bermudensis Benedict and Rathbun, 1891 would rank as extremely primitive among the Xanthidae on the basis of its first stage zoea (Lebour 1944); it would likely deserve recognition under a separate genus were larval characters considered as phylogenetically significant as the adult morphology Upon which its generic placement is presently based. This was noted by Wear (1970) and by Rice (1980). Detailed descriptions of additional genera and species likely will clarify questionable phylogenetic relationships among the many members of the Xanthidae. Future studies employing the larval characters given by Rice (1980) should, in particular, further clarify the phylogenetic signifi- cance of such larval characters as armature of the antennal exopod and telson within this group. ACKNOWLEDGMENTS Facilities for rearing the larvae and initial preparation of their descriptions were provided by the University of Georgia Marine Institute, Sapelo Island, Georgia. Darryl Felder, Harriet Perry, and Ken Stuck read and commented on the manuscript; their suggestions and comments are appreciated. The authors thank Vernon Henry and Robin Overstreet for their encouragement and support during various phases of this work. REFERENCES CITED Aikawa, H. 1937. Further notes on brachyuran larvae. Rec. Oceanogr. Works Jpn. 9(l-4>:87— 1 62. Birge. E. A. 1883. Notes on the development of Panopeus sayi (Smith). Johns Hopkins Univ. Stud. Biol Lab. 2(4):41 1 -426. Chamberlain, N. A. 1957, Larval development of Neopanope texana sayi. Biol. Bull. (Woods Hole) 113:338. . 1961. Studies on the larval development of Neopanope texana sayi (Smith) and other crabs of the family Xanthidae (Brachyura). Chesapeake Bay Inst. Johns Hopkins Univ. Tech. Rep. 22:1- 37 . 1962. Ecological studies on the larval development of Rhithropanopeus harrisii (Xanthidae, Brachyura). Chesapeake Bay Inst. Johns Hopkins Univ. Tech. Rep. 28:1-47. Connolly, C. J, 1925, The larval stages and megalops of Rhithro- panopeus harrisii (Gould). Com rib. Can . Biol. Stud. Biol. Stn. Can . 2(2):329-334. Costlow, J. D.&C. G. Bookhout. 1961. The larval stages of Panopeus /ier6r//7Milne-Edwards reared in the laboratory. J. Elisha Mitchell Sci. Soc. 77(1):33— 42. Fagotti, E. 8l 1. Campodonieo. 1973. Larval development oiPilum- noides perlatus (Brachyura: Xanthidae) under laboratory condi- tions. Mar. Biol. 1 8; 1 29 - 1 39 . Gore, R. H., C. L. van Dover, and K. A. Wilson. 1981. Studies on decapod Crustacea from the Indian River region of Florida. XX, Micropanope barhadensis (Rathbun, 1921): The complete larval development under laboratory conditions (Brachyura, Xanthidae). J. Crustacean Biol l(l):28-50. Guinot, D. 1977. Propositions pour une nouvelle classification des Crustaces Decapodes Brachyourcs, C. R. Hebd. Seances Acad. Sci. Ser. £>., Sci. Nat. 285:1049-1052. Gurney, R. 1942. Larvae of Decapod Crustacea. Ray Society, London. 1 23 pp. Hale, H. M. 1931 . The post-cmbryonic development of an Australian xanthid crab ( Pilumnus vestitus Haswell). Rec. S. Aust. Mus. 4 (3): 321 — 331 Hood, R. M. 1962. Studies on the larval development of Rhithro- panopeus harrisii (Gould) of the family Xanthidae (Brachyura). Gulf Res. Rept. !(3):122-130. Hyman, O. W. 1925. Studies on the larvae of crabs of the family Xanthidae. Proc. U.S. Nat. Mus. 67(3): 1-22. Kurata, II. 1970. Studies on the life histories of decapod Crustacea of Georgia: Part III. Larvae of decapod Crustacea of Georgia. Final Report. University of Georgia Marine Institute, Sapelo Island, GA. 274 pp. Lebour, M. 1928. The larval stages of the Plymouth Brachyura. Proc. Zool. Soc. London 1928:473-560. . 1944. Larval crabs from Bermuda, Zoologica ( N.Y .) 29(1 1 ) : 1 1 3-128. McMahan, M. R, 1967. The larval development of Neopanope texana texana (Stimpson) (Xanthidae). Vol. II, Immature invertebrates. Fla. Board Conserv. Mar. Res. Lab. Leaf l Ser. Part 1, No. 1: 1 16 . Rathbun, M. J. 1930. The cancroid crabs of America of the families Euryhalidae, Portunidae, Atelecyclidae, Cancridae and Xanthidae. U.S. Natl. Mus. Bull 152:1-609. Rice, A. L. 1980. Crab zocal morphology and its bearing on the classification of the Brachyura. Trans. Zool Soc. London 35: 271-424. Saba, M., M. Takeda & Y. Nakasone. 1978. Larval development of Epixanthus denratus (White) (Brachyura, Xanthidae). Bull. Natl. Sci Mus. Ser. A. (Zool) 4(2):151 - 161. Scotto, L. F., 1979. Larval development of the Cuban stone crab, Menippe mdifrons (Brachyura, Xanthidae), under laboratory conditions with notes on the status of Lire family Menippidae. U.S. Fish Wildl. Serv . Fish. Bull. 77(2):359-386. Teal, J. M. 1959. Respiration of crabs in Georgia salt marshes and its relation to their ecology. Physiol. Zool. 32(1 ): 1—14. Wear, R. G. 1967. Life-hislory studies on New Zealand Brachyura. 1. Embryonic and post-embryonic development of Pilumnus novaezealandiae Filhol, 1886, and of P. iumpinus Bennett, 1964 (Xanthidae, Pilumninae). N.Z. J. Mar. Freshw. Res. 1:482-535. ___ . 1968. Life-history studies on New Zealand Brachyura. 2. Family Xanthidae. Larvae of Heterozius rotundifrons A, Milne Edwards, 1867, Ozius truncatus H. Milne Edwards, 1834, and Heteroponope (Pilumnopeus) serratifrons (Kinahan, 1856). N.Z. J. Mar. Freshw. Res. 2:293-332. . 1970. Notes and bibliography on the larvae of xanthid crabs. Pac. Sci. 24:84 89. Williams, A. B. 1965. Marine decapod crustaceans of the Carolinas. U.S. Fish Wildl Serv. Fish. Bull 65:1-298. , 1974. Allactaea liihostrota, a new genus and species of crab (Decapoda: Xanthidae) from North Carolina, U.S.A. Proc. Biol. Soc. Wash. 87(3): 19 -26. , L. R. McCloskey &. I. E, Gray. 1968. New records of brachyuran decapod crustaceans from the continental shelf off North Carolina, U.S.A. Crustaceana 15(1 ):4 1 — 66. Gulf Research Reports Volume 7 | Issue 1 January 1981 Growth Kinetics and Longevity of the Salt Marsh Rush Juncus roemerianus Lionel N. Eleuterius Gulf Coast Research Laboratory John D. Caldwell Gulf Coast Research Laboratory DOI: 10.18785/grr.0701.04 Follow this and additional works at: http://aquila.usm.edu/gcr Part of the Marine Biology Commons Recommended Citation Eleuterius, L. N. and J. D. Caldwell. 1981. Growth Kinetics and Longevity of the Salt Marsh Rush Juncus roemerianus. Gulf Research Reports 7(1): 27-34. Retrieved from http://aquila.usm.edu/gcr/vol7/issl/4 This Article is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf and Caribbean Research by an authorized editor of The Aquila Digital Community. For more information, please contact Joshua. Cromwell(2)usm.edu. Gulf Research Reports, Vol. 7, No. 1, 27-34, 1981 . GROWTH KINETICS AND LONGEVITY OF THE SALT MARSH RUSH JUNCUS ROEMERIANUS LIONEL N. ELEUTERIUS AND JOHN D. CALDWELL Botany Section, Gulf Coast Research Laboratory, Ocean Springs, Mississippi 39564 ABSTRACT Vegetative development of shoots of the tidal marsh rush Juncus roemerianus was studied quantitatively in short (S), medium (M), and tall-leaved (T) populations. Shoot longevity varied between populations, with some shoots producing one leaf and living 4 months, while others produced seven leaves and lived over 4 years. An equation was developed from plastochron and leaf-age determinations to estimate shoot age in each population studied. Major morpho- logical events common to all populations were (1) cessation of growth of the first leaf produced on an erect stem when growth of the second leaf was initialed, and (2) death of the leaf from the tip downward. Although the time period was variable, growth rales of leaves equalled their death rates in each population during maximum periods of growth and subse- quent decline. While growth and death rates were similar between two of the populations (M, T) investigated, these rates were vastly different from those representative of the third population (S). Growth and death kinetics for leaves on indi- vidual shoots involved cyclic phenomena represented by a series of greatly overlapping harmonic curves. Each shoot reached a maximum carrying capacity expressed as linear biomass. Although living portions were often distributed over three or four leaves, the total equated to two mature living leaves for the medium (M) and tall-leaved (T) populations. In the short-leaved population (S), the maximum amount of biomass attained by a single shoot during its life span equalled that of one mature leaf. A peculiar steady-state or homeostasis in growth and net productivity exists in each population. Short-lived shoots in the short-leaved population (S) was shown to have a rapid turnover of replacement rate, which is responsible for a high net productivity equal to or exceeding the net productivity of both the medium and tall-leaved popu- lations. Although the cause of variation in basic growth patterns between the three populations was not investigated, both genetic and environmental factors may be involved. INTRODUCTION successive linear measurements extensively to record and Tidal marshes are composed primarily of a herbaceous analyze plant growth, flora, the major constituents of which possess rhizomes. The present work arose from previous studies to develop Through vigorous rhizome growth some of these herbaceous criteria for evaluating tidal marshes. We found that in some species dominate vast areas of tidal marsh. Black rush or populations of J. roemerianus from 1 to 8 leaves were needle rush, Juncus roemerianus Scheele, is a major con- produced sequentially in a synchronized system from the stituent of tidal marshes located in estuaries on the South erect stems and that these shoots bearing different numbers Atlantic and Gulf coasts of the United States (Eleuterius of leaves lived different lengths of time. In the present 1976a). Correspondingly, the species contributes to the study, our objectives were to provide a reliable method of energetics of many estuaries. Knowledge of shoot develop- studying the developmental pattern of the shoot; to deter- ment,ratesof leaf growth, and longevity of shoots is essential mine the morphological pattern of the shoot over a long and basic to our understanding and assessment of net period of time; to compare the growth rates of leaves, primary productivity, standing crop, and turnover of tidal shoot longevity, and leaf death rates of representative marsh angiosperms. Estimates of growth, expressed as or plants in populations of J. roemerianus with very short, based on standing crop, serve as a general index of compari- medium, and tall leaves (stand height); and to use the son, but fail to reveal the details or kinetics of growth, resulting data in estimating shoot age and turnover. Vegetative growth patterns of the ma jor kinds of herbaceous The three populations selected for study span the plants are very different, although this fact has not been major structural characteristics of most populations of elaborated upon previously. Furthermore, there often /. roemerianus in the coastal region bordering the northern appears to be considerable variation in growth rate, net Gulf of Mexico. These populations are located in tidal primary productivity, and turnover between separated marshes at Belle Fontaine Beach (BFB), Grand Bayou (GB), populations of the same species. and Salt Flats (SF) in the coastal area of Jackson County, Steward (1968), Richards (1969), Dormer (1972), and Mississippi. Hereafter in this paper the above codes are used Williams (1975) present excellent reviews of methodology in reference to the location of the respective rush popula- and discussions on the quantitative analysis of plant growth, tions. The plants with shortest leaves but greatest density whereas Pratt (194 1 ), Williams (1964), Williams and Rijven of shoots (N/m 2 ) are found in the SF population inhabiting (1965), Koller and Kigel (1972), and Evans (1972) used areas with very sandy surface soil underlaid with clay at 2 to 4 feet. Rushes with leaves of medium length and density of shoots intermediate to those found at SF and BFB are Manuscript received April l, 1981; accepted June 11, 1981. found at GB. The soil at GB is a sandy clay. At BFB the 27 28 Eleuterius and Caldwell soiJs are lughly organic, composed primarily of peat, and the plants have the longest leaves and lowest density of shoots. The soil water of the SF population is hypersaline (60 to 300 ppt). Soil water from the tidal marshes around GB is generally moderate-to-low in salinity (5 to 20 ppt) while that in the BFB marshes is relatively low (0 to 6 ppt) (Eleuterius 1974). METHOD Twenty young shoots, each bearing a First leaf less than 20 cm in length, were selected at random in each of the three plant populations. The shoots were marked with plastic rings and numbered during November 1976. Initiation of new leaves on each shoot was noted; the length of each live leaf and the length of the dead segment of older leaves were measured monthly for 28 months, A storm washed away our markers forcing us to conclude the study. Lon- gevity of individual shoots and their respective growth curves (leaf length plotted against time) were determined from the obtained data and were compared to other shoots within and between populations. RESULTS Shoot Development Sympodial branching characterizes the vegetative growth of mature plants of J. roemerianus (Eleuterius 1976b). As the rhizome apex turns upward, division of the apical meristem formed a rhizome apex (continuation bud) simul- taneously with the production of an erect shoot. This growth phenomenon is also common to other angiosperms(Bennett- Clark and Ball 1951, Holttum 1955). Thus, the youngest shoot, bearing one leaf, is always proximal to the rhizome apex of an interconnected series of rhizomes and shoots, and the oldest shoot, often with three or more leaves, is the most distal to the apex (Figure 1A). The number of mature leaves produced on an individual shoot, along with other data to be given later, can be used to estimate the age of that shoot (Figure IB) within a given population with relative precision. Young leaves of an individual shoot arise from short stems and grow through a slit in the base of the preceeding leaf in an alternating or distichous manner (Figure 1C). Leaf Production and the Plastochron The number of leaves produced on each erect stem was variable within and between the three populations (Table 1). About half of the shoots produced only one leaf in the SF and BFB populations. Erickson and Michelini (1957) des- cribed the plastochron as the time interval between two similar developmental events on the same shoot. Here the plastochron of J. roemerianus was variable and equal to the time required to produce one mature leaf. Figure 1. Morphological characteristics of Juncus roemerianus. An interconnected series of rhizomes and shoots are shown in A. Younger shoots with fewer leaves are found near the rhizome apex, older ones farther away. R. Diagram of short erect stem connected to rhizome segment. Numbered, close-set nodes indicate origin of sequentially produced leaves on each erect shoot. C. The distichous or alternating arrangement of leaves on single shoot. Numbers corres- pond to sequence of leaf production. TABLE 1. Distribution of leaves on shoots of Juncus roemerianus in three different populations. Shoots are ranked according to total and average number of leaves produced on each shoot selected for study. Number of leaves indicates total or maximum number attained prior to shoot death or termination of the study. Number of Leaves per Shoot Population 1 2 3 4 5 X Salt Flats (SF) 10 9 j 1.6 Grand Bayou (GM) 7 5 4 4* 2.3 Belle Fontaine Beach (BFB) 9 4 2 4* 1** 2.2 ♦One or more of these shoots may have produced a fifth leaf. ♦♦This shoot may have produced a sixth leaf. All second leaves were produced during the spring at SF, while in the GB and BFB populations, most second and third leaves were produced during the summer and following spring (1978), respectively (Figure 2). Although the seasonality Growth and Longevity of secondary leaf production on individual shoots was similar for both GB and BFB, some shoots at BFB exhibited a precocious leaf development indicative of accelerated growth in very early spring. ▲ 2 nd LEAF ■ 3 rd LEAF 'LEAF • 4 th LEAF ▼ 5 th LEAF SF - • 20 ▲▲▲ ■ 2 5 3 / GB - • AAAAAA ■ ■ ■ ♦♦ 20 14 3 31 1 3 4 1 3 1 BFB- • AAAA M ■■■ ♦ ♦ 20 3 4 22 1 ■ ♦ 2 1 112 1 2 ♦ ▼ / / NDJ FMAMJJ ASONDJ FMAMJ JASOND 19761 1977 \ 1978 MONTHS Figure 2. Populations! differences in leaf production. Symbols indicate chronological order and array of leaf production on indi- vidual shoots. Subscripted numbers indicate number of shoots producing a second, third, fourth, or fifth leaf during a particular month. Leaf Length The range and average of the maximum heights (lengths) attained by mature leaves of J. roemerianus were distinctly different between the three populations as shown graphi- cally in Figure 3. Leaves at BFB ranged from about 110 to 170 cm, and averaged 142 cm in length, and at GB from 65 to 133 cm, with an average of 104 cm. The population at SF had the shortest leaves, ranging from 11 to 64 cm and averaging 26 cm. Leaf Growth and Death Curves Representative growth and corresponding death curves for leaves produced on single shoots from three populations are shown in Figure 4. These size-versus-time plots show the cumulative increase in height (length) of successive leaves on three individual shoots, each of which represents a different population. The kinetics of shoot growth as shown in the BFB and GB curves are very similar (Figure 4: BFB, GB). Both illustrate several overlapping, yet, typical sigmoid curves with characteristic logarithmic (exponential), linear (grand), and senescent phases (Blackman 1919, Pope 1932). Plots of monthly averages from combined data (all shoots) for each population produced a similar but smoothed and flattened curve in comparison to that of individual shoots. Growth of the first leaf produced on an erect stem ceased when growth of the second leaf was initiated and represented a plastochron (Erickson and Michelini 1957). The process held for all subsequent leaves on an individual shoot and for all shoots producing more than one leaf in all populations. As the second leaf matured the first leaf began to die OF JUNCUS R OEM ERI ANUS 29 Figure 3. Population^ differences in leaf lengths. Comparative data showing range and average mature leaf lengths for three populations studied. Circled dot © indicates average leaf length based on array of first, second, and third leaves produced in each population. from the tip downward. This same relationship held between the third and second leaf and so on. Very little increase in leaf length occurred during winter months, whereas rapid growth characterized the late spring, summer, and early fall. Note the flattened curve for January and February in Figure 4. Although the reason for this is unclear, second leaves were generally slightly shorter than first or third leaves (see Figure 3). Growth of the third leaf began several months before the first and second were completely dead. No consistent pattern was obtained for the curve repre- senting senescence. The senescence phase of the growth curve often equalled the slope of the curve during the exponential phase, but senescence generally occurred very rapidly, represented by a graphically sharp decline. Death of leaf tissue represented by this steep decline in the senes- cent curve was not, however, restricted to any particular period of time and we could not assign any probable cause to it. Furthermore, there was a maximum amount of living leaf tissue sustainable on a single shoot and, although the living segments may have been distributed between two, three, or four leaves, the amount was not apparently greater than that of two entire living leaves representative of the mature component of the respective population. This obser- vation held true regardless of the location of the population. 30 Eleuterius and Caldwell Dead leaves remain standing for several years or more in the BFB population, but are rapidly swept away by tides at SF, Fewer dead-standing leaves were found in the GB population in comparison with those at BFB. Shoot development at SF is obviously an abbreviated process (Figure 4). Plots of all other SF shoots investigated are similar. Figure 4. Growth and death curves for leaves produced on a single shoot of Juncus roemerianus in three different populations. Solid and dotted lines show size of the living portions of leaves versus time, the accumulative increase in leaf length, the sequential initiation of new leaves, the corresponding cessation of growth and senescence of leaves of representative shoots from each population. Leaf Growth and Death Rates Calculation of growth rates also indicated that the period of greatest leaf growth was during spring, summer, and early fall (Table 2). Average growth rates during this study period were very similar in the GB and BFB populations (about 0.7 and 1 .0 cm per day, respectively). An average of 0.2 cm per day occurred during the period of maximum growth for the shoots observed in very early spring at SF. Although the growth rate of individual leaves was variable, we surmise that these estimates represent the exponential phase for new cohorts and, thus, are characteristic of the maximum sustainable or annual growth rate in the respective popula- tions, The maximum daily growth of a single leaf in the BFB, GB, and SF populations and the months of occurrence were 1.5 cm (July), 1.1 cm (September), and 0.4 cm (February), respectively. TABLE 2. Average growth rate (cm/day) of mature leaves of Juncus roemerianus during the months in which maximum growth occurred (shown in parenthesis). Number of leaves used in determining growth rate of successive leaves on individual shoots shown in brackets. Leaf 1 Leaf 2 Leaf 3 Population (Mar, Apr, May) (Jui, Aug, Sep) (Apr, May, Jun) Salt Flats (SF) Grand Bayou (GB) *0.2 [10] 0.7 113] 0.7 [8] 0.8 [4] Belle Fontaine Beach (BFB) LODI] 1.0 [5] 1.3(3] *(Feb, Mar) Calculation of death rates of leaves from the apex down- ward indicated that summer and fall were the periods of greatest leaf death (Table 3 and Figure 4) although some leaves died rapidly during winter. Average death rates during this period were also very similar in the GB and BFB popu- lations (about 0.8 and 1.0 cm per day, respectively). An average of 0.7 cm per day occurred in late spring at SF. During this period death rate briefly exceeded growth rate. The maximum daily rate of death of a single leaf in the BFB, GB, and SF populations, and the months of occur- rence were 4,2 cm (July), 2.2 cm (October), and 1.4 cm (May), respectively. Leaf Longevity Leaves of shoots in SF, GB, and BFB populations lived an average of 7.5, 16, and 14 months, respectively, based on ail leaves on all shoots investigated. However, average age of leaves, based on shoots that produced more than one leaf, was 7, 14, and 12 months for SF, GB, and BFB, respectively Growth and Longevity of Juncus roemerianus 31 (Table 4). On shoots producing more than one leaf, the first leaf generally lived longer than the second in all popu- lations examined. Third and fourth leaves usually lived as long as, or longer than, the second. Some leaves lived 22 months. Leaf longevity was very similar between the BFB and GB populations but contrasted sharply with that at SF. TABLE 3. Average death rate (cm/day) of mature leaves of Juncus roemerianus during the months in which maximum death occurred (shown in parenthesis). Number of leaves used in determining death rate of successive leaves on individuals shoots shown in brackets. Leaf 1 Leaf 2 Leaf 3 Population (Sep, Oct, Nov) (Jul, Aug, Sep) (Aug, Sep, Oct) Salt Flats (SF) Grand Bayou (GB) *0.7 [9] 0.6 [13] 1.0 18] f0.3 [4] Belle Fontaine Beach (BFB) 0.9 [10] 1.4 [4] t0.3 [3] *(May, Jun) f About one third of leaf was dead when experiment ended. TABLE 4. Leaf longevity. Average and maximum of months that leaves of Juncus roemerianus live in different populations. Leaves are grouped based on chronological development on individual shoots in each population. Number of leaves used in determinations shown in parenthesis. Population Leaf 1 Leaf 2 Leaf 3 Leaf 4 Leaf 5 X Max X Max X Max X Max X Max Salt Flats (SF) 8 17 7 16 (15) (8) Grand Bayou (GB) 15 22 13 17 15 16 06) 02) 06) Belle Fontaine Beach (BFB) 15 22 11 14 11 IS 12 14 15 (16) (8) (16) (4) (1) Shoot Longevity The number of leaves produced and the life span of each leaf on an individual shoot determine the longevity of that shoot. The shoots of the BFB and GB populations live about twice as long as those in the SF population (Figure 5). Mortality of shoots began 4 months after the study was initiated and continued periodically thereafter. The average shoot life at SF was 1 1 months with one shoot living 22 months. Average shoot life at GB was 25 months with seven shoots alive at the end of 28 months. Projected longevity, based on average life span and vitality of leaves studied in theGB population, indicated that some of the shoots studied probably lived about 40 months. Although seven shoots were alive at the end of the study period, no new leaves were produced and those living leaves present were dying. Figure 5. Shoot longevity. The life spans of three cohorts of shoots, each representative of a different population of Juncus roemerianus. Each cohort was composed of 20 shoots for a total of 60. Lines indicate mortality and survival of each group over time. Similarly, the average longevity of shoots at BFB was 21 months with two shoots alive at the end of 28 months. Projected longevity, estimated from average life span and vitality of leaves from this propuLation, indicated that 10% of the shoots may live about 40 months in the BFB popula- tion. Production of a sixth or seventh leaf certainly was possible on two of the shoots at BFB because both were very vigorous and new leaves had just been initiated. More- over, shoots with six and seven leaves, which have been observed in the GB and BFB populations, respectively, clearly indicate that some vegetative shoots of the rush J. roemerianus may live 4 years or longer. DISCUSSION We found during this study that: (1) frequent linear measurements of leaf length are a valuable and sensitive aid in the interpretation of growth phenomena in/ roemerianus , (2) growth curves of an individual rush shoot are actually a complex network of overlapping curves or series of correla- tions between linear growth and time, (3) considerable variation in the kinetics of growth occurs between popula- tions of X roemerianus , (4) these populational differences appear to be caused by the location and the environmental conditions peculiar to respective populations, although it certainly was possible that they represented genetically distinct ecotypes, (5) our data provided basic information for making numerous types of estimates, such as: biomass, shoot age, leaf age, net productivity, and turnover in popu- lations of J . roemerianus. For emphasis, we found that developmental events of the shoot were repealed with the initiation of each new leaf and that the time intervals between leaves on the same shoot were highly variable. Therefore, the plastochron or time interval determined from the present study is equivalent to 32 Eleuterius and Caldwell the period required to complete the several developmental stages of one leaf (Erickson and Michelini 1957). Linear measurements of individual leaves and the plastochron age of shoots are nondestructive ways of obtaining data basic to net productivity estimates. Although shoot development for the three populations examined is similar in the consistent morphological pattern of sequential leaf production and death, and in tracing the classical sigmoid growth curve, shoot characteristics are very different in other ways. These populational differences are summarized as follows: (l) leaf production-lhe number of leaves produced per shoot, (2) leaf length-the most obvious difference between the three populations, (3) leaf growth rate-equalled by leaf death rate within each popula- tion but variable between populations, and (4) leaf and shoot longevity-both lived much longer in the GB and BFB populations than at SF. The BFB population is composed of plants with long leaves (1 10 to 170 cm, X = 142 cm) which remain standing for a long time after they die. About two thirds of the aerial standing crop are dead leaves. A smaller number of living shoots (about 500/m 2 ) occupy the marsh surface at BFB in comparison to those found at GB (700/m 2 ) and SF (2,000/m 2 ) (Eleuterius 1980). The vitality of individual shoots at BFB is very different from one another with a small percentage of shoots in the population possessing great vigor and living several years. This contrasts with shoots in populations at GB and SF, where their growth patterns are most consistent. Furthermore, dead-standing leaves com- prise about one fourth of the standing crop at GB in com- parison to about one tenth of the vegetation at SF. The vigor of individual shoots is, as with all tidal marsh plants, ultimately tied to the physical and chemical ener- getics of the estuary. Dead leaves readily accumulate in populations protected from high wind and wave activity; consequently , growth of living shoots is suppressed, probably because of competition for light. Populations exposed to frequent tidal action, where dead-standing leaves are readily swept away, are more apt to represent a steady state of continuous robust growth. The BFB population is in a protected location and consequently has a high ratio of dead to living leaves. The GB population is more exposed and the SF population is very exposed to wind, wave, and tidal action in comparison to that at BFB. Other environ- mental factors, such as the concentration of sea salts in the soil solution, obviously affect, to some extent, the growth of J, roemerianus. In all of the populations studied, a reliable indication of the biomass can readily be obtained directly from plotted data. For example, there may be several living leaves on a shoot, but only one leaf increases its length at any living shoot, at any time. Therefore, the living component of leaves, which are not growing, decreases in size (linear measurement) because of leaf death. In the GB and BFB populations, the biomass sustained per shoot is equivalent to that of two entirely living, mature leaves. However, this living tissue may be distributed over 3 or 4 leaves, depending on the stage of shoot development. The “two living leaves” concept represents the maximum carrying capacity of an individual shoot in these two populations. In each popula- tion studied, leaf growth essentially equals leaf death, separated in time by a certain linear quantity of living leaves, in the above instances: two leaves. The maximum carrying capacity or biomass for shoots in the SF popula- tion is equivalent to one mature leaf for the life of the shoot. The number of leaves sustained by shoots of J. roemerianus varies between different populations and has an inherent physiological basis (Watson 1952). An annual steady-state pattern of stability and equilibrium or homeostasis operates in each population of J. roemerianus and compares favorably with that reported by Williams and Murdoch (1972). Since seasonal effects on leaf growth are minimal (Eleuterius 1974, 1976b), and because successive cohorts of new shoots are being produced in each population throughout the year, the average growth rate calculated for the cohort of shoots studied here during the periods of maximum growth is also the maximum sustainable growth rate. The period of active shoot growth is equiva- lent to maximum sustainable growth rate. The average rate of shoot growth is much less than the sustainable growth rate because the senescent leaf phase may be 2 to 4 times as long as the phase of active growth. The average rate of shoot growth calculated from total leaf length produced over shoot longevity showed a different rate than when calculated on the growth phase alone. For instance, at BFB the annual rate would be 0.5 cm/day, and at GB and SF the annual rates would be 0.3 cm and 0.1 cm/day, respectively. Wo feel that the maximum sustainable rates shown in Table 2 are accurate and more meaningful than annual rates shown above, especially in relationship to shoot growth and senescent patterns. Sustainable and average growth rates are obviously essential to an estima- tion of annual rates of growth. Reliable estimates (E) of shoot age can be calculated from the number of leaves present on a shoot (N), the average plastochron (P), and average leaf longevity (L) for each population studied using the equation: P (N 1) + L = E. For example: the age of a shoot that produced four mature leaves in the GB population would be approximately 38 months old, where P = 8, N - 4, L * 14. Similar estimates can be derived for shoots in the populations at BFB and SF. Comparison of estimates of shoot age with the actual age of a randomly selected group of tagged shoots from each population indicated that our method is reliable for any shoot within 1 or 2 months. Considering the wide variation in some populations of J. roemerianus, the method is very precise, has high usefulness, and represents a significant contribution to the biology of the rush. The pattern of shoot production in Spartina alterniflora and Scirpus olneyi on the mainland coast of Mississippi Growth and Longevity of J uncus roemerianus 33 greatly contrasts with that of /. roemerianus. Generally all shoots within separate populations of the tidal marsh grass Spartina alterniflora , and sedge Scirpus olneyi arise simul- taneously in the spring from the marsh surface in a synch- ronized manner in Mississippi. There are exceptions to this general pattern during years of mild winters. However, regardless of seasonality, all shoots within populations of Spartina alterniflora and Scirpus olneyi are about the same age. Consequently, all shoots reach maturity, produce flowers, and die at relatively consistent and predictable times within one year. This process, applicable to the Mississippi coast, may appear to contrast with reports on Spartina alterniflora by Hopkinson et al. (1978) for Louisiana, and Stout (1978) for Alabama. However, we feel that temperature differences related to latitudinal distances are responsible for these conflicting reports (Turner 1976). The lower part of Bayou La Fourche and Barataria Bay are located in the Mississippi River delta, a latitudinal distance of approximately 50 miles south of the Mississippi mainland coast. Stout (1978) worked in the marshes of Dauphin Island, a latitudinal distance of some 8 to 12 miles farther south than the mainland coast of Mississippi. However, Hopkinson et al. (1978) stated that Spartina cynosuroides and Sagittaria lancifolia have uniform developmental patterns represented by a single flush of growth. The point of our comparison here is to show that shoots of / roemeri- anus are produced continuously, and mature and die in all seasons, whereas several other tidal marsh species have a single annual Hush of growth. Thus, populations of the rush are composed of an array of shoots differing vastly in age. These wide ranges of shoot growth stages are described best and illustrated as a series of greatly overlapping harmonic curves. Changes in the vegetational structure of the rush stand cannot always be detected easily by direct observa- tion or by sampling techniques like the Harvest Method. Each population of /. roemerianus is homogeneous as to vegetational structure, new shoots being initiated through- out the year while other, older shoots are dying. Therefore, only a small component or percentage of shoots composing the population die each year and these deaths span the entire year with a peak reached during late summer. Stout (1978) showed growth occurring throughout the year for /. roemerianus in Alabama. Although seasonal conditions appear to affect individual shoots only moderately in our locale, these effects are generally not noticeable to the casual observer because all growth is suppressed equally on all shoots and the wide array of shoot growth stages obscures this process. Furthermore, in some populations, e.g., SF, two entire crops of shoots may turn over every 22 months while in others a complete vegetational turnover may occur every 4 years. Alone, the total significance of this information would not be apparent. However, from preliminary studies on the same three populations of X roemerianus, we learned that the recruitment of new crops of shoots or cohorts may be six times greater in the SF population in comparison to that at BFB, Recruitment at SF appeared to be three times greater than at GB. This preliminary knowledge, combined with that of the present study, suggests an important pattern of growth. The SF population which seemingly would be a population of low productivity, based on standing crop estimates, may be one of very high net productivity, based on the large number of shoots per unit area of marsh and the rapidity of turnover. Although we are unable to develop fully these modes of production here because of incomplete recruitment and biomass data, it is important to mention that the net productivity of the very short leaved SF popu- lation may equal or exceed the net productivity in the very long leaved BFB population over the same period of time. We surmise that this phenomenon would not have been revealed by assessing standing crop from clip quadrats because the replacement shoots were obscured by dead shoots and the precision of the Harvest Method cannot measure these changes. Our results agreed only in a general way with those of Stout (1978), Hopkinson et al. (1978), and Williams and Murdoch (1972), because our overall objective was different in that productivity as annual biomass or standing crop was not investigated. Stout (1978) used a combination of leaf counts and linear leaf measurements from random quadrats and related biomass for above ground to below ground determinations. Hopkinson et al. (1978) used standing crop from quadrats, and Williams and Murdoch (1972) used linear measurements of tagged leaves and standing crop making it more comparable to the present paper than the others. We disagree in the finer details of the growth kinetics reported by Williams and Murdoch (1972) in that there is no interval between the cessation of growth and onset of death, at least in the/, roemerianus of Mississippi. None of these papers showed clear patterns of shoot growth, longevity, senescence, and death. Furthermore, wc feel that the compartments used in the production model of Williams and Murdoch (1972) were too broad: live leaves = all green, dying leaves (dead and green), and all dead. We have never seen mature leaves of/, roemerianus in Mississippi or else- where that were entirely green. Hopkinson, et al. (1978) stated that the /. roemerianus marsh they studied was in “transition” or changing vegetatively. They concluded their work by pointing out the difficulty of measuring “true net production” by the Harvest Method and the need for refinement in productivity techniques. Our paper presents techniques basic to improving future productivity work. Our method is much simpler, less time consuming, and more accurate than those previously used. Additionally, linear growth measurements, coupled with shoot demog- raphy and standing crop, may allow considerable clarifica- tion and insight into population structure, growth kinetics, and production of /. roemerianus tidal marshes. 34 Eleuterius and Caldwell In conclusion we emphasize that growth kinetics and longevity peculiar to /. roemerianus are vastly different between populations, and that high net productivity may be common to all populations of this tidal rush, although accomplished in different ways. ACKNOWLEDGMENTS We thank other members of the Botany Section of the Gulf Coast Research Laboratory for assistance with various apsects of this study . Mrs. Helen Gill and Mrs. Lucia O'Toole typed the manuscript. REFERENCES CITED Bennett-Clark, T A. & N. G. Ball. 1951. The diageotropic behaviour of rhizomes. / Exp. Bot. 2:196—203. Blackman, V. H. 1919. The compound interest law and plant growth. Ann. Boi. 33:353-360, Dormer, K. J. 1972. Shoot Organisation in Vascular Plants. Syracuse University Press. 240 pp. Eleuterius, L. N. 1974. An autecological study of Juncus roemerianus. Ph.D. dissertation, Mississippi State University. 221 pp. _____ . 1976a. The distribution of Juncus roemerianus in the salt marshes of North America. Chesapeake Sci. 17(4):289-292. . 1976b. Vegetative morphology and anatomy of the salL marsh susb , Juncus roemerianus. Gulf Res. Kept. 5(2): 1 10. Erickson, R. O. & I\ J Michclini, 1957. The plastochron index. Am. J. Bot. 44:297-305. Evans, G. C. 1972. The Quantitative Analysis of Plant Growth. Blackwell Scientific Publications. Oxford, England. 734 pp. Holttum, R. E. 1955. Growth-habits of monocotyledons variations on a theme. Phytomorphology 5:399 413. Hopkinson, C. S., J. G. Gosselink & R. T. Parrondo. 1978. Above ground production of seven marsh plant species in coastal Louisiana. Ecology 59(4):760-769. Roller, D. & J. Kigel. 1972, Growth ol leaves and tillers in Qryzopsis miliacea Pages 115-134 in V. B. Younger and C. M. McKell (cds.), 77{e Biology and Utilization of Grasses. Academic Press, New York. Pope, M. N. 1932. The growth curve of barley. /. Agr. Res. 44; 323-341. Pratt, P. 1941. Validity of equations for relative growth constants when applied to sigmoid growth curves. Bull. Torrey Bot. Club 68:295-304. Richards, F. J. 1969. The quantitative analysis of growth. Pages 3-76 in F. C. Steward (cd.). Plant Physiology , A Treatise. Volume 5 A. Academic Press, New York. Steward, F. C. 1968. Growth and Organization in Plums. Addison- Wcsley Publishing Co., Reading, Massachusetts. 564 pp. Stout, J. P, 1978. An analysis of annual growth and productivity of Juncus roemerianus Scheele and Spartina alterniflora Loisel in coastal Alabama. Ph.D. dissertation, University of Alabama. 55 pp. Turner, R. E. 1976. Geographic variation in salt marsh macrophyte production: a review. Conlrib. Mar. Sci. 20:47 68. Watson, D. J. 1952. The physiological basis of variation in yield. Adv Agron 4:101 145. Williams, R. B. & M. B. Murdoch. 1972. Compartmental analysis of the production of Juncus roemerianus in a North Carolina salt marsh. Chesapeake Sci. 1 3(2):69- 79, Williams, R F 1964. The quantitative description of growth. Pages 89-101 in C. Barnard (ed.), Grass and Grasslands. MacMillan, London. . 1975. The Shoot Apex and Leaf Growth: A Study in Quantitative Biology. Cambridge University Press. 256 pp. & A. 11. G. C. Rijven. 1965. The physiology of growth in the wheat plant. 2. The dynamics of leaf growth, Aust. J. Bot. 18:721-743. Gulf Research Reports Volume 7 | Issue 1 January 1981 Effect of Mineral Deficiency on the Growth of the Salt Marsh Rush Juncus roemerianus Lionel N. Eleuterius Gulf Coast Research Laboratory John D. Caldwell Gulf Coast Research Laboratory DOI: 10.18785/grr.0701.05 Follow this and additional works at: http://aquila.usm.edu/gcr Part of the Marine Biology Commons Recommended Citation Eleuterius, L. N. and J. D. Caldwell. 1981. Effect of Mineral Deficiency on the Growth of the Salt Marsh Rush Juncus roemerianus. Gulf Research Reports 7 (l): 35-39. Retrieved from http://aquila.usm.edu/gcr/vol7/issl/5 This Article is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf and Caribbean Research by an authorized editor of The Aquila Digital Community. For more information, please contact Joshua. Cromwell(2)usm.edu. Gulf Research Reports, Vol. 7, No. 1, 35-39, 1981. EFFECT OF MINERAL DEFICIENCY ON THE GROWTH OF THE SALT MARSH RUSH JUNCUS ROEMERIANUS LIONEL N. ELEUTERIUS AND JOHN D. CALDWELL Botany Section , Gulf Coast Research Laboratory, Ocean Springs, Mississippi 39564 ABSTRACT Plants of the salt marsh rush Juncus roemerianus were grown in deficient and complete nutrient solutions, and the growth responses were compared qualitatively and quantitatively. Plants grown in solutions deficient in K, S, P, and Mg were similar in appearance, which exemplified severe growth retardation. Plants grown in solutions deficient in Ca, N, and Fe also were very similar in total growth response, but had much longer leaves, more shoots, and greater biomass than those grown in the K, S, P, and Mg deficient solutions. Plants grown in complete nutrient solutions, with various sources of Fe, were very robust. Growth was better with FeCh than with FeEDTA. The most robust growth occurred in plants grown in the nutrient medium deficient in micronutrients (8, Mn, Zn, Cu, Mo), indicating that J. roemerianus is very sensitive to specific or certain combined micronutrients or concentrations generally recommended for terrestrial, especially agricultural, plants. The qualitative and quantitative symptoms, such as color, length, and abundance of leaves and mots as a response to deficiency of specific elements, were similar to those deficiency symptoms previously described for numerous terrestrial plants. However, a deficiency of certain nutrients such as S and Mg has a much greater effect on /. roemerianus than is generally shown for terrestrial plants. INTRODUCTION Interest in mineral deficiency of agricultural plants has a long history and correspondingly voluminous literature (Chapman 1973a). Information is lacking on the effects of mineral deficiency on angiosperms inhabiting tidal marshes. This inadequacy probably exists because of the common assumption that most estuarine sediments contain an abun- dance of nutrients for plant growth. However, Adams (1963) found that plants of Spartina alterniflora become chlorotic in iron-deficient soils but marsh plant species found at higher elevations, such as Distichlis spicata and Juncus roemerianus, are unaffected. He also pointed out that S . alterniflora reponds to experimental foliar applications of ferrous sulphate or the addition of iron to a saline nutrient solution and is often restricted to low elevation marshes where the mean soluble iron content is in excess of 4 ppm. Adams (1963) also suggested that iron deficiency may limit the growth of S . alterniflora at high marsh elevations, because the greatest tendency toward chlorosis is in the higher, better-drained, rather than the lower, wetter sites. Tyler (1967) obtained a significant growth response from Juncus balticus in salt marsh plots treated with ammonium on the Baltic coast, indicating that the rush species grew naturally in depauperate soils in which the nitrogen concentration was not optimum. Furthermore, the substrata of salt marshes are highly variable in structure, ranging from organic peat to sand, which consequently reflects considerable variation in nutrient composition (Grim 1968; Richards 1969; Buckman and Brady 1969; Chabreck 1972;Cotnoir 1974; Boyd 1970;BrupbacheretaI. 1973; Eleuterius 1972, 1974), Additionally, certain plants Manuscript received April 1, 1981 ; accepted June 18, 1981. have relatively high or specific mineral requirements sug- gesting that soil nutrient deficiencies (low concentrations) may limit their growth (Brownell 1965, Rorison 1968, Wallace et al. 1966, Broyer et al. 1954). Zonation of flowering plants in coastal marshes has been shown to be influenced by mineral nutrition (Pigott 1969). Eleuterius (1974) observed red streaks on the leaves of numerous small plants of Juncus roemerianus which may have indicated a deficiency of phosphorous in some sandy, marsh soils. Sandy soils of salt flats,, in contrast, did not appear to be deficient because dwarf plants with very dark-green leaves also were observed there. The objectives of this study regarding the mineral nutrition of Juncus roemerianus were (1) to determine the individual qualitative and quantitative effects that seven deficient minerals and an array of micronutrients would have on growth of the rush, (2) to compare these responses to those obtained in complete nutrient solutions, (3) to assess and rank the resulting condition of the test plants, and (4) to evaluate the nutritional requirements of the tidal marsh plant. MATERIALS AND METHODS Standard nutrient media (Machlis and Torrey 1956) were used to determine the effects of mineral deficiency on J. roemerianus. Seven nutrient solutions were prepared, each deficient (-) in one of the following elements: nitro- gen (N), phosphorus (P), potassium (K), sulfur (S), calcium (Ca), iron (Fe), and magnesium (Mg). One solution deficient in an array of micronutrients (B, Mn, Zn, Cu. Mo) also was prepared as a test medium. Two complete nutrient solutions, differing in the source of iron, also were prepared as controls. One complete nutrient solution contained FeCL 3 , and another the chelated form FeEDTA. Distilled water also was used as a control. Plants grown from seed collected 35 36 Eleuterius and Caldwell from a single parental plant to reduce genetic variability were used in triplicate for each culture solution. The experi- ment was carried out during the spring in a greenhouse. Temperature varied from about 1 8°C to 30°C during the experiment. Seedlings of similar size were selected, based on the number of leaves and leaf length, from a large number of seedlings grown as individual units. Roots were thoroughly washed and freed of all peat and other organic material, and then placed in clean (washed) river sand for 5 weeks. A dilute (1%) solution of 10-30-20 soluble fertilizer (Robert Peters Co. Inc.) was used in a single application as a nutrient source. Prior experience showed that this procedure resulted in a proliferation of new roots, which replaced those lost and injured in the initial washing. New roots formed within a few weeks and the remaining old ones subsequently were easy to clean. Seedlings were carefully rinsed six times in distilled water. The number and length of leaves were determined. For statistical compari- son, a “total” leaf length was obtained by adding the length of all leaves on each plant. A single plant then was placed in each battery jar filled with nutrient media and Supported with specially prepared, waxed, plywood covers (Machlis and Torrey 1956). Observations were made weekly for survival and deficiency symptoms, and the general condition of the plants was recorded. Distilled water was added to the nutrient solutions as needed. At the end of 68 days, number of leaves, total leaf length, maximum leaf length (plant height), dry mass of leaves, maximum root length, and dry mass of roots were determined. Multidimensional plotting, a method of cluster analysis (Andrews 1972, Nance el al. 1975), was used for statistical analysis of the quantitative data representing the seedling at the beginning and at the end of the experiment. Statistical significance between treatments was tested by a l*way analysis of variance (ANOVA) test and a least significant difference (LSD) test. RESULTS AND DISCUSSION Seedlings were shown to have no significant difference at the beginning of the experiment by a 1-way ANOVA statistical test. Multidimensional plots also showed similarity between the seedlings for number of leaves, maximum leaf length (plant height), and total leaf length (Figure 1). Quali- tative characteristics of the plants in each treatment at the end of the experiment are shown in Table 1. The ANOVA test, which compared all test groups for each variable simul- taneously, showed a statistically significant difference between the 11 groups, except for the number of leaves produced per plant (Table 2). This means, because of the nature of the ANOVA test, that at least one test group was statistically different from at least one of the other groups. However, the ANOVA test does not indicate which groups were significantly different. When the resulting data were subjected to a LSD test all measured variables were shown to have a significant difference between certain test groups. Figure 1, Multidimensional computer plots using the number and length of leaves for seedlings of Jutxcus roemeriartus immediately prior to placing in complete and deficient nutrient solutions. Simi- larity and closeness of plotted lines indicate that plants are similar in size. TABLE 1. Mineral deficiency symptoms. Plant groups axe ranked by treatments according to qualitative characteristics.* - Micronutfients Leaves dark green. Minimal dead leaf tissue. Roots white or light tan, about 25 cm long, with pliable root hairs. Root hairs slightly shorter (2-8 cm) than those in complete FeEDTA. Complete (FeCLj) Leaves dark green. Very little (about 1%) dead leaf tissue. Roots while to light tan, 30 to 40 cm long, with obviously more mass than roots of plants in complete FeEDTA. Root hairs long (4-10 cm), pliable. Complete (FeEDTA) Leaves dark green. Very little (about 5%) dead leaf tissue. One plant dead. White to light tan roots, about 25 cm long, with long (4-10 cm), pliable root hairs. - Ca Leaves dark green, some dead young leaves. Roots short (10-15 cm), reddish-brown. Short stumpy root hairs about 0.5 cm long. - N Leaves pale or light green, about 15-20% dead leaf tissue. Roots white to light tan, very long (about 60 cm). Root hairs about 2 cm in length. - Fe Leaves brownish -yellow with four pale or light-green leaves, about 40% dead tissue and 50% dying, 10% living. Roots, white to lan, coarse, about .15 cm long. Short root hairs about 0.5 cm long. - K Leaves dark green, 25% dead leaf tissue (primarily young leaves). Roots long (30 35 cm), reddish-brown. Root hairs long (2-8 cm). - S Leaves dark to light green. About 15% leaf tissue dead. One plant almost dead (very little growth). Roots reddish-brown to tan, about 25 cin long. Root hairs coarse, less than 1 cm long. - P Leaves dark green, some leaves deep purplisb-red or dark green with streaks of red. About 20% leal' tissue dead. One plant dead. Roots reddish-brown to tan. Few roots formed but extremely long, about 60 cm. Root hairs sparse, long (2-10 cm). - Mg Leaves yellow-green. Leaf tissue, 10% dead, 70-75% dying. Roots short (about 15 cm), light tan. Root hairs short, about 0.5 cm. Distilled H 2 O Leaves light-green to yellow, brown or mottled with yellow or light to dark brown. About 20% leaf tissue dead, the remainder dying. Roots reddish-brown, short (10 cm), coarse. Root hairs short (0.5 cm) except on extreme tips of roots. ♦Three plants were grown in nutrient media for 63 days. MINERAL DEFFICIENCY OF THE SALT MARSH RUSH 37 TABLE 2. Mineral nutrition characteristics of Juncus roemenanus. Want groups are ranked by treatments according to quantitative characteristics. Values represent mean and standard error of the mean of three plants grown in nutrient media for 68 days. Nutrient Solution Number of Leaves Total Leaf Length (cm) Leaf Length Maximum (cm) Dry Mass Leaves (g) Root Length Maximum (cm) Dry Mass Roots (g) - Micronutrients 22 ±3.2 732.4 ± 78.1 78.1 ± 2.8 2.790 ±0.08 28.3 ± 3.7 0.421 ±0.02 Complete FeCL 3 15 ±2.5 415.2 ± 31.2 65.9 ± 5.9 1.593 ±0.06 39.5 ± 5.0 0.313 + 0.01 Complete FeEDTA* 12 ±5.9 348.0 ± 198.7 49.0 ±13.2 1,383 ±0.72 27.7 ±10.2 0.286 ±0.10 Ca 12 ± 3.1 255.2 ± 44.0 48.0 ± 5.7 1.103 ±0.04 15.9 ± 0.3 0.164 ±0,03 - N 13 ± 1.7 257.9 ± 10.7 44.9 ± 4.2 0.763 ±0.01 70.2 ± 4.1 0,457 +0.08 - Fe 14 ± 1.2 212.6 ± 41.9 27.5 ± 4.7 0.413 ±0.09 14.9 ± 4.3 0.081 ±0.01 - K 8 ±0.3 241.4 ± 12.5 56.1 ± 5.8 0.869 ±0.11 37.1 ± 2.8 0.108 ±0.01 -st 9 ± 2.4 200.5 ± 62.6 36.8 ± 4.2 0.734 ±0.29 25.0 ± 5.4 0.165 ±0.11 - P* 9 ±2.6 194.8 ± 69.1 38.0 ± 5.2 0.614 ±0.27 56.1 ±22.0 0.331 ±0.17 -Mg 9 ±1.2 186.7 ± 25.2 36.9 ± 1.9 0.435 ±0.09 18.0 ± 2.0 0.075 ±0.01 Distilled H 2 0 11 ±2.4 90.8 ± 16.0 19.9 ± 0.5 0.240 ± 0.04 11.3 ± 2.4 0.082 ±0.02 F (10,22) 1.97 5.34ft 8.13ft 7.84ft 5.18ft 3.44ft kSDo.os 7.7 205.0 16,2 0.716 22.3 0.211 ♦Contained 1 dead plant. fContained 1 plant which was almost dead. ff Significant at the 0.05 level. We believe the LSD test indicates a better analysis than the ANOVA test for our purposes because it compares each group of values against every other group individually for each variable (Table 2). Furthermore, all variables, which included all groups, were subjected to cluster analysis or multidimensional plotting (MDPLT). This analysis compares and evaluates collectively and simultaneously the entire array of data. MDPLT evaluates all variables measured for each group, resulting in an averaged or total value for each test group. The group values are then ranked. Ranking all quantitative responses by MDPLT resulted in six distinctly different groups as shown in Figure 2. The closer the curves, the more closely related or similar were the test plant groups based on total response (all variables). The most unexpected response was the robust growth of plants in nutrient medium without micronutrients (B, Mn, Zn, Cu, Mo). Table 2 shows that the longest leaves and greatest dry mass were produced on plants without micro- nutrients. Plants grown in both complete nutrient media were also robust, but the best growth was achieved with FeCl 3 rather than FeEDTA, Iron appeared to be necessary for strong root development in J. roemenanus. Plants in Fe, K, and Mg deficient media had very poorly developed root systems (Table 2). Although chelation (FeEDTA) may ensure availability of Fe to terrestrial plants (Steiner and Van Winden 1970), the requirement of Juncus roemenanus is apparently more readily satisfied by the FeCl 3 source. Apparently most of the Fe of FeCl 3 became chemically bound in soils and in nutrient media, where it precipitated out of solution. Chemically bound Fe was not available for plant growth (Brown 1961, Hewitt 1963). Conversely, J. roemenanus may have a low Fe requirement and a high concentration of Fe in the nutrient medium or soil may have a toxic effect. Plants grown in solutions deficient in Ca, N, and Fe had similar responses. These plants had shorter leaves, about one half of the number of shoots (reflected as a threefold -IT toT Figure 2. Multidimensional plots of plants of Juncus roemenanus grown in complete and deficient solution cultures for 68 days. The dotted, horizontal lines indicate the relative size of young plants at the beginning of the experiment. Curves shown in Figure 1 would center on the middle and fall within the upper and lower dotted lines. These dotted lines are provided to show the relative amounts of plant growth. Each curve represents the combined and relative condition of three plants in a particular series (triplicate) or deficient or complete nutrient media. 38 Eleuterius and Caldwell reduction in total leaf length), and one half of the biomass compared with plants in media without micronutrients. Plants grown in media deficient in K, S, P, and Mg were similar in appearance and all had a retarded growth habit. Plants grown in distilled water were severely retarded compared to other plants. 7. roemerianus appears to have a great capacity for survival under extremely depauperate conditions because the plants placed in distilled water survived and increased slightly in size, obviously utilizing stored nutrients. Gallagher (I975)stated that 7. roemerianus was capable of storing reserves of nitrogen in leaves (luxury supply or reserve) without an observable increase in plant size. It was possible that the distilled water contained trace amounts of nutrients but certainly not at concentrations to support growth or survival. The results of the present study indicate that the presence of Mg, P, S, and K, which are found in great quantities in highly organic tidal marsh soils (Pomeroy et al. 1969, Tyler 1971, Brupbacher et al. 1973) > are extremely important for growth of J. roemerianus. The presence of Fe,N, and Ca are also very important for growth, but are probably required in much lower quantities than other nutrients. The growth of 7. rocmerianus was suppressed in solutions with micronutrients. Apparently, one or more of the micio- nutrients was inhibitory to J. roetnerianus. Variable soii fertility accounts, at least in part, for length of leaves (stand height), rhizome and root development, inflorescence size, and other phenotypic characteristics which are known to vary between populations of 7. roemerianus found in Gulf and Atlantic coastal marshes (Eleuterius 1975). The qualitative and quantitative diagnostic symptoms of the rush 7. roemerianus arc very similar for each treatment to those mineral deficiency symptoms generally described for many agricullural and terrestrial plants (Epstein 1972, Devlin 1966, Chapman 1973b), with the exception of an apparent sensitivity to certain heavy metals. These similarities in physiological responses to an array of deficient elements links the intertidal and estuarine 7. roemerianus to the adjacent upland or terrestrial flora. However, the effects are different in 7. roemerianus in comparison to those generally seen in terrestrial plants especially in regard to the degree of severity. For example, the absence of Ca apparently had less of an effect on the growth of 7. roemerianus than that described for terrestrial plants (Chapman 1973b, McMurtrey 1932). The growth' of 7 . roemerianus was severely retarded by a deficiency of S and Mg, while such a severe effect on growth has not been generally described for terrestrial plants (Carolus 1935, Embleton 1973). The S and Mg requirements of 7. roemerianus were much greater than those of most terrestrial plants. The greater Sand Mg requirements of 7. roemerianus com- pared to those for terrestrial plants are obviously related to the higher concentrationsof those elements in salt water and soils of tidal marshes. Furthermore, concentrations of P and K arc much higher in the soils of tidal marshes than in those of most terrestrial areas. In contrast, there is little available Ca, N or Fe in estuarine waters or tidal marsh soils. The micro- nutrients B, Mn, Zn, Cu> and Mo occur in very low concen- trations in the relatively pristine aquatic habitats of estuaries and tidal marshes in comparison to the concentration of the respective nutrient medium used in this study. The abundance of water probably accounts for the dilution of naturally occurring micronutrient concentrations in tidal marshes. The present study indicates that 7. roemerianus is well adapted to the peculiar concentration and array of mineral nutrients in the soils and saline waters of pristine tidal marshes. The heavy metals B, Mn, Zn, Cu, and Mo are compounds of domestic and industrial effluent which enter into estuaries from factories, municipalities, and through runoff from highways, marinas, farms, lawns, etc. Therefore, the sensi- tivity of the salt marsh rush 7 roemerianus to heavy metal concentrations recommended for the culture of agricultural plants has profound and far-reaching importance to the future of estuaries, and indicates that 7. rocmerianus is physiologically distinct. The latter is not surprising because of the long evolutionary history of halophytes, and it points out the need for further physiological studies on 7. roemerianus and other tidal marsh plants. ACKNOWLEDGMENTS We thank other members of the Botany Section of the Gulf Coast Research Laboratory, for assistance with various aspects of this study. Mrs. Helen Gill and Mrs. Lucia O'Toole typed the manuscript. REFERENCES CITED Adams, D. A, 1963. Factors influencing vascular plant zonation in North Carolina salt marshes. Ecology 44:445- 456. Andrews, D. F, 1972. Plots of high-dimensional data. Biometrics 28:125-136. Boyd, C. E. 1970. Influence of organic matter on some character- istics of aquatic soils. Hydrobiologia 36:17-21. Brown, J. C. 1961. Iron chlorosis in plants. Adv.Agron. 13:329-369. Brownell, P. F. 1965. Sodium as an essential micronutrient element for ahigher plant (A trip lex vesicara), Plant Physiol. 40.460-468. Broyer, T. C., A. B. Carlton, C. M. Johnson & P. R. Stout. 1954. Chlorine: a micronu trierit element for higher plants. /Yam Physiol. 29:526- 532. Buckman, 11. D. &. N. C. Brady. 1969. The Nature and Properties of Soils. The Macmillan Company. New York. 653 pp. Brupbacher, R, H., J. E. Sedberry, Jr. & W. H Willis. 1973, The coastal marshlands of Louisiana. Chemical properties of the soil materials. La. Agr. Exp. Stn. Bull. No. 672. 15 pp. Carolus, R. L. 1935. The relation of potassium, calcium and sodium to magnesium deli dency.Proc.Am. Soc. llortic. Sci. 33:595 - 599. Chabreck, R, H. 1972. Vegetation, water and soil characteristics of the Louisiana coastal region. La. Agr. Exp. Stn. Bull. No. 664 .72 pp. Chapman, H. D. (ed.). 1973a. Diagnostic Criteria for Plants and Soils . University of California, Division of Agricultural Sciences. Riverside, CA. 793 pp. Mineral Defficiency of the Salt Marsh Rush 39 . 1973b. Calcium. Pages 65-92 in K D. Chapman (ed.), Diagnostic Criteria for Plants and Soils. University of California, Division of Agricultural Sciences. Riverside, CA. Cotnoir, L. J. 1974. Marsh soils of the Atlantic coast. Pages 441- 447 in R. J. RelmoJd and W. H. Queen (eds.), Ecology of Halophytes. Academic Press, New York. Devlin, R. M. 1966. Plant Physiology. Van Nostrand Reinhold Co., New York. 446 pp. Eleuterius, L. N. 1972. The marshes of Mississippi. Castanea 37: 153-168. . 1974. An autecological study of Juncus roemerianus. Ph.D. dissertation. Mississippi State University, Mississippi State, MS. 221 pp. .1975. The distribution of Juncus roemerianus in the salt marshes- of North America. Chesapeake Sci. 1 7(4) :289— 29 1 . Embleton, T. W. 1973. Magnesium. Pages 225-263 in H. D, Chap- man (ed.), Diagnostic Criteria for Plants and Soils. University of California, Division of Agricultural Sciences. Riverside, CA. Epstein, E. 1972. Mineral Nutrition of Plants; Principles and Per- spectives. John Wiley and Sons, Inc., New York. 4 12 pp. Gallagher, J. L. 1975. Effect of an ammonium nitrate pulse on the growth and elemental composition of natural stands of Spartina alterniflora and Juncus roemerianus. Am. J. Bot. 62:644-648. Grim, R. E. 1968. Clay Mineralogy. 2nd edition. McGraw-Hill, New York. 596 pp. Hewitt, E. J. 1963. The essential nutrient elements: requirements and interaction in plants. Pages 137-360 in F.C. Steward (ed.), Plant Physiology-A Treatise. Volume 3, Academic Press, New York and London. Machlis, L. & J. G. Torrcy. 1956. Plants in Action: A Laboratory Manual of Plant Physiology. W. H. Freeman and Co., San Fran- cisco, CA, 282 pp. McMurtrey, J. E. Jr. 1932. Relation of calcium and magnesium to the growth and quality of tobacco. J. Am. Soc. Agron. 24: 707-716. Nance, W. L., B. H. Polmer & G. C. Keith. 1975. Programming details for MDPLT: A program for plotting multi-dimensional data. Supp. U.S. For. Serv. South. For. Exp. Stn. Tech. Rep. S07. 26 pp. Pigott, C. D. 1969. Influence of mineral nutrition on the zona- tion of flowering plants in coastal salt marshes. Pages 25-35 in 1. H. Robison (ed.), Ecological Aspects of Mineral Nutrition of plants . Blackwell Scientific Publications, Oxford, England. Pomeroy, L. R., R. E. Johannes, E. P. Odum &. B. Roffman. 1969. The phosphorous and zinc cycles and productivity of a salt marsh. Symposium of Radioecology. USAEC Res. Dev. Rep. TID 4500: 412-419. Richards, L. A. (ed.), 1969. Diagnosis and Improvement of Saline and Alkali Soils. United States Salinity Laboratory. Agriculture Handbook No. 60. U.S. Gov. Printing Office, Washington, D.C. 160 pp. Rorison, I. H. 1968. The response to phosphorous of some ecologi- cally distinct plant species. I. Growth rates and phosphorous absorption. New Phytol. 67:913-923. Steiner, A. A, & H. Van Winden. 1970 Recipe for ferric salts of eth>lenediamine tetraacetic acid. Plant Physiol 46:862-863. Tyler. G. 1967. On the effect of phosphorous and nitrogen, supplied to Baltic shore-meadow vegetation. Botaniska Notiser 120: 433-447. _____ . 1971. Distribution and turnover of organic matter and minerals in a shore meadow ecosystem. Oikos 22:265 291. Wallace, A., E. Frolich & O. R. Lunt. 1966. Calcium requirements of higher plants. Nature 209:1 -634. Gulf Research Reports Volume 7 | Issue 1 January 1981 Ichthyofaunal Colonization of a New Artificial Reef in the Northern Gulf of Mexico Ronald R. Lukens Gulf Coast Research Laboratory DOI: 10.18785/grr.0701.06 Follow this and additional works at: http://aquila.usm.edu/gcr ifr Part of the Marine Biology Commons Recommended Citation Lukens, R. R. 1 98 1 . Ichthyofaunal Colonization of a New Artificial Reef in the Northern Gulf of Mexico. Gulf Research Reports 7 ( 1 ) : 41-46. Retrieved from http://aquila.usm.edu/gcr/vol7/iss 1/6 This Article is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf and Caribbean Research by an authorized editor of The Aquila Digital Community. For more information, please contact Joshua. Cromwell(2)usm.edu. Gulf Research Reports , Vol. 7, No. 1, 41-46, 1981. ICHTHYOFAUNAL COLONIZATION OF A NEW ARTIFICIAL REEF IN THE NORTHERN GULF OF MEXICO RONALD R. LUKENS Fisheries Research and Development Section , Gulf Coast Research Laboratory , Ocean Springs, Mississippi 39564 ABSTRACT Ichthyofaunal colonization of a new artificial reef was monitored from June 1975 through September 1977. Direct observations were accomplished using SCUBA. Theories of colonization and species equilibrium of islands and islandlike habitats were applied to the colonization data from the artificial reef. Sixty species of fishes from 33 families were recorded at the reef. Fifty-two percent of these species were primary reef fishes and 48*%> were secondary. Colonization data were produced only from the occurrence of primary reef fish. Data indicate that ichthyofaunal communities in the northern Gulf of Mexico are heavily influenced by seasonal changes in temperature, and that colonization by reef fish in that area does not conform to theories of immigration and extinction for island biotas. These results concur with similar work conducted on reef ichthyofauna in the eastern Gulf of Mexico. INTRODUCTION Ichthyofaunal colonization of a new artificial reef in the northern Gulf of Mexico was conducted from June 1975 through September 1977. Theories of colonization and species equilibrium of islands and islandlike habitats have been discussed by MacArthur and Wilson (1967), Simberloff (1968), and Shoener (1974a, 1974b). Cairns et al. (1969) developed a method of estimating rates of immigration and extinction, calling them colonization and decolonization rates, respec- tively. Smith (1979) applied these theories to the ichthyo- faunal colonization of patch reefs in the eastern Gulf of Mexico. This study attempts to apply the above theories of colonization and species equilibrium of island habitats to the colonization of a Liberty ship artificial reef in the northern Gulf of Mexico. METHODS AND MATERIALS This study was conducted on the scrapped hull of the BENJAMIN WATERHOUSE, a World War II Liberty ship. The scrapped ship, sunk on June 10, 1975, lies in 14 m of water about 8 km south of the western end of Horn Island (Figure 1), and represents approximately 76,200 m 2 of hard substrate. Monthly ichthofaunal observations began on July 21, 1975, using conventional sportfishing techniques and SCUBA diving. Hydrographic data, including temperature and salinity, were obtained for surface and bottom water masses during each survey. Turbidity of surface and bottom water masses was measured using a secclii disc. A list of fish species for each observation dive was compiled on underwater paper attached to a clipboard. Also, a debriefing session for divers/observers was held immediately after each dive. Manuscript received October 28, 1980; accepted March 26, 1981. Figure 1. Waterhouse Reef (W) site. A list was compiled of all species of fishes observed on any part of the artificial reef, and it included estimates of size and abundance. Whenever identification of a fish was uncertain, attempts were made to capture the specimen using hand nets, pole spears, and slurp guns Turbidity was highly variable. Whenever water clarity was adequate, 35 mm photographs were taken of reef fishes. When water visibility was less than approximately 3 in, no sampling was conducted due to increased difficulty in making accurate observations. RESULTS Hydrography Temperature and salinity from surface and bottom water were measured monthly at Waterhouse Reef from July 1975 through September 1977 (Table 1). Bottom water visibility ranged from 0 to 14 m. These data compare favorably with data from previous years (Christmas and Eleuterius 1973). 41 42 LUKENS TABLE 1. Surface (S) and bottom (B) water temperatures (°C), and salinity (ppm) at Waterhouse Reef. Month 1975 1976 1977 1978 Temperature Salinity Temperature Salinity Temperature Salinity Temperature Salinity S B S B S B S B S B S B S B S B January _ - _ _ _ _ _ _ _ _ . - _ _ - February - - - - 14.3 17.0 32.0 35.0 - - - - - - - - March - - - - 19.0 19.0 26.0 34.0 - - - - - - - - April - - - - 23.1 20.4 19.0 34.0 21.0* 19.0 23.0 35.0 - - - - 24.0 22.5 28.0 31.0 May - - - — 24.2 22.0 27.0 35.0 25,0 24.0 18.0 28.0 - - - - June - - - 25.3 23.1 24.0 30.0 28.0 25.0 28.0 34.0 - - - - July 28.8 25.8 29.5 35.0 28.6 22.0 26.0 38.0 30.0 30.0 34.0 35.0 - - - - August 20.0* 26.9 24.0 32.0 - - - - - - - - - - - - 30.0 25.8 24.0 38.0 September 29.5 29.5 28.0 28.0 29.2* 28.6 32.0 34.0 30.0 29.0 31.0 32.0 - - - - 27.0 27.5 30.0 31.0 October 22.8* 23.0 28.0 29.0 24.7 25.3 33.0 33.0 - - - - - - - - 23.0 23.0 25.0 30.0 November 23,0* 23.0 28.0 30.0 19.2 19.8 32.0 30.0 - - - - 22.0 25.0 32.0 32.0 19.3 19.8 33.0 34.0 December 16.0 17.8 29.0 31.0 14.0* 15.0 29.0 29.0 - - - - - - - - 13.0 15.0 30.0 38.0 ♦Hydrography measured twice in month. Species Composition All fishes identified from Waterhouse Reef were classified according to Starck (1968) into two groups: primary reef fishes, and secondary reef fishes (Table 2). Primary reef fishes are those which almost exclusively are found inhabit- ing reef or reeflike habitats. Secondary reef fishes are those which can be found on reefs but are more numerous at other habitat types, i.e., grassbeds, sand or mud flats, or open water. Smith (1976), working in the eastern Gulf of Mexico, also used the groupings developed by Starck (1968). For those species not covered by Starck or Smith, 1 con- sulted work by Hastings (1972), Christmas et al. (1973) Walls (197S), and Hoesc and Moore (1977). Sixty species of fishes from 33 families occurred at Water- house Reef (Table 2). Fifty-two percent were primary reef fishes and 48% were secondary reef fishes. Nearly half of the secondary reef fish group was composed of pelagic species. Colonization of Primary Reef Fish Colonization of a habitat and the approach of species equilibrium within that habitat can be followed by calcu- lating immigration and extinction rates, described by the rate at which new species enter a habitat and old species leave it. Lapses of time between observations in this study made it impossible to calculate the actual rates of immi- gration and extinction. Therefore, I followed a method developed by Cairns et al. (1969) for calculating coloniza- tion and decolonization rates, a method which compensates for those time gaps between observations. The colonization curve, colonization rate curves, and decolonization rate curves (Figures 2, 3, 4, 5, and 6) were produced from the occurrence of primary reef fish listed in Table 2. The colonization curve (Figure 2) increased rapidly during the first 14 months of the study, then began to level off, and finally achieved an asymptote at the 17th month. The colonization rate for Waterhouse Reef was calculated by combining new species per observation with recurring species (those species which disappeared from the reef but later reappeared), and dividing by the amount of time between observations. Figure 3 represents the rate of colonization of fish species per day (scatter plot) plotted over the duration of the study. An exponential curve (solid Figure 2. Colonization curve for Waterhouse Reef. Colonization of a New artificial Reef 43 TABLE 2. List of fish species from Waterhouse Reef classified as primary and secondary reef fishes following Starck (1968). PRIMARY REEF FISH Antennariidae Antennarius ocellatus Ocellated frogfish Serranidae Centropristis philadelphica Rock sea bass Diplectrum formosum .... Sand perch Epinephelus nigritus Warsaw grouper Mycteropcrca microlepis Gag Serraniculus pumilio Pygmy sea bass Serranus subligarius . . . .Belted sandfish Grammistidae Rypricus macula tus Wliitespotted soapfish Priacanthidue Priacanthus arenatus Bigeye Apogonidae Apogon pseudomacula tus Twospot eurdinalfish Lutjanidae Lutjanus campechanus . . . Red snapper L. griseus Gray snapper I,, synagris Lane snapper Pomacentridae Pomaccntrus partitus Bicolor damselfish P. variabilis. Cocoa damselfish Pomadasyidac Haemulon aurolineatum Tomtate Onhopristis chrysoptera Pigfish Sparidae Archosargus probat ocephalus Sheepshead Diplodus holbrooki . . . .Spottail pinfish Lagodon rhotnboides Pinfish Sciaenidae Equetusumbrosus Cubbyu Kphippidae Chaeiodipterus faber Atlantic spadefish La b rid a e Halichoeres bivittatus. . . . Slippery dick H. caudalis Painted wrasse Sphyraenidae Sphyraena barracuda Great barracuda Blenniidae Blennius marmoreus Seaweed blenny Hyplcurochilus geminatus Crested blenny Chactodontidae Chaetodon ocellatus Spotfin butterflyfish Holocahthus bermudensis Blue angelfish Gobiidae Gobiosoma longipala . . . Twoscale goby Balistidae Balistes capriscus .... Gray trigger fish SECONDARY REEF FISH Careharhinidae Carcharhinus maculipirmis Spinner shark Rhizoprionodon terra novae Atlantic sharpnose shark Sphyrnidae Sphyrna sp Hammerhead shark Clupeidae Harengula jaguana Scaled sardine Ariidae Arius felis Sea catfish Antennariidae Antennarius radiosus Singlespot frogfish Ophidiidae Brotufa barbata Bearded brotula Syngnathidae Hippocampus zostcrac Dwarf seahorse Serranidae Diplectrum bivittatum Dwarf sand perch Pomatomidae Pomatomus saltatrix Bluefish Rachycentridae Rachycentron canadum Cobia Echeneidae Echerteis naucrates Sharksucker Carangtdae Caranx crysos . . C. hippos Seriola zonata . . Trachu ru slat ham i Vomer setapinnis Coryphacnidae Coryphaena hippurus Dolphin Sparidae Stenotomus caprinus . . Longspinc porgy Blue runner Crevallejack . . Banded rudderfish Rough scad . . Atlantic moonfish Sciaenidae Bairdiella chrysoura Silver perch Leiostomus xanthurus Spot Micropogonias undulatus Atlantic croaker Scombri due Scomberomorus sp Mackerel Stromateidae Peprifus burti Gulf butterfish Scorpaonidae Scorpaena brasiliensis Barbfish Bothidac Paralichthys lethostigma Southern flounder Balistidae Monacanthus hispidus Planehead filefish Tetraoduntidae Sphocroidcs parvus Least puffer 44 LUKE NS DAYS Figure 3. Colonization rate for Waterhouse Reef (using recurring species). Figure 4. Decolonization rate for Waterhouse Reef (with recurring species). DAYS Figure 5. Modified colonization rate for Waterhouse Reef (without recurring species). line) was fitted to the colonization rate by regressing the number of species colonized per day on the logarithm of timefr = 0.357). The decolonization rate (Figure 4 . scatter plot) was calculated by determining the number of species eliminated from the reef per observation, and dividing by the time between observations. An exponential curve (solid line) was fitted to the decolonization rate by regressing the number of species eliminated from the reef per day on the logarithm of time (r - -0.067). Neither of these regressions proved significant (a = 0.05 ). Colonization and decolonization rates also were calcu- lated for these data without considering recurring species. Instead, if a species disappeared and reappeared regularly, initial colonization was the only one cwnsidered. An expo- nential curve was fitted to the modified colonization rate (Figure 5) by regressing the number of new species per day on the logarithm of time (t = 0.783, a - 0.01 ). An expo- nential curve was fitted to the modified decolonization rale (Figure 6) by regressing the number of species eliminated per day on the logarithm of time (r - ~ 0.390. a = 0. 1 0) Figure 6. Modified decolonization rate for Watethousc Reef (without recurring species). DISCUSSION Recruitment Rate of recruitment of species (all species observed) to Waterhouse Reef throughout the 28 months of the study was approximately two species per month. A 28-month study of a Liberty ship reef in Alabama waters revealed a recruitment rate of almost five species per month (Crozier 1977), and an inshore jetty in northern Florida showed a recruitment rate exceeding eight species per month over 31 months (Hastings 1972), The Alabama and Florida artificial reefs mentioned apparently exhibited higher rates of recruitment because of their proximity to other recruit- ment areas and to deeper water. In each case, observed recruitment was decreased or eliminated during winter months, as reported in this study, but as water temperature increased above 20°C, recruitment increased considerably. Colonization and Species Equilibrium Mac Arthur and Wilson (1967) postulated that an island community proceeds through a series of successional changes leading to a point of equilibrium whereby immigra- tion of new species is offset by extinction of other species. At the point of equilibrium, species composition is dynamic over time, theoretically a slow process, as some species are replaced by others, l classified Waterhouse Reef as an island because there is a vast expanse of fiat bottom consisting of mud and silt surrounding the artificial substrate, The study reef is at least 9 km from the nearest hard substrate. Colonization of a New Artificial Reef 45 For this discussion, only primary reef fish species (Table 2) Were considered. A species was considered an unsuccessful colonizer if it appeared only once. Since observations of Waterhouse Reef ichthyofauna began immediately after the hull was sunk, the fish popula- tion was monitored from its inception through 28 months of colonization. Colonization of Waterhouse Reef was initially rapid and decreased with time. The cessation of colonization is illustrated by the asymptote on the coloni- zation curve (Figure 2). The two depressions in this curve that precede the asymptote were the result of decreased recruitment of new species during winter monLhs. Several species unsuccessfully attempted to colonize after month 1 7 of the study which could indicate that the maximum num- ber of species for that habitat had been approached by that time. Some of these species, such as Pomacentrus partitus and Halichoeres caudalis, possibly reacted negatively to several factors in combination which resulted in their failure to colonize. Increased species number and tempera- ture changes are possibly two of those factors, and a third factor may have been competition from congeners (P. variabilis and H. bivittatus) present prior to their arrival. Smith et al. (1975) concluded that fluctuating water temperature, turbidity, red tides, and anoxia following phytoplankton blooms were the major stress factors opera- ting on the ichthyofaunal communities in the eastern Gulf of Mexico. Temperature fluctuations appeared to be the major stress factor operating on the ichthyofauna of Waterhouse Reef. Decreasing water temperature during winter periods markedly affected the species composition of the study reef. Many species, such as Pomacentrus variabilis, Chaetodon ocellatus, and Holocanthus bermu- densis, disappeared from the reef during the winter months. An influx of recurring species occurred as water temperature rose in spring and summer. Although the recruitment process of the recurring species was repeated each year, the resources sustaining a particular species were not being depleted by new species having the same niche require- ments; therefore, competitive exclusion from the community was not occurring. Seasonal disappearance and reappearance of many of the same species at Waterhouse Reef could affect the pattern of colonization if recurring and new species were given the same importance. The colonization rate curve (Figure 3) does not accurately describe coloni- zation of new species on the reef. The reason for this is the importance placed on recurring species in the formula used to calculate that rate. The decolonization rate curve (Figure 4) also provides an inaccurate view of actual decolonization due to the recurring species phenomenon. If seasonal reoccurrance of a species is not new coloni- zation but rather is continued utilization of a resource already colonized, then it is necessary to consider the rates of colonization and decolonization disregarding recurring species. These modified colonization and decolonization rates are calculated as described above with the exception that recurring species are not given the same importance as new species. The modified colonization rate (Figure 5) adequately represents the colonization of new species to the study reef, and is consistent with the colonization theory as set forth by Mac Arthur and Wilson (1967). These findings agree also with those of Smith (1979). who did a similar study on patch reefs in the eastern Gulf of Mexico. The modified decolonization rate (Figure 6) does increase with time as stated by theMacArthur-Wilson theory; however, there are factors which indicate that this curve does not represent the actual decolonization of Waterhouse Reef ichthyofauna. Six species reported as eliminated from the reef fauna were Lutfanus synargris, Diplodus holbrooki, Epinephelus nigritus , Serraniculus pumilio , Holocanthus bermudensis, and Blennius martnoreus. Lutjanus synagris. D. holbrooki , S, pumilio . H. bermudensis, and B. marmoreus frequently were present on the reef but were never abundant. I believe they probably were over- looked in sampling rather than actually eliminated from the reef fauna. Epinephelus nigritus was one of the initial colonizers and, with few exceptions, always was present during my observations. Juveniles of this species (200 to 250 mm total length) were recorded initially; however, the size of the fish observed increased with time during the study. As the size of fish observed increased, their abun- dance decreased. Mycteropcrca microlepis , another grouper, began to colonize the reef in July 1976, It is possible that, due to the low numbers of E. nigritus , M. microlepis was able to displace the former. Because of behavioral differ- ences between the two species, that conclusion is unlikely. Rather, it is more probable that E, nigritus was overlooked in sampling because of its decreased numbers and its secretive behavior. If these assumptions arc valid, virtually no decolonization took place on (he artificial reef during this study. The dynamic species composition expected from the MacArthur-Wilson theory was not evident at Waterhouse Reef, but rather, as Smith (1979) found, species compo- sition exhibited considerable stability, with 92% of the reef fish reported herein already having been colonized by the end of the first year. Those species continued to dom- inate the primary reef fish group throughout the remainder of the study. CONCLUSIONS My findings coincide with those of Smith (1979), indi- cating that reef-fish communities in the northeastern Gulf of Mexico do not conform to theMacArthur-Wilson model of immigration and extinction for island biotas. It was necessary to disregard recurrent species for these data to correspond to the findings of Smith (1979); however, I believe this was justified because of the strong seasonal 46 LUKENS influence operating on the ichthyofauna of Waterhouse Reef, coupled with the lack of species replacement when life-sustaining resources were abandoned by a seasonally absent species. These findings in no way refute the theory proposed by MacArthur and Wilson (1967), and it is probable that the strong influence exerted by temperature changes on t he study reef make such an equilibrium situation impossible to attain. ACKNOWLEDGMENTS This paper is an exerpt from Master’s research conducted by the author. The author thanks Drs. S. T. Ross, E. W. Cake, Jr., A. G. Fish, and R. A. Woodmansee for their careful review of this material. Gratitude is also expressed to Dr. T. D. Mdlwain, to the anadromous and ecology sections of the Gulf Coast Research Laboratory, and to the many people who assisted the author in field work. REFERENCES CITED Cairns, J., Jr., M. D. Duhlberg, K. L Dickson, N. Smith, & W. T. Waller. 1969. The relationship of fresh water protozoan com- munities to the MacArthur-Wilson equilibrium model. Am. Nat. 103:439-454. Christmas, J. Y, & C, K. Eleuterius. 1973. Hydrology, Pages 74 -121 in Cooperative Gulf of Mexico Estuarine Inventory and Study Mississippi. Gulf Coast Research Laboratory, Ocean Springs, MS. Christmas, J. Y., A. Perry, & R. Waller. 1973. Investigations of coastal pelagic fishes. Dep. of Co in me r., NOAA, PL 88-309, NMFS Project No. 2-128-4. Gulf Coast Research Laboratory. Ocean Springs, Mississippi 78 pp. (mimeographed) Crozier, G. F. 1977. Development of gulf coast artificial reefs. NOAA/Sea Grant 04 -05 — 1 58- 54—07(1) 23 pp. (unpublished) Hastings, R. W. 1972. The origin and seasonality of the fish fauna on a new jetty in the northeastern Gulf of Mexico. PhD. disserta- tion. Florida State University, Tallahassee, Florida. 55$ pp. Hocse, II. D. & R. H. Moore. 1977. Fishes of the Gulf of Mexico, Texas, Louisiana, and Adjacent Waters. Texas A&M University Press. College Station and London. 327 pp. MacArthur, R. H. & E. O. Wilson, 1967. The Theory of Island Biogeography. Princeton University Press. 203 pp. Shoener, A. 1974a. Colonization curves for planar marine islands. Ecology 55:81 8—827 , . 1974b. Experimental zoogeography. Colonization of marine mini-islands. Am. Nat. 1 08(964):? 1 S —737 . Simberloff, D. S. 1968. Experimental zoogeography of islands: A model for insular colonization. Ecology 50(2). 296- 3 14. Smith, G. B. 1976. Ecology and distribution of eastern Gulf of Mexico reef fishes. Fla. Mar. Res. Puhl. No. 19. 78 pp. , 1979. Relationship of eastern Gulf of Mexico reef-fish communities to the species equilibrium theory of insular biogeog- raphy. J. Biogeogr. 1979(6):49-6l. . , H- M. Austin, S. A. Borlone, R. W. Hastings, & L. H. Ogren. 1975. Fishes of the Florida Middleground with comments* on ecology and zoogeography. Fla. Mar. Res. Puhl 9:1-14. Starck, W. A. 1968. A list of fishes of Alligator Reef. Florida with comments on the nature of the Florida reef fish fauna. Undersea Biol. 1 (13:5-40. Walls. J. G. 1975. Noteworthy marine fishes from eastern Louisiana. Q. J. Fla. Acad . Sci. 35(2): 109-1 12. Gulf Research Reports Volume 7 | Issue 1 January 1981 Silica and Ash in Several Marsh Plants F.C. Lanning Kansas State University Lionel N. Eleuterius Gulf Coast Research Laboratory DOI: 10.18785/grr.0701.07 Follow this and additional works at: http:/ / aquila.usm.edu/ gcr Part of the Marine Biology Commons Recommended Citation Lanning, F. and L. N. Eleuterius. 1981. Silica and Ash in Several Marsh Plants. Gulf Research Reports 7 (l): 47-52. Retrieved from http://aquila.usm.edu/gcr/vol7/issl/7 This Article is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf and Caribbean Research by an authorized editor of The Aquila Digital Community. For more information, please contact Joshua.Cromwell(S>usm.edu. Gulf Research Reports, Vol. 7, No. 1, 47-52, 1981. SILICA AND ASH IN SEVERAL MARSH PLANTS F, C. LANNING AND L. N. ELEUTERIUS Department of Chemistry, Kansas State University, Manhattan, Kansas 66506, and Botany Section, Gulf Coast Research Laboratory, Ocean Springs, Mississippi 39564 ABSTRACT Ash and silica content and their depositional patterns in tissues of Spartina alterniflora Loisel., Distichlis spicata (L.) Greene, Scirpus validus Vah L, Zizania aquatica L.. and Limonium carolinianum (Walt-) Britt, were determined. Zizania aquatica leaves had the highest silica content (6.0%) of any of the plant parts tested; silica making up over half of the ash. Silica in the plants was opaline in character. Limonium carolinianum did not accumulate silica in any great amount. However, ash content was very high in Linumium carolinianum and Scirpus validus making up over 17% of the dry weight of the leaves. X-ray diffraction showed the presence of halite (NaCl) and calcium sodium phosphate (2.4 CaO • 0.6 Na^O * P 2 O s ) in the ash of the leaves of all the plants from Mississippi except Zizania aquatica. Mineral deposition (silica and other minerals) in Zizania aquatica occurs in rows lengthwise of the leaf, and there are bowtie- and oval-shaped phytoliths. In Distichlis spicata leaves, mineral deposits occur in rows of elongate, serrated units. Spongy mineral deposition occurs lengthwise of the leaves of Spartina alterniflora and some of these deposits, including the silica, are fibrous. In Scirpus validus heavy deposits occur lengthwise of the leaf. Silica occurs in a sheetlike pattern and in rows of oval particles. INTRODUCTION Silica content of agricultural plants has been shown to be variable and to depend primarily on soil type and plant species (Jones and Handreck 1967, Lewin and Reimann 1969, Lanning and Linko 1961). Certain cultivated grasses such as rice may contain up to 20 times that of crimson clover Trifolium incarnatum (Russell 1961). Based on available information, monocotyledons generally have much more silica than dicotyledons (Metcalfe and Chalk 1950a, 1950b; Metcalfe 1960). Sangster (1978) suggested that the ability of plant species to absorb, transport, and deposit silica in similar aggregate formations may indicate a common origin or epicenter and subsequent migration of the species to other biogeographical realms. However, it is equally possible that the ability of a plant species to absorb and deposit silica within their tissues may have changed with evolution and migration to different regions. Silica deposits in the aerial portion of crop plants contri- bute several beneficial effects. Leaves of rice are stiff and erect when silica content is high, but droop when it is low (Ishizuka 1971). Elect leaves arc more photosynethetically active than drooping leaves (Ishizuka 1971); furthermore, high silica content enhances seed retention and prevents shattering, a common characteristic of grasses which complicates harvesting of seed in some species (McWilliams 1963). Lodging (bending of the culm: weak culm) of cereal plants also can be prevented by additions of silica to the soil (Mulder 1954). There is evidence that increasing the silica content of the soil (Monteith 1966) may cause a decrease in transpiration. A reduction in suseeptability to fungal and insect attacks of rice and other gramineous crops has been attributed to a high silica content of the respective plants (Vlamis et al. 1958, Jones and HandTeck 1967, Manuscript received July 21, 1980; accepted November 26, 1980. Ishizuka 1971). Relatively high concentrations of silica in plants also are known to prevent manganese toxicity, apparently by decreasing manganese uptake (Vlamis and Williams 1967). Rice plants with a high silica content also have a low iron content (Jones and Handreck 1967). High concentration of nitrogen or phosphorous in cultivated fields causes a decrease in the concentration of silica in barley, wheat, and other crops grown in those areas (Jones and Handreck 1967). Ponnamperuma (1964) has shown that silica improves oxygen supply to the root by increasing the volume and rigidity of gas channels in the root and shoot. Other edaphic factors such as soil pH also are known to affect silica uptake by cultivated plants. If those facts hold true for wild plant species, they have important implications regarding our understanding of natural ecosystems. Little is known about silica content or the factors affecting silica uptake in wild plant species (Chen and Lewin 1969). The same distribution patterns and factors affecting silica deposition may or may not be similar between wild and cultivated plant species. There may or may not be major differences between silica content of terrestrial and aquatic species. Does the same plant species found in different geo- graphical areas have the same silica uptake ability? Do native grasses and other wild monocotyledons, as present evidence indicates, have more silica as a rule than native dicotyledons? Furthermore, most work on native plants has been done on terrestrial species. To our knowledge no work has been done on floating or submerged aquatic plant species. Recently, however, Lanning and Eleuterius (1978) investigated silica content and depositional patterns of Juncus roemerianus Scheele, a common rush (Eleuterius 1975, 1976) of salt marshes of the South Atlantic and Gulf coasts. Juncus roemerianus was found to contain consid- erable opaline silica but no a-quartz. The amountof silica in plants corresponded to the amount found in soil, and silica content increased during the growing season. Lanning (1 972) 47 48 Lanning and Eleuterius showed that Juncus interior Weig and J uncus bufunius L., rush species of inland low areas, contained considerable silica, both opaline and a-quartz, and that silica content of Juncus interior increased nearly eightfold over the growing season. The present study entailed five objectives: (1) to compare silica content of grass and sedge species from wetlands of different geographical locations; (2) to investigate silica content of grass and sedge species which grow under con- tinuously but partially submerged conditions; (3) to com- pare silica content of several wetland monocotyledons with at least one dicotyledon from coastal wetlands; (4) to des- cribe the Silica depositional patterns in each species; and (5) to access the analytical results for these wetland plant species in view of knowledge of silica in agricultural plants. Specifically we were to determine: (1) the types and quantity of silica, if present, in several species of marsh plants, and (2) the ash (A) and silica (Si) contents of the various parts of the plants. The four monocotyledons studied were Spartina alterni- flora Loisel., Distichlis spicata (L.) Greene, Scirpus validus Vahl., 3nd Zizania aqualica L. Limonhtm curolinianum (Walt.) Britt, was the dicot species analyzed. Scirpus validus and Zizania qquuiica (wild rice) typically grow along rivers and bayous with the lower portion of the plants submerged. Distichlis spicata, Spartina altemiflora, and Limonium carolinianum are intertidal, with Spartina altemiflora occupying the lowest position on the tidal plane. METHODS AND MATERIALS Zizania aquatica was collected from Pascagoula River in Mississippi, and Limonium carolinianum and Distichlis spicata were collected from Deei Island off the coast of Mississippi and from a marsh in Cloud County, Kansas. Scirpus validus also was collected from Pascagoula River, Mississippi, and from marshes near St. George, Kansas, and in Decatur County , Kansas. Spartina altemiflora plants were from a marsh associated with Davis Bayou in Mississippi. Plant materials were thoroughly washed and then oven dried at 110°C. Whole plants were separated into above- ground parts, rhizomes, and roots. All plant materials were ground in a Wiley mill before analysis. Ash and silica contents of plant materials were deter- mined by classical gravimetric techniques. Tissue samples were ashed in platinum crucibles at approximately 500°C, and the ash was treated repeatedly with 6N hydrochloric acid to remove other mineral impurities. The silica was filtered out and ignited. Silicon dioxide content of plant materials was determined as the difference in weights before and after treatment in a platinum crucible with a few diops of 45% aqueous hydrofluoric acid (Kolthoff and Sandell 1952). Determinations were made in duplicate. The X-ray diffraction patterns for identifying the nature of the mineral deposits in the plants were made as described by Lanning et al. (1958). Scanning electron micrographs of mineral deposits in leaves of the plants were made with an ETEC Autoscan E-l Electron Microscope. Tissues were ashed between microscope slides as described below. Ash was transferred to an aluminum stub covered with double-faced sticky tape by lightly pressing the stub on the glass slide; then the ash was coated with Au-Pd alloy and carbon. In some cases, tissue was ashed in a small platinum crucible and treated with 6N HC1 to remove soluble minerals before it was mounted on the stub. Spodograms were prepared by the Ponnaiya (1951) modification of the Uber (1940) method. Material to be examined was placed between microscope slides for ashing in a muitle furnace at 50Q°C, Ash was prepared for light microscopy by removing the upper slide, adding Canada balsam directly to the ash, and covering with a cover glass. A petrographic microscope was used to determine the nature of silica in the deposits. RESULTS Ash and Silica Contents of Plant Tissues Petrographic microscope studies of plants other than Limonium carolinianum showed silica to be clear, colorless, and isotropic with an index of refraction of 1.45. These are properties of the mineral opal (Lanning et al. 1958). Silica content of Limonium carolinianum was quite low, and both petrographic microscope studies and X-ray diffraction patterns showed the presence of a-quartz. Silica in L. caro- linianum was probably detrital quartz. There also was some detrital quartz in Scirpus validus leaves. The ash and silica contents of the tissues of the plants analyzed are given in Tables 1 and 2, Ash content of Lim- onium carolinianum leaves was very high, and low silica content indicated an unusual mineral content. X-ray diffraction patterns of the ash of leaves showed a large amount of halite (sodium chloride) and a calcium sodium phosphate (2.4 CaO • 0.6 Na 2 0 • P 2 O s ). Ando (1958) prepared this substance by fusing CaC 2 0 4 with Na 2 C(>3 and H3PO4 for 1/2 an hour at i,300°C, and determined its X-ray diffraction pattern to be an a-rhenanite structure. X-ray diffraction of leaves also showed the halite. Other peaks were loo small for positive identification but indicated that calcium sodium phosphate was present in the leaves of Limonium carolinianum. X-ray diffraction also showed the presence of considerable halite and calcium sodium phos- phate in the ash of Spartina altemiflora, Distichlis spicata r and Scirpus validus leaves of plants from Mississippi. However, halite was not present in Zizania aquatica. Minerals tend to deposit in leaves as shown by both higher ash and silica contents, Limonium carolinianum differs from other plants in that it does not accumulate silica in any great amount. Zizania aquatica leaves have the highest silica content of any of the plant parts tested, and silica makes up half of the ash. The nodes of the culms of Zizania Silica and Ash in Several Marsh Plants 49 TABLE 1. TABLE 2. Percentage of Ash in Marsh Plants. Percentage of Silica in Marsh Plants. Plant Leaves Rhizomes Roots Inflo- rescence Culm Culm Nodes Plant Leaves Rhizomes Roots Inflo- rescence Culm Culm Nodes Scirpus validus St. George, Kansas 17.88 7.31 Scirpus validus St. George, Kansas 3.39 3.66 Scirpus validus Mississippi 17.86 8.33 17.85 Scirpus validus Mississippi 2.34 1.50 7.02 Limonium carolinianum Mississippi 17.11 4.70 Limonium carolinianum Mississippi 0.44 0.14 Spartina alterniflora Mississippi 11.95 8.45 15.76 Spartina alterniflora Mississippi 0.83 0.95 1.63 Zizania aquatica Mississippi 1 1.71 8.88 13.72 Zizania aquatica Mississippi 6.00 2.04 5.21 Scirpus validus Decatur County, Kansas 10.65 5.43 Scirpus validus Decatur County, Kansas 1.39 2.49 Distichlis spicata Cloud County, Kansas 10.24 9.31 Distichlis spicata Cloud County, Kansas 4.55 4.24 Distichlis spicata Mississippi 8.18 5.92 19.48 Distichlis spicata Mississippi 2.07 0.21 2.77 aquatica also have a high silica content. The ash and silica values for Spartina alterniflora, Distichlis spicata, and Scirpus validus roots are all very high. Although silica content of roots is generally high, some inaccuracy may exist because of residual soil particles. Soil is difficult to wash from roots; therefore. the samples may not have been thoroughly cleaned, thus the very high values. Scirpus validus plants grown at St. George, Kansas, had considerably more silica in the leaves than those from Missis- sippi, and the latter had considerably more than those from Decatur County, Kansas .Distichlis spicata leaves from Cloud County, Kansas, had twice as much silica as those from Mississippi. Inflorescences of Kansas plants had nearly as much or somewhat more silica than the leaves; silica in each inflorescence made up almost half of the ash. Patterns of Ash and Silica Depositions Electron micrographs of mineral deposition in ashed leaf tissue of Zizania aquatica leaves are shown in Figure 1 . The deposits are in rows lengthwise of the leaves. Figure 1A shows rows of solid deposition, a row of “bowtie” phy toliths, and a row of the bowtie phy toliths joined together at the sides. Also there are oval phy toli ths and open spaces that appear to be stomata. These are shown highly magnified in Figure IB. The bowtie-shaped phytolilhs are shown in Figure 1C, and the bowtie phy toliths joined together in Figure ID. Petrographic microscope examination of silica deposits in Zizania aquatica leaves shows that they occur in bowtie- shaped particles. Silica also occurs in cell walls. These silica deposits in cell walls run in strips lengthwise of the leaves, and form bands three cells wide. Figure 2Aisan electron micrograph of mineral deposition in ashed leaf tissue of Distichlis spicata leaves. Mineral deposits occur in rows of elongate, serrated units with the longer dimension lengthwise of the leaf. There are also some small rectangular particles and some irregular oval particles. Examination of acid-treated deposits with a light microscope shows silica deposition to be in rows of elongate units, and it appears to be in cell walls. 50 Lanning and Eleuterius Figure 1. Scanning electron micrographs of ash deposits in Zizania aquatica leaves, A. Leaf surface showing all types of mineral deposition including rows of solid deposition (laige arrowhead), a row of bowtie-shaped phytoliths (large arrow), a row that appears to be bowtie-shaped phytoliths joined together at the sides (small arrow), oval phytoliths (small arrowhead), and open spaces that appear to be stomata (small long arrow). X 250. B. A portion of leaf tissue with oval particles (arrowhead) and stomata (small arrow). X 1000. C. A portion of leaf showing the row of bowtie-shaped phytoliths (large arrow). X 1000. D. A portion of leaf showing the row of bowtie-shaped phytoliths joined together (large arrow). X 1000. Heavy deposits of minerals occur in ridges lengthwise in Spartina alterniflora leaves. Ashed leaf tissue with a spongy deposition running continuously lengthwise of the leaf are shown in the electron micrograph of Figure 2B. Figure 2C, another electron micrograph of leaf tissue lengthwise of the leaf, shows a more Fibrous character of mineral deposition. An electron micrograph of acid-treated mineral deposits shows that silica deposition is largely fibrous in character with some irregular particles (Figure 2D), In Scirpus validus, deposits of minerals also occur in ridges lengthwise of the leaf, and rows of oval particles were observed with a light microscope. Silica occurs in a sheetlike Silica and Ash in several Marsh Plants 51 Figure 2. Scanning electron micrographs of ash deposits. A. Leaf surface showing deposits in Dhtichlis spicata. Note the rows of elongate, serrated units lengthwise of the leaf (large arrow), small rectangular particles (arrowhead), and irregular oval particles (small arrow). X 1000. B. Ash deposit from Spartina altemiflora leaf. Note the spongy deposition running continuously lengthwise of the leaf (large arrow). X 1000, C. Electron micrograph of Spartina altemiflora leaf. Note the fibrous character of mineral deposition (large arrow). X 1000. D. Silica in Spartina altemiflora leaf. Specimen was acid washed to remove other minerals. Note the fibrous character of the deposits (large arrow). X 125. pattern and in rows of oval particles. Limonium carolinianum leaves do not show a distinct pattern of mineral deposition other than heavier deposits in the veins. DISCUSSION Scirpus validus plants grown at St. George, Kansas, had con- siderably more silica in the leaves than those from Mississippi, and the latter had considerably more than those grown in Decatur County, Kansas. Dhtichlis spicata plants grown in Cloud County, Kansas, had twice as much silica in the leaves as those from Mississippi. These differences may be due to the amount of available silica in soils at the different locations. However, within a species genetic differences (local adapta- tion) in uptake capability may exist. Resolution of this question may be obtained by growing plants of the same species collected from widely separated localities in a common environment. Jones and Handreck (1965, 1969) 52 Lanning and Eleuterius contend that silica uptake is passive, but Barber and Shone (1966) obtained evidence that uptake of silica may be meta- bolic. Thus, environmental differences may account for variation between species. Attention should be focused on the fact that wild rice (Zizania aquatica ), a close relative taxonomically to culti- vated rice ( Oryza satinaf had the highest silica content of the plant species studied. This is an interesting discovery since highly bred cultivated rice also has the ability to accumulate large quantities of silica. Furthermore, silica of Zizania aquatica is deposited in a very unusual pattern. Spartina alterniflora had a relatively low silica content. Although this plant is often found with the lower portion submerged in water and is generally found on muddy shores, the collections analyzed in this study were from a very sandy area. The rectangular silica deposits in the leaf ridges of Spartina alterniflora may aid in reducing transpiration. Trans- piration presumably is lowered by increasing thickness and compactness of silica cellulose membranes in the epidermal cells (Yoshida et al. 1959). Leaves of Spartina alterniflora during periods of very high temperatures become rolled. Rectangular silica deposits also occur in Distichlis spicata linking these two grass species. The bowtie-or dumbbell- shaped silica deposits in Zizania aquatica are an entirely new type of structure, with no parallel in cultivated rice. The low silica content of Limonium carolinianum, a dicot- yledon, is consistent with previous evidence in that the mono- cotyledon analyzed had consistently higher silica contents. This preliminary study on grasses, sedges, and a dicot species, and previous work on the rush Juncus roemerianus, suggests that at least some of the information determined for cultivated plants also holds true for wetland species. However, each of the species investigated had peculiar depositional characteristics and various quantities of silica. Further study of wetland species is needed before there can be any clear understanding or definite statements relating our work to the agriculture literature and to that pertaining to upland species. In closing, we point out that the continued release of domestic sewage into estuarine waters is very likely to raise the nitrogen and phosphorous concentrations of wetlands soils. High nitrogen and phosphorous concentrations are known to decrease silica content of domestic plants as shown above with corresponding detrimental effects: weakened plants, reduced photosynthesis, and increased fungal and insect attacks. In view of these facts and possibilities, it is timely and prudent to carry out work that would lead to a better understanding of the role of silica in wetland and aquatic plant species. ACKNOWLEDGMENTS The authors thank Mr. L. J. Krchma for technical assis- tance in obtaining the scanning electron micrographs, and Mr. John Caldwell of the Botany Section, Gulf Coast Research Laboratory, for assistance in the field. REFERENCES CITED Ando, J. 1958. Phase diagrams of Ca3(P04)2'Mg 3 (P0ft)2 and Ca3(P04) 2 -CaNaP04 systems. Bull. Chem. Soc.Jpn. 31:201-205. Barber, D. A. & M. G. T. Shone. 1966. The absorption of silica from aqueous solutions by plants. / Exp. Bot. 1 7:569—578. Chen, C. H. & J. Lewin. 1969. Silicon as a nutrient element for Equisetum arvense. Can. J. Bot. 47:1 25- 131. Eleuterius, L. N. 1975. The life history of the salt marsh rush, Juncus roemerianus. Bull. Torrey Bot. Club 102:135-140. . 1976. The distribution of Juncus roemerianus in the salt marshes of North America. Chesapeake Sci . 17:289-292. Ishizuka, Y. 1971. Physiology of the rice plant. Adv. Agron. 23:241-315. Jones, L. H. P. & K. A. Handreck. 1965. Studies of silica in the oat plant. III. Uptake of silica from soils by the plant. Plant Soil 23:79 96. . 1967. Silica in soils, plants and animals. Adv. Agron. 19:107-149. . 1969. Uptake of silica by Trifolium in carna turn in relation to the concentration in the external solution and to transpiration. Plant Soil 30:71-80. Kolthoff, I. M. & E. B. Sandell. 1952. Textbook of Quantitative Inorganic Analysis. 3rd Edition. Macmillan & Co., New York, N Y. 759 pp. Lanning, F. C. 1972. Ash and silica in Juncus. Bull. Torrey Bot. Club 99: 196-198. & L. N. Eleuterius. 1978. Silica and ash in the salt marsh rush, Juncus roemerianus. Gulf Res. Rept. 6(2): 169-1 72. & Y. Y. Linko. 1961. Absorption and deposition of silica by four varieties of sorghum. J. Agric. Food Chem. 9:463-465. , B. W. X. Pannaiya & C. F. Crumpton. 1958. The chemical nature of silica in plants, Plant Physiol. 33:339 343. Lewin, J. & B. E. F. Reimann. 1969. Silicon and plant growth. Annu. Rev. Plant Physiol. 20:289-304. McWilliams, J. R. 1963. Selection for seed retention in Phalaris tuberosa L. Aust. J. Agric. Res , 14:755-764. Metcalfe, C. R. I960- Anatomy of the Monocotyledons. Oxford University Press, Amen House, London E.C.4. 715 pp. & L. Chalk. 1950a. Anatomy of the Dicotyledons. Volume 1. Oxford University Press, Amen House, London, pp. 1 -724. 1950b. Anatomy of the Dicotyledons. Volume 2. Oxford University Press, Amen House, London, pp. 725-1459. Monteith, J. L, 1966. Photosynthesis and transpiration of crops. Exp. Agric . 2:1-14. Mulder, E. G- 1954. Effect of mineral nutrition on lodging of cereals. Plant Soil 5:246—306. Ponnaiya, B. W. X. 1951. Studies in the genus sorghum: The cause of resistance in sorghum to the insect pest Antheriogna indica M. Madras University Journal XXI, Section B. No. 2:203-217. Ponnamperuma, F. N. 1964. Dynamic aspects of flooded soils and the nutrition of the rice plant. Pages 295-328 in The Mineral Nutrition of the Rice Plant. Johns Hopkins Press, Baltimore, Md. Russell, E- W. 1961. Soil Conditions and Plant Growth. 9th Edition. Longmans Green and Co., London. Sangster, A. G. 1978. Silicon in the roots of higher plants. Am. J. Bot. 65(9):929~935. Uber, F. M. 1940. Microincinecation and ash analysis. Bot. Rev. 6:204 226. Vlamis, J. & D. E. Williams. 1967. Manganese and silicon interaction in the Gramineae. Plant Soil 2:1 31 -140. Volk, R. J., R. P. Kahn & R.L Wcintraub. 1958. Silicon content of the rice plant as a factor influencing its xesistence to infection by the blast fungus, Piricularta oryzae. Phytopathology 48(4): 179 184. Yoshida, S., Y. Obnishi & K. Kilagishi. 1959. Role of silicon in rice nutrition. Soil Scl Plant Nutr. S(3):127-133. Gulf Research Reports Volume 7 | Issue 1 January 1981 Pseudomma heardi, a New Peracarid (Crustacea: Mysidacea) from Continental Shelf Waters Off Mississippi Kenneth C. Stuck Gulf Coast Research Laboratory DOI: 10.18785/grr.0701.08 Follow this and additional works at: http:/ / aquila.usm.edu/ gcr Part of the Marine Biology Commons Recommended Citation Stuck, K. C. 1981 .Pseudomma heardi, a New Peracarid (Crustacea: Mysidacea) from Continental Shelf Waters Off Mississippi. Gulf Research Reports 7 (l): 53-57. Retrieved from http:// aquila.usm.edu/gcr/vol7/iss 1/8 This Article is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf and Caribbean Research by an authorized editor of The Aquila Digital Community. For more information, please contact Joshua. Cromwell(2)usm.edu. Gulf Research Reports, Vol. 7, No. 1, 53-57, 1981. PSEUDOMMA HEARDI, A NEW PERACARID (CRUSTACEA: MYSIDACEA) FROM CONTINENTAL SHELF WATERS OFF MISSISSIPPI KENNETH C. STUCK Fisheries Research and Development Section, Gulf Coast Research Laboratory . Ocean Springs, Mississippi 39564 ABSTRACT Pseudomma heardi n. sp. is described and illustrated. Specimens were obtained from plankton samples taken in 18 to 60 meters depth in offshore waters of Mississippi. This new species can be distinguished from other species of Pseudomma by the presence of 16 to 21 serrations on the anterior and lateral margins of the ocular plate, strong lateral spine of antennal scale which extends well beyona apex of scale and 4 to 6 spines on lateral margins of telson. INTRODUCTION The offshore mysid fauna of the Gulf of Mexico is poorly known. While approximately 28 species of mysids have been reported from Gulf waters {Tattersall 1951; Brattegard 1969, 1970; Stuck et al. 1979a; Stuck and Heard 1981), the majority arc known only from estuarine and nearshore waters. Examination of plankton samples taken in offshore waters of Mississippi revealed the presence of an undes- cribed species of mysid referable to the genus Pseudomma Sars, 1879. Stuck et al. (1979a) first recorded the occurrence of the present species of Pseudomma from eastern Gulf of Mexico waters. A brief description of the female{Stuck et al. 1979b) was presented; however, a complete description awaited the collection of male specimens. Sars (1870) erected the genus Pseudomma within the tribe Erythropini to include two species,/’, affine Sars, 1870 and P. roseum Sars, 1870. Murano (1974) reviewed the genus, described 1 1 new species from the central and western Pacific and provided a key for the identification of 34 species. Pseudomma californica Bacescu and Gleye, 1979 has since been described from California waters (Bacescu and Gleye 1979). With the addition of the present material, the genus now contains 36 species. All species of Pseudomma are easily distinguished from other species of Erythropini by the possession of a large ocular plate formed by the fused eyestalks which lacks a prominent spinous process on its anterolateral margin. MATERIALS AND METHODS Specimens used in the present study were obtained from plankton samples collected from continental shelf waters off Mississippi through a National Marine Fisheries Service grant, Public Law 88-309, Project 2— 42-R. Samples were obtained using a 0.5 m plankton net with 0.5 mm mesh netting and equipped with flow meter and opening-closing device. Simultaneous surface, midwater, and bottom samples were taken at each sampling site. Measurements of total length were made from the anterior margin of the Manuscript received March 4. 1981 ; accepted April 2. 1981. rostral plate to the distal tip of the telson. The holotype and one paratype specimen were deposited in the United States National Museum of Natural History (USNM), Washington, D.C. Additional paratype material has been deposited in the museum of the Gulf Coast Research Laboratory, Ocean Springs, Mississippi. TAXONOMIC DESCRJPTION Pseudomma heardi new species Pseudomma sp., Stuck et al. 1979b: p.233, figs. 2e, 3e,4e, 5e Material Examined - 2 males (3.8 mm, 3.7 mm); 3Q°02'30"N, 88°'10'15"W; bottom water plankton tow; depth 18 meters; 1 1-20-68. 1 female (3,8 mm); 29°42'00"N, 88°27'30"W; mid water plankton tow; depth 37 meters; 11-12-68. 2 females (3.5 mm, 3.7 mm); 29°24 15"N, 88° 1 7*00 "W; bottom water plankton tow; depth 60 meters; 1 1 - 20 - 68 . Diagnosis - Lateral tooth of antennal scale extending well beyond apex. Anterior and lateral margins of ocular plate with 16 to 21 coarse teeth. Terminal segment of endopod of male fourth pleopod without single long modified seta. Endopods of uropods extending well beyond distal tip of telson, slightly shorter than exopods. Lateral margin of telson with 4 to 6 spine-like serrations, apex armed with 3 pairs of long spines increasing in length medially. Description General body form (Figure 1) — slender, small, adult males and females to 3.8 mm; thorax and abdomen dis- tinctly separate. Anterior margin of carapace evenly convex, anterolateral comers rounded; dorsal gastric region just anterior to cervical sulcus swollen in appearance; posterior margin emarginate, exposing eighth thoracic segment. Frontal lamina (Figure 2A) — scarcely visible below ocular plate in dorsal view, anterior margin armed with about 13 dorsally pointed serrations. Antennular peduncle (Figure 2B) more robust in males than females, first segment twice length of second, slightly 53 54 Stuck shorter than third; dislolaleral margin of first segment somewhat produced, bearing pair of large plumose setae and pair of smaller simple setae; distomedial margin of second segment hearing pair of large plumose setae and several simple setae; distolateral margin of third segment with few simple setae, distomedial margin with I or 2 plumose setae and pair of simple setae, males with densely setose lobe on ventral margin; flagellum typical of genus. Antennal scale (Figure 2C) - about 3.8 times as long as maximum width, lateral margin straight, devoid of setae, ending in strong lateral tooth which extends well beyond apex, inner margin and apex setose; second and third seg- ments of peduncle subequal in length, distomedial margin of third segment bearing cluster of simple setae, outer margin with single simple seta, second segment with pair of stout plumose setae and single long simple seta on disto- inedial margin; first segment very small, barely distinguish- able from sympod; flagellum typical of genus. Eyestalks fused into large rectangular ocular plate, cleft in midline, anterior and lateral margins armed with 16 to 21 coarse teeth. Mandible (Figure 2D) — typical of genus; palp with enlarged second segment, bearing row of about 8 plumose setae on inner margin, outer margin with about 12 long simple setae and several plumose setae; third segment about 0.6 times as long as second, reduced in width, bearing row of about 18 pectinate setae on posterior margin and a single long barbed, curved spine distally. Maxillule (Figure 2E) - typical of genus; inner lobe with 3 large spined “setae'’ and several smaller simple and plumose setae; outer lobe with about 10 stout, serrate apical spines and cluster of 3 plumose subapical setae. Maxilla (Figure 2F) - typical of genus, exopod large, bearing about 1 1 plumose setae along outer margin ; endopod 2-segmented, bearing about 15 long plumose setae on apex and inner margin; third sympodal segment trilobed, bearing numerous serrate spines and plumose setae; lobe of second sympodal segment enlarged, hearing about 25 long plumose setae on distal margin. Endopod of first thoracic limb (Figure 3A) robust, dactyl bearing strong simple spine on distal tip, posterior margin bearing two strong serrate “setae.” anterior margin with cluster of 4 plumose setae; carpo-propodus subequal in length with merus and ischium, bearing cluster of 3 plumose setae and single simple seta on posterior distal corner, one plumose seta on anterior margin; posterior margins of merus, ischium and preischium with 8, 7, and 5 stout plumose setae, respectively, decreasing in length proximally, anterior margins of each segment with single plumose seta; posterior margin of basis pubescent, bearing pair of plumose setae on inner, lateral, and distal margins. Endopod of second thoracic leg (Figure 3B) - stout; dactyl one-half length of carpo-propodus, with strong simple spine on distal lip, anterior margin bearing 5 plumose “spines” and single simple seta, posterior margin with Figure 1. Entire body, dorsal (3.7 min male). A New Species of Psfajdomma 57 plumose setae; merus slightly longer than carpo-propodus, twice length of ischium. Endopod of third thoracic leg (Figure 3C) - slender; dactyl bearing simple spine on distal tip, partially obscured by dense duster of simple and plumose setae extending from distal margin of propodus; distal margin of carpus also with cluster of simple setae; anterior margins of ischium, merus, and carpus with scattered clusters of simple setae. First male pleopod (Figure 3D) with 1 -segmented endopod bearing 4 plumose setae distally and pseudo- branchial lobe furnished with 4 plumose setae, exopod 7 -segmented, Fourth male pleopod (Figure 3E) - with 7-segmented endopod bearing pseudobranchial lobe similar to first pleopod; lacking extremely long simple seta on terminal segment; exopod 7-segmented. All pleopods of female reduced to simple setose, uni- ramous plates. Uropods (Figure 3F) - slender, exopod about 1.25 times as long as endopod, 1 .6 times as long as telson; exopods and endopods devoid of spines, setose along both inner and outer margins. Telson (Figure 3G) linguiform, shorter than sixth abdominal segment, apex armed with 3 pairs of spines increasing in length medially and a pair of delicate plumose setae, apical spines longer in males than females, lateral margins slightly concave, bearing 4 to 6 “serrations,” Holotype - USNM 181984, male (3.8 mm); 30°02'30"N;88°40'I5''W. Paratype - USNM 181985, female (3.8 mm); 29°42'00"N;88°27'30"W. Type habitat — Mid- and bottom-water plankton in 18 to 60 meters depth, continental shelf waters off Mississippi coast. Etymology - This species is named in honor of Richard Heard in recognition of his work on Crustacea of the northern Gulf of Mexico. Remarks Pseudornma heartli n. sp. appears to fit best into the Affine species group (sensu Murano 1974). This group is characterized by serrate eyeplates and telsons with 3 to 6 lateral and 3 or 4 pairs of apical spines. Certain peculiarities should, however, be noted in the present species. A vertically descending serrated frontal lamina beneath the ocular plate as illustrated here has not been noted in other species of the genus. The lateral margins of the telson in all specimens examined did not bear distinct spines, but rather appeared serrate as i nP. crassidentatum Murano (1974, Fig. I8e). The following combination of characters best distinguish P. heardi from the other described species of Pseudornma'. 1. Ocular plate with 16 to 21 teeth on the anterior and lateral margins. 2. Lateral tooth of antennal scale extending well beyond apex. 3. Pleopods of male with endopods and exopods sub- equal in length and not bearing long specialized setae on terminal segments. 4. Telson with 4 to 6 serrations on lateral margins and 6 apical spines. Pseudornma heardi is the first species of Pseudornma reported from Gulf of Mexico waters. Three species, P. truncatum, P. affine , and P. roseum , have been reported from the western North Atlantic (Tattcrsall 1951), Murano (1974) has described the habitat of the genus Pseudornma as living on or close to the seafloor, having taken most species by bottom-water plankton nets and from the stomachs of benthic fishes. Wigley and Burns (1971) reported P. affine from benthic samples taken from the Gulf of Maine and south of Georges Bank. They reported the bathymetric range of all records from the North Atlantic as 80 to 914 meters. While very few specimens of P. heardi were obtained, all were taken from bottom and midwater plankton samples in relatively deep shelf waters. ACKNOWLEDGMENTS 1 thank Lucia O’Toole of the Gulf Coast Research Laboratory Word Processing Office for her assistance in preparation of the manuscript. This work was supported through a grant from the Department of Commerce, NOAA, National Marine Fisheries Service, under Public Law 88-309, Projects 2 42 R and 2— 215 R. REFERENCES CITED Bacescu, M. & L. G. Gleye. 1 979. New mysidaeea from the Californian waters. Trav. Mus. Hist. Nat. ‘Grigore Antipa' 20(1): 131-141. Brattegard, T. 1969. Marine biological investigations in the Bahamas. 10. Mysidaeea from shallow water in the Bahamas and southern Florida. Part 1. Sarsia 39: 1 7 106. . 1970. Marine biological investigations in the Bahamas. 1 1. Mysidaeea from shallow water in the Bahamas and southern Florida. Pari 2 . Sarsia 41:1-35. Murano, M, 1974. Mysidaeea from the central and western Pacific. I. Genus Pseudornma (Tribe Erythropini). Pu hi Seto Mar. Biol. Lab . 21(5) 287 343. Sars, G. O. 1870, Carcinologiske Bidrag til Norges Fauna. 1. Mono- graph! over de ved Norges f auna Kyster forckommende Mysider. Hefte UnfallheilkD 1:1 64 Stuck, K. C., H. M. Perry & R. \V. Heard. 1979a. Records and range extensions of Mysidaeea from coastal and shelf waters of the eastern Gulf of Mexico, Gulf Res. Kept. 6(3):293 248. __ 1979b. An annotated key to the mysidaeea of the north central Gulf of Mexico. Gulf Res. Rept. 6(3):225 238. Stuck, K. C. & R W. Heard. 1981. Aina thimy sis hratlegardi. a new peracarid (Crustacea. Mysidaeea) from continental shelf waters off Tampa Bay, Florida. J. Crust. Biol (tn press). Tattersall, \V. M. 1951, A review of the Mysidaeea of the United States National Museum, U.S. Nat. Mus. Bull. 201 : 1 292. Wigley, R. L. & B. R. Burns. 1971. Distribution and biology ot ntysids (Crustacea, Mysidaeea) from the Atlantic coast of the United Stales in the NMFS Woods Hole collection. U.S. Fish Wildl. Serv. Fish. Bull. 69(4):7 1 7 - 746. Gulf Research Reports Volume 7 | Issue 1 January 1981 Trends in Ex- Vessel Value and Size Composition of Reported May - August Catches of Brown Shrimp and White Shrimp from the Texas, Louisiana, Mississippi, and Alabama Coasts, 1960-1978 Charles Wax Caillouet National Marine Fisheries Service , Galveston Dennis Brian Koi National Marine Fisheries Service, Galveston DOI: 10.18785/grr.0701.09 Follow this and additional works at: http://aquila.usm.edu/gcr Part of the Marine Biology Commons Recommended Citation Caillouet, C. W. and D. B. Koi. 1981. Trends in Ex- Vessel Value and Size Composition of Reported May - August Catches of Brown Shrimp and White Shrimp from the Texas, Louisiana, Mississippi, and Alabama Coasts, 1960-1978. Gulf Research Reports 7 (l): 59-70. Retrieved from http://aquila.usm.edu/gcr/vol7/issl/9 This Article is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf and Caribbean Research by an authorized editor of The Aquila Digital Community. For more information, please contact Joshua.Cromwell(3)usm.edu. Gulf Research Reports, Vol. 7, No. 1, 59-70, 1981. TRENDS IN EX-VESSEL VALUE AND SIZE COMPOSITION OF REPORTED MAY-AUGUST CATCHES OF BROWN SHRIMP AND WHITE SHRIMP FROM THE TEXAS. LOUISIANA, MISSISSIPPI, AND ALABAMA COASTS, 1960-1978' CHARLES WAX CAILLOUET AND DENNIS BRIAN KOI National Marine Fisheries Service, Galveston Laboratory Galveston, Texas 77550 ABSTRACT Exponential models were used to characterize (1) ex-vessel value (in dollars) per shrimp by size category (count; i.c., number of shrimp per pouud, heads off); (2) size composition (expressed as cumulative weight of the catch in pounds, heads off, by size category); and (3) ex-vessel value composition (expressed as cumulative ex-vessel value, in dollars, of the catch by size category) for reported May August catches (inshore and offshore combined) of brown shrimp ( Penacus aztecus) and white shrimp ( P . setiferus) from the Texas, Louisiana, Mississippi, and Alabama coasts (statistical areas 10-21) from i960 to 1978, Exponents of the models were used as indices to investigate trends in ex-vessel value per shrimp, size composition, and ex-vessel value composition of the May- August catches during this period. This approach to analysis of catch statistics can be used to monitor these fisheries, and the results can be compared with changes that may be brought about by the closure of the fishery conservation zone off Texas, as proposed by 1981 by the Gulf of Mexico Fishery Management Council, in the fishery management plan for the shrimp fishery of the Gulf of Mexico. INTRODUCTION The fishery management plan for the shrimp fishery of the Gulf of Mexico, prepared by the Gulf of Mexico Fishery Management Council (GMFMC 1980), proposed a simul- taneous closing of the territorial sea of the Stale of Texas and the adjacent fishery conservation zone (FCZ) to shrimping during the time of the year when brown shrimp (Penaeus aztecus ) in these waters are, for the most part, smaller than 65 count (refers throughout this paper to number of shrimp per pound, heads removed). The territorial sea is the area under state jurisdiction extending from the coastal baseline to 9 nautical miles off Texas (Figure 1). The FCZ is the area under federal jurisdiction beginning at the outer limit of Texas" territorial sea and extending 200 miles from shore. The closing of Texas" territorial sea to shrimping normally begins June 1 and extends to July 15, However, a 15-day flexibility in the closing and opening dates is allowed to accommodate effects of climatic variations on shrimp growth, within the restriction that the period of closure does not exceed 60 days. The inclusive dates for the closure in 1981 were May 22- July 1 5. The management plan encouraged the State of Texas to continue its seasonal closure of the territorial sea, to eliminate minimum size restrictions on shrimp caught in open waters before and after the closure, and to evaluate the effect of allowing white shrimp [P. setiferus) fishing to continue within the closed areas during the closure. Rationale for the proposed closure was an expected increase in yield from additional growth of the protected brown shrimp, and from the elimination of waste due to discarding of undersized brown shrimp in the FCZ Contribution No. 81-24G from the Southeast Fisheries Center, Galveston Laboratory, National Marine Fisheries Service, NOAA. Manuscript received March 24, 1 981 .accepted June 15, 1981. (GMFMC 1980). The management plan recognized that the closure might affect other fishing areas (e.g., the coasts of Louisiana, Mississippi, and Alabama) by shifting fishing effort to those areas. Therefore, it was the intent of the management plan that the biological, ecological, social and economic impacts of the closure be monitored in 1981 so that revisions could be made if warranted. Figure 1. Boundaries of statistical areas 10-21, the Texas territorial sea, and the fisheries conservation zone off Texas (based on Infor- mation from GMFMC 1980). As might be expected, the proposed closure of the FCZ off Texas has become a highly controversial issue. There is considerable interest and concern on the part of the fishing industry, the Gulf states, the GMFMC, the National Marine Fisheries Service (NMFS), and fishery scientists regarding the potential impacts of the proposed closure. We expect that the redistribution of fishing effort, the changes in fishing strategy , and the additional shrimp growth that may result from the closure will cause changes in size composition of the combined inshore and offshore catch. 59 60 Caillouet AND KOI Inshore waters generally are considered to be landward of the barrier islands, and are represented by bays or estuaries. Offshore waters are seaward of the barrier islands. According to Henderson (1972) and Ricker (1975), an increase in average size of individuals in the catch could indicate a decrease in mortality (usually equated with a decrease in fishing mortality) or an increase in growth (e.g., if recruit- ment were poor, and if population density were low as a consequence). A decrease in average size might be brought about after the closure by retention and landing of large quantities of small shrimp, previously discarded at sea. Also a decrease in average size might be caused by an intensifi- cation of fishing in offshore and inshore waters open to shrimping in other areas during the closure. Socioeconomic factors leading to changes in strategies of fishing, culling of the catch, and marketing of the landings also could influence size composition of the catch. Caillouet et al. (1980) developed a simple exponential model to characterize the size composition (expressed as cumulative percentage of weight of catch by size category) of annual catches of shrimp. They showed that the size of brown and white shrimp in the reported annual catches from Texas and Louisiana decreased from 1959 to 1976. Caillouet and Koi (1980) modified the model by applying it to cumulative weight by size category instead of cumula- tive percentage of weight by size category, and used it to investigate trends in size composition of the annual landings of brown, pink (P. duorarum ), and white shrimp from the Gulf and southeast coast fisheries of the United States from 1961 to 1977. Caillouet and Koi (1980) also used exponen- tial models to investigate trends in ex-vessel value per shrimp by size category, size composition, and ex-vessel value composition of these annual landings. Usiug the methods of Caillouet and Koi (1980), Caillouet and Koi (1981) investigated trends in ex-vessel value per shrimp by size category, size composition, and ex -vessel value compo- sition of reported annual catches of pink shrimp from the Tortugas fishery off south Florida from 1960 to 1978. The effect of shrimp size on the ex-vessel value of the catch has also been recognized by Neal (1967), Griffin et al.(1974), Griffin and Nichols ( 1 976), and Griffin et al. ( 1 976). The NMFS has the responsibility for monitoring impacts of closing the FCZ off Texas. The purposes of this paper are to propose a procedure for monitoring the brown and white shrimp fisheries of Texas, Louisiana, Mississippi, and Alabama, based on the methods of Caillouet and Koi (1980), and to use these methods to investigate trends in ex-vessel value per shrimp by size category, size compo- sition and ex-vessel value composition of the reported May- August catches from 1960 to 1978. This approach can then be used as one means of assessing the impacts of closing the FCZ off Texas in 1981. The period May-August was chosen for these analyses to assure that the period of closure of Texas' territorial sea and the FCZ would be encompassed, considering the allowed flexibility in the starting and ending dates for the closure, including May and August in the time interval of coverage for the years 1960— 1978 will assure that some catch statistics will be available from the Texas coast for future comparison with those from Louisiana, Mississippi, and Alabama for the May- August period in 1981. DESCRIPTION OF DATA Summaries of the May— August catches of brown and white shrimp and their ex -vessel value were compiled from data files available from the NMFS, Southeast Fisheries Center (SEFC) Technical and Information Management Services (TIMS), Miami, Florida. The combined weight of the reported May-August catches (inshore and offshore combined) was expressed in pounds (heads off) and the ex- vessel value in dollars, by year (1960-1978); coastal area (statistical areas 10-12, 13-17, and 18—21, Figure 1); species (brown and white shrimp); and size category (< 15, 15-20, .21-25, 26-30, 31-40, 41-50, 51-67, and ^ 68 count, and “pieces," representing parts of shrimp tails that could not be assigned to a count category). Comparable data for the years 1979 through 1981 were not available at the time of this writing. The three coastal areas are defined as (1) Texas coast (statistical areas 18-21 combined); (2) Mississippi River to Texas (statistical areas 13—17 combined), representing that part of the Louisiana coast west of the Mississippi River; and (3) Pensacola to the Mississippi River (statistical areas 10-12 combined), representing that part of the Louisiana coast east of the Mississippi River, the Mississippi coast, the Alabama coast, and a small part of the upper coast of Florida (catches from Pensacola Bay are not included in this area; they are allocated to the adjacent Apalachicola area by TIMS). Note that part of statistical area 17 is included in the area that was. closed in 1981 (Figure 1). Therefore, for the years 1960 to 1978, the May-August catch statistics for the Mississippi River to Texas coastal area represent a somewhat larger zone open to shrimping than was the case in 1981, as a result of the closure. This should be considered in any future analyses applying our methods to data for the Mississippi River to Texas coastal area. English rather than metric units are used throughout our paper because they have been used historically, and infor- mation would have been lost in their conversion to metric units. Catches used herein represent those portions of the actual catches that were landed by domestic commercial fishermen at domestic ports and reported by the National Marine Fisheries Service or its predecessor, the Bureau of Commercial Fisheries, U.S. Fish and Wildlife Service. ANALYSES AND RESULTS May -August Catches by Year The general trends in reported May-August catches, and Value and Size of Brown and White Shrimp 61 their ex-vessel value for both species and the three coastal areas are shown in Figures 2 through 7. In each coastal area, the catch of brown shrimp exceeded that of white shrimp. The general trends in catch were upward, except for white shrimp from Pensacola to the Mississippi River (Figure 7) for which the trend was downward. In all cases, the general trend in ex-vessel value of the catch was upward, but this was not adjusted to account for inflation. May -August Ex-vessel Value per Shrimp by Size Category We calculated the May-August average ex-vessel value per shrimp, V, by size category, C, for each year, according to the methods of Caillouet and Koi( 1980, 1981), to obtain the following exponential model which described the Figure 2. Weight (millions of pounds, heads off) and ex-vessel value (millions of dollars) of reported May August catches (inshore and offshore combined) of brown shrimp from the Texas coast (statistical areas 18-21 combined), 1960-1978. YEAR Figure 3. Weight (millions of pounds, heads off) and ex-vessel value (millions of dollars) of reported May-August catches (inshore and offshore combined) of white shrimp from the Texas coast (statistical areas 18-21 combined), 1960-1978. relationship between Vj and Q for each species, coastal area, and year: Vj = a (exp bCj) (1) where V[ = May-August average ex-vessel value per shrimp for the ith size category ; Cj = lower limit (count) of the ith size category (Ci = 15, C 2 - 21, C 3 - 26, C 4 = 31, C s =41, C 6 = 51, and C 7 “ 68); and 1=1,2,..., 7. The logarith- mic form of model 1 was used to estimate parameters a and b by linear regression (Tables 1 through 3). The very high coefficients of determination, r 2 , indicated that the straight lines fitted the data very well. All slopes, b, were negative, showing that the value per Figure 4. Weight (millions of pounds, heads off) and ex -vessel value (millions of dollars) of reported May- August catches (inshore and offshore combined) of brown shrimp from the Mississippi River to Texas (statistical areas 13-17 combined), 1960-1978. Figure 5. Weight (millions of pounds, heads off) and ex-vessel value (millions of dollars) of reported May-August catches (inshore and offshore combined) of white shrimp from the Mississippi River to Texas (statistical areas 13-17 combined), 1960-1978. 62 CAILLOUET AND KOI i960 1962 190-4 1966 1968 1970 1972 1974 1976 1 9?8 YEAR Figure 6. Weigh! (millions of pounds, heads off) and ex -vessel value (millions of dollars) of reported May-August catches (inshore and offshore combined) of brown shrimp from Pensacola to the Missis- sippi River (statistical areas 10-12 combined), 1960-1978. TABLE 1. Relationship between transformed ex-vessel value (dollars) per shrimp, InV, and count, C, for reported May-August catches (inshore and offshore combined) of brown and white shrimp from the Texas coast (statistical areas 18-21 combined), 1960-1978.* Year Brown Shrimp White Shrimp a b i 2 a b r 2 1960 0.07492 -0.04629 0.966 0.07379 -0.04900 0,939 1961 0.08534 -0.04876 0.992 0.07594 -0.04376 0.992 1962 0.12142 -0.04926 0.994 0.11820 -0.05124 0.985 1963 0.11596 -0.05782 0.987 0.09864 -0.05236 0.957 1964 0.09822 -0.05076 0.985 0.09053 -0.04974 0.980 1965 0.11088 -0.05347 0989 0,09313 -0.04807 0.982 1966 0.15149 -0.05204 0.986 0.12842 -0.04775 0.993 1967 0.11772 -0.05380 0.981 0.11758 -0.05076 0.957 1968 0.16950 -0.05686 0.983 0.12651 -0.04732 0.926 1969 0.18600 -0.05580 0.992 0.19635 -0.06037 0.995 1970 0.17010 -0.05730 0.988 0.15597 -0.05546 0.979 1971 0.25218 -0.05918 0.987 0.19029 -0.04982 0.981 1972 0.26745 -0.05896 0.992 0.27621 -0.05965 0.985 1973 0.30651 -0.05136 0.993 0.23322 -0.04344 0.996 1974 0.29912 -0.06135 0.962 0,31702 -0.06005 0.968 1975 0.37610 -0.05334 0.995 0.36948 -0.05330 0.997 1976 0.59955 0.06131 0.982 0.57544 -0.05680 0.989 1977 0.51261 -0.05869 0.981 0.53091 -0.05931 0.968 1978 0.59723 -0.05899 0.996 0.41271 -0.04753 0.967 ♦Based on the linear regression of InV on C, where V = May-August average ex-vessel value per shrimp in each of seven size categories, C = lower limit (count) of each of the seven size categories, in(a) = intercept, b = slope, and r 2 = coefficient of determination; all slopes, b, were significantly different from 0 at the 99% level of confidence, and the high r 2 values indicated a very good fit of the straight lines to the data points. ' ■ 5_ I PENSACOLA TO THE MISSISSIPPI RIVER J WHITE SHRIMP 1960 1962 1964 1966 1968 1970 1972 197-4 1976 1978 YEAR Figure 7. Weight (millions of pounds, heads off) and ex-vessel value (millions of dollars) of reported May-August catches (inshore and offshore combined) of white shrimp from Pensacola to the Missis- sippi River (statistical areas 10-12 combined), 1960-1978. TABLE 2. Relationship between transformed ex-vessel value (dollars) per shrimp, InV, and count, C, for reported May-August catches (inshore and offshore combined) of brown and white shrimp from the Mississippi River to Texas (statistical areas 13-17 combined), 1960-1978.* Year Brown Shrimp White Shrimp a b r 2 a b r 2 1960 0.07177 -0.04518 0.960 0.08062 0.04922 0.950 1961 0.07807 -0.04540 0.976 0.07230 -0.04069 0.987 1962 0.10589 0.04496 0.982 0.10262 -0.04317 0.964 1963 0.10710 -0.05525 0.979 0.11971 -0.05634 0.954 1964 0.09336 -0.05032 0.977 0.08392 -0.04693 0.958 1965 0.09448 -0.04770 0.980 0.09079 -0.04550 0.975 1966 0.13860 -0.04983 0.993 0.11432 -0.04402 0.977 1967 0.11373 -0.05142 0.978 0.13192 -0.05004 0.967 1968 0.16711 -0.05673 0.983 0.15812 0.05335 0.974 1969 0.18027 -0.05456 0.993 0.16861 -0.05167 0.982 1970 0.16396 -0.05586 0.983 0.15779 -0.05146 0.979 1971 0.26244 -0.06079 0.991 0.22663 -0.05676 0.988 1972 0.25174 -0.05603 0.991 0.27206 -0.05543 0.981 1973 0.28208 -0.04830 0.996 0.23883 0.04253 0.991 1974 0.31893 -0.06200 0.963 0.34038 -0.06098 0.953 1975 0.44343 -0.05921 0.998 0.39411 -0.05521 0.997 1976 0.54890 -0.05990 0.990 0.64588 -0.06011 0.992 1977 0.50268 -0.05870 0.979 0.51734 -0.05844 0.971 1978 0.55672 -0.05896 0.998 0.47111 -0.05203 0.990 ♦Based on the linear regression oflnV on C ( where V= May-August average cx-vessel value per shrimp in each of seven size categories, C - lower limit (count) of each of the seven size categories, In (a) = intercept, b = slope, and r 2 = coefficient of determination; all slopes, b, were significantly different from 0 at the 99% level of confidence, and the high r 2 values indicated a very good fit of the straight lines to the data points. Value and Size of Brown and White Shrimp 63 TABLE 3. Relationship between transformed ex vessel value (dollars) per shrimp, InV, and count, C, for reported May-August catches (inshore and offshore combined) of brown and white shrimp from Pensacola to the Mississippi River (statistical areas 10-12 combined), 1960-1978.* Yeax Brown Shrimp White Shrimp a b r 2 a b r 2 1960 0 06459 -0.04092 0.950 0.07132 -0.04533 0.954 1961 0,06892 -0.04052 0.953 0.06839 -0.03821 0.965 1962 0.09940 -0.04296 0.953 0.09536 -0.04022 0.962 1963 0.08738 0.04806 0.951 0.09655 -0.05245 0.950 1964 0.08482 -0.04654 0.963 0.08617 -0.04676 0.977 1965 0.08664 -0.04376 0.956 0.08619 -0.04278 0.944 1966 0.12705 -0.04682 0,986 0.11061 -0.04302 0.956 1967 0.09783 -0.04687 0.952 0.12206 -0.05243 0.929 1968 0.15802 -0.05362 0.974 0.14762 -0.05040 0.963 1969 0.16800 -0.05224 0.981 0.14203 -0.04660 0.940 1970 0.14682 -0.05182 0.966 0.14364 -0.05006 0.951 1971 0.24106 -0.05768 0.982 0.21810 -0.05502 0.984 1972 0.23786 -0.05198 0.974 0.03587 0.0 191 7f 0.063f 1973 0.29481 -0.04925 0.991 0.25034 -0.04056 0.995 1974 0.31528 -0.05927 0.968 0.34052 -0.06087 0.943 1975 0.38841 -0.05390 0.996 0.34995 -0.05095 0.987 1976 0.54194 -0.05741 0.980 0,54105 -0.05609 0.966 1977 0.47724 -0.05660 0.967 0.50089 -0.05739 0,977 1978 0.50039 -0.05555 0.995 0.43380 -0.04895 0.987 *Based on the Linear regression of InV on C, where V = May- August average ex-vessel value per shrimp in each of seven size categories, C = lower limit (count) of each of the seven size categories, ln(a) = intercept, b — slope, and r = coefficient of determination; all slopes, b, except one, were significantly different from 0 at the 99% level or confidence, and the high r 2 values indicated a very good fit of the straight lines to the data points. fThe slope, b, for white shrimp in 1972 did not differ significantly from 0 at the 95% level of confidence, and the r 2 value was very low, because no catch was reported for the 5 s 68 count category. shrimp decreased with increase in count (decrease in size), as expected. Lower limits rather than midpoints or upper limits of the seven size categories were used in constructing model 1, as in Caillouet and Koi (1980, 1981). The < 15 category represented < 3% of the May— August catches of brown shrimp in each of the three coastal areas in any given year. However, for white shrimp, the < 15 category represented as high as 23% of the May-August catches from the Texas coast, 15% from the Mississippi River to Texas, and 28% from Pensacola to the Mississippi River in certain years. We did not include the < 15 size category in model 1 to be consistent with previous work, and because the logarithmic form of model 1 Is not a straight line in the region of < 1 5 count (Caillouet and Koi 1980, 1981 ; Caillouet et al. 1980), The category “pieces” was excluded from the model because it represented parts of shrimp tails which could not be assigned to a count category. The constant, a, reflected the elevation of the straight line which was influenced in part by our use of lower limits of size categories and exclusion of the < 15 size category in fitting the model. The slope, b, of the straight line is a simple index of the ex-vessel price spread among the size categories of shrimp, i.e., it is an index of ex-vessel price structure. There were significant downward trends in b for brown shrimp in all three coastal areas, and for white shrimp in all coastal areas except the Texas coast from 1960 to 1978 (Table 4). For white shrimp from the Texas coast, the general trend was downward, but it was not statistically significant. The downward trends indicated that the May- August ex-vessel price spread among the size categories of shrimp increased from 1960 to 1978. Whitaker (1973) also observed an increase in price spread between large and small “southern” shrimp during the period from 1957 to 1971. The data point for 1972 was excluded from calcula- tion of the trend for white shrimp from Pensacola to the Mississippi River because no catch was reported for the ^ 68 count category in 1972 and, therefore, the fit of the model was poor (Table 3). May-August Cumulative Catch by Size Category We calculated the cumulative weight, P, of the May August catch in each of the same seven size categories, for each species, coastal area, and year (see Caillouet and Koi 1980, 1981), These catches were cumulated, starting with the size category of smallest shrimp (highest count, > 68) and continuing toward the size category of largest shrimp (lowest count, 15-20). The following exponential model described the relationship between Pj and C[ for each species, coastal area, and year: Pi = c (exp dCi) (2) where Pj = cumulative weight of the May August catch in the ith size category. The logarithmic form of model 2 was used to estimate parameters c and d by linear regression (Tables 5 through 7). The coefficients of determination for the straight lines were very high. All slopes, d, were negative, which reflected the construction of model 2 by cumulating catches from small- to large-shrimp si 2 e categories (see Caillouet and Koi 1980, 1981). There were significant upward trends in d for brown shrimp, but no significant trends in d for white shrimp, in all three coastal areas from 1960 to 1978 (Table 4). The upward trends indicated that the size of brown shrimp in the reported May-August catches decreased from 1960 to 1978, The values of d for brown and white shrimp from the Texas coast (Table $) were lower ihan those from the other two coastal areas (Tables 6 and 7), indicating that the shrimp in the May August catch from the Texas coast generally were larger than those in the other two coastal areas. The data point for 1972 was excluded from calcula- tion of the trend for white shrimp from Pensacola to the Mississippi River (Table 7) as in the previous section. 64 CAILLOUET AND KOI TABLE 4. Trends in ex-vessel value (dollars) per shrimp by size category, in cumulative catch (pounds, heads off) by size category, and in cumulative ex-vessel value (dollars) of catch by size category, for reported May August catches (inshore and offshore combined) of brown and white shrimp from the Texas coast, the Mississippi River to Texas, and Pensacola to the Mississippi River during 1960-1978 (based on data from Tables 1-3, 5-7 and 9-1 1). For ex -vessel value For cumulative For cumulative per shrimp by size catch by size ex-vessel value of Species Coastal Area category category catch by size category Brown Shrimp Texas Coast Trends 1 Trend coefficients -0.0006 2 0.0024 2 0.0022 2 of determination 0.532 0.560 0.505 Brown Shrimp Mississippi River to Texas Trends Trend coefficients -0.0008 2 0.0003 2 0.0001 of determination 0.632 0.362 0.030 Brown Shrimp Pensacola to Mississippi River Trends Trend coefficients -0.0009 2 0.00 10 2 0.0006 of determination 0.770 0.405 0.191 White Shrimp Texas Coast Trends Trend coefficients -0.0004 0.0003 -0.0001 of determination 0.179 0.006 0.000 3 White Shrimp Mississippi River to Texas Trends Trend coefficients -0.0007 2 0.0009 0.0003 of determination 0.378 0.160 0.017 White Shrimp Pensacola to Mississippi River Trends Trend coefficients -0.0007 2 -0.0006 -0.0015 4 of determination 0.365 0.086 0.294 Represents slopes of the linear regressions of b,d,and h, respectively, onx, where x represents the last two digits of each year, 1960-1978. The values b, d, and h are defined in Tables 1-3, 5-7, and 9-1 1, respectively. Data for 1972 were excluded from regressions for white shrimp from Pensacola to the Mississippi River (see Tables 3, 7, and 11). 2 The trend (slope) was significantly different from 0 at the 99% level of confidence. 3 Indicates >0.000 but *^0.005, which would not round to 0.001. 4 The trend (slope) was significantly different from 0 at the 95% level of confidence. There were no significant correlations between the weight of the May-August catch (including “pieces,” Figures 2 through 7) each year and corresponding levels of d (Table 8). A lack of correlation suggested that size composition was not the major factor affecting the weight of the May— August catch. This would be expected if another factor (e.g., year-to-year variations in recruitment) played a larger role than changes in size composition in determining varia- tions in weight of the May- August catch. May -August Cumulative Ex-vessel Value of Catch by Size Category For each species, coastal area, and year, we calculated the cumulative ex-vessel value, D, of the catch in each of the seven size categories, starting with the size category of smallest shrimp and cumulating toward the size category of largest shrimp (see Caillouet and Koi 1980, 1981). The following exponential model described the relation- ship between Dj and Q for each species, coastal area, and year: D i = g(exphC i ) (3) where Dj = cumulative ex-vessel value of catch in the ith size category. The logarithmic form of model 3 was used to estimate parameters g and h by linear regression (Tables 9 through 11). Very good fits were indicated by the very high coefficients of determination. All slopes, h, were negative, reflecting the construction of model 3 by cumu- lating ex-vessel value of catch from small- to large-shrimp size categories. Only the upward trend in h for brown shrimp from the Texas coast and the downward trend in h for white shrimp from Pensacola to the Mississippi River from 1960 to 1978 were statistically significant (Table 4). The upward trend for brown shrimp from the Texas coast indicated that the proportions of the ex -vessel value of the May-August catch represented by the size categories of smaller shrimp increased from I960 to 1978. The downward trend for white shrimp from Pensacola to the Mississippi River indicated that the proportions of the cx-vessel value of the May-August catch represented by the size categories of larger shrimp increased from 1960 to 1978. The data point for 1972 Value and Size of Brown and White Shrimp 65 TABLE 5. Relationship between transformed cumulative weight (pounds, heads off) of catch, InP, and count, C, for reported May- August catches (inshore and offshore combined) of brown and white shrimp from the Texas coast (statistical areas 18-21 combined), 1960-1978.* TABLE 6. Relationship between transformed cumulative weight (pounds, heads off) of catch, InP, and count, C, for reported May- August catches (inshore and offshore combined) of brown and white shrimp from the Mississippi River to Texas (statistical areas 13-17 combined), 1960-1978.* Brown Shrimp White Shrimp Brown Shrimp White Shrimp Year c d r 2 c d r 2 Year c d r 2 c d r 2 1960 183,811,255 -0.10258 0.934 7,182,658 -0.08253 0.783 1960 16,792,619 -0.01158 0.982 6,735,954 -0.03286 0.859 1961 48,575,993 0.07323 0.960 1,873,296 -0.03948 0.975 1961 9,683,268 -0.01507 0.980 746.104 -0.03511 0.935 1962 23,996.295 -0.04965 0.922 2,666,134 -0.03786 0.951 1962 7,121,864 -0.00946 0.969 1,989,691 0.04671 0.851 1963 53.600,556 -0.06741 0.966 6,724,244 -0.07125 0.942 1963 19,298,733 -0.01274 0.970 22,225,926 0.05003 0.847 1964 42,618,117 -0.06161 0.971 5,706,520 -0.04442 0.991 1964 10,538,439 -0.01378 0.874 16,440,034 -0.06129 0.994 1965 39,567,158 -0.04776 0.967 2,765,052 -0.03578 0.974 1965 16,842,736 -0.00975 0.997 7,148,335 -0.0729S 0.986 1966 36,003,258 -0.05231 0.963 3,536.330 -0.052S7 0.959 1966 17,312,685 -0.00957 0.984 10,533,487-0.05470 0.979 1967 120,211,109 -0.06731 0.963 1,559,694 -0.03168 0,976 1967 31,665,870 -0.00988 0.979 7,354,846 -0.05329 0.995 1968 88,261.098 -0.07819 0.926 3,392,237 -0.03486 0.896 1968 23,600,064 -0.00816 0.985 3,793,463 0.02737 0.957 1969 42,957,422 -0.05614 0.918 7,858,608 -0.06541 0.992 1969 20,210,847 -0.00425 0.998 7,408,659 0.04606 0.959 1970 44,769,157 -0.05286 0.968 8,412,422 -0.05276 0.976 1970 26,922,152 -0.00958 0.969 10,952,300-0.03839 0.997 1971 52.S64.419 -0.05110 0.941 4,334,297 -0.08055 0.998 1971 30,789,368 -0.00887 0.970 13,765,830 -0.04732 0.995 1972 87,278,961 -0.06344 0.948 7,807,770 -0.06981 0.966 1972 28,351,769 -0.01058 0.987 9,644,902 - 0.05248 0.995 1973 37,018,191 -0.03611 0.938 3,725.606 -0.03378 0.943 1973 16,561,644 -0.00387 0.996 3,607,660-0.04251 0.992 1974 47,553,217 -0.05093 0.964 8,407,460 -0.08301 0.972 1974 17.059.026 -0.00594 0.987 2.836,382 - 0.0251 1 0.912 1975 36,279,377 -0.03871 0.958 6,147,586 -0.07249 0.991 1975 13,688,820 -0.00535 0.989 4.586.097 -0.03938 0.955 1976 33,851,030 -0.03720 0.971 3,487,480 -0.03433 0.991 1976 33,812,124 -0.00735 0.987 8,155,067 -0.02722 0.983 1977 46,903,835 -0.03852 0.966 2,876,486 -0.02481 0.956 1977 48,701,481 -0.01097 0.972 7,897,209 0.02105 0.984 1978 29,219,592 -0.02498 0.934 4,231,047 -0.04206 0.946 1978 45,423,493 -0.00804 0.946 9,211,470 -0.04247 0.995 *Based on the linear regression of InP on C, where P = cumulative weight of May-August catch in each of seven size categories, C - lower limit (count) of each of the seven size categories, ln(c) = intercept, d = slope, and r 2 = coefficient of determination; all slopes, d, were significantly different from 0 at the 99% level of confidence, and the high r values indicated a very good fit of the straight lines to the data points. “'Based on the linear regression of InP on C, where P = cumulative weight of May-August catch in each of seven size categories, C = lower limit (count) of each of the seven size categories. ln(c) = intercept, d = slope, and r 2 = coefficient of determination, all slopes, d, were significantly different from 0 at the 99% level of confidence, and the high r 2 values indicated a very good fit of the straight lines to the data points. was excluded from calculation of the trend for white shrimp from Pensacola to the Mississippi River (Table 1 1) as in the two previous sections. Simulations Models 1 and 2 provided information useful in simula- ting the impacts of predictable changes in model parameters, barring any major changes in fishery management such as the closure of the FCZoff Texas. We conducted simulations to estimate what the overall average ex-vessel value per pound of the May— August catches of brown and white shrimp in the three coastal areas would have been for selected levels of b , to explore the possible consequences of changes in both the size composition of the catches and the ex-vessel price spread among size categories. Because there were significant inverse relationships between ln(a) and b for both species in each coastal area (Table 8), we were able to estimate parameter a for selected levels of parameter b for each species and coastal area, to simulate Vi in equation 1. We then calculated the corresponding ex-vessel value per pound by size category from the simulated Vj, In each case, we used the ex-vessel value per pound obtained for the 15-20 size category as an approximation of the minimum ex-vessel value per pound for the < 1 5 size category, because the model did not encompass the < 15 size category. We then multiplied the simulated ex -vessel value per pound in each size cate- gory by the reported pounds caught in each size category to simulate the ex-vessel value of the May-August catches by size category- The weight of catch in the category “pieces” was excluded from these calculations. The resulting values were summed over size categories to simulate the cx-vessel value of the May-August catches (pieces excluded). The simulated ex-vessel value was then divided by the reported May-August catch (pieces excluded) to obtain the simu- lated May— August average ex-vessel value per pound for each level of b for both species, for each coastal area, and for each year. Straight lines were fitted to the simulated ex-vessel value per pound versus d by linear regression (Table 12, Figures 8 through 13). An increase in size of shrimp in the catches (as indicated by a decrease in d), coupled with an increase in price spread 66 CAILLOUET AND KOI TABLE 7. Relationship between transformed cumulative weight (pounds, heads off) of catch, lnl\ and count, C, for reported May- August catches (inshore and offshore combined) of brown and white shrimp from Pensacola to the Mississippi River (statistical areas 10-12 combined), 1960-1978.* Brown Shrimp White Shrimp Year c d r 2 c dr 2 1960 18,688,894 -0.03557 0.888 1,116,568 -0.01835 0.898 1961 9,525,281 -0.03397 0.932 141,706 -0.02710 0.911 1962 5,783,676 -0.02557 0.877 306,285 -0.03999 0.904 1963 20,786,826 -0.04541 0.895 1,028,879 -0.03534 0.944 1964 10,320.162 -0.02472 0.889 1,610,427 -0.03872 0.941 1965 18,107,921 -0.02888 0.816 575.779 -0.03509 0.923 1966 11,184,171 -0.01133 0.888 531,682 -0.02285 0.884 1967 22,420,583 -0.02483 0.870 816,760 0.02479 0.921 1968 20,390,303 -0.01797 0 884 499,633 -0.02806 0.923 1969 17,867,965 -0.02162 0.861 767,505 -003124 0.974 1970 17,263.241 -0.02010 0.890 1,360,986 -0.05002 0.977 1971 19,287.350 -0.01938 0.930 542,037 -0.06344 0.944 1972 14,473,790 -0.01703 0.938 21, 844,069f -0.22577f 0.937 1973 6,980,981 -0.01775 0.948 113,404 -0.04673 0.968 1974 8,348,897 -0.01229 0.929 155,550 -0,02484 0.871 1975 7,967,968 -0.01717 0.890 218,716 -0.03676 0.606 1976 12,660,152 -0.01700 0.882 331,522 -0.02700 0.918 1977 24,861,227 -0.02879 0.888 404.477 -0.02900 0.980 1978 13,224,609 -0.01398 0.874 616,522 -0.04736 0.988 ♦Based on the linear regression of LnP on C, where P = cumulative weight of May-August catch in each of seven size categories, C = lower limit (count) of each of the seven size categories, ln(c) = intercept, d = slope, and r 2 = coefficient of determination; all slopes, d, were significantly different from 0 at the 99% level of confidence, and the high r 2 values indicated a very good fit of the straight lines to the data points. fBoth c and d for white shrimp in 1972 are distorted because no catch was reported i'or the ^68 count category. among size categories (as indicated by a decrease in b), clearly results in pronounced increases in the average ex-vessel value per pound for brown and white shrimp (Table 12, Figures 8 through 13). Decreases in b produce greater increases in ex-vessel value per pound than equiva- lent decreases in d. Because catches also depend upon recruitment each year (Christmas and Etzold 1977), the simulated average ex-vessel value per pound can be used as a multiplier For estimating the ex-vessel value For a given weight of May -August catch of a given size composition, for selected levels of b, for both species, and for each coastal area. DISCUSSION The extent to which the exclusion of unreported catches from our analyses affected our results and conclusions cannot be determined. Because reported catches of shrimp are not equivalent to actual catches, and because there are errors in assignment of catches to size categories, size composition of reported catches is not identical to that of actual catches. Unknown portions of catches were not reported, e,g., shrimp discarded because they did not meet minimum size limits or for economic reasons, catches by recreational fishermen, catches sold directly to the consumer, and catches by Foreign Fishing craft (prior to 1976). Also unknown is the extent of errors of misclassification of catches by size category as a result of shrimp-grading practices. Such misclassification errors may average out in aggregated catches. However, a thorough investigation of the effects of shrimp grading practices (“machine grading” and “box grading”) on size distributions of shrimp assigned to various size categories would be necessary to determine the extent and magnitude of misclassification errors. TABLE 8. Linear regressions of catch (in millions of pounds, heads off; includes “pieces") on d, and ln(a) on b for reported May- August catches (inshore and offshore combined) of brown and white shrimp from the Texas coast, the Mississippi River to Texas, and Pensacola to the Mississippi River, 1960-1978 (based on data from Tables 1-3 and 5-7). Texas Coast Mississippi River to Texas Pensacola to Mississippi River Brown Shrimp White Shrimp Brown Shrimp White Shrimp Brown Shrimp White Shrimp 1 For catch on d Slope - 20.437 - 5.329 586.502 -16.268 48.870 0.874 Intercept 15.3468 1.8985 24.8956 3,6975 9.8000 0.4291 Coefficient of Determination 0.006 0.019 0.035 0.011 0.019 0.002 For In(a) on b Slope -103.513 2 -65.392 s - 95.262 2 -78.860 2 -105.387 2 -70.076 2 Intercept - 7.3187 - 5.1176 - 6.7862 - 5.7348 - 7.0505 - 5.2073 Coefficient of Determination 0.495 0.288 0.627 0.509 0.752 0.417 l Data for 1972 were excluded (see Tables 3, 4, 7, and 1 1). 2 The slope was significantly different from 0 at the 99% level of confidence. 3 The slope was significantly different from 0 at the 95% level of confidence. Value and Size of Brown and White Shrimp 67 TABLE 9. Relationship between transformed cumulative ex-vessel value (dollars) of catch, InD, and count, C, for reported May- August catches (inshore and offshore combined) of brown and white shrimp from the Texas coast (statistical areas 18-11 combined), 1960-1978 * Brown Shrimp White Shrimp Year g h r 2 g hr 2 TABLE 10. Relationship between transformed cumulative ex-vessel value (dollars) of catch, InD, and count, C, for reported May- August catches (inshore and offshore combined) of brown and white shrimp from the Mississippi River to Texas (statistical areas 13-17 combined), 1960-1978.* Brown Shrimp White Shrimp Year g h r 2 g hr 2 1960 108,230,092 -0.11393 0.936 3,736,986 -0.09477 0.805 1960 6,294,080 0.01689 0.984 2,791,110 0.04070 0.912 1961 36,397,112 -0.09024 0.963 1.311,025 -0.05347 0.974 1961 4,367,232 -0.02222 0.970 458,704 -0.04443 0.940 1962 21,729,036 -0.06461 0.924 2,031,327 -0.05238 0.959 1962 3.779,680 -0.01413 0.978 1,465,285 0,05469 0.890 1963 45,022,368 -0.09025 0.970 4,415,890 0.08604 0.955 1963 7,578.910 -0.02356 0.967 12,757,629 -0.06392 0.919 1964 32,308,471 -0.07813 0.973 3,882.035 -0-06032 0.993 1964 4,030,859 -0.02011 0.932 11,132,619 -0.07464 0.996 1965 32,423,045 -0.06730 0.964 1.852,691 -0.04951 0.969 1965 7,214,764 -0.01621 0.996 6,237,562 -0.08630 0.986 1966 45,338,631-0.07277 0.963 3,972,436 -0.06882 0.953 1966 9,857,173 -0.01814 0.989 10,406,072 0.06669 0.988 1967 1 10*407,652 -0.08742 0.967 1,105,745 -0.04500 0.963 1967 13,749,184 -0.01786 0.984 7,436,940 0.06960 0.993 1968 95,090.535 -0.09680 0.932 2,409,621 -0.0421S 0.934 1968 11,181,487 -0.01686 0.987 3,573,443 -0.04375 0.933 1969 52,890,802 -0.07507 0.918 12,070,439 -0.09252 0.989 1969 9,291,959 0,00974 0.990 8.477,109 -0.06181 0.980 1970 50,876,414 -0.07431 0.973 9,425,600 -0.07358 0.984 1970 13,512,017 -0.01775 0.997 11,711,596 -0.05426 0.997 1971 79,798,080 -0.07275 0.947 7.645,440 -0.09942 0.998 1971 19,940,033 -0.02048 0.980 22,632,331 0.07031 0.996 1972 161,353,796 -0.08626 0.943 18,067,946 -0.09807 0.970 1972 23,692,521 -0.02099 0.992 20,043,390 -0.07449 0.991 1973 79,172,534 -0.05277 0.929 7,133,410 -0.04512 0.944 1973 16,002,252 -0.00780 0.992 7,756,874 -0.05436 0.992 1974 71,254,604 -0.07047 0.975 22,639,800 -0.11129 0.973 1974 11,394,827 -0.01407 0.947 4,675,188 -0.04562 0.860 1975 88,198,455 -0.05577 0.961 20,209,432 -0.09447 0.992 1975 13,595,100 -0.01574 0.971 13,742,173 -0.06326 0.963 1976 114,877,856 -0.06065 0.963 12,554,629 -0.05527 0.985 1976 45,458,483 -0.0173R 0.976 27,191,908 -0.04896 0.978 1977 131,374,161 -0,05818 0.969 5,995,621 -0.03921 0.986 1977 70,647,268 -0.02095 0.990 16,625,530 -0.03588 0.992 1978 82,262,836 -0.04355 0.935 11,590,079 -0.05261 0.963 1978 64,185,636 -0.01841 0.974 31.609,871 -0.06042 0.996 68 Caillouet AND KOI TABLE 12. Linear regressions of simulated average ex -vessel value (dollars) per pound (heads off) on d for reported May— August catches (inshore and offshore combined) of brown and white shrimp from the Texas coast, the Mississippi River to Texas, and Pensacola to the Mississippi River, 1960- 1978, and for selected levels of b (based on data from Tables 1-3 and 5-8). b 1 Species Coastal Area -0.04 -0.05 -0.06 -0.07 Brown shrimp Texas coast Slopes Intercepts Coefficients of determination -0.8265 2 0.2918 0.761 - 2.495 2 2 0.5404 0.724 - 6.4834 2 1.0216 0.694 -15.7231 2 1.9686 0.666 Brown shrimp Mississippi River to Texas Slopes Intercepts Coefficients of determination -5.7716 2 0.2432 0.979 -14.261 3 2 0.3388 0.956 — 31.4732 2 0.4837 0.930 -65.9078 2 0.7139 0.901 Brown shrimp Pensacola to Mississippi River Slopes Intercepts Coefficients of determination -3.1418 2 0.3214 0.959 8.4739 2 0.5283 0.956 -20.4354 2 0.8867 0.950 46.667S 2 1.5235 0.942 White shrimp Texas coast Slopes Intercepts Coefficients of determination -1.4162 2 0.5788 0.745 - 3.2351 2 0.7834 0.598 - 6.1219 2 1.0953 0.501 -10.6932 2 1.5770 0.433 White shrimp Mississippi River to Texas Slopes Intercepts Coefficients of determination -1.8251 2 0.5165 0.723 - 4.S334 2 0.7830 0.614 — 10.5496 2 1.2303 0.538 -21.2666 2 1.9960 0.484 White shrimp Pensacola to Mississippi River Slopes Intercepts Coefficients of determination -3.0922 2 0.5750 0.726 - 8.5463 2 0.7221 0.557 -18.2301 2 0.9275 0.475 -3S.2227 2 1.2195 0.424 1 Levels of b selected for the simulations encompassed the observed ranges in b, for the most part. 2 The slope was significantly different from 0 at the 99% level of confidence. Figure 8. Simulated average ex-vessel value (dollars) per pound (heads off) for reported May-August catches (inshore and offshore combined) of brown shrimp from the Texas coast (statistical areas 18-21 combined), at selected levels of b over the range of d (based on data from Tables 1,5, and 8). Lines fitted by linear regression (Table 12). Figure 9. Simulated average ex-vessel value (dollars) per pound (heads off) for reported May -August catches (inshore and offshore combined) of white shrimp from the Texas coast (statistical areas 18-21 combined), at selected levels of b over the range of d (based on data from Tables 1,5, and 8). Lines fitted by linear regression (Table 12). VALUE AND SIZE OF BROWN AND WHITE SHRIMP 69 MISSISSIPPI RIVER TO TEXAS Figure 10. Simulated average ex-vessel value (dollars) per pound Figure 12. Simulated average ex-vessel value (dollars) per pound (heads off) for reported May-August catches (inshore and offshore (heads off) for reported May-August catches (inshore and offshore combined) of brown shrimp from the Mississippi River to Texas combined) of brown shrimp from Pensacola to the Mississippi River (statistical areas 13-17 combined), at selected levels of b over the (statistical areas 10-12 combined), at selected levels of b over the range of d (based on data from Tables 2, 6, and 8). Lines fitted by range of d (based on data from Tables 3, 7, and 8). Lines fitted by linear regression (Table 12). linear regression (Table 12). PENSACOLA TO THE MISSISSIPPI RIVER WHITE SHRIMP Figure 11. Simulated average ex-vessel value (dollars) per pound Figure 13. Simulated average ex-vessel value (dollars) per pound (heads off) for reported May- August catches (inshore and offshore (heads off) for reported May -August catches (inshore and offshore combined) of white shrimp from the Mississippi River to Texas combined) of white shrimp from Pensacola to the Mississippi River (statistical areas 13-17 combined), at selected levels of b over the (statistical areas 10-12 combined), at selected levels of b over the range of d (based on data from Tables 2, 6, and 8). Lines fitted by range of d (based on data from Tables 3, 7, and 8). Lines fitted by linear regression (Table 12). linear regression (Table 1 2). There were significant decreases in size of brown shrimp For this reason, Caillouet et al. (1980) suggested that the in the reported May— August catches from the three coastal observed decreases in size of brown shrimp may be the areas from 1960 to 1978. Caillouet et al. (1980) detected effects of increased fishing effort leading to the harvesting significant decreases in size of brown shrimp in reported of increasing quantities of small shrimp before they grow annual catches from Texas and Louisiana from 1959 to to larger sizes. However, in the absence of a decline in total 1976, and Caillouet and Koi (1980) detected significant catch or conclusive evidence that shrimp are being harvested decreases in size of brown shrimp in reported annual landings at rates in excess of that which would maximize yield, this from the northern Gulf from 1961 to 1977. Fishing effort cannot be construed as growth overfishing. The decrease in has increased substantially in the northern Gulf coast size of brown shrimp in catches from the Texas coast may since 1960 (Christmas and Etzold 1977, GMFMC 1980). be reversed as a result of closure of the FCZ off Texas due 70 Caillouet AND KOI to postponement of fishing until the shrimp grow to larger sizes. Coupled with continued increase in the price spread among size categories, an increase in size of brown shrimp in the Texas coast catch could greatly enhance the value of that catch. On the other hand, the closure may increase fishing effort along the coasts of Louisiana, Mississippi, and Alabama (GMFMC 1980), with the possible consequence of exacerbating the trends toward decrease of size of brown shrimp in the catches from these areas. In addition, the increased competition among offshore units could force some of the smaller ones to fish inshore as an alternative, thereby increasing the fishing pressure inshore. To our surprise, there were no significant changes in size composition of reported May August catches of white shrimp in the three coastal areas from 1960 to 1978. However, if fishing pressure on the white shrimp stock were increased as a result of closure of the FCZ off Texas, the size of white shrimp in the May-August catch could decrease. Caillouet et ah (1980), and Caillouet and Koi (1980) detected decreases in size of white shrimp in reported annual catches and landings, respectively, from the northern Gulf. Therefore, these decreases in size must have been generated by an overwhelming influence of size composition of the catches during months other than May -August. Our analyses do not account for the impact of overall inflation on the trends in ex vessel value of shrimp catches. However, they do indicate that the rate of inflation in ex-vessel value per shrimp is higher for larger than for smaller shrimp, a phenomenon that should be considered in studies of inflationary effects on the ex-vessel value of shrimp catches. We have characterized the ex-vessel value per shrimp by size category, size composition, and ex -vessel value compo- sition of the reported May-August catches of brown and white shrimp from the Texas, Louisiana, Mississippi, and Alabama coasts from 1960 to 1978. Comparisons, by similar analyses, with catch statistics for 1979, 1980, and 1981, should be of particular use and interest as one means of assessing the impacts of the closure of the FCZ off Texas. ACKNOWLEDGMENTS We are especially grateful to those who had the foresight to design and implement the gathering of data on weight and ex-vessel value of shrimp catches by statistical area, species, and size category, because they have made our analyses possible. Notable among them are Charles H. Lyles, Director, Gulf States Marine Fisheries Commission (formerly of the USFWS), George W. Rounsefell (formerly Director, Galveston Laboratory, BCF, IJSFWS, deceased), Joseph H. Kutkuhn, Director, Great Lakes Fisheries Laboratory, USFWS, Ann Arbor. Michigan (formerly Assistant Director, Galveston Laboratory, BCF, USFWS), and George W. Snow (formerly Chief, Division of Statistics and Market News, NMFS, New Orleans. Louisiana, retired). The manuscript was reviewed by Dr. Edward F. Klima, NMFS, Galveston Laboratory; John P. Wise, NMFS, Washington, D.C.; Dr. Clarence P. Idyll, National Council on Oceans and Atmosphere, NOAA, Washington, D.C.; and John Ward, NMFS, Miami, Florida, who provided many helpful suggestions. Beatrice Richardson, clerk-typist, NMFS, Galveston Laboratory', typed the manuscript. REFERENCES CITED Caillouet, C. W. & D. B. Koi. 1980. Trends in ex-vessel value and size composition of annual landings of brown, pink and white shrimp from the Gulf and south Atlantic coasts of the United States. Mar Fish, Rev. 42(1 2): 18- 27. . 1981 Trends in ex -vessel value and size composition of reported annual catches of pink shrimp from the Tortugas fishery, 1960-1978. Gulf Res. Rept. 7(l):71-78. Caillouet, C. W., F. J. Patella & W. B. Jackson. 1980. Trends toward decreasing size of brown shrimp, Penaeus aztecus, and white shrimp. Penaeus setiferus, in reported annual catches from Texas and Louisiana. Nail Mar. Fish. Serv ., Fish. Bull. 77(4):985 —989 . Christmas, J. Y & D. J. Etzold (eds.). 1977. The Shrimp Fishery of the Gulf of Mexico United States : A Regional Management Plan Technical Report Series No. 2 , Gulf Coast Research Laboratory, Ocean Springs, MS. 128 pp. Griffin, W. L., R. D. Laccwell & W. A. Hayenga. 1974. Estimated costs, returns, and financial analysis: Gulf of Mexico shrimp vessels. Mar. Fish. Rev. 36(1 2): 1 -4. Griffin, W. L. & J. P. Nichols. 1976. An analysis of increasing costs to Gulf of Mexico shrimp vessel owners: 1 97 1 — 1 975. A/izr. Fish. Rev . 38<3):8 — 1 2. Griffin, W. L., N. J. Wardlaw & John P. Nichols. 1976. Economic and financial analysis of increasing costs in the Gulf shrimp fleet. Nall. Mar. Fish. Serv., Fish. Bull. 74(2): 74 190-74308. Gulf of Mexico Fishery Management Council (GMFMC). 1980. Fishery management plan for the shrimp fishery of the Gulf of Mexico. Fed. Reg. 45(21 8):74 190 74308. Henderson, P. 1972. The dynamics of the mean-size statistic in a changing fishery. FAQ Fish. Tech. Paper No. 116. 16 pp. Neal, R, A. 1967. An application of the virtual popuhriion technique to penaeid shrimp, Pages 264-272 in Proceedings of the 21st Annual Conference, Southeastern Association of Game and Fish Commissioners. Ricker, W. E. 1975. Computation and interpretation of biological statistics of fish populations. Bull. Fish. Res. Board Can. 191: 382 pp. Whitaker, D. R. 1973. The U.S. shrimp industry: past trends and prospects for the 1970’s. Mar. Fish. Rev. 35(5-6):23-30. Gulf Research Reports Volume 7 | Issue 1 January 1981 Trends in Ex- Vessel Value and Size Composition of Reported Annual Catches of Pink Shrimp from the Tortugas Fishery, 1 960- 1978 Charles Wax Caillouet National Marine Fisheries Service, Galveston Dennis Brian Koi National Marine Fisheries Service, Galveston DOI: 10.18785/grr.0701.10 Follow this and additional works at: http://aquila.usm.edu/gcr Part of the Marine Biology Commons Recommended Citation Caillouet, C. W. and D. B. Koi. 1981. Trends in Ex- Vessel Value and Size Composition of Reported Annual Catches of Pink Shrimp from the Tortugas Fishery, 1960-1978. Gulf Research Reports 7 (l): 71-78. Retrieved from http : // aquila.usm.edu/gcr/vol7 /issl/10 This Article is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf and Caribbean Research by an authorized editor of The Aquila Digital Community. For more information, please contact Joshua. Cromwell(2)usm.edu. Gulf Research Reports, Vol. 7, No. 1, 71-78, 1981. TRENDS IN EX-VESSEL VALUE AND SIZE COMPOSITION OF REPORTED ANNUAL CATCHES OF PINK SHRIMP FROM THE TORTUGAS FISHERY, 1960-1978 1 CHARLES WAX CAILLOUET AND DENNIS BRIAN KOI National Marine Fisheries Service, Galveston Laboratory, Galveston, Texas 77550 ABSTRACT Exponential models were used to characterize (1) ex-vessel value (in dollars) per shrimp by size category (count; i.e., number of shrimp per pound, heads off), (2) size composition (expressed as cumulative weight of the catch in pounds, heads off, by size category), and (3) ex-vessel value composition (expressed as cumulative ex-vessel value, in dollars, of the catch by size category) for reported annual catches (inshore and offshore combined) of pink shrimp (fenaeus duorarum duorarum) from the Tortugas fishery (statistical areas 1 and 2 combined) from 1960 to 1978. Exponents of the models were used as indices to investigate trends in ex-vessel value per shrimp, in size composition, and in ex-vessel value composi- tion of the annual catches during that period. Both the spread in ex-vessel value per shrimp among size categories and the size of shrimp in the annual catches increased from 1960 to 1978. Also, the proportion of the ex-vessel value made up of shrimp of larger sizes increased from 1960 to 1978. This approach to analysis of catch statistics can be used to monitor the fishery, and the results can be compared with changes that may be brought about by permanently closing the Tortugas shrimp sanctuary in 1981, as proposed by the Gulf of Mexico Fishery Management Council in the fishery management plan for the shrimp fishery of the Gulf of Mexico. INTRODUCTION The fishery management plan for the shrimp fishery of the Gulf of Mexico, prepared by the Gulf of Mexico Fishery Management Council (GMFMC 1980), recommended perma- nently closing the Tortugas shrimp sanctuary (Figure 1) off southern Florida to all shrimping. The purpose of the closure is to protect small pink shrimp ( Peneaus duorarum duorarum ) so that they might survive and grow to sizes larger than 69 count (refers throughout this paper to number of shrimp per pound, with heads removed) before harvest. Essentially, this measure would reestablish most of the original Tortugas shrimp nursery which, until recently, had served as a sanctuary for pink shrimp recruited to the Tortugas and Sanibel shrimping grounds off southern and southwestern Florida, respectively. The management plan also encouraged the State of Florida to allow fishermen to retain all shrimp (including those of 69 count or smaller) caught in the open waters of the Fishery conservation zone (FCZ), the area under federal jurisdiction beginning at the outer limit of Florida’s territorial sea and extending 200 miles from shore. Growth and mortality estimates by Lindner (1966) and Berry (1970) indicated that pink shrimp yield would be maximized if harvest were limited to shrimp larger than 70 count. However, Florida’s minimum legal size limit of 70 count may have led to the discarding of large quantities of undersized pink shrimp caught in the FCZ. Thus, there is considerable interest on 1 he part of the fishing industry, the State of Florida, the GMFMC, the National Marine Fisheries Service (NMFS), and Fisheries scientists regarding ‘Contribution No. 81 21 G from the Southeast Fisheries Center, Galveston Laboratory, National Marine Fisheries Service, NOAA. Manuscript received March 30, 1981 ; accepted June 15, 1981 the potential impacts of permanently closing the Tortugas shrimp sanctuary on the yield of pink shrimp from the Tortugas Fishery. Apart from changes in yield caused by annual fluctua- tions in recruitment, changes in yield that may result from the closure probably will be accompanied by changes in size composition of the catch. Mean size is a simple criterion used for assessing status of an exploited stock (Henderson 1972, Ricker 1975). An increase in average size of individuals could indicate a decrease in mortality (usually equated with a decrease in fishing mortality) or an increase in growth. A decrease in average size mighl be brought about by reten- tion of large quantities of small shrimp that formerly were discarded. Socioeconomic factors affecting strategies of fishing, culling of the catch, and marketing of the landings also could influence the size composition of the catch. Caillouet et al. (1980) developed a simple exponential model to characterize the size composition (expressed as the cumulative percentage of weight of catch by size category) of reported annual catches of shrimp. Using a logarithmic transformation, they converted the model to one of a straight line, the slope (= exponent of the exponen- tial model) of which was estimated by linear regression analysis. The mode! was used as an index to investigate fluctuations and trends in size composition of brown shrimp ( P . aztccus ) and white shrimp (P. setiferus) catches in Texas and Louisiana from 1959 to 1976. Caillouet and Koi (1980) modified the model by expressing size composition in terms of cumulative weight of catch by size category, instead of cumulative percentage of weight by size category. They used the modified model to investigate trends in size com- position of the reported annual landings of brown, pink, and white shrimp from the Gulf and southeast coast Fisheries of the United States from 1961 to 1977. They recognized 71 72 CAILLOUET AND KOI Figure 1. Boundaries of the Tortugas fishery (statistical areas 1 and 2 combined), the Tortugas shrimp sanctuary, the territorial sea, and the fishery conservation zone off south Florida (adapted from GMFMC 1980). that the exponent of the model would be unaffected by the modification. They also used exponential models to investi- gate trends in the ex-vessel value per shrimp by size category and the ex-vcssel value composition of the annual landings, and conducted simulations to predict the results of continued trends. Similar analyses were performed by Caillouet and Koi (1981) on reported May-August catches of brown and white shrimp from the Texas, Louisiana, Mississippi, and Alabama coasts from 1960 to 1978. The effect of shrimp size on the ex -vessel value of the catch has also been recog- nized by Neal (1967), Griffin et al. (1974), Griffin and Nichols (1976), and Griffin et ah (1976). The NMFS has responsibility for monitoring the impacts of the permanent closure of the Tortugas shrimp sanctuary. The purposes of this paper are to propose a procedure for monitoring the Tortugas pink shrimp fishery based on the methods of Caillouet and Koi (1980), and to use their methods to investigate trends in ex-vessel value per shrimp by size category, size composition, and ex-vessei value com- position of reported annual catches from I960 to 1978. This approach then can be used as one means of assessing the impacts of permanently closing the Tortugas shrimp sanctuary and of retaining small shrimp harvested within the FCZ. DESCRIPTION OF DATA Annual summaries of the weight and ex-vessel value of the reported catches were compiled from data files available from the NMFS, Southeast Fisheries Center (SEFC), Technical and Information Management Services (TIMS), Miami, Florida. The weight of the reported annual catches (inshore and offshore combined) of pink shrimp from the Tortugas fishery (statistical areas I and 2 combined. Figure 1) was expressed in pounds (heads off), and the ex-vessel value in dollars, by size category (< 15, 15-20, 21—25, 26-30, 31-40, 41-50, 51-67, and > 68 count, and “pieces 1 ') and by year (1960-1978). The “pieces” category represented parts of shrimp tails that could not be assigned to a numerical size category. Data for 1979 and 1980 were not available at the time of this writing. English rather than metric units are used throughout this paper because they have been used historically, and information would be lost in their conversion to metric units. The reported annual catch represents that part of the actual annual catch reported by the NMFS, SEFC, TIMS, or its predecessor, the Bureau of Commercial Fisheries (BCF), U.S. Fish and Wildlife Service (USFWS). ANALYSES AND RESULTS Reported Annual Catches Reported annual catches of pink shrimp from the Tortugas fishery showed a gradual downward trend from 1960 to 1978, while the reported ex-vessel value of these Value and Size of Pink Shrimp 73 catches showed an upward trend (Figure 2). However, the ex-vessel value was not adjusted to account for inflation. TORTUGAS FISHERY YEAR Figure 2. Weight (millions of pounds, heads off) and ex-vessel value (millions of dollars) of reported annual catches (inshore and offshore combined) of pink shrimp from the Tortugas fishery (statistical areas 1 and 2 combined), 1960-1978. Annual Ex-vessel Value per Shrimp by Size Category We divided dollars by pounds in each of seven size cate- gories (1 5-20, 21-25, 26—30, 31-40, 41-50, 51-67, and >68 count) to obtain annual average ex -vessel value per pound by size category for each year. Next, we divided annual average ex-vessel value per pound in each of the seven size categories by the lower limit, C, of the respective size categories to obtain annual average ex-vessel value per shrimp, V, in each of the seven size categories for each year. Because lower limits of size categories were used as divisors, the calculated value per shrimp was the highest that could be obtained from the data for each size category. The following exponential model described the relation- ship between Vj and Cj for each year: Vi = a (exp bQ) (1) where Vj = annual average ex-vessel value per slump for the ith size category, Cj = lower limit (count) of the ith size category (Ci = 15, C 2 = 21, C 3 = 26, C 4 = 31, C s = 41, C 6 = 51, and C 7 = 68), and i = 1, 2, . . . , 7. The loga- rithmic form of the exponential model was used to estimate parameters a and b by linear regression (Table 1). The high coefficients of determination, r 2 , indicated that the fits of the straight lines to the points were very close. All slopes, b, were negative, reflecting the decrease in ex- vessel value per shrimp with increase in count (decrease in size). Note that the straight lines were obtained by a double transformation. The value per shrimp was transformed to natural logs, and the weight per shrimp (in pounds) was transformed to its reciprocal, count. TABLE I . Relationship between transformed ex-vessel value (dollars) per shrimp, InV, and count, C, for reported annual catches (inshore and offshore combined) of pink shrimp from the Tortugas fishery (statistical areas 1 and 2 combined), 1960-1978.* Year a b r 2 1960 0.08055 -0.05105 0.992 1961 0.07934 -0.04703 0.982 1962 0.10499 0.04549 0.991 1963 0.11350 -0.05259 0.987 1964 0.10157 -0.05134 0.996 1965 0.09966 -0.04762 0.989 1966 0.10238 -0.04363 0.985 1967 0.12016 -0.04807 0.990 1968 0.14652 -0.05343 0.990 1969 0.16510 -0.05231 0.990 1970 0.16200 -0.05304 0.994 1971 0.22503 0.06109 0.997 1972 0.31373 -0.06409 0.996 1973 0.25167 -0.05121 0.999 1974 0.28464 -0.05747 0.975 1975 0.31197 0.05378 0.995 1976 0.51520 -0.05762 0.997 1977 0.44743 -0.05526 0.981 1978 0.40966 -0.05079 0.979 ♦Relationship was based on the linear regression of InV on C, where V = annual average ex-vessel value per shrimp in each of seven size categories, C = lower limit (count) of each of the seven size cate- gories, ln(a) = intercept, b = slope, and r 2 = coefficient of deter- mination; all slopes, b, were significantly different from 0 at the 99% level of confidence, and the high r 2 values indicated very good fits of the lines to the data points. Lower limits, rather than midpoints or upper limits of the seven size categories, were used in constructing model 1 because the size categories had unequal intervals, and an upper limit could not be determined for the > 68 category. A lower limit of zero for the <15 size category was not realistic, and that category represented only a small fraction (< 1%) of the reported annual catches of pink shrimp from the Tortugas fishery. Therefore, the < 15 size category was excluded from model l. Also excluded was the category “pieces/* which represented parts of shrimp tails, assuming it represented the other size categories in proportion to their relative contributions to the catch. The constant, a, reflected the elevation of the straight line, which was influenced in part by our use of lower limits of size cate- gories and exclusion of the < 15 size category in fitting the straight line. The slope, b, of the straight line is a simple index of the spread in ex-vessel value per shrimp among the seven size categories; i.e., the ex-vessel price structure. There was a significant downward trend in b from 1960 to 1978 (Tables 1 and 2). This trend indicated that the differences in value per shrimp among the size categories increased with time; i.e,, the value per shrimp increased more rapidly for larger shrimp than for smaller shrimp from 74 CAILLOUET AND KOI 1960 to 1978. Whitaker (1973) also observed an increase in price spread between large and small “southern” shrimp during the period from 1957 to 1971. TABLE 2. Trends in ex -vessel value (dollars) per shrimp by size category, in cumulative catch (pounds, heads off) by size category, and in cumulative ex-vessel value (dollars) of catch by size category for reported annual catches (inshore and offshore combined) of pink shrimp from the Tortugas fishery (statistical areas 1 and 2 combined) from I960 to 1978 (based on data in Tables 1,3, and 4). For ex-vessel value per shrimp by size category For cumulative catch by size category For cumulative ex- vessel value of catch by size category Trends* Trend coefficients of -O.OOOSf -0.0009$ -0.0012$ determination 0.303 0.346 0.364 ♦Represent slopesof the linear regressions of b ( d, and h, respectively, on x, where x is the last two digits of each year, 1960-1978. ■{■Indicates that the trend (slope) was significantly different from 0 at the 95% level of confidence. ^Indicates that the trend (slope) was significantly different from 0 at the 99% level of confidence Annual Cumulative Catch by Size Category We calculated the cumulative weight, P, of the catch in each of the same seven size categories for each year. Catch by size category was cumulated starting with the size category of smallest shrimp (highest count, > 68), and con- tinuing toward the size category of largest shrimp (lowest count, 15 -20). The following exponential model described the relation- ship between Pi and Q for each year: Pi = c (exp dCO (2) where Pi = cumulative weight of catch in the ith size cate- gory. The logarithmic form of the exponential model was used to estimate parameters c and d by linear regression (Table 3). The coefficients of determination were high indicating close fits of the lines to the points. All slopes, d, were negative, which rctlected the construction of model 2 by cumulating catch from small-shrimp to large-shrimp size categories. These slopes, d, would have been the same had they been calculated by the method of Caillouet et al. (1980). The constant, c, reflected the elevation of the straight line and the magnitude of the annual catch, but c was influenced by our use of lower limits of size categories and exclusion of the < 15 size category in fitting the straight line. The slope, d, of the straight line is a simple index of the size composition of the annual catch. There was a significant downward trend in d from 1960 to 1978 (Tables 2 and 3). This indicated that the size of shrimp in the reported annual catches increased from 1960 to 1978. TABLE 3. Relationship between transformed cumulative weight (pounds, heads oft) of catch, InP, and count, C, for reported annual catches (inshore and offshore combined) of pink shrimp from the Tortugas fishery (statistical areas 1 and 2 combined), 1960-1978.* Year c d r 2 1960 28,961,850 -0.03542 0.947 1961 16,893,678 -0.02889 0.986 1962 19,594,706 -0.04238 0.952 1963 17,562,210 -0.02974 0.950 1964 21,648,787 -0.03264 0.941 1965 24,949,641 -0.03586 0.931 1966 26,482,905 -0.03863 0.924 1967 21,646,839 0.04588 0.904 1968 26,254,291 -0.05073 0.904 1969 24,944,402 -0.04799 0.891 1970 23,114,946 -0.03684 0.898 1971 21,252,179 -0.04797 0.88 J 1972 22,106,008 -0.05647 0.852 1973 27,914,589 -0.05364 0.826 1974 27,500,370 -0.05349 0.881 1975 19,683,081 -0.04593 0.857 1976 18,398,874 -0.04559 0.848 1977 17,051,010 -0.04233 0.878 1978 15,703,277 -0.03979 0.924 ♦Relationship was based on the linear regression of InP on C, where P = cumulative weight of annual catch in each of seven size cate- gories, C - lower limit (count) of each of the seven size categories, ln(c) - intercept, d - slope, and r 2 = coefficient of determination; all slopes, d, were significantly different from 0 at the 99% level of confidence, and the high r 2 values indicated very good fits of the lines to the data points. Annual Cumulative Ex-vessel Value of Catch by Size Category We calculated the cumulative ex-vessel value, D, of the catch in each of the same seven size categories for each year. Ex-vessel value of catch was cumulated starting with the size category of smallest shrimp and continuing toward the size category of largest shrimp. The following exponential model described the relation- ship between D} and Ci for each year: Di = g (exp hCj) (3) where Dj = cumulative ex -vessel value of catch in the ith size category. The logarithmic form of the exponential model was used to estimate parameters g and h by linear regression (Table 4), Close fits of the lines to the points Value and Size or Pink Shrimp 75 were indicated by the high coefficients of determination. All slopes, h, were negative, which reflected the construc- tion of model 3 by cumulating ex-vessel value of catch from small-shrimp to large-shrimp size categories. TABLE 4. Relationship between transformed cumulative ex-vessel value (dollars) of catch, InD, and count, C, foi reported annual catches (insli ore and offshore combined) of pink shrimp from the Tortugas fishery (statistical areas 1 and 2 combined), 1960-1978.* Year 8 h r 2 1960 14,791,896 -0.04965 0.953 1961 9,023,023 -0.04032 0.988 1962 16,035,571 -0.05418 0.956 1963 11,014,906 -0.04335 0.958 1964 14,248,184 -0.04797 0.942 1965 16,841,893 -0.04747 0.938 1966 20,560,247 -0.04783 0.934 1967 18,349,264 -0.05825 0.919 1968 24,312,471 -0.06668 0.927 1969 26,218,347 -0.06296 0.916 1970 21,866,361 -0.05150 0.924 1971 28,397,169 -0.07106 0.899 1972 41,023,269 -0.08218 0.872 1973 49,716,628 -0.06940 0.850 1974 42,427,615 -0.07076 0.934 1975 43,790,173 -0.06451 0.858 1976 53,794,404 -0.06424 0.886 1977 41,799,294 -0.05768 0.925 1978 39,534,727 -0.05277 0.959 *ReIationship was based on the linear regression of InD on C> where D = cumulative ex-vessel value of catch in each of seven size cate- gories, C = lower limit (count) of each of the seven size categories, ln(g) = intercept, h = slope, and r 2 = coefficient of determination; all slopes, h, were significantly different from 0 at the 99% level of confidence, and the high r 2 values indicated very good fits of the lines to the data points. The constant, g, reflected the elevation of the straight line and the magnitude of the ex -vessel value of the annual catch, but g was influenced by our use of lower limits of size categories and exclusion of the < 15 size category in fitting the straight line. The slope, h, of the straight line is a simple index of the ex-vessel value composition of the annual catch. There was a significant downward trend in h from 1960 to 1 978 (Tables 2 and 4). This indicated that the proportions of the ex -vessel value of the catch represented by the size categories of larger shrimp increased from 1960 to 1978. Size Composition and Annual Catch There was no significant correlation (at the 95% level of confidence) between the weight of the annual catch (including “pieces,” Figure 2), and the annual levels of d (Tables 3 and 5). A lack of correlation would be expected if another factor (e.g., recruitment) played a larger role than variations in size composition in determining weight of the annual catch of shrimp. TABLE 5. Lincai regressions of ln(a) on b, and of weight (in millions of pounds, heads off) of annual catch on d, for reported annual catches (inshore and offshore combined) of pink shrimp from the Tortugas fishery (statistical areas 1 and 2 combined), 1960-1978 (based on data from Tables I and 3). For ln(a) on b For annual catch* on d Slope -77,035f 91.977 Intercept -5.7697 12.5611 Coefficient of determination 0.428 0.170 •Expressed in millions of pounds (Figure 2). Includes “pieces.” ■{■Indicates that ihe slope was significantly different from 0 at the 99% level of confidence. Simulations Models 1 and 2 provided information useful in simulating the impacts of further changes in ex-vessel price structure and size composition of the annual catches. Our simulations were based upon the hypothesis that the observed trends (Table 2) would continue, at least for a few years beyond 1978, were it not for the permanent closure of the Tortugas shrimp sanctuary. We conducted simulations to estimate what the average ex -vessel value per pound of past annual catches of pink shrimp would have been for selected levels of b, to explore the possible consequences of concurrent changes in size composition (as expressed by d) and ex- vessel price structure (as expressed by b). Because there was a significant inverse relationship between ln(a) and b (Table 5), we were able to estimate parameter a for selected levels of parameter b, to simulate Vi in model 1. We then calculated the corresponding ex-vessel value per pound by size category from the simulated Vj. We used the simulated ex-vessel value per pound for the 15-20 size category as an approximation (minimum) of the ex-vessel value per pound for the < 15 size category. We then multiplied the simulated ex-vessel value per pound in each size category (including the < 15 size category) by the reported pounds caught in each size category to simulate the ex-vessel value of the catches in each size category for each selected level of b and for each year. Pounds caught in the size category “pieces” were excluded from these calculations. The resulting values were summed over size categories to simulate annual ex-vessel value of shrimp catches (pieces excluded) for each level of b and for each year. The simulated annual cx-vessel value was then divided by the reported annual catch (pieces excluded) lo obtain simulated annual average ex-vessel value per pound for each level of b and for each year. Straight lines were fitted to 76 CAILLOUET AND KOI the simulated annual average ex-vessel value per pound for each level of b by linear regression (Table 6, Figure 3). An increase in size of shrimp in the catch (as indicated by a decrease in d), coupled with an increase in price spread among size categories (as indicated by a decrease in b), resulted in a pronounced increase in the annual average ex-vessel value per pound for pink shrimp catches from the Tortugas fishery (Figure 3). Decreases in b produced greater increases in simulated annual average ex-vessel value per pound than did equivalent decreases in d . TABLE 6. Linear regressions of simulated average ex-vessel value (dollars) per pound (heads off) on d for reported annual catches (inshore and offshore combined) of pink shrimp from the Tortugas fishery (statistical areas 1 and 2 combined), 1960-1978, for selected levels of b (based on data from Tables 1, 3, and 5). b* -0.04 -0.05 -0.06 -0.07 Slope -1.3908f -3.0989f -6.0663f -1 1.238t Intercept 0.4609 0.6449 0.9219 1.3426 Coefficient of determination 0.854 0.788 0.715 0.648 ♦Levels of b selected for the simulations encompass as well as extend the observed range in b (see Table 1), f Indicates that the slope was significantly different from 0 at the 99% level of confidence. 3 . 00 —, T0RTU6AS FISHERY PINK SHRIMP - 0.06 -0 05 -0 04 - 0.03 - 0.02 d Figure 3. Simulated average ex-vessel value (dollars) per pound (heads off) for selected levels of h, the price structure index, over the range of d, the size composition index, for reported annual catches (inshore and offshore combined) of pink shrimp from the Tortugas fishery (statistical areas 1 and 2 combined), 1960-1978 (based on data from Tables 1, 3, and 5). Lines fitted by linear regression (see Table 6). DISCUSSION The extent to which the inclusion of unreported catches would have changed our results and conclusions cannot be determined. We assume that the bulk of the actual catches of pink shrimp from the Tortugas fishery was represented by the reported catches. Discarded undersized shrimp (GMFMC 1980) and shrimp landings sold to bait dealers probably constituted most of the unreported portion of the actual catches (T. J. Costello, NMFS, Miami, Florida, personal communication). A small part of the unreported portion of the actual catches also was made up of catches by foreign fishing craft prior to 1976, and of landings by recreational fishermen. Because the magnitude of the unreported portion of the actual catches was not known, size composition and ex-vessel value composition of the reported catches could be different from the size composi- tion and ex-vessel value composition of the actual catches of pink shrimp from the Tortugas fishery. Furthermore, errors of misclassification of catches by size category occur as an outgrowth of differences in shrimp grading practices (“box” grading versus “machine” grading). However, the extent of such misclassification errors is unknown, as is their effect on size composition of the reported catches. The trend of increase in ex-vessel price spread among size categories of shrimp, coupled with the trend of increase in size of shrimp in the catches, produced an even more pronounced trend of change in the ex-vessel value composi- tion of the catches (Table 2). This helps explain why the ex-vessel value of the annual catches increased while the weight of the catches decreased from 1960 to 1978 (Figure 2). Inflation also accounted in part for the increase in ex-vessel value of the annual catches. While we did not determine the overall effects of inflation on the increase in ex-vessel value of the annual catches, our results clearly showed that this increase occurred partly because the rate of inflation in ex -vessel price was greater for large than for small shrimp. The results of our simulations (Figure 3) further illustrated the effects of concurrent changes in price spread and size composition. Hooker (1972) and Toevs and Johnson (1978) suggested that the price of a given size category of shrimp depended on its relative abundance within the supplies available to the market. Hooker (1972) recognized that imported shrimp and cold storage holdings might influence size composition of available shrimp supplies, but postulated that the price spread was influenced more by the size composition of current landings. Size composition of the reported catches was determined by the combined effects of shrimp growth and mortality (natural and fishing), shrimp discarding, gear selectivity, shrimp grading practices, and catch sampling and reporting procedures. Finally, the price spread probably was influenced to some extent by the realtive demand for shrimp of various sizes. In exploring possible causes of annual fluctuatons in size composition of catches (Table 3), we considered the Value and Size of Pink Shrimp 77 influences of major changes in regulations concerning the Tortugas fishery during the period from 1960 to 1978. For this purpose, we used an historical review of Florida legisla- tion relating to management of the Tortugas fishery (Costello 1 979). House Bill No. 2475, enacted in June 1961, redefined the geographical limitsof the Tortugas shrimp beds, changed the size limits governing the opening and closing of the controlled area from 50 to 60 count, and established nursery areas within which no shrimping was allowed, except for live bait. Enactment of these regulations, intended to pro- tect small shrimp, was fallowed by an increase in size of shrimp in the catch in 1962. In 1963, the size composition was similar to that of 1961 (Table 3). In 1964, a trend of increasing size of shrimp in the catch began and continued through 1968. In 1969 and 1970, there again was a shift toward decreasing size of shrimp in the catch. We have no explanation for these changes. Senate Bill No. 1370, enacted in July 1970, defined new boundaries for the Tortugas shrimp beds and prohibited shrimping, except for live bait, in those beds after July 1, 1970. It also repealed the size limit restriction governing the opening and closing of the controlled area, because the limit was no longer needed in the context of the redefinition of the Tortugas shrimp beds and the prohibition of shrimping in those beds. These regulations were intended to further restrict the catch of small shrimp. In 1971 and 1972, the size of shrimp in the catch increased (Table 3). Senate Bill No. 241, enacted in October 1972, made minor changes covering penalties for violations of regulations. In 1973, the shrimping industry began to feel the effects of a critical fuel shortage. Increases in the cost of fuel may have encouraged shrimping closer to home ports. In 1973 and 1974, the size of shrimp in the catch decreased (Table 3). Senate Bill 505, enacted in April 1974, redescribed the boundaries of the Tortugas shrimp beds in unambiguous terms, as a response to previouscourt actions and to facilitate enforcement of regulations. However, there was limited enforcement of the seasonal closure of the controlled area to shrimping through 1 978 (T. J. Costello, personal communica- tion). In 1975, there was a substantial decrease in size of shrimp in the catch, and the trend of decreasing size con- linued through 1978. It remains to be determined what changes, if any, took place in 1979 and 1980, and what the impacts of permanently closing the Tortugas nursery area in 1981 may be on the weight, size composition, and ex-vessel value of the annual catch. While the observed shifts in the size composition of the catch may have been related to historical changes in the regulations affecting the temporal-spatial distribution of fishing effort, it also could be argued that the changes in size composition may have been related to changes in quantity of fishing effort. Our analysis does not distinguish biological from socioeconomic influences on size composi- tion of the catch, so any conclusions as to cause and effect are speculative at this time. The trend of increase in ex -vessel price spread among size categories of shrimp probably reflects trends in supply versus demand for shrimp of various sizes in the market. Differences in costs of harvesting shrimp close to ports versus farther from ports, as well as other factors, also may have affected the supplies of shrimp of various sizes and, therefore, the ex -vessel price spread. Further investigations of costs, supply and demand, inflationary effects, other economic factors, and changes in Fishing effort are needed to explain the trends we observed (sec Christmas and Etzold 1977,GMFMC J980). Future analyses similar to ours, based on additional catch statistics as they become available, will be one means of moni- toring the Tortugas fishery. If the closure of the Tortugas shrimp sanctuary is effective in saving significant quantities of small pink shrimp to grow to larger sizes before harvest, an increase should occur in size of shrimp in the annual catch. On the other hand, if Florida allows shrimp >70 count caught in the FCZ to be retained rather than discarded by fishermen, and if the fishermen land and market significant quantities, that might decrease the size of shrimp in the annual catch. As expected, our simulations show that the average ex-vessel value of a given weight of catch increases substan- tially when an increase in ex -vessel price spread among size categories is coupled with an increase in size of shrimp in the catch (Figure 3). This is reflected by the observed trend of increase in ex-vessel value of the annual catch despite the trend of decrease in weight of the catch (Figure 2), although the ex-vessel value of the catch also is influenced by inflation. However, at some point, further decrease in total weight of the annual catches may override the influences of increasing price spread among size categories and inflation. Thus, the ex-vessel value of the catch may reach an upper limit at some point when losses through natural mortality begin to override the increase in size of shrimp in the catch, the increase in the price spread between large and small shrimp, and the effects of inflation. acknowledgments We are especially grateful to those who had the foresight to design and implement the gathering and tabulation of shrimp catch data by statistical area, species and size category, because they have made our analyses possible. Notable among them are Charles H. Lyles, Director, Gulf States Marine Fisheries Commission: George W. Rounscfell (formerly Director, Galveston Laboratory, BCF, USFWS, deceased); Joseph H. Kutkulm, Director, Great Lakes Fisheries Laboratory, USFWS, Ann Arbor, Michigan; and George W. Snow (formerly Chief, Division of Statistics and Marker News, NMFS, New Orleans, Louisiana, retired). The manuscript was reviewed by Dr. Edward F. Klima, NMFS, Galveston Laboratory; John P. Wise, NMFS, Washington, D.C.; Dr. Clarence P. Idyll, National Advisory Committee on Oceans and Atmosphere, NOAA, Washington, D.C.; and John Ward, NMFS, Miami, Florida. Beatrice Richardson, NMFS, Galveston Laboratory, typed the manuscript. 78 CAILLOUET AND KOI REFERENCES CITED Berry, R. J. 1970. Shrimp mortality rates derived from fishery statistics. Proc. Gulf Caribb. Fish. Inst . 22:66-78. Caillouet, C. W. &. D. B. Koi. 1980. Trends in ex-vessel value and sire composition of annual landings of brown, pink, and white shrimp from the Gulf and south Atlantic coasts of the United States. Mar, Fish. Rev. 4 2(1 2): 1 8- 27. . 1981. Trends in ex-vessel value and size composition of reported May-August catches of brown and white shrimp from the Texas, Louisiana, Mississippi, and Alabama coasts, 1960- 1978. Gulf Res. Kept. 7(J):59-70. Caillouet, C. W., F. J. Patella & W. B. Jackson. 1980. Trends toward decreasing size of brown shrimp, Penaeus aztccus, and white shrimp, Penaeus set i ferns, in reported annual catches from Texas and Louisiana. Natl. Mar. Fish. Serv.. Fish. Bull. 77(4): 985 989. Christmas, J. Y, & D. J. Etzold (eds.). 1977. The Shrimp Fishery of the Gulf of Mexico United States: A Regional Management Plan. Technical Report Series No. 2, Gulf Coast Research Laboratory, Ocean Springs, MS, 128 pp. Costello, T. J. 1979, A historic review of State of Florida regulations relating to the Tortugas pink shrimp fishery and rationale under- lying these regulations. National Marine Fisheries Service, SEFC, Miami, Florida. 8 pp. (unpublished). Griffin, W. L., R. D. Lacewell & W. A. Hayenga. 1974. Estimated costs, returns, and financial analysis: Gulf of Mexico shrimp vessels .Mar. Fish. Rcy. 36(1 2): 1-4. Griffin, W. L. & J. P. Nichols. 1976. An analysis of increasing costs to Gulf of Mexico shrimp vessel owners: 1971 -1975. Mar. Fish. Rev. 38(3): 8 — 12. Griffin, W. L., N- J. Wardlaw & John P. Nichols. 1976, Economic and financial analysis of increasing costs in the Gulf shrimp fleet, Nat. Mar. Fish. Serv., Fish. Bull. 74(2):301 -309 Gulf of Mexico Fishery Management Council (GMFMC). 1980. Fishery management plan for the shrimp fishery of the Gulf of Mexico. Fed. Reg 45(218):74190-74308. Henderson, F. 1972. The dynamics of the mean-size statistic in a changing fishery. FAO Fish. Tech. Paper No. 1 16. 16 pp. Hooker, P. T. 1972. Systems analysis of U.S. management strategies in the Gulf of Mexico shrimp industry. PhJD. dissertation. Uni- versity of Florida, Gainesville, FL, 185 pp. Lindner, M J. 1966. What we know about shrimp size and the Torlugas fishery. Proc. Gulf Caribb. Fish. Inst. 1 8: 18-26. Neal, R A. 1 967. An application of the virtual population technique to penaeid shrimp. Pages 264-272 in Proceedings of the 21st Annual Conference, Southeastern Association of Gam t 1 and Fish Commissioners. Sept. 24 27, 1967, New Orleans, LA, Ricker, W. E. 1975. Computation and interpretation of biological statistics of fish populations, Bull. Fish. Res. Board Can. 191. 382 pp. Toevs, A. L. & D. B. Johnson. 1978. Economic Characterization of the U.S. Gulf of Mexico Shrimp Fishery. Louisiana State Uni- versity, Center for Wetland Resources, Baton Rouge, LA. 168 pp. Whitaker, D. R. 1973. The U.S. shrimp industry. Past trends and prospects for the 1970’s. Mar. Fish. Rev. 35(5-6):23-30. Gulf Research Reports Volume 7 | Issue 1 January 1981 Observations of Deep-Reef Ichthyofauna from the Bahama and Cayman Islands, with Notes on Relative Abundance and Depth Distribution Ronald R. Lukens Gulf Coast Research Laboratory DOI: 10.18785/grr.0701.11 Follow this and additional works at: http://aquila.usm.edu/gcr Part of the Marine Biology Commons Recommended Citation Lukens, R. R. 1981. Observations of Deep-Reef Ichthyofauna from the Bahama and Cayman Islands, with Notes on Relative Abundance and Depth Distribution. Gulf Research Reports 7 (l): 79-81. Retrieved from http:// aquila.usm.edu/gcr/vol7/issl/! 1 This Short Communication is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf and Caribbean Research by an authorized editor of The Aquila Digital Community. For more information, please contact Joshua.Cromwell(2)usm.edu. Gulf Research Reports, Vol. 7, No. 1, 79-81, 1981. SHORT COMMUNICATIONS OBSERVATIONS OF DEEP-REEF ICHTHYOFAUNA FROM THE BAHAMA AND CAYMAN ISLANDS, WITH NOTES ON RELATIVE ABUNDANCE AND DEPTH DISTRIBUTION RONALD R LUKENS Fisheries Research and Development Section, Gulf Coast Research Laboratory, Ocean Springs, Mississippi 39564 ABSTRACT Observations of fish species inhabiting vertical wall habitats were conducted in the Bahama and Cayman islands. Twenty-three species from 12 families were recorded from various sites during the study. Number of species and abundance of individuals decreased with depth on the escarpments observed. Gramma melacara was the only species found throughout the depth ranges on all escarpments observed. Information about these habitats is sparse and more investigations are warranted. INTRODUCTION In situ observations of deep-reef fishes have been sparse, most often conducted from submersibles, as in Colin (1974, 1976) and Starck and Colin (1978). Observations of fish species inhabiting vertical wall habitats were conducted at three sites along the northernmost section of the Tongue of the Ocean in the Bahama Islands from September 22, 1980, through October 2, 1980, and on one site in the Cayman Islands, British West Indies, from November 21, 1980, through November 28, 1980 (Table I). TABLE 1. Location, date, and depth of each wall dive conducted. Site Location Geographical Location Date Depth of Dive 1 Chub Cay, Berry Islands 25°22.5'N 77°48.0'W 9-25-80 61 m 2 Andros Island 24°42.o'N 77°43.5 W 9-28-80 67 m 3 New Providence Island 25°02.S'N 77°34.o'w 9 29-80 52 m 4 Little Cayman Island 19°41.0'N 80°03.5'W 11-23-80 46 in METHODS AND MATERIALS All observations were conducted using SCUBA. Dives in the Bahama Islands were conducted from the R/V OLI of the Ocean Learning Institute in West Palm Beach, Florida. Dives off Little Cayman Island were conducted from the Manuscript received March 27, 1981 ; accepted May 28, 1981. beach. A total of 2.55 man-hours of underwater observation were completed. Fish counts were conducted by swimming over the escarpment edge to maximum depth and making observations upon ascent. Notes on the depth distribution and relative abundance of fish species encountered were written on a piece of plastic slate using a standard graphite pencil. Immediately upon surfacing from a dive, identifica- tion of fish species observed was compared with references from Bohlke and Chaplin (1968) and Randall (1968); underwater notes were transferred to a field notebook. Collection of specimens was not attempted due to the limited time available for each dive. DESCRIPTION OF STUDY SITES An abundance of hard corals, gorgonian corals, and sponges covered the wall habitats observed in this study, providing considerable habitat space for small cryptic fishes. Unfortunately, the limitations of using SCUBA at the depths encountered precluded anything more than a cursory examination of the species composition of the wall habitats. The first observation site was located off the southern coast of Chub Cay, Berry Islands, In the Bahamas, approxi- mately 2 miles offshore of Chub Cay Club Marina. The wall drop-off occurred at 37 m. The slope preceding the drop-off was marked by a series of ridges and channels, probably formed by sediment scounng. Coral growth was sparse on the slope, typically covering only the ridges. On the wall face, gorgonian corals and sponges were abundant with sparse hard coral growth. Small overhangs and crevices were abundant. Site 2 was located off the eastern coast of Andros Island, Bahamas, about 2 miles offshore of Fresh Creek. The escarp- ment occurred at 46 m. Bottom topography and coral growth were similar to those described for Site 1. 79 80 LUKENS Site 3 was located at the northwestern tip of New Providence, Bahamas. The escarpment was encountered at 15 m. Hermatypic coral growth above the escarpment was well developed. On the wall face, large formations were replaced by small coral heads, luxuriant gorgonian corals, and sponges. At approximately 24 m, a small horizontal ledge jutted out from the wall face. Below the ledge the wall was nearly vertical. Site 4 was located off the northern coast of Little Cayman Island, British West Indies, about 1 mile offshore from Jackson’s Point. The escarpment began at 21 m. Extensive reef development occurred on the shelf above the escarpment. A large ridge of staghorn coral occurred on the edge of the drop-off. The first 1 1 m formed a steep slope (approximately 50°), becoming nearly vertical at approxi- mately 30 m. Again the wall face was occupied by an abun- dance of gorgonian corals, sponges, and small, low-profile heads. RESULTS Table 2 lists fish species observed, maximum depth of occurrence during observations, abundance estimates, and locality. DISCUSSION Thirteen of the 23 species recorded during this study also were reported from deep-reef escarpments in Jamaica and British Honduras by Colin (1974). As reported by Colin (1974), and by Starck and Colin (1978), Gramma melacara was by far the most abundant species on the deep wall faces observed during this study. Colin (1976) found G. melacara to be the most abundant fish from 90 to 1 10 m off Whale Cay, Berry Islands, Bahama Islands. During observations off Chub Cay and Andros Island, both in the Bahamas, the escarpment was encountered in relatively deep water, 37 m and 46 m, respectively. Fish TABLE 2. Maximum depth of observation and abundance estimates of fish species observed during study. Observation Depths (m) Family, Genus, and Species Site 1 Site 2 Site 3 Site 4 Species Abundance Holocentridae IJolocentrus rufus (Walbaum) Serranidae 48 1 juvenile Cephalopholis fulva (Linnaeus) 24 2 adults Epinephehts gvttatus (Linnaeus) 24 1 adult Hypoplectrus puella (Cuvier) 52 1 adult IJopropoma sp. 50 1 adult Mycteroperca bonaci (Poey) 30 1 adult Serranus baldwini (Evermann and Marsh) Grammidae 55 1 adult Gramma lorcto Poey 24 Many adults and juveniles Gramma melacara Bohlke and Randall Lutjanidae 61 67 52 46 Very many adults and juveniles Luljanus apodus (Walbaum) 28 4 adults Ocyurus chrysurus (Bloch) Haemulidae 30 5 adults Haemulon plumieri (Lacepede) Chactodonlidae 50 1 adult Holacanthus tricolor (Bloch) 24 30 1 adult and 1 juvenile Prognathodes aculeatus (Poey) 24 30 3 adults Pomacentridae Chromis cyaneus (Poey) 24 30 Many adults Chrornis insolaius (Cuvier) 24 Many adults and juveniles Chromis multUmeaius (Guichenot) 24 Many adults Pomacentrus partitas Poey Labridae 50 52 7 adults Bodicnus pulchellus (Poey) 52 1 juvenile Clepticus parrai (Bloch and Schneider) Spbyraenidae 52 30 Many adults Sphyraena barracuda (Walbaum) Gobiidae 40 4 juveniles Go biosoma sp. 46 1 adult Tetraodontidae Canthigaster rostrata (Bloch) 24 1 adult Short Communications 81 fauna associated with the sparse coral growth at the escarp- ment edge was represented by scattered individuals of the families Serranidae, Chaetodontidae, Pomacentridae, Labridae, and Scaridae. On the wall face off Chub Cay from 37 to 61 m, only two species were recorded, and off Andros Island from 46 to 67 m, only six species were recorded, four of which were represented by only one individuaL In contrast to the first two observations, observations off New Providence, Bahamas, and Little Cayman Island, B.W.I., revealed the escarpment in 15 m and 21 m of water, respectively. Coral growth at the escarpment edge was well developed, and the associated fish fauna was extensive. Over 60% of the species listed in Table 2 were recorded only from the New Providence and Little Cayman escarp- ments. I attributed this difference in abundance of species and individuals to the fact that the escarpment edge at those two sites was located in relatively shallow water, thus placing the “drop off' in closer proximity to the highly populated shallow reef habitat. As observation depth on the vertical face of those walls increased, species abundance decreased, as did abundance of individuals with the exception of Gramma melacara. I believe a secondary factor influencing species and individual abundance at site 3 was the occurrence of the horizontal ledge on the wall face approximately 9 m below the escarpment edge. Observations around that ledge revealed 9 of the 13 species recorded on that escarpment. I believe that reef fish probably migrate freely from the well-developed reef above the escarpment to the ledge and back, since the two sites are separated by only 9 m. Gramma loreto was common above the escarpment and was the most abundant fish at the ledge. Above the ledge on the wall face and below the ledge, G. melacara replaced G. loreto. Overlap of the two species was slight, corresponding with the findings of Starck and Colin (1978). It is likely that the differences in ichthyofauna between the shallow coral reef and the deep vertical wall face are influenced by water depth as well as by substrate orientation. More extensive observations along with acquisition of quan- titative data would be required to arrive at any acceptable conclusions. In situ observations and sampling are important to study adequately the deep reef and escarpment habitats. Open circuit SCUBA as well as deep submersibles have been used in these areas, and both have assets and drawbacks. Perhaps both methods used in conjunction would prove effective. Lock-out diving from a submersible is another alternative. More intense examination of this unique and interesting habitat type is warranted, as little is known of the ichthyofaunal species composition, community struc- ture, and potential existence of undescribcd species occurring there. ACKNOWLEDGMENTS I thank the Mississippi-Alabama Sea Cxrant Consortium and the Ocean Learning Institute for their support of the Bahama observations. My thanks to Drs. James I. Jones and Richard Heard, and to Max Flandorfer and Timothy White without whom the Bahama field work could not have been accomplished. My thanks also go to the family of Lloyd Rhian of Hattiesburg, Mississippi, for their support during the Cayman Island phase of this study. The assistance of Walter Rhian during the Little Cayman field work is grate- fully acknowledged. Thanks are extended to Dr. Robert Shipp of the University of South Alabama, Mobile, for his suggestions during the planning stage of this study. REFERENCES CITED Bohlke, J. E. & C. C. G. Chaplin. 1968. Fishes of the Bahamas and Adjacent Tropical Waters. Published for the Academy of Natural Sciences of Philadelphia by Livingston Publishing Co., Wynne- wood, PA. 771 pp. Colin, P. L. 1974. Observation and collection of deep-reef fishes off the coasts of Jamaica and British Honduras (Belize). Mar. Biol. 24(1):29-38. . 1976. Observations of deep-reef fishes in the Tongue-of- the-Ocean, Bahamas. Bull. Mar. Sci. 26(4):603-605. Randall, J. E. 1968 Caribbean Reef Fishes. T. F. H. Publ., Inc., Jersey City, N.J. 318 pp. Starck, W. A. & P. L. Colin. 1978. Gramma linki: A new species of grammid fish from the tropical western Atlantic. Bull. Mar. Sci. 28(1) 146-152 Gulf Research Reports Volume 7 | Issue 1 January 1981 First Recorded Observance of the Dinoflagellate Prorocentrum minimum (Pavillard) Schiller 1933 in Mississippi Sound and Adjacent Waters Harriet M. Perry Gulf Coast Research Laboratory Jerry A. McLelland Gulf Coast Research Laboratory DOI: 10.18785/grr.0701.12 Follow this and additional works at: http:/ / aquila.usm.edu/ gcr Part of the Marine Biology Commons Recommended Citation Perry, H. M. andj. A. McLelland. 1981. First Recorded Observance of the Dinoflagellate Prorocentrum minimum (Pavillard) Schiller 1933 in Mississippi Sound and Adjacent Waters. Gulf Research Reports 7 (l): 83-85. Retrieved from http:// aquila.usm.edu/gcr/vol7/issl/12 This Short Communication is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf and Caribbean Research by an authorized editor of The Aquila Digital Community. For more information, please contact Joshua.Cromwell(2)usm.edu. Gulf Research Reports, Yol. 7, No. 1, 83-85, 1981. FIRST RECORDED OBSERVANCE OF THE DINOFLAGELLATE PROROCENTRVM MINIMUM (PAVILLARD) SCHILLER 1933 IN MISSISSIPPI SOUND AND ADJACENT WATERS 1 HARRIET M. PERRY AND JERRY A. McLELLAND Fisheries Research and Development , and Ecology Sections Gulf Coast Research Laboratory ; Ocean Springs, Mississippi 39564 ABSTRACT The present paper documents the occurrence of the dinoflagcllatc Prorocentrum minimum in Mississippi Sound and adjacent coastal waters. Outbreaks of discolored water are attributed to blooms of P. minimum in February 1977 and in January and February 1981. Data are presented on the seasonality of the organism in St. Louis Bay. Observations on water appearance and a descriptive analysis of the cells are presented for the 1981 blooms. INTRODUCTION Major outbreaks of discolored water caused by phyto- plankton blooms periodically occur in Mississippi coastal waters (Perry etal. 1979,Eleuteriuset al. 1981). In addition, the occurrence of localized plankton blooms appears to be commonplace and is suggested as the cause of fish kills and jubilees along the Mississippi coast (Gunter and Lyles 1979). OBSERVATIONS The most recent outbreaks of discolored water occurred 'This study was conducted in cooperation with the U.S. Department of Commerce, NOAA, National Marine Fisheries Service, under PL 88-309, Project 2-296 -R Manuscript received June 30, 1981; accepted July 2, 1981. in Mississippi Sound and adjacent coastal waters in January and February 1981. Areas of “reddish” water were observed in the Sound south of the Intracoastal Waterway between the mainland and the east end of Horn Island and in St. Martin Bayou, an inlet off the Back Bay of Biloxi (Figure 1). Samples of the discolored water were taken by personnel of the Gulf Coast Research Laboratory parasitology section and given to the authors for analysis. Examination of these samples revealed the presence of large numbers of the dinoflagella te Prorocentrum minimum. Though the samples were not quantitative, cell numbers were estimated to be in the millions per liter. Water at the St. Martin Bayou site was reported to be viscous and “orange-brown” in color. Numerous spot ( Leiostomus xanthurus) were observed swimming erratically or floating belly-up. No Fish kills were 84 Perry and McLelland reported in association with the bloom in the Sound. Hydrographic data were not available from either site. From 1-ml sample aliquots placed on microscope slides, randomly selected cells were measured using an eyepiece micrometer (Table 1). Photomicrographs displaying cell characteristics are shown in Figure 2. Cells from the Sound site were slightly larger than those from the Bayou site. The anterior spine, characteristic of the genus, was present on most but not all of the specimens examined. The speci- mens exhibited subtle variations in shape from ovoid- quadrangular to near circular. Such variations in shape and presence or absence of the spine are typical of the species as seen in Hulburt’s (1965) study of dense growths of P. minimum in New England estuaries. All specimens dis- played poroid valve surfaces with striate margins (inter- calary band), a large vacuole near the anterior end, and two flagella, one circular and one trailing, protruding from a shallow depression adjacent to the anterior spine. Although the majority of cells were free-swimming, clumps of up to 100 or more cells were frequently observed in the samples, possibly accounting for the “rust-colored” suspended sedi- ment noticed at the Bayou site. TABLE 1. Measurements (N = 15) of Prorocentruin minimum cells collected in Mississippi waters. Standard error in parenthesis. Site Length (pt ) Width (pi) Mississippi Sound 19.5 (±0.27) 19.3 (±0.32) St. Martin Bayou 17.3 (±0,29) 17.3 (±0.34) In addition to the 1981 blooms, the junior author observed a bloom of P. minimum in February 1977. Samples of discolored water were collected near the mouth of Fort Bayou (Figure 1) and brought to the Laboratory for analysis. All samples contained large numbers of P. minimum. The cells were estimated to be in the millions per liter, averaging between 18 and 20 microns in length and 14 to 1 6 microns in width. No hydrographic data were available. Prorocentrum minimum appears to be an occasional component of the phytoplankton community in local waters. It was present periodically in phytoplankton samples collected from December 1977 through December 1978 at six stations in St. Louis Bay, Mississippi (Gulf Coast Research Laboratory, unpublished data). Peak abundance of 22,500 cells per liter occurred in March during a period of low salinity and high river discharge. The dinoflagellate was sporadic in occurrence from May through July, dis- appearing entirely from August through November. It reappeared in December 1978 and was more abundant at stations near the head of the Bay. The St. Louis Bay observations are somewhat disparate Figure 2. Prorocentrum minimum , Mississippi coastal waters. (A) Preserved specimen showing anterior spine (arrow). (B) Dried specimen showing poroid valve surface and striate margin (intercalary band). (Nomiarski optics, X 2300) from those of Campbell (1973) who found P. minimum present throughout the year in the Gales Creek estuary of North Carolina, with densities reaching 206 cells per ml in April. Campbell described the species as euryhaline. occuning in salinities from 1 to 33 ppt (but seemingly preferring salinities toward the higher ranges), and eury- thermal in temperatures from 3 to 31°C. The authors regret that very little quantitative data have been collected that would suggest the factors con- tributing to the development of phytoplankton blooms in Mississippi coastal waters. Most observations are made in the course of routine sampling trips for various projects. To the present, there has been no baseline monitoring of biological, hydrological, and meteorological parameters that specifically may be of importance in producing and sustaining bloom conditions. Short Communications 85 ACKNOWLEDGMENTS minimum and Mr. Jack Fournie, Mrs. Kay Richards, and Mr. Louis Eaton for providing samples and field observations. The authors thank Dr. R. B. Channel of Vanderbuilt Uni- Photographs were provided by Dr. Bill Hawkins of the Gulf versity for confirming the identification of Prorocentrum Coast Research Laboratory microscopy section. REFERENCES CITED Campbell, F. H. 1973. Studies on Brackish Water Phytoplankton. Sea Grant Publication UNC-SG-73-07. Sea Grant Program, School of Public Health, University of North Carolina, Chapel Hill, NC. 406 pp. Eleuterius, L, N., H. M. Ferry, C. K. Eleuterius, J. R. Warren, and J. D. Caldwell. 1981. Causative analysis on a near-shore bloom of Oscillatoria erythraea (Trichodesmiumj in the northern Gulf of Mexico. Northeast Gulf Sci. fin press) Gunter, G. & C. H. Lyles. 1 979. Localized plankton blooms and jubilees on the Gulf Coast. Gulf Res. Rept. 6(3): 297-299. Hulburt, E. M. 1965. Three closely allied dinoflagellates. J. Phycol. 1(2):95 — 96. Perry, H. M., K. C. Stuck & H. D. Howse. 1979. First record of a bloom of Gonyaulax monilata in coastal waters of Mississippi. Gulf Res. Rept. 6(3):313 316. Gulf Research Reports Volume 7 | Issue 1 January 1981 Preliminary Observations of the Effect ofEimeriafunduli (Protozoa: Eimeriidae) on the Gulf Killifish Fundulus grandis and Its Potential Impact on the Killifish Bait Industry Mobashir A. Solangi Gulf Coast Research Laboratory John T. Ogle Gulf Coast Research Laboratory DOI: 10.18785/grr.0701.13 Follow this and additional works at: http:/ / aquila.usm.edu/ gcr Part of the Marine Biology Commons Recommended Citation Solangi, M. A. andj. T. Ogle. 1981. Preliminary Observations of the Effect of Eimeriafunduli (Protozoa: Eimeriidae) on the Gulf Killifish Fundulus grandis and Its Potential Impact on the Killifish Bait Industry. Gulf Research Reports 7 (l) : 87-88. Retrieved from http:// aquila.usm.edu/gcr/vol7/issl/13 This Short Communication is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf and Caribbean Research by an authorized editor of The Aquila Digital Community. For more information, please contact Joshua.Cromwell(2)usm.edu. Gulf Research Reports, Vol. 7, No. 1 , 87-88, 1981 . PRELIMINARY OBSERVATIONS OF THE EFFECT OF EIMERIA FUN DU LI (PROTOZOA: EIMER11DAE) ON THE GULF KILL1FISH FUNDULUS GRANDIS AND ITS POTENTIAL IMPACT ON THE KILLIFISH BAIT INDUSTRY' MOBASHIR A. SOLANGI AND JOHN T. OGLE Parasitology and Oyster Biology Sections, Gulf Coast Research Laboratory, Ocean Springs, Mississippi 39564 ABSTRACT Liver infections of Eimeria funduli, a pathogenic coccidium, greatly affected growth of Fundulus graridis (Gulf killifish) maintained in an aquaculture facility for 55 days. At termination of the experiment, average weight gained by uninfected killifish was 877.5% compared to 308.0% in diseased fish. There appeared to be no correlation between mortality and disease in this study. INTRODUCTION Epizootics of Eimeria funduli Duszynski, Solangi, and Overstreet, 1979, a pathogenic hepatic coccidian of killi- fishes, have occurred in several coastal areas of the northern Gulf of Mexico and probably other areas (Solangi and Overstreet 1980, Foumie and Solangi 1980). Although 80 to 85% of both the liver and pancreatic tissues of heavily infected Fish can be replaced by oocysts of E funduli (Solangi and Overstreet 1980; Hawkins, Solangi, and Over- street 1981), the disease does not appear to cause mortality in affected Fish maintained in the laboratory. However, Solangi and Overstreet (1980) suspected that the parasite affected the growth of diseased fish. The Gulf killifish Fundulus grandis is an important mem- ber of the salt marsh ecosystem, supports a growing bait industry, and can be reared commercially (Mcllwain 1977; Solangi and Overstreet 1980; Tatum et al. 1978), Conse- quently, the disease could have a considerable impact on the economic potential of Gulf killifish. This paper reports the effect of E. funduli on growth of F. grandis, possible impact of the coccidian on the killifish bait industry, and means of preventing the disease in aqua- culture facilities. MATERIALS AND METHODS Laboratory-reared Fundulus grandis were obtained by stripping gravid male and female killifish collected from Halstead Bayou, Ocean Springs, Mississippi. Parasite-free fish were 2 1/2 months old al the beginning of the experi- ment, and were maintained in the laboratory at a tempera- ture of 25 ± 2°C and salinity of 20 t 3 ppt. Infected indi- viduals of the grass slump Palaemonetes pugio Holthuis were collected from ponds adjacent to Halstead Bayou. A group of 50 fish, randomly picked, were fed a single dose of infected grass shrimp to initiate the coccidian infections, whereas, 48 fish constituting a second group were fed Bama® Minnow Chow and they served as controls. Fish 1 This study was conducted in cooperation with U.S. Department of Commerce, NOAA, National Marine Fisheries Service, under PL 88- 309, Project 2-235-R. Manuscript received February 4, 1981 ; accepted March 9, 1981. in both groups were fed Bama® Minnow Chow throughout the remaining days of the experiment. Diseased and control fish were maintained in separate 3500-liter recirculating tanks containing 15 ppt seawater seeded with unicellular algae to provide supplemental food. Prior to being intro- duced into culture tanks, all killifish were weighed in grams and their total length measured in millimeters. At the end of the study, all surviving fish from both groups were weighed and measured. Growth was calculated by differences in weight gained and statistical analyses on the growth data were conducted using procedures of Campbell (1967) and of Steel and Torrie (1960). RESULTS Infections of Eimeria funduli had a considerable impact on growth of Fundulus grandis (Table 1). Infected killifish weighed significantly less than their uninfected counterparts. Diseased fish weighed an average of 24.8% more than unin- fected fish prior to the experiment; however, by termination of the study (55 days) average weight of control fish exceeded that of parasitized fish by 91.6% (Table 1). Eimeria funduli infections did not appear to cause mortality in this study. Survival of killifish after the 55-day experiment was 64.0% and 87 5% in control and diseased fish, respectively. However, most deaths occurred during the last 7 days of the study when there was an overnight decrease in water temperature from 26°C to 13°C. DISCUSSION In commerical bait-fish operations, about 45 to 52 days are required for killifish to reach marketable size (Tatum and Helton 1977; Tatum et al. 1978). Any factor that increases this grow-out period would reduce profits for bait- fish farmers. Based on data presented in Table 1, E, funduli greatly affects the growth of F. grandis maintained in an aquaculture facility and, consequently, could increase the grow-out period of killifish. Also, the assumed small stocks of F. grandis in panzootic areas reported by Solangi and Overstreet (1980) may be related to coccidian infections. Although, in view of our findings, it is apparent that the parasite could have a significant impact on the economic 87 88 S0LANG1 AND OGLE TABLE 1 . Average weight (g) and total length (mm) gain of Fundulus grandis after 55-day infection of Eimeria funduli. Control Diseased Number Weight Length 1 Weight Length 1 Mean ± Standard Error Mean ± Standard Error Number Mean ± Standard Error Mean ± Standard Error 27 August 1980 2 50 0.129 ±0.008 18.66 ±0.395 48 0.161 ±0.001 19.58 ±0.508 22 October 1980 3 32 1.261 ±0.261 43.41 ±2.567 42 0.658 ±0.023 38.67 ±0.471 Average gain, % 877.5 132.6 308.0 97.5 1 Average lengths of control and diseased fish at the beginning and ter- 95% confidence limit (t-Tcst). minution of experiments are equal at 95% confidence limit (t-Test). 3 Average weight of control fish is greater than that of diseased fish 2 Average weight of control fish is less than that of diseased fish at at 95% confidence limit (t-Test). potential of Gulf killifish, a detailed study on the effect of E. funduli on wild populations of killifish is urgently needed. At present we do not have evidence suggesting a correla- tion between mortality and disease. Since most deaths in this study occurred during the period when the water tem- perature dropped abruptly, it appears that temperature shock coupled with undetermined stresses in the culture system could have contributed to the mortality. For the past 3 years we have maintained numerous groups of exper- imentally and naturally infected killifish in the laboratory for at least 3 months and have not witnessed any mortality. However, even though mortality cannot be ascribed to the parasite per se, heavily infected fish probably have difficulty surviving environmental and nutritional stresses. To achieve maximum yield of killifish in bait operations, the parasite should be eliminated from the culture system. Although no chemotherapeutic treatment is available cur- rently, isolation of the intermediate host from the culture facility appears to be the only practical alternative available at this time. The grass shrimp and possibly other crustaceans serve as intermediate hosts (Solangi and Overstreet 1980), and have to be eaten to complete the life cycle. Exclusion of the infective intermediate host in pond-culture facilities, the predominant method of killifish rearing, can be a formidable task. On the other hand, closed recirculating systems such as the one developed by Ogle and Solangi at the Gulf Coast Research Laboratory in Mississippi appear to be an attractive alternative to pond rearing. In addition to effectively eliminating the intermediate host and providing good growth, the solar-heated recirculating system of Ogle and Solangi gives the aquaculturist control over many environmental factors not possible in pond culture. ACKNOWLEDGMENTS The authors are grateful to the following persons of the Gulf Coast Research Laboratory: Dr. Adrian Lawler for pro- viding laboratory-reared killifish, and Drs. Robin Overstreet and William Hawkins for their comments on the manuscript. REFERENCES CITED Campbell, R. C, 1961 .Statistics for Biologists. Cambridge University Press, London. 242 pp. Fournie, J. W. & M. A. Solangi, 1980. Prevalence of Eimeria funduli (Protozoa: F.imeriidae) in the Iongnose killifish Fundulus similis from Morn Island, Mississippi. Gulf Res. Rept. 6(4):427 -428. Hawkins, W. t., M. A. Solangi & R. M. Overstreet. 1981. Ultrastruc- tural effects of the coccidiu m , Eimeria funduli Duszynski, Solangi and Overstreet, 1979 on the liver of killifishes. / Fish. Diseases 4:281-295. Mcilwain.T. D, 1977. Bait fish rearing. Mississippi Marine Resources Commission, Mississippi. Project GR-76-005. 14 pp. Solangi, M. A. & R. M. Overstreet, 1980. Biology and pathogenesis of the coccidium Eimeria funduli infecting killifishes. J. Parasit. 66(3):513— 526. Steel, R. G. D. & J. H. Tome. 1960. Principles and Procedures of Statistics. McGraw-Hill Book Company. New York. 481 pp. Tatum, W. M. & R. F, Helton. 1977. Preliminary results of experi- ments on the feasibility of producing bull minnows ( Fundulus grandis) for die live bait industry. Pages 49-54 in Proc. 8th Annu. Meet. World Mariculture Soc. San Jose, Costa Rica. Tatum, W. M„ W. C. Trimble & R. F. Helton. 1978. Production of Gulf killifish in brackish water ponds. Proc , Annu. Cortf. Southeast. Assoc. Fish & Wildl. Agencies 32:502-508. Gulf Research Reports Volume 7 | Issue 1 January 1981 Status of Turtles on the Mississippi Coast Gordon Gunter Gulf Coast Research Laboratory DOI: 10.18785/grr.0701.14 Follow this and additional works at: http://aquila.usm.edu/gcr Part of the Marine Biology Commons Recommended Citation Gunter, G. 1981. Status ofTurtles on the Mississippi Coast. Gulf Research Reports 7 (l): 89-92. Retrieved from http://aquila.usm.edu/gcr/vol7/issl/14 This Short Communication is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf and Caribbean Research by an authorized editor of The Aquila Digital Community. For more information, please contact Joshua.Cromwell(3)usm.edu. Gulf Research Reports, Vol. 7, No. 1 , 89-92, 1981 . STATUS OF TURTLES ON THE MISSISSIPPI COAST GORDON GUNTER Gulf Coast Research Laboratory, Ocean Springs, Mississippi 39564 ABSTRA CT Sea turtles have declined in numbers and federal agencies have become concerned with the numbers drowned in trawls by commercial shrimpers. Records are given of freshwater turtles and of the gopher tortoise in low-salinity waters. These include the Florida cooler Pseudemys panda na, the snapping turtle Chelydra serpentina, the alligator snapper Macrodemy & ternmincki, and the gopher Gopherus polyphemus. The diamondbaek terrapin Malaclemys terrapin pileata is common in brackish waters of Alabama and Mississippi, All sea turtles of the western Atlantic Ocean may be expected in Mississippi waters except for the Pacific rid ley Lepidochelys olivacea, indigenous in northern South America in the Atlantic. INTRODUCTION In the past few years considerable interest in sea turtles has developed in the commercial shrimp fishery because of laws of the federal government. Turtles are caught in trawls of shrimp fishermen, and animals pulled for more than 2 hours or so are drowned. As a preliminary to some action, both State of Mississippi and United States authorities have asked the Gulf Coast Research Laboratory (GCRL) for a summary of information on sea turtles. These words are written as a summary of the information known about Mississippi coastal lurtles. CLASSIFICATION The Order Testudinata of the Class Reptilia of the Sub- phylum Vertebrata includes all turtles that have lived on Earth. This group of animals arose during the Lower Triassic approximately 185 million years ago. BRACKISH WATER TURTLES A few freshwater turtles are washed down into low-salinity watery following freshets, floods, and rain storms on Ihe coast. The writer once picked Up a snapping turtle ( Chelydra serpentina ) at the mouth of Biloxi Bay (Gunter ct al. 1973). Water salinity was 16.9 ppt. During the period of August 26 through September 19, 1969, a unit of Seabees assisted in cleaning up the GCRL following Hurricane Camille of August 17—1 8, 1969. During that process, a very lively alligator snapping turtle (. Macro - clemys ternmincki) was dug up from about 2 feet under the bottom of the innermost pond at the head of the boat slip. Salinity of the water was not taken. The pond was about 60 yards from the shore of Davis Bay, a tributary of Biloxi Bay. This turtle was dug up in September, virtually at the end of summer. A gopher tortoise, Gopherus polyphemus , had a den between the buildings and the shore of Davis Bayou and every few days it swam the Laboratory boat slip and pro- ceeded to high ground to the north. I never saw this event, but had it reported to me. I placed this turtle in a large sink of fresh waler and found it floated very well. 1 made this Manuscript received November 7, 1980; accepted March 3, 1981. determination at the written instigation of Chapman Grant, who wondered if gopher tortoises could float. Christmas and Waller (1973) reported three Pseudemys florklana, the Florida Cooler, from waler with a salinity of 5,5 and 5.6 ppt from the lower Tchouticabouffa River. The diamondbaek terrapin (Malaclemys terrapin) is the common turtle of low-salinity waters from Maryland to south Texas, and it has been divided into several subspecies along the way. In Mississippi, the subspecies pileata is common in low-salinity waters and in marshes, but seems to have fallen in numbers in recent years in the area of this Laboratory, possibly because of resurgence of the alligator. The same turtle is found in Alabama and, according to Mount (1975), it has declined in Mobile Bay due to Hurricane Camille in 1969. All of the turtles listed above, except the diamondbacks and the gopher, are essentially freshwater species which only venture into low-salinity water as strays. The diamond- back is essentially a brackish-water turtle ; the gopher tortoise is terrestrial. SEA TURTLES Marine turtles have strong resemblances in that the feet are all flippers made for swimming and not much else. The largest is the leatherback turtle {Dermochelys coriacea) with parallel ridges down the back, and a leatherlike carapace undivided into plates. Ingle and Smith (1949) said a speci- men from British Columbia weighed 1,450 pounds. It is worldwide in the tropics and subtropics, but not of great abundance anywhere. However, Leary (1957) reported seeing 100 along one rip current over a distance of 30 miles on the Texas coast. The leatherbacks belong to the Family Dermochelidae while all other sea lurtles belong to the Family Cheloniidae, Although all species come close to shore and enter the estuaries at times, apparently all of them venture to the high seas and have been seen there far from land. However, they seem to be restrained by cold water. In North America, Dermochelys coriacea goes to Newfound- land and British Columbia. Its presence in most oceans led Hvass (1958) to say that it is probably the most widely distributed of all reptiles. De Sola (1939) said that the leatherback is the largest reptile on Earth, and he reported a weight of 1 ,900 pounds. However, I think that this is less 89 90 Gunter than the huge alligators this country formerly produced, one of which measured more than 19 feet in length. Records of nesting of this species on the south Florida coast have been given by Caldwell et al. (1955), Allen and Neill (1957), and Caldwell (1959). Occurrence records and scattered nesting records of this turtle along the northern Gulf coast of Florida have been given by Verger (1965). We know of no other nesting records of this turtle else- where on the United States Gulf coast, but it is seen occa- sionally (see Leary 1957), and once I found a large dead one in Copano Bay, Texas, following a hard cold spell (Gunter and Hildebrand 1951). Although we have no precise record of D. coriacea in Mississippi waters, we may assume with fidelity that, like the much rarer manatee, these animals occasionally swim through the waters of the state. Mount (1975) similarly has listed it in the salt waters of Alabama. Viosca (1961) in his listing of Louisiana turtles says of the leatherback, “Rare along our Coast.” The Atlantic loggerhead (Caretta caretta) is the largest chelonid. Caldwell et al. (1959) give the nesting range as from Cape Lookout, North Carolina, to the Caribbean Sea and Mexico. It has been tagged off South Carolina, and taken off Pass a la Loutre of the Mississippi River, The flesh is not highly esteemed and there is no known fishery for the species today. Groups of five or six of these turtles were seen off the western end of Horn Island in 1976, hut we have no record on nesting in Mississippi. The green turtle ( Chelonia my das) is noted for its culinary qualities and there are West Indian records of specimens up to 850 pounds. The animal is primarily herbivorus in con- trast to the loggerhead. Several thousand acres of seagrasses in Mississippi Sound must be a special attraction to this species. Seagrass beds of Mississippi have been described by Eleuterius (1977). According to Marquez-M ( 1 966), the green turtle is called La Tortuga Blanca in Spanish because that is its color; the green refers only to internal fat, or calipash, which colors the soup. The eggs also have a greenish tinge. In some parts of the Pacific, the shells of cognate subspecies are almost black (Hirth 1971), Until the turn of the century, the so-called green turtle and the ridley were shipped alive from south Texas ports to New York. These hapless animals were flipped onto their backs and carried that way on the open deck of coastwise steamers with the forelegslashed together to impede struggles to right themselves. We might reasonably surmise that in heavy weather some of these were freed by being washed overboard, but it was not a common loss. The inability of sea turtles to right themselves was taken advantage of in their capture. One old Texas fisherman told me that the turtles came ashore on islands at night and went to sleep, whereupon fishermen crept up quietly and rushed about flipping the turtles on their backs; they returned and picked up the turtles later. In all likelihood the expression “turned turtle” derives from experiences of such a nature. There seem to be no similar accounts of sea turtles on the Mississippi coast, but in 1918, over 337 pounds of green turtles were listed as sold (Rebel 1974, p. 1 16). A record card in our turtle file is worded as follows: Atlantic green turtle identified by David Burke, caught at Chandeleur, Louisiana, on 27 October 1972 by Mark Compton, a boatman. Turtle is about five or six years old and had 1 10 turtle barnacles, Chelon- ibia testudinaria , on his shell. He was caught in three feet of water. Carapace length 263 mm. On August 21, 1972, Mr. Richard Waller saw a Gulf ridley at longitude 29°26'5"N and latitude 88°56'l "W. This is approximately 80 miles south of Horn Island, Mississippi. Viosca (1961) said the ridley was the most abundant turtle off the Louisiana coast and that coincides with my observations over some 50 years off the northern Gulf coast. Viosca (1961) said the Gulf ridley preferred to nest in the loose sand of the Chandeleur Islands rather than the com- pacted beaches west of the delta of the Mississippi River. Apparently it formerly nested on the eastern coast of northern Mexico, and the adults extended to the Bermudas and occasionally to the British Isles. There is a cognate species on the western coast of Mexico and on the Pacific coast, generally. The ridley is the smallest of the edible sea turtles. It has no known large nesting grounds on the northern Gulf coast. It is a small white turtle growing to about 100 pounds in size. Fishermen often take it home to eat when it is caught. It has been noted in the case of the leatherback, the green turtle, and the Gulf ridley, that there is a peculiar gap in the distribution of young growing turtles. From the time the young escape to sea until the adults come ashore to lay, the intermediate sizes are not seen. Intermediate sizes are extremely rare and virtually unrecorded. Carr (1967) expounded on this matter at some length. This situation is not unknown in other animals and is particularly puzzling in the case of the tarpon. With regard to turtles, it may well be that the young ones hunt attached beds of sargassum or even the floating sargassum. Here the trouble is that the dis- tribution of attached and floating sargassum is very diffuse and not well known. It could be that one little turtle per square mile would absorb all the annual production from La Tortuguero, the Costa Rican nesting area, without appearing excessively numerous. The hawksbili ( Eretmochelys imbricata Linnaeus) has such a glistening, beautiful shell compared to all other turtles that it must be seen to be believed. The flesh is not favored and, in the Far East, it is said to be poisonous at times (De Sola 1939). In the northern Gulf only animals \Vz feet in carapace length or less are seen. In the southern Caribbean specimens 3 feet in carapace length have been reported. Most biologists who spend time afloat have seen a few hawksbilis in the northern Gulf. They are reputed Short Communications 91 to be active and aggressive. Mr. Richard Waller of this Laboratory once took a foot-long specimen at the surface about 40 miles south of Horn Island, Mississippi, where it was apparently asleep on a floating mat of sargassum. His chief impression was of the terrible fright of the captured animal and its violent attempts to escape. Because of that he let it go in a very short while. The hawksbill is not known to nest on the northern Gulf coast. SOME GENERALITIES AND MINOR POINTS Turtles were contemporaries of early dinosaurs and they have long outlived them. Their evolutionary strategy has been highly successful even though there seems to be a temporary recession of sea turtle populations caused by over-exploitation by man. Carr (1967) has suggested that this crisis may be met by a successful cultivation of turtles. The recent increased interest inmariculture gives some hope for this development. Wetjen (1948) and Carr (1967) have documented the great importance of sea turtles in the tropics of two and three generations ago. Carr (1967) has also told about the decline, but he has outlined a hopeful prognostication regarding management. A laying place for the green turtle still exists in Costa Rica; one for the Gulf ridley on the northeastern Mexican coast recently died out (see Carr 1967). Nesting of the hawkshill probably has occurred only in the Caribbean region in historic times. There are reported single or scat- tered nestings of the ridley, leatherback, green turtle, and loggerhead on the Gulf and South Atlantic coasts north to Virginia from time to time, and apparently these scattered nestings now maintain the species. Hopefully they will continue to do so until mankind remarshals its conservation forces and comes to the rescue of these antediluvean monsters which have existed for about a fifth of a billion years. Back in the first decades of this century, when diamond- back terrapins were selling for as high as $90 a dozen, S. F. Hildebrand (1929) was successful in raising these animals; commercial ventures also were successful in Louisiana, North Carolina, and Virginia. However, when wine was prohibited, preeminence of turtle soup declined, and sales of turtles and calipash declined as prices fell. Similarly, hawksbills were given some respite by the invention of a synthetic substitute for turtle shell. Several authors state that marine turtles never come ashore except to lay their eggs and that only the females, of course, come ashore. However, Stebbins (1954) said that various Pacific species come ashore to “bask”, and other authors said they come ashore to sun themselves. In this connection we should note from the statement above that turtles along the Texas coast come ashore at night to sleep. The leatherback is said to be one of the fastest of all swimmers. It has been stated that they can get up to 32 miles per hour, but I have seen no precise clockings of the swim- ming speed of this animal. But we may conclude that it is a very fast swimmer when disturbed or startled because it has impressed various observers. In the literature there are also statements that this turtle likes to remain at depths of 150 feet, but I have seen no statements as to how this was determined. With the exception of the ridley, female turtles come ashore after dark at which time they may be scared back to the water by the distant striking of a match, according to Carr (1967). The ridleys. in contrast, will crowd ashore in the daytime, or at least the Gulf subspecies does so. There is a peculiar anomaly in the distribution of the Pacific ridley. This species is also found in the southern Caribbean in the Guianas, but nowhere else on the eastern shores of the western hemisphere. Carr (1967) discussed this at length and showed that these animals were also found on the West African shore. He assumed that it comes around Africa from the east and is connected with Pacific ridleys all the way around the world to the western shore of Mexico. An alternate theory may be that this population was cut off from the Pacific when Isthmus America was formed approx- imately 5.7 million years ago (Emiliani et al. 1972). In any case the Gulf species of this lurtle is found only in the Atlantic but the Pacific subspecies is found widely in the Pacific and also in the restricted area of Atlantic South America, In summary, on the eastern shores of the western hemi- sphere we have Dermochelys coriacea, Eretmochelys imbricata, Caretta caretta, Chelnnia mydas. Lepidochelys kempi y and L olivacea. The Pacific species generally are given subspecific standing. Sea turtles were very numerous in Colonial days; they were widely used as food. In some cities such as Charleston, South Carolina, their eggs were highly prized for the baking of cakes. All species seem to have declined greatly in the past 100 years, but it is to be hoped that, as the knowledge of their biology increases, effective conservation measures will lead to restoration of their populations. The most recent review is lhal of Rebel (1974). It cites most of the literature and gives information on past commercial production in the Gulf and South Atlantic areas. Just as this manuscript was completed the volume con- taining the recent study of south Texas sea turtles by Rabalais and Rabalais (1980) was received. It must be mentioned in connection with the present remarks. The hawksbill (j Eretmochelys imbricata) and the leatherback ( Dermochelys coriacea ) were listed as rare and strandings of these two were not listed, although sightings and pre- vious records were given. Subadult loggerheads {Caretta caretta ) were listed as the most abundant turtles on the south Texas coast with Kemp’s ridleys as the second most abundant. Sporadic nesting of ridleys and green turtles on Padre Island was noted. 92 Gunter REFERENCES CITED Allen, E. Ross & Wilfred T. Neill. 1957. Another record of the Atlantic leatherback, Dermochelys c. coriacea nesting on the Florida coast. Copeia 1 957(2)4 143—1 44 . Caldwell, David K. 1959. On the status of the Atlantic leatherback turtle Dermochelys coriacea coriacea, as a visitant to Florida nesting beaches, with natural history notes. Q. J. Fla. Acad. Sci . 21(3):285-291 . __ , Archie Carr & Thomas R. Hellier, Jr. 1955. Natural history notes on the Atlantic loggerhead turtle, Caretta caretta caretta. Q. J Fla. Acad. Sci. 1 8(4); 292- 302. & Larry H. Ogren. 1959. Nesting and migration of the Atlantic loggerhead turtle. Bull. Fla, State Mus. 4(10). 295-308. Carr, Archie. 1967. So Excellent A Fishe . The American Museum of Natural History Press, Garden City, New York. 248 pp. Christmas J. Y. & Richard S. Waller. 1973. Estuarine vertebrates, Mississippi. Pages 320-403 in J. Y. Christmas (ed.), Phase IV: Biology. Cooperative Gulf of Mexico Estuarine Inventory and Study, Mississippi. Gulf Coast Research Laboratory, Ocean Springs, Mississippi. De Sola, Ralph (ed.). 1939. Reptiles and Amphibians . J. J. Little and Ives Company, New York. 253 pp. Eleutcrius, Lionel Nr 1977 The seagrasses of Mississippi. J. Miss. Acad. Sci. 33:57-79. Emiliani, C., S. Gaertner & B. Lidz. 1972. Neogene sedimentation on the Blake Plateau and the emergence of the Central American isthmus, Palaeogeogr. Palaeoclimatogr. Palaeoecol. 11:110. Gunter, G., B. S. Ballard & A. Venkataramiah 1973. Salinity prob- lems of organisms in coastal areas subject to the effect of engi- neering works, Contract Report H -73-3, U.S. Army Engineer Waterways Experiment Station, Vicksburg, Mississippi. 176 pp. & H. H. Hildebrand. 1951. Destruction of fishes and other organisms on the south Texas coast by the cold wave of January 28-February 3, 1951. Ecology 32(4):731 736. Hildebrand, Samuel F. 1929. Review of experiments on artificial cul- ture of Diamond-back Terrapin. Bull. U.S. Bur. Fish. 45:25-70. Hirth, H. F, 1971. Synopsis of biological data on the green turtle Chelonia mydas (Linnaeus) 1758. Food and Agriculture Organ- ization of the United Nations, Rome. FAO Fish. Synop. No. 85, F1RM/S85. Hvass, Hans. 1958. Reptiles and Amphibians of the World. Methuen & Co, Ltd. London. 125 pp. Ingle, Robert M. & F. G. Walton Smith. 1949. Sea Turtles and the Turtle Industry of the West Indies, Florida and the Gulf of Mexico, with Annotated Bibliography. The Marine Laboratory, University of Miami, University of Miami Press. 106 pp. Leary, Terrance R. 1957. A schooling of leatherback turtles, Dermo- chelys coriacea coriacea , on the Texas coast. Copew 1957(3):232. Marquez-M., Rene. 1966. La cria artificial de la tortuga blanca ( Chelonia mydas mydas Linnaeus) en Tortuguero, Costa Rica. Inslituto Nacional de Investigaciones Biologico-Pesqueias, Mexico. 28 pp. Mount, Robert H. 1975. The Reptiles and Amphibians of Alabama. Auburn Printing Company, Auburn. Alabama. 347 pp. Rabalais, S. C. & Nancy N. Rabalais. 1980. The occurrence of sea turtles on the south Texas coast. Contrib. Mar. Sci. 23:123-129. Rebel, Thomas P. 1974. Sea Turtles and the Turtle Industry of the West Indies, Florida, and the Gulf of Mexico. (Revised Edition) University of Miami Press, Coral Gables, Florida. 250 pp. Stcbbins, Robert C. 1 954. Amphibians and Reptiles of Western North America. McGraw-Hill Book Company, Inc., New York. 528 pp. Viosca, Percy, Jr. 1961. Turtles, tame and truculent. La. Conserv. 1 3(7-8):5-8. Wctjen, Atbert Richard. 1948. Harvest of the sea. Adventure 1 19(1) : 102 109. Yerger, Ralph W. 1965. The leatherback turtle on the Gulf coast of Florida. Copeia 1963(3):365- 366. Gulf Research Reports Volume 7 | Issue 1 January 1981 Observations on the Distribution and Seasonality of Portunid Megalopae in Mississippi Coastal Waters Kenneth C. Stuck Gulf Coast Research Laboratory Harriet M. Perry Gulf Coast Research Laboratory DOI: 10.18785/grr.0701.15 Follow this and additional works at: http://aquila.usm.edu/gcr Part of the Marine Biology Commons Recommended Citation Stuck, K. C. and H. M. Perry. 1981. Observations on the Distribution and Seasonality of Portunid Megalopae in Mississippi Coastal Waters. Gulf Research Reports 7 (l): 93-95. Retrieved from http : // aquila.usm.edu/gcr/vol7 /issl/15 This Short Communication is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf and Caribbean Research by an authorized editor of The Aquila Digital Community. For more information, please contact Joshua.Cromwell(o)usm.edu. Gulf Research Reports, Vol. 7, No. 1, 93-95, 1981. OBSERVATIONS ON THE DISTRIBUTION AND SEASONALITY OF PORTUNID MEGALOPAE IN MISSISSIPPI COASTAL WATERS 1 KENNETH C. STUCK AND HARRIET M. PERRY Fisheries Research and Development Section, Gulf Coast Research Laboratory, Ocean Springs, Mississippi 39564 ABSTRACT Observations on the distribution and seasonality of common coastal portunid megalopae are presented. Callinectes sapidus megalopae were abundant from May through November. The megalopae of C. similis, though present throughout the year, peaked in numbers from February through April. With the exception of January, Portunus spp. mega- lopae occurred in all months, with maximum numbers collected in April. Callinectes sapidus megalopae commonly occurred at all stations, whereas, the megalopae of C. similis and Portunus spp. appeared to be limited by salinity. INTRODUCTION There have been few studies on the distribution of portunid larvae in coastal and offshore waters of the north central Gulf of Mexico, In Texas, Daugherty (1952), More (1969), and King (1971) discussed the movement of Callin- ectes megalopae through coastal passes. In Louisiana, Darnell (1959) speculated on the occurrence of blue crab larvae in Lake Pontchartrain, and Adkins (1972) presented data on the seasonality of blue crab larvae from Whiskey Pass. Andryszak (1979) studied the summer distribution of brachyuran larvae in offshore waters of southeastern Louisiana. The distribution of Callinectes larvae in Missis- sippi coastal waters was investigated by Perry (1975). Menzel (1964) studied the summer distribution of blue crab larvae in Gulf waters off Alligator Harbor, Florida. The present study is the first in which the distribution and seasonality of C. sapidus Rath bun, 1896, C. similis Williams, 1966, and Portunus spp. megalopae are treated separately. MATERIALS AND METHODS Monthly quantitative nekton samples were collected in Mississippi coastal waters from July 1974 to September 1979, using 1-m nekton nets fitted with 1,050-jt netting. Nets were equipped with flowmeters, and opening and closing devices. Simultaneous, 20-minute surface and bottom tows were taken at sites 3 miles south of (1) Horn Island Pass (station 86), (2) Dog Keys Pass (station 84), and (3) Ship Island Pass (station 82). All portunid megalopae were removed from the samples, counted and identified. In samples containing over 200 megalopae, an aliquot of 100 specimens was examined. Identifications were made using characters developed in a concurrent rearing program in which megalopae were collected monthly for 1 year and reared through early crab stages in the laboratory. i This study was conducted in cooperation with the U.S. Department of Commerce, NOAA, National Marine Fisheries Service, under PL 88-309, Project 2-296-R. ManuscripL received June 30, 1981; accepted August 21, 1981. RESULTS AND DISCUSSION A total of 33,422 portunid megalopae was recovered from the 360 nekton samples examined (Table 1). The megalopae of Callinectes sapidus composed 70.8% of the total catch; C. similis, 1 1 .5%; Portunus spp., 17.5%; and other Portunidae, < 0.1%. Although several species may be included under Portunus spp., all reared Portunus megalopae were P. gibbesii. Included under “other Portunidae” were several specimens of an undescribed giant megalopa and another undescribed form which appeared to share characters distinctive of both Callinectes and Portunus. TABLE 1. Total catch of portunid megalopae by taxa. Taxa Total Catch* Total Standard Catchj" %of Standard Catch Callinectes sapidus 24,171 31,681.1 70.8 C. similis 4,396 5,157.3 11.5 Portunus spp. 4,839 7,853.0 17.6 Other Portunidae 16 21.0 < 0.1 Total 33,422 44,712.4 100.0 The sum of megalopae caught (numbcr/20-minute tow) from each sample. ■fThe sum of the standardized numbers (number/1,000 m 3 ) of mega- lopae from each sample. Concurrent trawl data were taken in coastal and estua- rine waters. Callinectes sapidus juveniles and adults con- stituted approximately 53% of the total catch while C. similis contributed 38%; Portunus spp., 9%; and other portunids, < 1 .0%. Total catch of portunid megalopae at all three stations was similar; however, the percent composition of the catch differed greatly (Table 2). 93 94 Stuck and Perry TABLE 2. Catch of major portunid taxa by station. Station Taxa Total Catch* Total Standard Catchf %of Standard Catch 86 C sapidus 6,662 7,950.2 49.5 C. similis 2,730 3,159.7 19.7 Portunus spp. 2,882 4,932.6 30.8 Total 12,274 16,042.5 100.0 84 C sapidus 7,672 11,851.9 73.1 C. similis 1,431 1,739.9 10.7 Portunus spp. 1,709 2,624.9 16.2 Total 10,812 16,216.7 100.0 82 G sapidus 9,837 11,880.9 95.5 C. similis 235 257.7 2.1 Portunus spp. 248 295.5 2.4 Total 10,320 12,434.1 100.0 ♦The sum of megalopae caught {number/20-minute tow) from each sample. fThe sum of the standardized numbers (number/1 ,000 m 3 )of mega- lopae from each sample. Station 86 contributed 35.9% of the total catch consisting of C sap id us (49.5%), C. similis (19.7%), Portunus spp. (30.8%), and unidentified Portunidae (0.1%), Station 84 yielded 36.3% of the total catch consisting of C. sapidus (73.1%), C similis (10.7%), and Portunus spp. (16.2%). Station 82 was somewhat less productive, providing 27.6% of the total catch. Callinectes sapidus dominated the catch (95.5%), with C. similis (2.1%) and Portunus spp. (2.4%) far less abundant. Overall percent composition as well as total numbers of C. sapidus megalopae increased from east to west, whereas the catch of C. similis and Portunus spp, was greatly decreased. This trend corresponds with an east-west salinity gradient characteristic of Mississippi coastal waters. Salinities were highest at station 86 throughout the sampling period with bottom waters averaging 32.1 ppt and surface waters, 25.5 ppt. A similar salinity regime was noted at station 84; bottom waters averaged 3 1 .4 ppt and su rface waters averaged 25.1 ppt. Salinities were lowest at station 82, averaging 28.3 ppt for bottom and 23.5 ppt for surface waters, with individual values seldom above 30.0 ppt. Although informa- tion on salinity preference of C. similis and Portunus gibbesii megalopae is not available, adults and juveniles are known to prefer coastal waters of high salinity (Christmas and Langley 1973). Bookhout and Costlow (1974) reported that salinities below 30.0 ppt were not favorable for develop- ment of Portunus spinicarpus larvae. Salinities optimal to maximum survival of C. sapidus megalopae (Costlow 1967) were observed at all stations, however; C. sapidus megalopae were more abundant at the lower salinity station 82. King (1971) reported greatest influx of Callinectes sp. megalopae to occur at 26.0 ppt salinity in Cedar Bayou. Based on overall catch, portunid megalopae showed no affinity for surface or bottom waters (Table 3), Although twice the number of C. similis megalopae were caught in surface than bottom waters, the difference can be accounted for by a single large catch (1,434.8/1,000 m 3 ) taken at station 86 in March 1976. Most (15 of 20) large catches of C. sapidus megalopae (3Q0+/tow) were taken on rising or peak tides; however, no preference for surface or bottom waters was observed. Individual large catches (100+ indi- viduals) of C. similis and Portunus spp. megalopae weie commonly taken during both rising and falling tides. TABLE 3. Catch of major portunid taxa by depth. Taxa Total Catch* Total Standard Catchf %of Standard Catch Surface C. sapidus 11,534 i 3,632.6 65.2 C. similis 3,290 3,780.3 18.1 Portunus spp. 2,467 3,493.5 16.7 Total 17,291 20,906.4 100.0 Bottom C. sapidus 12,637 18,048.4 75.9 C. similis 1,106 1,377.1 5.8 Portunus spp. 2,372 4,359.5 18.3 Total 16,115 23,785.0 100.0 *Tbe sum of megalopae caughi (number/20-minute tow) from each sample, fThe sum of the standardized numbers (number/ 1 ,000 m 3 ) of mega- lopae from each sample. Previous reports on the vertical distribution of Callinectes megalopae appear conflicting. Williams (1971), King (1971). Perry (1975), and Smyth (1980) reported Callinectes megalopae to be in greatest abundance in surface waters. In contrast, 96% of the Callinectes megalopae collected by Tagatz (1968) and all of the megalopae collected by Sandifer (1973) were from bottom waters. A definite seasonal pattern of abundance for portunid megalopae was observed (Figure 1). Callinectes similis mega- lopae were collected throughout the year, occurring in greatest abundance from February through April with a March peak. This was followed by an April peak of Portunus spp. during which concentrations of up to 1,670.3/1,000 m 3 were observed. Callinectes sapidus megalopae were collected in every month except January and February. Two peaks in abundance were observed, the first in late spring-early summer, and a second, larger peak in the late summer-early fall during which maximum densitites of 2,530. 8/ 1,000 m 3 were obtained. Large catches of C. sapidus megalopae were not made between December and April. Short Communications 95 The seasonal occurrence of C. sapidus megalopae reported here conflicts, in part, with previous studies from the northern Gulf. More (1969) and King (1971) reported a February-March peak of Callinectes spp. megalopae and suggested these megalopae represented an overwintered spawn from the previous fall. While a February-April peak of portunid megalopae was also observed in the present study, it consisted almost entirely of C. similis and Portunus spp. Adkins (1972) also reported a February peak of blue crab megalopae from Whiskey Pass, Louisiana. Portunid megalopae and early crabs collected from this same site during February and March 1981 were provided to the authors by Mr. Adkins. All were found to be C similis. Perry (1975) also reported a February occurrence of C. sapidus megalopae based on identification of young crabs reared from megalopae. Subsequent examination of these crabs found them to be C. similis. Abundance of Callinectes sapidus megalopae during thelate spring through fall months observed in the present study is in general agreement with previous studies. ACKNOWLEDGMENTS The authors thank Shiao Wang, formerly of the Gulf Coast Research Laboratory, who assisted in the rearing of megalopae, and Gerald Adkins, of the Louisiana Department of Wildlife and Fisheries, for supplying samples from the Whiskey Pass area. For their help in field collections, appreciation is extended to Tommy Van Devender, Myron Loman, James Warren, Kenneth Melvin, and Leroy Ladner. REFERENCES CITED Adkins, G. 1972. A study of the blue crab fishery in Louisiana. La. Midi, Fish. Comm. Tech, Bull. 3:1-57. Andryszak, B. L. 1979. Abundance, distribution and partial des- criptions of reptant decapod crustacean larvae collected from neritic Louisiana waters In July, 1976. Master’s thesis, Louisiana State University, Baton Rouge, Louisiana. 102 pp. Bookhout, C. G. & J. D. Costlow, Jr. 1974. Larval development of Portunus spinicarpus reared in the laboratory. Bull. Mar. Sci. 24:20-51. Christmas, J. Y. & W. Langley. 1973. Estuarine invertebrates, Mississippi. Pages 255—319 in J. Y. Christmas (ed.). Gulf of Mexico Estuarine Inventory and Study, Mississippi. Gulf Coast Research Laboratory, Ocean Springs, Mississippi. Costlow, J. D. 1967. The effect of salinity and temperature on survival and metamorphosis of megalops of the blue crab Callin- ectes sapidus. Helgol. wiss. Meeresunters. J 5:84-97. Darnell, R. M. 1959. Studies of the life history of the blue crab (Callinectes sapidus Rathbun) in Louisiana waters. Trans. Am. Fish.Soc. 88(4):294-3Q4. Daugherty, F. M., Jr. J952. The blue crab investigation, 1949-50. Tex.J. Sci. 4(l);77-84. King, B.D., III. 1971 .Study of migratory patterns of fisli and shellfish through a natural pass. Tex. Parks Wildl. Dep., Tech. Ser. 9:1-54. Menzel, R. W. 1964. Report on preliminary studies on the blue crab in Alligator Harbor and adjacent Gulf of Mexico with some observations on stone crab larvae. Oceanographic Institute, Florida State University. 12 pp. More, W. R. 1969. A contribution to the biology of the blue crab (Callinectes sapidus Rathbun) in Texas, with a description of the fishery. Tex. Parks Wildl. Dep., Tech. Ser. 1:1—31. Perry, H. M. 1975. The blue crab fishery in Mississippi. Gulf. Res. Rept. 5(1): 39-57. Sandifer, P. A. 1973. Distribution and abundance of decapod crustacean larvae in the York River estuary and adjacent lower Chesapeake Bay, Virginia, 1968-1969. Chesapeake Sci. 14(4): 235-257. Smyth, P. 0. 1980. Callinectes (Decapoda: Portunidae) larvae in the Middle Atlantic Bight, 1975 -77. Fish. Bull. 78(2): 251 -265. Tagatz, M. E. 1968. Biology of the blue crab, Callinectes sapidus Rathbun, in the St. Johns River, Florida. l/.S. Fish. Wildl. Serv., Fish, Bull. 67(1): 17 -33. Williams, A. B. 1971. A ten-year study of meroplankton in North Carolina estuaries: annual occurrence of some brachyuran developmental stages. Chesapeake Sci. 1 2:53- 61 , Gulf Research Reports Volume 7 | Issue 1 January 1981 Observations on the Distribution and Seasonality of Portunid Megalopae in Mississippi Coastal Waters Kenneth C. Stuck Gulf Coast Research Laboratory Harriet M. Perry Gulf Coast Research Laboratory DOI: 10.18785/grr.0701.15 Follow this and additional works at: http://aquila.usm.edu/gcr Part of the Marine Biology Commons Recommended Citation Stuck, K. C. and H. M. Perry. 1981. Observations on the Distribution and Seasonality of Portunid Megalopae in Mississippi Coastal Waters. Gulf Research Reports 7 (l): 93-95. Retrieved from http : // aquila.usm.edu/gcr/vol7 /issl/15 This Short Communication is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf and Caribbean Research by an authorized editor of The Aquila Digital Community. For more information, please contact Joshua.Cromwell(o)usm.edu. Gulf Research Reports, Vol. 7, No. 1, 93-95, 1981. OBSERVATIONS ON THE DISTRIBUTION AND SEASONALITY OF PORTUNID MEGALOPAE IN MISSISSIPPI COASTAL WATERS 1 KENNETH C. STUCK AND HARRIET M. PERRY Fisheries Research and Development Section, Gulf Coast Research Laboratory, Ocean Springs, Mississippi 39564 ABSTRACT Observations on the distribution and seasonality of common coastal portunid megalopae are presented. Callinectes sapidus megalopae were abundant from May through November. The megalopae of C. similis, though present throughout the year, peaked in numbers from February through April. With the exception of January, Portunus spp. mega- lopae occurred in all months, with maximum numbers collected in April. Callinectes sapidus megalopae commonly occurred at all stations, whereas, the megalopae of C. similis and Portunus spp. appeared to be limited by salinity. INTRODUCTION There have been few studies on the distribution of portunid larvae in coastal and offshore waters of the north central Gulf of Mexico, In Texas, Daugherty (1952), More (1969), and King (1971) discussed the movement of Callin- ectes megalopae through coastal passes. In Louisiana, Darnell (1959) speculated on the occurrence of blue crab larvae in Lake Pontchartrain, and Adkins (1972) presented data on the seasonality of blue crab larvae from Whiskey Pass. Andryszak (1979) studied the summer distribution of brachyuran larvae in offshore waters of southeastern Louisiana. The distribution of Callinectes larvae in Missis- sippi coastal waters was investigated by Perry (1975). Menzel (1964) studied the summer distribution of blue crab larvae in Gulf waters off Alligator Harbor, Florida. The present study is the first in which the distribution and seasonality of C. sapidus Rath bun, 1896, C. similis Williams, 1966, and Portunus spp. megalopae are treated separately. MATERIALS AND METHODS Monthly quantitative nekton samples were collected in Mississippi coastal waters from July 1974 to September 1979, using 1-m nekton nets fitted with 1,050-jt netting. Nets were equipped with flowmeters, and opening and closing devices. Simultaneous, 20-minute surface and bottom tows were taken at sites 3 miles south of (1) Horn Island Pass (station 86), (2) Dog Keys Pass (station 84), and (3) Ship Island Pass (station 82). All portunid megalopae were removed from the samples, counted and identified. In samples containing over 200 megalopae, an aliquot of 100 specimens was examined. Identifications were made using characters developed in a concurrent rearing program in which megalopae were collected monthly for 1 year and reared through early crab stages in the laboratory. i This study was conducted in cooperation with the U.S. Department of Commerce, NOAA, National Marine Fisheries Service, under PL 88-309, Project 2-296-R. ManuscripL received June 30, 1981; accepted August 21, 1981. RESULTS AND DISCUSSION A total of 33,422 portunid megalopae was recovered from the 360 nekton samples examined (Table 1). The megalopae of Callinectes sapidus composed 70.8% of the total catch; C. similis, 1 1 .5%; Portunus spp., 17.5%; and other Portunidae, < 0.1%. Although several species may be included under Portunus spp., all reared Portunus megalopae were P. gibbesii. Included under “other Portunidae” were several specimens of an undescribed giant megalopa and another undescribed form which appeared to share characters distinctive of both Callinectes and Portunus. TABLE 1. Total catch of portunid megalopae by taxa. Taxa Total Catch* Total Standard Catchj" %of Standard Catch Callinectes sapidus 24,171 31,681.1 70.8 C. similis 4,396 5,157.3 11.5 Portunus spp. 4,839 7,853.0 17.6 Other Portunidae 16 21.0 < 0.1 Total 33,422 44,712.4 100.0 The sum of megalopae caught (numbcr/20-minute tow) from each sample. ■fThe sum of the standardized numbers (number/1,000 m 3 ) of mega- lopae from each sample. Concurrent trawl data were taken in coastal and estua- rine waters. Callinectes sapidus juveniles and adults con- stituted approximately 53% of the total catch while C. similis contributed 38%; Portunus spp., 9%; and other portunids, < 1 .0%. Total catch of portunid megalopae at all three stations was similar; however, the percent composition of the catch differed greatly (Table 2). 93 94 Stuck and Perry TABLE 2. Catch of major portunid taxa by station. Station Taxa Total Catch* Total Standard Catchf %of Standard Catch 86 C sapidus 6,662 7,950.2 49.5 C. similis 2,730 3,159.7 19.7 Portunus spp. 2,882 4,932.6 30.8 Total 12,274 16,042.5 100.0 84 C sapidus 7,672 11,851.9 73.1 C. similis 1,431 1,739.9 10.7 Portunus spp. 1,709 2,624.9 16.2 Total 10,812 16,216.7 100.0 82 G sapidus 9,837 11,880.9 95.5 C. similis 235 257.7 2.1 Portunus spp. 248 295.5 2.4 Total 10,320 12,434.1 100.0 ♦The sum of megalopae caught {number/20-minute tow) from each sample. fThe sum of the standardized numbers (number/1 ,000 m 3 )of mega- lopae from each sample. Station 86 contributed 35.9% of the total catch consisting of C sap id us (49.5%), C. similis (19.7%), Portunus spp. (30.8%), and unidentified Portunidae (0.1%), Station 84 yielded 36.3% of the total catch consisting of C. sapidus (73.1%), C similis (10.7%), and Portunus spp. (16.2%). Station 82 was somewhat less productive, providing 27.6% of the total catch. Callinectes sapidus dominated the catch (95.5%), with C. similis (2.1%) and Portunus spp. (2.4%) far less abundant. Overall percent composition as well as total numbers of C. sapidus megalopae increased from east to west, whereas the catch of C. similis and Portunus spp, was greatly decreased. This trend corresponds with an east-west salinity gradient characteristic of Mississippi coastal waters. Salinities were highest at station 86 throughout the sampling period with bottom waters averaging 32.1 ppt and surface waters, 25.5 ppt. A similar salinity regime was noted at station 84; bottom waters averaged 3 1 .4 ppt and su rface waters averaged 25.1 ppt. Salinities were lowest at station 82, averaging 28.3 ppt for bottom and 23.5 ppt for surface waters, with individual values seldom above 30.0 ppt. Although informa- tion on salinity preference of C. similis and Portunus gibbesii megalopae is not available, adults and juveniles are known to prefer coastal waters of high salinity (Christmas and Langley 1973). Bookhout and Costlow (1974) reported that salinities below 30.0 ppt were not favorable for develop- ment of Portunus spinicarpus larvae. Salinities optimal to maximum survival of C. sapidus megalopae (Costlow 1967) were observed at all stations, however; C. sapidus megalopae were more abundant at the lower salinity station 82. King (1971) reported greatest influx of Callinectes sp. megalopae to occur at 26.0 ppt salinity in Cedar Bayou. Based on overall catch, portunid megalopae showed no affinity for surface or bottom waters (Table 3), Although twice the number of C. similis megalopae were caught in surface than bottom waters, the difference can be accounted for by a single large catch (1,434.8/1,000 m 3 ) taken at station 86 in March 1976. Most (15 of 20) large catches of C. sapidus megalopae (3Q0+/tow) were taken on rising or peak tides; however, no preference for surface or bottom waters was observed. Individual large catches (100+ indi- viduals) of C. similis and Portunus spp. megalopae weie commonly taken during both rising and falling tides. TABLE 3. Catch of major portunid taxa by depth. Taxa Total Catch* Total Standard Catchf %of Standard Catch Surface C. sapidus 11,534 i 3,632.6 65.2 C. similis 3,290 3,780.3 18.1 Portunus spp. 2,467 3,493.5 16.7 Total 17,291 20,906.4 100.0 Bottom C. sapidus 12,637 18,048.4 75.9 C. similis 1,106 1,377.1 5.8 Portunus spp. 2,372 4,359.5 18.3 Total 16,115 23,785.0 100.0 *Tbe sum of megalopae caughi (number/20-minute tow) from each sample, fThe sum of the standardized numbers (number/ 1 ,000 m 3 ) of mega- lopae from each sample. Previous reports on the vertical distribution of Callinectes megalopae appear conflicting. Williams (1971), King (1971). Perry (1975), and Smyth (1980) reported Callinectes megalopae to be in greatest abundance in surface waters. In contrast, 96% of the Callinectes megalopae collected by Tagatz (1968) and all of the megalopae collected by Sandifer (1973) were from bottom waters. A definite seasonal pattern of abundance for portunid megalopae was observed (Figure 1). Callinectes similis mega- lopae were collected throughout the year, occurring in greatest abundance from February through April with a March peak. This was followed by an April peak of Portunus spp. during which concentrations of up to 1,670.3/1,000 m 3 were observed. Callinectes sapidus megalopae were collected in every month except January and February. Two peaks in abundance were observed, the first in late spring-early summer, and a second, larger peak in the late summer-early fall during which maximum densitites of 2,530. 8/ 1,000 m 3 were obtained. Large catches of C. sapidus megalopae were not made between December and April. Short Communications 95 The seasonal occurrence of C. sapidus megalopae reported here conflicts, in part, with previous studies from the northern Gulf. More (1969) and King (1971) reported a February-March peak of Callinectes spp. megalopae and suggested these megalopae represented an overwintered spawn from the previous fall. While a February-April peak of portunid megalopae was also observed in the present study, it consisted almost entirely of C. similis and Portunus spp. Adkins (1972) also reported a February peak of blue crab megalopae from Whiskey Pass, Louisiana. Portunid megalopae and early crabs collected from this same site during February and March 1981 were provided to the authors by Mr. Adkins. All were found to be C similis. Perry (1975) also reported a February occurrence of C. sapidus megalopae based on identification of young crabs reared from megalopae. Subsequent examination of these crabs found them to be C. similis. Abundance of Callinectes sapidus megalopae during thelate spring through fall months observed in the present study is in general agreement with previous studies. ACKNOWLEDGMENTS The authors thank Shiao Wang, formerly of the Gulf Coast Research Laboratory, who assisted in the rearing of megalopae, and Gerald Adkins, of the Louisiana Department of Wildlife and Fisheries, for supplying samples from the Whiskey Pass area. For their help in field collections, appreciation is extended to Tommy Van Devender, Myron Loman, James Warren, Kenneth Melvin, and Leroy Ladner. REFERENCES CITED Adkins, G. 1972. A study of the blue crab fishery in Louisiana. La. Midi, Fish. Comm. Tech, Bull. 3:1-57. Andryszak, B. L. 1979. Abundance, distribution and partial des- criptions of reptant decapod crustacean larvae collected from neritic Louisiana waters In July, 1976. Master’s thesis, Louisiana State University, Baton Rouge, Louisiana. 102 pp. Bookhout, C. G. & J. D. Costlow, Jr. 1974. Larval development of Portunus spinicarpus reared in the laboratory. Bull. Mar. Sci. 24:20-51. Christmas, J. Y. & W. Langley. 1973. Estuarine invertebrates, Mississippi. Pages 255—319 in J. Y. Christmas (ed.). Gulf of Mexico Estuarine Inventory and Study, Mississippi. Gulf Coast Research Laboratory, Ocean Springs, Mississippi. Costlow, J. D. 1967. The effect of salinity and temperature on survival and metamorphosis of megalops of the blue crab Callin- ectes sapidus. Helgol. wiss. Meeresunters. J 5:84-97. Darnell, R. M. 1959. Studies of the life history of the blue crab (Callinectes sapidus Rathbun) in Louisiana waters. Trans. Am. Fish.Soc. 88(4):294-3Q4. Daugherty, F. M., Jr. J952. The blue crab investigation, 1949-50. Tex.J. Sci. 4(l);77-84. King, B.D., III. 1971 .Study of migratory patterns of fisli and shellfish through a natural pass. Tex. Parks Wildl. Dep., Tech. Ser. 9:1-54. Menzel, R. W. 1964. Report on preliminary studies on the blue crab in Alligator Harbor and adjacent Gulf of Mexico with some observations on stone crab larvae. Oceanographic Institute, Florida State University. 12 pp. More, W. R. 1969. A contribution to the biology of the blue crab (Callinectes sapidus Rathbun) in Texas, with a description of the fishery. Tex. Parks Wildl. Dep., Tech. Ser. 1:1—31. Perry, H. M. 1975. The blue crab fishery in Mississippi. Gulf. Res. Rept. 5(1): 39-57. Sandifer, P. A. 1973. Distribution and abundance of decapod crustacean larvae in the York River estuary and adjacent lower Chesapeake Bay, Virginia, 1968-1969. Chesapeake Sci. 14(4): 235-257. Smyth, P. 0. 1980. Callinectes (Decapoda: Portunidae) larvae in the Middle Atlantic Bight, 1975 -77. Fish. Bull. 78(2): 251 -265. Tagatz, M. E. 1968. Biology of the blue crab, Callinectes sapidus Rathbun, in the St. Johns River, Florida. l/.S. Fish. Wildl. Serv., Fish, Bull. 67(1): 17 -33. Williams, A. B. 1971. A ten-year study of meroplankton in North Carolina estuaries: annual occurrence of some brachyuran developmental stages. Chesapeake Sci. 1 2:53- 61 ,