ISSN 0038-3872 SOULHRWNeeeALIERORNIA ACADEMY ©F SCIENCES BULLETIN Volume 94 Number 3 BCAS-A94(3) 179-226 (1995) DECEMBER 1995 Southern California Academy of Sciences Founded 6 November 1891, incorporated 17 May 1907 © Southern California Academy of Sciences, 1995 ¥ OFFICERS David L. Soltz, President Edward J. Kormondy, Vice-President Kristine B. Hartney, Secretary Margaret A. Neighbors, Treasurer Daniel A. Guthrie, Editor BOARD OF DIRECTORS 1993-1995 1994-1996 1995-1997 Jack W. Anderson Donald G. Buth Robert S. Grove Hans M. Bozler Martin F. Golden Kristine B. Hartney Margaret A. Neighbors Daniel A. Guthrie Edward J. Kormondy Jane R. Peterson R. Nichols Hazelwood David L. Soltz Maria E. Zavala Gloria J. Takahashi Susan E. Yoder Membership is open to scholars in the fields of natural and social sciences, and to any person interested in the advancement of science. 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Send Two Copies of the Abstract/Information Form to the: SOUTHERN CALIFORNIA ACADEMY OF SCIENCES 900 EXPOSITION BOULEVARD LOS ANGELES, CA 90007 SAMPLE ABSTRACT & INFORMATION FORM MICROBIAL ACTIVITY IN THE DIGESTIVE TRACT OF THE HALFMOON, Medi- aluna californiensis. J. S. Kandel', J. R. Paterek? and M. H. Horn’. 'California State Univ. Fullerton. CA 92634 and *Agouron Institute, La Jolla, CA 92037. _ We report the presence of a diverse microbial flora and of microbial fermentation products in the hindgut region of the halfmoon, Medialuna californiensis, a seaweed-eating fish from southern California coastal waters. Viable aerobic and anaerobic bacteria were found in all sections of the gut, but were of highest concentration (10°—108/ml) in the hindgut. Microscopy revealed vibrios, spirilla, rod-shaped bacteria and flagellated protozoa in the midgut and hindgut. but primarily vibrios and rods in the stomach and foregut. Acetic, isobutyric and butyric acids. the volatile products of microbial breakdown of carbohydrates, were found only in the hindgut. as was ethanol, a nonvolatile product. These results provide the first evidence for microbial fermentation and its possible contribution to the energy supply in a north-temperate herbivorous fish. 1. Judy S. Kandel, Department of Biology, California State University, Fullerton, Fullerton, CA 92634, 714-773-2546. FAX 714-773-3426, jkandel@fullerton.edu. Nonmember. pA) R. Paterek, Agouron Institute, La Jolla, CA 92037. Nonmember Michael H. Hom, Department of Biology, California State University, Fullerton, Fullerton, CA 92634, 714-773-3707. Member 3. Professional 4. Contributed paper 5. Marine Biology, Microbiology, or Ichthyology 6. Kodak 35 mm slide carousel projector Pe ee ake Pliage HT a i ja 1 i ’ ‘1 eo . { sk j : \ - - i * 7 x r 2 : j Bull. Southern California Acad. Sci. 94(3), 1995, pp. 179-189 © Southern California Academy of Sciences, 1995 Recruitment, Growth, and Survivorship of Black Abalone on Santa Cruz Island following Mass Mortality Brian N. Tissot Marine Science Department, University of Hawaii at Hilo, 200 West Kawili Street, Hilo, Hawaii 96720-4091 Abstract. —Populations of black abalone experienced major declines in abundance throughout the California Channel Islands in the late 1980’s. The focus of this research was to monitor the potential recovery of populations on Santa Cruz Island in 1990-1993 following mass mortality in 1987-1989. Abalone continued to decline in abundance between 1990-1993. These declines were associated with low survivorship and low relative weights, indicating that individuals were con- tinuing to die from the withering syndrome (WS) which was associated with the principal mass mortality. Recruitment, and the movement of small abalone from their cryptic juvenile habitat unto open surge channels, was an important process maintaining adult abundance. However, major declines in the density of juvenile abalone occurred between 1991-1993. Small abalone (<70 mm in length) exhib- ited the greatest effects of WS and these effects decreased with increasing size. Temperature was indicated to be the single most important factor influencing population recovery. Oceanographic factors that result in elevated seawater tem- peratures, such as El Nino, will have a strong negative impact on the recovery of black abalone populations in southern California. Prior to the mid-1980’s populations of black abalone, Haliotis cracheroidii, occurred at extremely high densities (~ 50-75 m7) throughout the California Chan- nel Islands (Bergen 1971; Douros 1985, 1987). Shortly thereafter, populations on most of the islands began dramatic declines in abundance, often exceeding 90% (Davis et al. 1992; Haaker et al. 1992; Tissot 1988a). This precipitous decline, or mass mortality, occurred in conjunction with the “withering syndrome” (WS): abalone were shrunken in appearance, weakly attached to the substratum, and did not actively feed (Tissot 1991). At present the ultimate causes of the mortality are unclear, but possible factors include the effects of elevated temperatures, fluctuations in the abundance of drift algal foods, high abalone densities, and the spread of a pathogen (Culver and Richards 1992; Davis et al. 1992; Haaker et al. 1992; Lafferty and Kuris 1993; Steinbeck et al. 1992; Tissot 1991). The focus of this research is to monitor changes, and potential recovery, of populations on Santa Cruz Island in 1990-1993 following major declines in 1987— 1989 (Tissot 1991). I address the following questions: @ Did populations display any indication of recovery? @ Did WS continue to occur and did it influence survivorship? @ Was recruitment occurring and did it influence abundance? 179 180 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES I addressed these questions by monitoring the growth and survivorship of tagged abalone located along permanent transects established in 1987. Recruitment was monitored by surveying the abundance of juvenile black abalone, which primarily occur under rocks in boulder fields (Tissot 1988b). Materials and Methods Study sites were located on the west end of Santa Cruz Island (34°00'N, 114°50’W), California. Intertidal transects were located in two general areas that differed in their exposure to ocean waves. The “‘wave-protected”’ site (hereafter referred to as ““protected’?) was located 1 km SE of Forney Cove on the south side of the island. The “‘wave-exposed” site (hereafter referred to as ‘““exposed’’) was located 0.2 km NE of Fraser Point on the north side of the island (see Tissot 1991). In 1987, I established 3-4 permanent intertidal transects in surge channels at each study site. In 1990 I established 2 additional permanent transects in a boulder field at the protected site. Surge channel transects were 1 m wide and 5-15 m long; boulder field transects were 4 m wide and 25 m long. Transects were oriented perpendicular to the shore and extended from the mid- to the low-intertidal zones. I conducted surveys on a quarterly basis (winter, spring, summer, fall) between January 1987 and January 1990, and on an annual basis during the summer between 1990 and 1993. I determined abalone abundance on each transect by counting the total number of individuals present. Density was calculated by dividing the total number of individuals by the total transect area after removing areas that were deemed uninhabitable by abalone. In 1990, I began measuring the shell length of all individuals on transects. During surveys I tagged 5-75 haphazardly chosen abalone on, or adjacent to, each surge channel transect. Abalone were removed from the substratum using an abalone iron, their shells were cleaned with a wire brush, and they were tagged with an identifying number from a Dymo label maker applied to the shell with marine epoxy putty (Z-spar Splash Zone Compound). Damage to the foot resulting from handling was noted. Statistical comparisons between damaged and undam- aged abalone revealed no significant differences in survivorship, rates of shell growth, weight gain, or net total movement (T-test, all P > 0.05). For each individual I measured the length of the shell in the longest dimension with a caliper, and beginning in June 1988, the total wet abalone weight after the removal of shell growths, with a spring scale. Individuals that were abnormally underweight in appearance were noted. Survivorship was measured by the recapture rate of tagged individuals. In order to make valid comparisons among survey intervals, which varied in duration, I calculated all recapture rates based on annual survivorship (e.g., summer 1987 to summer 1988). I calculated shell growth as the change in length per unit time (mm/month). I derived an index of abalone “condition” using total abalone weight, hereafter referred to as “relative weight.’ Relative weight was calculated by measuring the percent deviation of abalone weight from a predicted weight, which was based on a logged length-weight regression calculated from field recaptured individuals SURVIVORSHIP OF BLACK ABALONE 181 displaying both shell growth and increases in total weight between surveys in 1988-1990: Log.predicted weight = —9.36 + 3.15 x Log.length (r2 = 0.97, N = 87, P < 0.01). Relative weight was then calculated as a percent deviation from predicted weight: Weight — Predicted weight Weight Although the calculation of a relative weight index using growing individuals as a standard was somewhat arbitrary, it served as a standard by which to make weight comparisons among years. Of the 49 individuals that were observed to be abnormally underweight during surveys, 88% (N = 43) of their calculated relative weights were 0.05) indicating that declines were not related to initial abalone density. Patterns of variation in abalone size differed among exposed and protected surge channel transects (Fig. 2). Individuals <80 mm and >100 mm decreased in abundance and eventually disappeared along exposed coast transects between 1990-1992. In contrast, the relative proportion of individuals <40 mm increased and individuals >100 mm decreased along protected coast transects during the same time period. There was a significant negative correlation between the mean 182 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES —e— Protected —O— Exposed Density (no./m?) 1987 1988 1989 1990 1991 1992 1993 at oO Percent change ) © 19875) 1988, , 1989, 1990) 19911 aiSS2aaiess Fig. 1. Patterns of decline in abundance, 1987-1993. A. Mean density (+1 S.E.) on exposed vs. protected study areas. B. Percent change in mean density (+1 S.E.) relative to initial densities on exposed vs. protected study areas. size of abalone on transects in 1990-1993 and their 1993 density (rk = —0.62, N = 8, P < 0.05), indicating that sites where abalone were relatively more abundant were composed primarily of small individuals. Individuals on boulder field transects exhibited significant variation in size and density among years (Fig. 3). There were major declines in the density of all size classes between 1991 and 1992-1993. Total mean density varied from a high of 1.4/m? in 1991 to a low of 0.51/m? in 1993. Percent of total Chee 2Omm 40tc1GOmm 180) 100) 112097140 size class (mm length) Fig. 2. Size frequency of abalone on surge channel transects in exposed and protected study areas = samp nce urvivorship, as me es the ea of tagged abalone on sae , wa eh een cerenta on urveys he kal-Wa ale S, We 1.96, N = 24, ‘P= re 2 oasis e rat Se ce = een summer surveys in 1987-1991 a nd 1992 ieoae which w gnifi d 31% bet eTWw' re 6 ntly differe nt frome eel nthe 1991-1992s cane °s ee Ps < Ouor 184 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES (0) 5 AT. 0-20mm © ‘= 5,4 1 20-40mm © S 40-60 mm , & = a’ | 60-80 mm” A é : 2 i = ; | 6 7) A AN o - A IN dL > O on ee Percent 0 40 80 120 0 40 80 120 0 40 80 120 Fig. 3. Changes in mean density (+1 S.E.) of four size classes and size frequency of abalone on boulder fields (N = sample size). The relative weight of individuals fluctuated during the study period (Fig. 4B). Mean weights were significantly different among years (Kruskal-Wallis, H = 39.5, N = 405, df = 5, P < 0.01): 1989 weights, which averaged 6.3% above predicted weight, were significantly different from all other years, which averaged 4.0% below predicted weight (Tukey’s test, P < 0.01). Mean relative weight of abalone =70 mm, which averaged 8.1% below predicted weight, was significantly different from abalone >70 mm, which averaged 1.5% below predicted weight (T-test, T — OB di — N92. Ps 0.05). Surface seawater temperatures were elevated above normal levels during all years of the study (Fig. 5). Average annual temperature anomalies were signifi- cantly different among years (Kruskal-Wallis, H = 24.5, N = 84, df = 6, P < 0.01) and varied from a mean of 1.2°C above average for 1987, 1988, 1990, 1992 and 1993, which were not significantly different from each other, to a mean of 0.41°C above average in 1989 and 1991 (Tukey’s test, all P < 0.01). Mean relative weights were significantly negatively correlated with mean winter temperature anomalies in 1987-1992 (rx = —0.88, N = 6, P < 0.01), but not with mean spring, summer, or fall temperature anomalies (all P > 0.05). SURVIVORSHIP OF BLACK ABALONE 185 60 ne ZO 14) AG 848 29 A 40 20 0 = | lk 1987 1988 1989 1990 1991 1992 1993 Recapture rate n= O 154 116 48 Relative weight Shell growth rate (mm/mo) 1987 1988 1989 1990 1991 1992 1993 Survey year Fig. 4. Patterns of variation in growth and survivorship of tagged abalone (N = sample size). A. Mean recapture rate (+1 S.E.). B. Mean relative weight (+1 S.E.) (see text). C. Mean shell growth rates (+1 S.E,). Discussion Black abalone on Santa Cruz Island exhibited a net decline in abundance throughout the seven-year study period. Annual survivorship of tagged individ- uals, which averaged 8% in all years except 1991-1992, were low compared to other studies. Mean annual survivorship of ten species of abalone ranged from 0-92% but averaged 39% (Shepherd and Breen 1992). A better comparison can 186 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES 20 Normal Actual - -@ - % e “e 18 5 =: & e a) — i " - e ) 5 e = set + oa ae eet 5 : Sg = i A ; ‘ ; 3 164 ¢ d fe ? 5 Q : 1 ey : Se = ca] : : ; Pg eee oO ‘ ‘ . ‘ ® ' = ie: @. - © e ic} orcs 14-@6 ‘jese; @\ @' ‘@ se 2 = @ 2 ‘ 1¢ * e Co) ® e | e 12 i | Piititi pri i An ! Sannin 1 ! ] | | 1 1987 1988 1989 1990 1991 1992 1993 Year Fig. 5. Relationship between monthly seawater temperatures during the study period and average annual temperatures based on Robinson (1976). be made using tagged black abalone on Ano Nuevo Island in central California during 1987-1990 which did not exhibit WS, where annual survivorship averaged 33% (Tissot, unpublished data). In conjunction with low survivorship, relative abalone weights at Santa Cruz Island averaged 4.0% below predicted in all years except 1989. In contrast, using the same methodology to calculate relative weight at Ano Nuevo Island, mean relative weights averaged 1.9% above predicted in 1988-1990. Thus population declines on Santa Cruz Island occurred in conjunc- tion with low survivorship and low relative weights, indicating that elevated mortality rates continued to be associated with the withering syndrome. Important issues to be addressed are the effects of WS on the decline and recovery of the population and the role of ecological factors, such as seawater temperature, kelp abundance, and recruitment as they influence growth and survivorship. The abundance of abalone on surge channel transects exhibited major declines between 1987 and 1993. Tissot (1991) has shown that these declines were pri- marily associated with mortality and not from handling injury, human distur- bance, or emigration from study areas. Overall, the total decline between 1987 and 1993 has been 99.5%. In 1987 there were a total of 2630 abalone on all transects; 14 remained in 1993. Abundance has been reduced to zero on two of the eight transects, one each in exposed and protected study areas. If the current rate of decline continues, black abalone will be locally extinct on my study areas by 1997 (+2 years). There was a strong relationship between the persistence of abalone on surge channel transects and their size composition. Study areas on the protected coast with the highest densities in 1993 exhibiting an influx of small abalone <40 mm into the study area. In contrast, lower density transects on the exposed coast were associated with an absence of small abalone. These observations indicate that recruitment, and the movement of small abalone from their cryptic juvenile SURVIVORSHIP OF BLACK ABALONE 187 habitat into open surge channels, is an important process maintaining adult abun- dance. Similar observations have been made by Blecha et al. (1992) in central California. Boulder habitats suitable for small abalone are uncommon on the exposed coast of west Santa Cruz Island but are abundant on the protected coast. Therefore, a prediction from this study is: should abalone recovery occur in southern California, it will be higher in areas adjacent to intertidal boulder fields. Newly recruiting and juvenile abalone in boulder fields exhibited high variation in abundance during 1990-1993. Declines in the density ofall size classes occurred between 1991-1993 during abnormally warm temperatures associated with the 1992-1993 El Nino. There are at least two ways El Nino could have a negative effect on abalone recruitment and juvenile survivorship. First, ocean currents in southern California generally flow to the north during El Nino, transporting pelagic larvae from south to north (Cowen 1985). Because black abalone populations were decimated by mass mortality throughout southern California (Culver and Richards 1992), a northern flowing current might be sparsely laden with abalone larvae. In contrast, under normal oceanographic conditions, southern flowing currents would transport abalone larvae south from central California, where abalone are still abundant (Tissot 1991). A second mechanism is that elevated temperatures during El Nino enhance the effects of withering syndrome on juvenile abalone, resulting in elevated mortality. Tissot (1991) demonstrated a strong relationship between the survivorship of tagged abalone and their relative weight, which thus served as a measure of the severity of WS. In this study relative weights of abalone were similar in 1990- 1993 to those in 1988, when major mortality occurred. These observations dem- onstrate that WS has been present throughout the seven-year study period and associated with the continued high mortality. Perhaps more importantly, relative weight was strongly size dependent. Abalone <70 mm in length exhibited the greatest effects of WS and these effects decreased with increasing size. Thus, the continued presence of WS is having two major impacts on the populations: 1) low survivorship of adults; and 2) low survivorship of recruiting abalone which maintain adult populations. Previous work by Steinbeck et al. (1992) and Tissot (1991) has shown feme perature to have a strong effect on the incidence and severity of WS and resulting survivorship. Similar strong relationships between temperature, WS, and survi- vorship were evident in this study. Relative weights and survivorship were low during warm years in 1988, 1990, and 1992 but increased during oceanograph- ically more normal years in 1989 and 1991. Moreover, low abalone weights were significantly correlated with elevated seawater temperatures during the winter season. Because black abalone store excess energy in the form of polysaccharides in the foot during the winter (Webber and Giese 1969), abalone mortality may be occurring due to a disruption of energy storage. Although the abundance of drift kelp, the principal food of black abalone, was unusually low during 1987- 1988 during peak population declines (Tissot 1991), it did not appear to exhibit significant variation between 1989-1993, and thus was unlikely to be the contin- ued cause of WS (Tissot, unpublished data). Therefore, temperature is the single most important factor influencing population recovery. Oceanographic factors that result in elevated seawater temperatures, such as El Nino, will have a strong negative impact on the recovery of black abalone populations. 188 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES Acknowledgments I thank Brandie Erbe, Jeremy Robinson, Eric Smith, John Steinbeck, and Susan Gaughan Tissot for assistance in the field. I would especially like to thank Eric Smith, who conducted the 1993 survey with Andy Barberena, Brandie Erbe, and Don Smith. I thank the US Navy and the Nature Conservancy for access to Santa Cruz Island and Lyndal Laughrin for invaluable logistic support. This work was partially supported by a grant from the University of Hawaii at Hilo. Literature Cited Bergen, M. 1971. Growth, feeding and movement in the black abalone, Haliotis cracherodii Leach 1817. Master’s Thesis, University of California, Santa Barbara. 59 pp. Blecha, J. B., J. R. Steinbeck, and D. C. Sommerville. 1992. Aspects of the biology of the black abalone (Haliotis cracheroidii) near Diablo Canyon, central California. Chapter 18 in Proceed- ings of the First International Abalone Symposium: biology, fisheries, and culture. La Paz, Mexico. (S. Shepherd and M. Tegner, eds.), Blackwell Scientific Publications Ltd., Sydney. Cowen, R. K. 1985. Large scale patterns of recruitment by the labrid, Semicossyphus pulcher: causes and implications. Journal of Marine Research, 43:719-742. Culver, C. S., and J. B. Richards (editors). 1992. Black abalone mortality: establishing a research agenda. Summary of a Sea Grant workshop. Report No. T-CSGCP-024, California Sea Grant College, La Jolla, California. 32 pp. Davis, G. E., D. V. Richards, P. L. Haaker, and D. O. Parker. 1992. Abalone population declines and fishery management in southern California. Chapter 19 in Proceedings of the First Inter- national Abalone Symposium: biology, fisheries, and culture. La Paz, Mexico. (S. Shepherd and M. Tegner, eds.), Blackwell Scientific Publications Ltd., Sydney. Douros, W. J. 1985. Density, growth, reproduction, and recruitment in an intertidal abalone: effects of interspecific competition and prehistoric predation. Master’s Thesis, University of California, Santa Barbara. 112 pp. . 1987. Stacking behavior of an intertidal abalone: an adaptive response or a consequence of space limitation? Journal of Experimental Marine Biology and Ecology, 108:1-14. Haaker, P. L., D. V. Richards, C. Friedman, G. E. Davis, D. O. Parker, and H. Togstad. 1992. Mass mortality and withering syndrome in black abalone, Haliotis cracherodii, in California. Chapter 17 in Proceedings of the First International Abalone Symposium: biology, fishieries, and culture. La Paz, Mexico. (S. Shepherd and M. Tegner, eds.), Blackwell Scientific Publications Litd., Sydney. Lafferty, K. D.,and A. M. Kuris. 1993. Mass mortality of abalone Haliotis cracherodii on the Channel Islands: tests of epidemiological hypotheses. Marine Ecology Progress Series, 96(3):239-248. National Oceanographic and Atmospheric Administration. 1987-1993. Oceanographic Monthly Summary. National Weather Service, Camp Springs, Maryland. Robinson, M.K. 1976. Atlas of North Pacific Ocean monthly mean temperatures and mean salinities of the surface layer. NavOcean Reference Publication 2. Shepherd, S. A., and P. A. Breen. 1992. Mortality in abalone: its estimation, variability and causes. Chapter 21 in Proceedings of the First International Abalone Symposium: biology, fisheries, and culture. La Paz, Mexico. (S. Shepherd and M. Tegner, eds.), Blackwell Scientific Publications Ltd., Sydney. Steinbeck, J. R., J. M. Groff, C. S. Friedman, T. McDowell, and R. P. Hedrick. 1992. Investigations into a mortality among populations of the California black abalone Haliotis cracherodii, on the central coast of California, USA. Chapter 16 in Proceedings of the First International Abalone Symposium: biology, fisheries, and culture. La Paz, Mexico. (S. Shepherd and M. Tegner, eds.), Blackwell Scientific Publications Ltd., Sydney. Tissot, B. N. 1988a. Mass mortality of black abalone in southern California. American Zoologist, 28:69A. . 1988b. Morphological variation along intertidal gradients in a population of black abalone Haliotis cracherodii Leach 1814. Journal of Experimental Marine Biology and Ecology, 117:71—90. SURVIVORSHIP OF BLACK ABALONE 189 . 1991. Geographic variation and mass mortality in the black abalone: the roles of development and ecology. Ph.D. Dissertation, Oregon State University, 271 pp. Webber, H. H., and A. C. Giese. 1969. Reproductive cycle and gametogenesis in the black abalone Haliotis cracherodii (Gastropoda: Prosobranchia). Marine Biology, 4:152-159. Accepted for publication 26 December 1994. Bull. Southern California Acad. Sci. 94(3), 1995, pp. 190-203 © Southern California Academy of Sciences, 1995 Distribution of Brittlestar Amphiodia (Amphispina) spp. in the Southern California Bight in 1956 to 1959 ~ Mary Bergen Southern California Coastal Water Research Project, 7171 Fenwick Lane, Westminster, California 92683 Abstract.—Brittlestars Amphiodia (Amphispina) spp., particularly Amphiodia (Amphispina) urtica (Lyman 1860), are of interest in southern California because they are rare or absent adjacent to municipal wastewater outfalls even where they are expected to be the community dominant. In the monitoring programs for the outfalls, impacts to benthic communities are determined by comparing abun- dances near the outfall to the abundance in “reference” areas. In order help define reference conditions, data from a survey conducted between 1956 and 1959 were used to determine the effect of latitude, depth and sediment grain size on the distribution and abundance of Amphiodia (Amphispina) spp. Brittlestars Amphiodia (Amphispina) spp. were most abundant in water depths of 48 to 102 m in sediments with median grain size between 0.035 and 0.093 mm, a diameter classified as coarse silt to very fine sand. Amphiodia (Amphispina) spp. were rarely collected in less than 15 or more than 85 m of water. The abundance of Amphiodia (Amphispina) spp. was generally lower north of Ventura than elsewhere in the Bight. The difference in abundance can, in part, be attributed to the character of the sediment. However, even in areas with suitable sediment, the abundance of Amphiodia (Amphispina) spp. north of Ventura was relatively low. The reason for this difference is unknown. It is also not known if Amphiodia (Amphispina) spp. are, at the present time, less abundant north of Ventura than elsewhere in the Bight. The brittlestar Amphiodia urtica (Lyman 1860) has become a subject of study in recent years because it is rare or absent in areas adjacent to municipal wastewater outfalls in southern California even where it is the expected community dominant (County Sanitation Districts of Orange County 1990; City of Los Angeles 1990; City of San Diego 1990). For this reason, it has been used as an indicator organism in monitoring programs. In these programs alterations in benthic communities are determined by comparing areas adjacent to the outfall areas to “reference” areas. However, there has been some dispute as to what constitutes an appropriate reference area. The objective of this study was to use the data from an extensive oceanographic, geological and biological survey of the southern California Bight (hereinafter called the State survey) to help determine reference conditions for Amphiodia urtica. More specifically, the objective was to determine the effect of latitude, depth, and sediment grain size on the abundance of Amphiodia urtica in the Bight. The State survey was conducted between 1956 and 1959 by scientists of the Allan Hancock Foundation, under contract to the State Water Pollution Control 190 AMPHIODIA DISTRIBUTION IN THE SOUTHERN CALIFORNIA BIGHT 191 Board. For the first six months, the objective of the survey was to provide de- scriptive information about the Bight. During this period, stations were randomly chosen within a systematic grid pattern. Then the sample design was changed in order to assess the effect of waste discharges and to determine seasonality in benthic invertebrate populations. The mainland shelf was divided into 15 geo- graphic zones, each classified according to present and possible future effects of wastewater discharges. Transects with three to six stations were established in each zone. To measure seasonality, stations were to be sampled two or more times per year. This sample design was, however, abandoned because it was not possible to determine seasonality or the effect of the discharges given the variability caused by such factors as substrate type and navigational error. Therefore, a stratified design was adopted, in which the Bight was divided into eight geographic zones, each with six depth zones. This design assured good spatial coverage of the Bight. In the end, samples were, more or less, evenly distributed throughout the Bight. From Point Arguello to 4 km south of the Mexican Border, hydrographic infor- mation was collected at 2582 stations; 862 biological and 900 sediment samples were collected (Jones 1969). To date, this is the only truly Bight-wide survey that has been done. The analyses of macroinvertebrate distributions and descriptions of infaunal communities which appeared in reports for the project (Allan Hancock Foundation 1959, 1965; Stevenson 1961) and in published papers (Barnard and Hartman 1959; Barnard and Ziesenhenne 1960; Jones 1969) form the foundation of our knowledge of the benthos of the Bight. While previous reports based on the State survey data discussed the distribution of Amphiodia urtica, they did not specifically focus on Amphiodia; nor did they use all available data. For instance, the description of ophiuroid communities by Barnard and Ziesenhenne (1960) was based on data from 176 samples, supple- mented by visual inspection of an additional 400 samples for faunal dominance. However, all organisms were identified in 322 samples and all echinoderms were identified in 240 samples. Therefore, there are potentially 562 samples that c can be used to delimit the distribution of Amphiodia urtica. As discussed below, examination of specimens suggest that, during the State survey, there was some confusion in the identification of Amphiodia urtica and a closely related species, Amphiodia digitata Nielson, 1932. For this reason, data for the two species were combined under the subgeneric designation Amphiodia (Amphispina) spp. Even though this designation is used, over 80% of the specimens were Amphiodia urtica. Methods In the State survey, most of the benthic samples were taken with a Hayward Orange Peel Grab with a rated capacity of 56.6 1, sampling a surface of approx- imately 0.25 m2. A modified Van Veen grab was used to sample areas in less than 10 m of water. This grab has a capacity of two liters and samples 0.1 m?. A Campbell grab was used on three occasions; however, data from these samples were not used in the analysis. Samples taken with the Orange Peel grab were screened through 1.0 mm mesh in the field, preserved in 10% formalin and transported to the laboratory for 192 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES sorting and identification. Sediment taken with the Van Veen was preserved and taken to the laboratory for screening, sorting and identification. Prior to screening, approximately 0.5 1 of sediment was taken fromi the grab for sediment grain size analysis. These samples were not refrigerated or preserved. They often dried before analysis. Before processing, the sample was soaked in water and then wet-sieved through 0.062 mm mesh screen to remove the gravel and sand fraction. The percent sand and gravel was determined by settling (Emery 1938). The silt/clay fraction was washed in acetone and filtered several times to remove salts and organic matter. The percent silt and clay was determined by pipette anlysis (Rittenhouse 1939). The median grain size diameter was calculated by the method of Trask (in Krumbein and Pettijohn 1938). The echinoderms taken in the State survey were identified by Fred Ziesenhenne, a taxonomist with the Allan Hancock Foundation. Mr. Ziesenhenne published a number of papers on echinoderms, including descriptions of species. To verify the quality of the taxonomy, Dr. Gordon Hendler of the Los Angeles County Museum of Natural History checked the identifications in approximately 17 sam- ples. He found that most specimens were Amphiodia urtica, as identified. How- ever, there was some confusion in the identification of a closely related species, Amphiodia digitata Nielson 1932. In addition, many specimens identified as Amphipholis squamata (delle Chiaje 1828) were juvenile Amphiodia urtica. Since 80% of all the ophiuroids collected were identified as Amphiodia urtica and only 1% were identified as Amphiodia digitata, this taxonomic confusion does not materially affect the data. However, to resolve the taxonomic uncertainty, the data for A. urtica and A. digitata were combined under the designation Amphiodia (Amphispina) spp. Other species of Amphiodia, including A. occidentalis and A. psara, were collected during the survey. However, these species lack the points on the ventral scales that are characteristic of the subgenus Amphispina. Thus the designation Amphiodia (Amphispina) spp. serves to distinguish A. urtica/A. dig- itata from other species of Amphiodia collected in the survey. Specimens identified as Amphipholis squamata were not included in the data because it was not possible to determine which specimens had been misidentified. Thus the numbers for Amphiodia urtica are probably underestimated; however, since only 10% of all ophiuroids collected were identified as Amphipholis squamata, the magnitude of the underestimate is small. All echinoderms were sorted and identified in 562 samples; 537 of the 562 samples were used in the following analyses (Fig. 1). 457 of 537 samples were taken with an Orange Peel grab (OPG); 96 samples were taken with a Van Veen grab. The other samples were excluded either because no sample volume was recorded (16 samples), there was uncertainly about the taxonomy (six samples), or the samples were taken with a Campbell grab (three samples). In order to make data from samples taken with an OPG and a Van Veen roughly comparable, the number of animals per grab was converted to number per m?. Since the area sampled by the Van Veen is 0.1 m? regardless of the depth of penetration of the grab, the conversion simply involves multiplying the number of animals per grab by ten. However, with the OPG, the area sampled varies with the depth of penetration of the grab up to the maximum gape of the jaws. During the State survey, a field test was run in order to determine the relationship between sample volume and surface area sampled (Jones 1961). The results are as follows: AMPHIODIA DISTRIBUTION IN THE SOUTHERN CALIFORNIA BIGHT 193 SOUTHERN CALIFORNIA STATIONS SAMPLED FOR AMPHIODIA BETWEEN 1956-1959 IN THE SO. CALIF. BIGHT “PT. CONCEPTION KILOMETERS (SANTA BARBARA VENTURA se -£- LOS ANGELES | Fig. 1. Chart showing location of samples used in the analyses in this report. 194 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES Volume of Grab Area Conversion Factor (ft?) (m7) (for number/m_?) 1e5) O25 4 1.0 0.20 5 4 0.75 0.17 6 0.50 0.15 7 0.25 0.135 8 For this study, the conversion factor was formularized as follows: Mt Vel CV =8 — (4*(V — 0.25)) GPW Be hss 1.5, CV —5 —'27(V — 120)) ite Vee aleos CV =4 where V = volume of the grab CV = conversion factor. Results The range in median grain size in samples with more than 1500 Amphiodia (Amphispina) spp. per square meter was 0.035 to 0.093 mm (Fig. 2), a diameter which is classified as coarse silt to very fine sand. If the one outlying sample with median grain size 0.093 mm is excluded, the range in median grain size in samples with more than 1500 Amphiodia (Amphispina) spp. per square meter was 0.035 to 0.073 mm. Amphiodia (Amphispina) spp. were less abundant in sediments with smaller or larger median diameters. The depth range for samples with more than 1500 Amphiodia (Amphispina) spp. per square meter was 48 to 102 m (Fig. 3). The maximum abundance of Amphiodia (Amphispina) spp. generally decreased outside of this depth range. Amphiodia (Amphispina) spp. were rarely collected in samples taken in less than 15 or in more than 185 m of water. Since grain size is generally correlated with depth, it is possible that the rela- tionship between depth and abundance of Amphiodia (Amphispina) spp. is sec- ondary, that is, the relationship is caused by the change in sediment texture rather than by depth. However, when median grain size is plotted against depth (Fig. 4), it is clear that samples with median grain size between 0.035 and 0.073 mm were taken at all depths. When the plot of Amphiodia (Amphispina) spp. abun- dance versus depth for samples with median grain size between 0.035 and 0.073 mm (Fig. 5) is compared to the plot of Amphiodia (Amphispina) spp. abundance versus depth for all samples (Fig. 3), the pattern is similar A box plot of median abundance of Amphiodia (Amphispina) spp. in 50-km sections of the coast is shown in Fig. 6. Amphiodia (Amphispina) spp. were, on the whole, less abundant in San Pedro Bay and between Ventura and Point Conception than elsewhere in the Bight. It is possible that the geographical pattern in abundance is caused by differences in distribution of sediment types. However, when the geographical pattern in sediment grain size is considered (Fig. 7), it is clear that the sediment in San Pedro Bay is similar to sediment found in other AMPHIODIA DISTRIBUTION IN THE SOUTHERN CALIFORNIA BIGHT 195 4000 3000 2000 ABUNDANCE (NO/M?) 1000 MEDIAN GRAIN SIZE (MM) 4000 3000 2000 ABUNDANCE (NO/M?) 1000 ~ >) OLOR ~,0 ~t% 90 @ (@) 9, fe) o> 5 Aor 0.00 0.01 002 0.03 0.04 005 0.06 0.07 008 0.09 0.10 oy C YOUrS e MEDIAN GRAIN SIZE (MM) Fig. 2. Abundance of Amphiodia (Amphispina) spp. vs. median grain size. An expanded view of the data for samples with median grain size <0.10 mm is shown in Part B. areas of the Bight. The sediment just north of Ventura is slightly finer and the sediment just south of Point Conception is slightly coarser than elsewhere in the Bight. However, the sediment off of Santa Barbara is similar to that found in San Pedro Bay and other areas of the Bight. When the distribution in abundance of Amphiodia (Amphispina) spp. in samples with median grain size between 0.035 196 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES A f 4000 N = 537 = = 3000 = Ww S < 2000 ja) Zz = mM