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CONTRIBUTIONS OF THE ROYAL ONTARIO MUSEUM OF ZOOLOGY AND PALAEONTOLOGY
No. 40 "Op WN
A STUDY OF VARIATIONS IN THE MASKINONGE FROM THREE REGIONS IN CANADA
By A. S. Hourston
TORONTO MAY 15, 1955
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ROYAL ONTARIO MUSEUM OF ZOOLOGY AND PALAEONTOLOGY CONTRIBUTION NO. 40
A STUDY OF VARIATION IN THE MASKINONGE* FROM THREE REGIONS IN CANADA
by A. S. HOURSTON**
Two subspecies of Esox masquinongy have been recognized (Dymond, 1947) in Canadian waters namely, E.m. masquinongy Mitchill (St. Lawrence maskinonge) and E.m. immaculatus Garrard(northern maskinonge). They are distinguished by their pattern of markings, the typical subspecies having ‘‘round or squarish black- ish spots of varying size’’ (Jordan and Evermann, 1896-1900), while the immacula- tus form has spots, cross-bars or both, generally very indistinct except on the tail (Weed, 1927). Although some of the earlier workers (Mitchill, Garrard, Weed) appear to have considered these forms as separate species, most recent authors (Eddy and Surber, 1943; Hubbs and Lagler, 1947) refer to them as subspecies of E. masquinon- gy. All of these authors give a pattern of markings as the basis of distinction, but in some cases a scepticism of the value of classification on the basis of colour pat- tern is indicated (Eddy and Surber, 1943).
The problem of subspecific classifications in maskinonge is open to more thor- ough study and revision. The present study is designed to determine the nature and extent of the taxonomic differences between maskinonge from different parts of its Canadian range. Where practical, the level of identification of 75 per cent of a group has been set as the goal of comparison, as this level of difference is often used in describing subspecies. It is a generous expression of the requirement outlined by Hubbs (1943) that ‘‘much more than half of the given population be distinguishable; not necessarily at all times and places, but at least in one sex, at some given stage of development.’’
A taxonomic study of the maskinonge is further complicated by a form known lo- cally as the ‘‘true tiger’? maskinonge which is now known to be an infertile hybrid between E. masquinongy and E. lucius(Cameron, 1948). This hybrid has distinct dark cross-bars sloping forward and occasionally broken by distinct dark spots; the cheek and opercle are distinctly marked. It is found along with the northern maskin- onge in Maskinonge Lake and Little Vermilion Lake near Sioux Lookout in the Ke-
nora district of Ontario.
*The name of this fish has appeared in as many as forty-five different forms such as muskel- lunge, muscalonge, masquinonge, maskinonje, moscononge, etc. However, the spelling mas- kinonge (or the French maskinongé) seems preferable since it is the one used in the statutes of the provinces of Ontario and Quebec. The derivation of the name is likewise disputed, but most authors seem to favour an Indian source. Chambers (1922) discusses this etymology and favours a derivation from the Chippewa mis or mas (large) kenosha (pike).
**Now with the Fisheries Research Board of Canada, c/o Pacific Biological Station,
Nanaimo, B.C.
2 R.O.M.Z. AND P. CONTRIBUTIONS MATERIALS AND METHODS
Locality of the Investigation
In Canada the maskinonge is found in baysof the Great Lakes, medium sized lakes and larger rivers from the St. Lawrence River to the upper reaches of the Winnipeg River (Dymond,1947). Rather than attempting to gather specimens over the entire ex- tent of the known range of the fish, an investigator was sent for one summer to each of three general areas in Canada where maskinonge have been reported to be rela- tively abundant. These areas are indicated in Figure 1, and may be outlined as fol- lows:
(i) Western. This region, from which specimens were examined in 1946, com- prises the Kenora and Rainy River districts in North-western Ontario. In the course of the study the following lakes were visited: Little Vermilion, Big Vermilion, Mas- kinonge, Eagle, Mud (Hooch), Cedarbough, Cedar, Clay, Class, Corner, Indian and Fluke. The Sabascong and Whitefish Bays on Lake of the Woods were also visited. All of these waters drain into Hudson Bay.
(ii) Central. This area was studied in 1947 and covers the Kawartha Lakes and Georgian Bay region of central and northern Ontario. The waters visited include Buckhorn, Lovesick, Pigeon, Rice, Scugog and Stony Lakes, Indian River, Deer Bay and Georgian Bay (at Sans Souci). These waters all drain into the Great Lakes. No specimens were taken from Lake Erie which has been reported to contain a spot- ted form quite different in appearance from the maskinonge of the Kawartha Lakes region (Hubbs, personal communication, 1949).
(iii) Eastern. In general, this district, which was sampled in 1948, includes the St. Lawrence River (and tributary waters) from the Ontario border to about eighty- five miles east of Montreal. The majority of fish examined were taken from Lake St. Francis, Lake St. Louis, and Lake of Two Mountains in the St. Lawrence River
near Montreal.
Collection of Data |
Since the maskinonge is a comparatively rare fish, the capture and collection of specimens by an individual investigator would not likely provide sufficient material for a study of this nature. By examining specimens taken by the numerous anglers fishing in the region under study it was possible to overcome this difficulty to a large extent. One of the drawbacks to this method was that it was sometimes im- possible to gather complete data on each fish. It was easier to do so in the eastern region, where the Department of Fish and Game for the Province of Quebec offered a three dollar reward to any angler who caught a maskinonge and submitted it for a complete examination. In this manner data were collected on a relatively large num- ber of specimens at a reasonable cost.
Mr. G.S. Cameron gathered the field data during 1946 and 1947 while the author and Mr. Cameron worked together in 1948. The original field data (body measure- ments in millimetres, fin and scale counts, photographs of each specimen, colour photographs of most of the specimens, and field notes) are permanently on file at the Royal Ontario Museum of Zoology and Palaeontology where they are available for examination and further analysis.
HOURSTON: A STUDY OF VARIATION IN THE MASKINONGE 3
RESULTS
Comparison of Markings
Hitherto, the maskinonge has usually been divided into taxonomic categories main- ly on the basis of the pattern of its markings. To test the reliability of this criterion and investigate it further, photographs were taken of each specimen examined. Col- our photographs were also taken when conditions were suitable. From a study of en- largements made of these photographs and notes made when the fish were examined , the specimens from each region were classified according to their markings. The types of marking found included:
(i) Spots. — marks with their vertical height less than four times their horizon- tal width (Figures 2, 3). (ii) Bars. — marks with their vertical height more than four times their horizon-
tal width and with a definite “‘straight’’ shape and direction of slope (Figures 4, 6).
(iii) Bars and Spots. — a combination of the above two types of marks (Figure 7).
(iv) Vermiculations. — ‘‘wormlike’’ dark streaks with an irregular path and no definite shape (Figure 8).
(v) Clear. — without any dark marks or blotches imposed on the background ex- cept in the caudal region where indistinct marks were often visible (Figures 9-11). Any fish whose markings could not be classified clearly under the above head- ings was listed as doubtful. This category included faded specimens on which the
marks could be detected but were not distinct enough to be defined. These fish comprised 14.7 per cent of the total number examined and were excluded from the analysis. The classification according to markings is given for size groups of 200 mm. in Table I. All types of markings were found in every region except the spot- ted type in the central region. The tendency of spots to persist in the larger speci- mens, which has been considered characteristic of E.m. masquinongy, prevailed among maskinonge from the eastern region. The marking pattern characteristic of E.m. immaculatus (bars, fading with age) was shown by the fish from the western and central regions where the barred specimens are mainly in the smaller size groups and the larger fish show a greater tendency to be clear.
Considering only the types of markings used to identify E. m. masquinongy and E.m. immaculatus, (spots, and bars or clear), the percentage of each type has been tabulated below by region, with the number of specimens examined given in paren-
theses.
Western Central Eastern Spots 15? * £5) 0 (0) 64 (90) Bars, clear 85 (28) 100 (30) 36 (51)
Thus, well over three-quarters of the western and central fish are distinguished by the markings of bars or clear and nearly two-thirds of the eastern maskinonge may be distinguished by persistent spotted markings.
When all the types of markings found are included, the results do not differ ap-
preciably. Western Central Eastern
Spots, bars and spots 7a 19) 6 (2) 61 (112) Bars, vermiculations, clear 77 (44) 94 (31) 39. GH
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HOURSTON: A STUDY OF VARIATION IN THE MASKINONGE 5
The inclusion of vermiculations in the immaculatus-like markings seems justified since the markings on the barred fish seem to break up with age into vermiculations, and even the ‘‘spotted’’ fish from the western region (Figure 3) show a rather ver- miculated pattern with squarish irregular spots. On the other hand the fish with mark- ings in the form of “‘bars and spots’’tended to resemble the spotted fish more than the barred fish.
The classification ‘‘clear’’ may be open to some question as it is possible that the markings on some of these specimens faded subsequent to capture and that this had not been recognized. Thus, considering only actual marks, the results become:
Western Central Eastern Spots, bars and spots 26 (13) 12). (2) 73%€112) Bars, vermiculations 74 (37) 88 (15) 2]. (41)
On this basis, about three-fourths of the specimens are separable, but over 20 per cent of the specimens taken are not included. While a large portion of the latter may have had to be excluded because of technical difficulties, some of these fish must have been clear of markings in their natural state.
The general pattern of markings of the immaculatus-like form found in the western region has already been described by Cameron (1948) from the specimens taken dur- ing this study. His description, with appropriate changes in figures and figure num- bers, states that: ‘‘Small specimens of the typical form (up to about 30 inches in length) are predominantly bluish green on the sides, with distinct dark vertical bars (Figure 12). Larger fish show a gradual darkening of colour, while the markings be- come gradually obscured (Figure 13). The back is often so dark a shade as to be al- most black. This colour shades down through bronze to sides that have a ruddy ground colour. As a fish ages, the bars break up into obscure blotches which remain more distinct in the caudal region (Figure 14). In the largest specimens (over 40 inches) the sides are usually of a uniform, dirty brownish colour. The belly is usu- ally white, although that of some young maskinonge is marked by faint dark patch- es. The fins are typically of a brownish colour with obscure darker blotches; the fins are often of a vivid red colour.”’
This general description may be applied also to maskinonge from the central region. In the east, however, the marking pattern typical of E. m. mas quinongy predominates. Markings break up at an early stage (about 500 millimetres) into relatively small spots (Figure 15), and these spots tend to persist. They are found on specimens larger than 1150 millimetres (Figure 16). The general coloration is similar to that found in the west, the back being a dark olive-brown, almost black in many cases. This fades into a bluish or brownish green on the sides, some- times marked with faint dark patches in the younger fish, which in turn fades into the white belly. The fins are similar to those described for the western form.
Comparison of Body Proportion Measurements, Fin Ray Counts, and Scale Counts From each maskinonge examined, a set of 26 measurements and counts was taken. These included head length, depth of head, length of eye, snout length, least (bony) interorbital width, length of upper jaw, length from snout to occiput, body depth, body width, length of caudal peduncle, depth of caudal peduncle, length of longest ray, length of base and number of rays for dorsal, anal, pectoral and pelvic fins, lateral line scale count, branchiostegal rays and mandibular sen-
6 R.O.M.Z. AND P. CONTRIBUTIONS
sory pores. Body measurements were made as outlined by Hubbs and Lagler (1947) with the exception that the opercular membrane was not included in the head length and that the length of the caudal peduncle was measured along the lateral line from a point directly above the insertion of the anal fin to the end of the ver- tebral column. The following additional measurements were employed. 1. Length of longest pelvic ray — measured as for the longest pectoral ray. 2. Length of pectoral and pelvic bases — measured as for the dorsal and anal fins. 3. Body width — the maximum width of the body. 4, Length from snout to occiput — defined as the distance from the anterior tip of the snout to the occiput.
Fork length was used as the measurement of body length. The number of speci- mens examined from each region is given for length groups of 200 mm. in Table II. This table also gives the mean fork length for each group and the conversion fac- tor for changing fractions of fork length to fractions of standard length and natural tip length. The latter measurement was taken with the tail fin in its natural posi- tion, and was the distance from the snout to a perpendicular drawn from the longer lobe of the caudal fin, measured along the mid line of the body. The individual body proportion measurements and counts were plotted for indications of sexual di- morphism but no such differences were noted. The sexes were then lumped and the
data compared by region and size group.
TABLE Il
Number of specimens, mean fork length and conversion factors for changing fractions of fork length to fractions of standard length and natural tip length for maskinonge from each of the five length groups in the three regions studied.
Fork length in mm.
301-500 | 501-700); 701-900] 901-1100} 1101-1300
Number of Eastern 1 10 98 76 28 specimens Central 1
Western _
Eastern Mean fork length Central Western
Conversion factor Eastern to thousandths of Central standard length Western Conversion factor Eastern 9259 to thousandths of Central .9116
natural tip length Western -
HOURSTON: A STUDY OF VARIATION IN THE MASKINONGE 7
None of the counts showed an apparent difference between size ranges, and so their frequency distributions were compared by region. The western fish tended to have one less ray in their dorsal and anal fins while the eastern fish tended to have one more mandibular sensory pore than those fromthe other two regions. Neither of these differences were statistically significant. The large variation found in the lateral line scale count within the individual regions precluded signi- ficant comparisons of this character between regions. The other characters failed to differ in their regional modes.
The data on all measurements and counts were tabulated in the form of range, mean, standard deviation and dispersion of body measurements, expressed in thousandths of the fork length.
The dispersion is defined as 0.6745 times the standard deviation and the range of mean + dispersion includes half of the observations in a normal frequency distribu- tion, so that a quarter are excluded on either end. These tabulations are on file at the R.O.M.Z. P.; means and standard deviations of all characters are given in Table III.
A tendency to increase proportionately with an increase in body length was shown by the depth of head, least interorbital width, and length of upper jaw; whereas the length of eye, length of caudal peduncle, length of longest ray for all fins, and the length of anal base, all showed a tendency to decrease proportionately with in- creasing size. These differences were comparatively small in most cases but indi- cate the necessity of the size group breakdown as employed herein.
Each of the individual size ranges of the characters compared were tested for significant differences using the ‘“‘t’’ test (Snedecor, 1937) in order to ensure that any distinctions found were statistically significant. The three populations differ significantly in respect to average size of the majority of the characters studied. In all, 98 out of 168 comparisons showed differences at the P= .01 level of signi- ficance, and 112 at the P= .05 level of significance. Since each of the groups in- cludes fish from several populations, these represent regional differences in the character of the species.
Characters showing approximately 75 per cent distinction were length of longest pectoral ray (eastern from western and central regions), and depth of caudal pe- duncle, length of pectoral base, and length of pelvic base (western from central and eastern regions). This lack of overlap in the 75 per cent range was also noted for one size class of head length, least interorbital width, length of anal base, and lateral line scale count, but these differences were not considered to be sufficient- ly distinct for consideration at this level.
On the basis of the length of the longest pectoral ray, the eastern fish were dis- tinct from those of the other two regions in four of the five comparisons made and nearly so in the fifth. On the other hand, the western and central fish show consid- erable overlap in their 75 per cent ranges for this character. Thus it would seem that the eastern fish may be distinguished from those in the western and central regions by the length of the longest pectoral ray.
The western fish tended to be distinct on the basis of caudal peduncle depth, (for three of the four comparisons), length of pectoral base (two of four compari- - sons), and length of pelvic base (for three of four comparisons). The 75 per cent
CHARACTER
Head Length Depth of Head Length of eye Snout Length
Least (bony) inter- orbital width Length of upper jaw
Length from snout to occiput Body depth
Body width
Length of caudal peduncle
Depth of caudal peduncle
Length of longest dorsal ray
Length of dorsal base
Length of longest anal ray
Length of anal base
Length of longest pectoral ray
Length of pectoral base
Length of longest pelvic ray
Length of pelvic base
Lateral line scale count
Branchiostegal rays
Mandibular sensory pores
Dorsal fin rays
Anal fin rays
Pectoral fin rays
Pelvic fin rays
301-500
TABLE III, ?
EASTERN REGION
501-700
701-900
BODY PROPORTIONS
250.8 (6.6) 102.2 (7.7) 026.0 (1.6) 105.3 (4.1) 060.4
(0.8)
901-1100
(0.5)
1101-1300 .
lean and Standard Deviation (in parentheses) of Body Proportion Measure- ents (expressed in rhousandths of the fork length) and Counts, According Region and Length Groups.
| CENTRAL REGION WESTERN REGION 301-500 501-700 701-900 901-1100 1101-1300 591-700 701-900 901-1100 1101-1300
BODY PROPORTIONS
256 254.9 251.0 249.0 254.5 264.5 251.0 259.1 254.5 (—) (6.3) (9.0) (6.5) (—) (—) (5.7) (7.9) (—) 123 098.9 096.0 100.2 102.5 109.0 103.7 109.0 106.0 (—) (6.6) (5.6) (6.3) (—) (—) (8.6) (7.6) (—) 028 026.6 025.7 023.3 021.5 030.0 027.0 024.8 023.5 (—) (1.6) (1.5) (1.1) (—) (—) (1.6) 1.45) (— 114 104.8 104.5 103.4 109.0 107.5 103.7 108.3 109.0 (—) (2.9) (3.0) (5.1) (=) (—) (2.9) (3.9) (—) 056 057.7 059.0 059.9 063.0 061.0 961.0 063.3 063.0 (—) (3.3) (1.5) (2.1) hi) =) (2.4) (2.3) (—) 120 121.4 i224 123.3 28.5 125.0 120.2 128.2 12535 (—) (4.8) (3:6) (4.6) i) (—) (6.6) (4.3) (-) 195 176.8 174.4 725 WP) 181.0 174.3 178.0 175 (—) (5.3) (4.0) (7.6) (=) (—) (4.4) (6.1) (—) 128 151.5 154.6 159.1 157.0 174.5 167.5 168.0 182.0 (—) (10.7) (10.8) (13.7) (=) (~) (11.6) (12.8) i 084 085.7 086.i 094.8 084.5 104.0 099.3 099.0 112.0 (—) (6.3) (6.7) (5.8) — i (6.1) (5.6) (—) A17 115.6 108.2 105.1 105.5 113.6 115.7 L10,3 108.5 (—) (5.9) (6.8) (6.1) 3 (—) (8.1) (7.5) = 056 062.4 061.9 061.0 059.5 073.5 068.6 068.6 070.0 =) (2.6) (2.6) (3.9) —-) f—) (3.3) (4.5) a 128 114.3 107.2 097.2 094.0 FL 7.0 105.8 100.5 096.5 (—) (3.8) (5.2) (3.6) =) i} (5.1) (5.4) (—) 120 115.4 114.3 110.5 106.5 126.0 L111 109.0 110.5 ) (3.6) (4.9) (4.2) (—) — (6.7) (4.4) J 131 119.4 EELS 100.2 097.0 E720 106.5 100.1 095.5 (—) (4.6) (5.4) (4.9) (=) (—) (6.0) (5.0) o 100 101.8 098.6 093.9 089.5 093.0 O91. 088.8 089.0 ) (5.5) (5.2) (5.1) ee &, (4.9) (4.4) > 100 106.0 105.4 098.8 098.0 116.0 106.7 103.1 100.5 ae (7.4) (3.7) (4.1) (—) oa (5.5) (6.7) = 028 030.7 030.3 030.1 030.0 036.5 033.4 033.0 034.5 (—) (1.6) (2.4) (1.8) ie =, (2.6) (2.3) = 095 097.1 092../ 085.2 082.5 095.5 093.3 089.6 086.5 (—) (4.5) (3.9) (4.6) Se (—) (4.9) (4.8) (—) 028 029.4 029.4 030.2 030.0 035.5 033.0 032.4 035.0 =) (1.8) (1.3) (1.3) cS ees. (1.8) (1.6) 3 COUNTS 151 ea Fy £51,0 150.4 149.0 148.5 148.7 149.7 151.5 (—) (3.2) (5.9) (4.6) at = (4.7) (4.2) (—) 17 17.6 17.8 Evid 16.5 17.0 17.8 17.8 18.5 (=) (0.7) (0.7) (0.5) (—) (—) (0.7 (0.5) (—)
8 7.4 73 cpr 7.0 8.0 TG 7.4 7d - (0.6) (0.8) (0.5) = (—) (1.1) (1.0) {—*} 23 22.1 22.5 22.7 22,5 2155 7 22.0 22.5 (—) (0.8) (0.8) (0.6) ee (—) (1.1) (0.9) (~) 20 20.7 20.9 20.8 “0:9 21.0 20.3 20.1 21.0 (—) (0.7) (0.6) (0.9) (0.5) (—) (0.8) (0.9) (=) 18 17.4 7.) SG 2 75 18.0 ye 18.2 18.5 (—) (0.6) (0.7) (0.5) = =} (0.8) (0.6) =) 12 12.0 11.9 ea 12.0 13.0 12.5 12.3 12.5
10 R.O.M.Z. AND P. CONTRIBUTIONS TABLE IV
The 75 percent range is given by region and length group for charac- ters for which this range shows a lack of overlap between regions.
Fork Length in mm.
Churaerm 501-700 901-1100 1101-1300
Length of.Jongest| Eastern 087-099 089-096 084-093 086-096 pectoral ray Central 101-111 103-108 096-102 > Western ~ 103-110 099-108 - Depth of caudal Eastern 062-066 062-066 063-067 060-065 peduncle Central 061-064 060-064 058-064 = Western — 066-071 066-072 - Length of Eastern 027-030 029-031 029-032 029-032 pectoral base Central 030-032 029-032 029-031 - Western vas 032-035 031-035 = Length of Eastern 026-030 028-031 029-032 028-033 pelvic pase Central 028-031 028-030 030-031 = Western = 032-034 031-034 =
range of these characters as calculated from the dispersion is given in Table IV. The 75 per cent range in the 901-1100 mm. length group showed an overlap for the eastern-western comparison, but these two groups of fish may be distinguished by the length of their longest pectoral ray and by the pattern of their markings. The western fish proved to be distinct in other comparisons of the three characters, except the 701-900 mm. length group in the central-western comparison of the length of the pectoral base and it was nearly so. It would thus seem that 75 per cent of the western fish may be distinguished from those of the other two regions; this difference is especially evident at the small size levels. These Lake of the Woods maskinonge have also been shown to differ from the Kawartha Lakes and St. Lawrence River fish in their length-weight relationship, the western fish being heavier for their length than those from the cther two regions (Hourston, 1952).
The effect of sexual differences on the variations in these characters was check- ed by the “‘t’’ test (Snedecor, 1937). Length groups of 100 mm. were employed in order to minimize the effects of any variations with body length. The eastern fish showed dimorphism significant at the P = .01 level in the depth of the caudal pe- duncle between 32 males and 23 females in the 801-900 mm. length groups (t= 3.908) and between 21 males and 26 females in the 901-1000 mm. length group (t= 3.248). This dimorphism would not affect the conclusion drawn since the sexes are more or less evenly divided at this length range. In any case this character is used mainly to distinguish the western and central fish since the eastern fish may be distingui- shed from the others by other means. Differences significant at the P=.05 level were found in the length of the pelvic base for 11 males and 18 females in the 1001- 1100 mm. size group from the eastern region (t= 2.058), and for 7 males and 12 fe- males in the 701-900 mm. size group from the central region (t= 2.834). However;
HOURSTON: A STUDY OF VARIATION IN THE MASKINONGE ll
since these are two of the most poorly sampled size ranges, and since the differ- ence did not show up among other size ranges, their reality is not assured.
DISCUSSION
The results of this study might be taken to indicate the existence of subspecific differences between populations investigated. The population in the St. Lawrence River district in Quebec (eastern region) is distinguished from the central and west- ern populations by its spotted markings and shorter pectoral fins. The Lake of the Woods (western) population may be distinguished from the Kawartha Lakes (central) population by a deeper caudal peduncle and longer pectoral and pelvic fin bases.
It has been suggested that some of the differences found may not be as signifi- cant as the data would indicate. The basis of this suggestion is that since each of the three populations was studied in a different year, the method of making measure- ments may have unconsciously varied from year to year. Indeed, the difference in the length of pectoral and pelvic fin bases was not reflected by a difference in fin ray counts. The possibility of later repeating the measurements made at different times was precluded by the fact that all specimens were measured in the field on fresh material. Also caudal peduncle depth could be affected to some extent by the nutritional condition of the fish. Finally, the degree of variation in markings and their tendency to fade after capture makes their quantitative assessment difficult. Nevertheless, the results of the study tend to confirm the assumption that there are significant differences between the eastern (St. Lawrence) and western (Lake of the Woods) populations of the maskinonge. They suggest, however, that the Kawar- tha lakes population cannot be regarded as belonging to a St. Lawrence River sub- species, which is also found in the Great Lakes (Hubbs and Lagler, 1947). The study emphasizes the difficulty in recognizing subspecies in the maskinonge.
SUMMARY
1. A total of 212 maskinonge from the St. Lawrence River (eastern region), 67 from the Kawartha Lakes and Georgian Bay (central region), and 76 from the Lake of the Woods district (western region) were compared for differences in their taxonomic characters. A series of 19 body proportion measurements, 7 sets of counts and the patterns of markings were employed in the comparisons, which were made in length of intervals of 200 mm.
2. Of the 168 comparisons made between regions, 98 showed differences at the P=.01 level of significance and 112 at the P=.05 level of significance, thus in- dicating that the three groups of fish were recognizably different.
3. The recognition of 75 per cent or more of a stock of fish is often accepted as a criterion for subspecific distinction. On this basis, fish in the St. Lawrence River were distinguished from the others by their spotted markings and their longest pec- toral fin ray being shorter than that of the other fish. The Lake of the Woods mas- kinonge were distinguished from the Kawartha Lakes maskinonge by a deeper cau- dal peduncle and a longer base on their pectoral and pelvic fins. However, the possibility of variation in the methods of measuring body parts and the difficulty of interpreting marking patterns suggest that some of these differences may not be
12 R.O.M.Z. AND P. CONTRIBUTIONS
as significant as the data would indicate.
4, The assumption that there are significant differences between maskinonge from the St. Lawrence River and Lake of the Woods region is supported by the results of this study. On the same basis, however, the Kawartha Lakes population cannot be regarded as belonging to a St. Lawrence River subspecies.
ACKNOWLEDGEMENTS
The field studies, which were directed by Dr. J. R. Dymond and conducted by Mr. G. S. Cameron, were made possible by the financial support of the Carling Conser- vative Club. The author is deeply grateful ro Dr. W. B. Scott for his advice and criticism in the preparation of this publication, and to Dr. C. L. Hubbs of the Scripps Institution of Oceanography and Dr. W. E. Ricker of the Fisheries Research Board of Canada, both of whom gave valuable advice on the analysis of the data. I wish also to thank Dr. G. Prevost and his staff of the Department of Fish and Game, Province of Quebec, for their wholehearted co-operation in the field studies carried out in that province.
LITERATURE CITED
Cameron, G. S. 1948. An unusual maskinonge from Little Vermilion Lake, Ontario. Can.
Journ. Res., vol. 26, no. 5, pp. 223-229.
Chambers, E.7.D.
1922. The maskinonge. A question of priority in nomenclature. Trans. Amer. Fish. So0c:, vol..52, pp..1 71-177.
Dymond, J.R. 1947. A list of the freshwater fishes of Canada east of the Rocky Mountains, with keys. Roy. Ont. Mus. Zool. Misc. Pub. no. 1, pp. 1-36.
Eddy, S. aad. Surcber 1943. Northern fishes. Univ. Minn. Press, pp. 1-276.
Hourston,; A.S. 1952. The food and growth of the maskinonge (Esox masquinongy Mitchill) in Canadian waters. Journ. Fish. Res. Bd. Can., vol. 8, no. 5, pp. 347-368.
Hubps.8C.L. 1943. Criteria for subspecies, species and genera, as determined by researches on fishes. Annals N.Y. Acad. Sci., vol. 44, no. 2, pp. 109-121.
Hubbs, C.L. and K.F. Lapler
1947. Fishes of the Great Lakes region. Cranbrook Inst. Sci. Bull. no. 26, pp. 1-186.
HOURSTON: A STUDY OF VARIATION IN THE MASKINONGE 13
Jordan, D.S. and B.W. Evermann 1896-1900. The fishes of North and Middle America. U.S. Natl. Mus. Bull. no.
47, vol. 1, pp. 1-1240.
Radforth, I. 1944. Some considerations on the distribution of fishes in Ontario. Roy. Ont.
Mus. Zool. Contr. no. 25, pp. 1-116.
Snedecor, G.W. 1937. Statistical methods. Iowa State Coll. Press. pp. 1-341.
Weed, A.C. 1927. Pike, pickerel and muskalonge. Field Mus. Nat. Hist. (Chicago) Zool.
Leaflet no. 9, pp. 1-52.
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Figure 2. A 765 mm. maskinonge with spotted markings from Lake St. Francis in the eastern region.
Figure 3. An 860 mm. maskinonge with spotted markings from Little Vermilion Lake in the western region.
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Figure 4. A 784 mm. maskinonge with barred markings from Lake St. Louis in the eastern region.
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Figure 6. A 751 mm. maskinonge with barred markings from Maskinonge Lake in the western region.
Figure 7. An 814 mm. maskinonge from Cedarbough Lake in the western region showing markings in the form of bars and spots.
Figure 8. A 1110 mm. maskinonge from Lake St. Francis in the eastern region
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Figure 9. An 813 mm. maskinonge clear of markings from Indian Lake in the west- ern region.
Figure 10. A 940 mm. maskinonge clear of markings from the Thousand Islands River in the eastern region.
Figure 11. A 978 mm. maskinonge clear of markings from Buckhorn Lake in the central region.
Figure 12. A 687 mm. maskinonge from Little Vermilion Lake in the western region showing distinct dark vertical bars.
Figure 13. A 929 mm. maskinonge from Little Vermilion Lake in the western region showing the remains of dark vertical bars.
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Figure 14. A 1106 mm. maskinonge from Little Vermilion Lake in the western re- gion showing only traces of dark vertical bars.
Figure 15. A 508 mm. maskinonge from Lake St. Francis in the eastern region showing distinct roundish spots.
Figure 16. A 1153 mm. maskinonge from Lake St. Louis in the eastern region showing the persistence of roundish spots in large specimens.
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