BREEDING HABITS OF LAKE TROUT IN NEW YORK 



By William F. Royce, Fishery Research Biologist 



The several races of lake trout (Salcelinus 

 [ = Cristii'omer] namaycush) are widely sought in 

 all the more accessible parts of their range. In 

 tlie Great Lakes, where this species is one of the 

 most valued food fishes, it is the object of a major 

 fishery. In smaller lakes of the northeastern 

 I'nited States and southern Canada, where com- 

 mercial fishing usually is prohibited, it is sought 

 as a game fish. 



This popularity has been accompanied by 

 severe declines in the populations of lake trout in 

 some lakes, notably the Great Lakes. Detailed 

 knowledge of the species, particularly of the eggs, 

 larvae, and juveniles below the sizes commonly 

 caught, is needed for devising measures to prevent 

 such declines, and for successfully introducing 

 this desirable species in additional lakes. 



Almost nothing is known of the habits of young 

 lake trout, probably because of their deep-water 

 habitat ; in fact, very few wild lake trout less than 

 8 inches long have even been seen. The re- 

 productive habits of the species have been im- 

 perfectly known, and very little has been published 

 on size and age at maturity. Accordingly, a 

 study of the breeding habits of this species and 

 the life history of its young was made in 1939, 

 1940, and 1941, on several lakes in the State of 

 New York. 



SEXUAL DIMORPHISM 



The lake trout, unique among the salmon family, 

 lacks almost completely the malformed jaws or 

 kype common to mature males of other species. 

 Examination of several hundred lake trout from 

 various lakes in New York State showed that it is 

 almost impossible to distinguish the sex of mature 

 lake trout by examination of the head alone. The 

 males have only a slight tendency toward a more 

 j pointed snout — although J. R. Westman reported 

 in a personal communication that he had seen a verv 



Note.— This paper is a revision of a thesis that was submitted to Cornell 

 I'niversity in 1943 in partial fulfillment of the requirements for the depree 

 of doctor of philosophy. 



large male lake trout from Lake Simcoe, Ontario, 

 with a well-developed kype. 



It is pertinent to compare the jaws of the lake 

 trout with those of the Pacific salmon, in which 

 the kype attains its maximum development. 

 The Pacific salmon migrate enormous distances 

 to the spawning ground and live entirely on stored 

 food for almost a year before spawning. Mottley 

 (1936) ' suggests that the development of the kype 

 in the male may occur because its demand on the 

 material mobilized for the development of the 

 gonads differs from that of the female. He 

 postulates that the ovaries would have a general 

 requirement for stored materials, while the testes 

 would require little albuminoid or fat. Thus, 

 these materials might be utilized in the growth of 

 the kype instead of being excreted. 



The lake trout would appear to be a diametric 

 opposite. It rarely has a kype, migrates only the 

 short distance from the deep to the shoal waters 

 of a lake, and feeds up to and through the spawning 

 period.- Inasmuch as the lake trout does not ac- 

 quire a kype and as the maturation of the gonads 

 parallels that of the salmon, Mottley's suggestion 

 leaves some things to be explained. Possibly, 

 since the lake trout feeds right up to and through 

 the spawning season, the gonads can develop from 

 ingested food instead of mobilizing stored material 

 from the body. 



Alike in external structure, male and female 

 lake trout are also very similar in color when 

 removed from the water. However, in New York 

 State, the normal coloration of both sexes varies 

 widely from lake to lake. The lake trout of the 

 large, clear Finger Lakes are light olivaceous, 

 almost silvery on the back and sides, with a little 

 yellow or orange in the fins. There are all grada- 

 tions between the color of these trout and the very 

 dark trout of the brown-water Adirondack lakes. 



I Publications referred to parenthetically by dale are listed in Literature 

 Cited, p. 75 



' Rayner (194 1) found that stomachs of ripe lake trout taken on the spawn- 

 ing area contained fish, lake-trout eftRS, and miscellaneous invertebrates. 



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