74 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



10 to 130 feet. Fifty -nine tows of a trawl were 

 made over a similar range of depths. A set line 

 equipped with 80 No. 7 hooks was set for 4 days 

 covering depths from 15 to 40 feet. Minnow 

 traps were set for 8 days at depths from 40 to 80 

 feet. 



Included in the catch were 41 lake trout (all 

 caught in gill nets) of which 13 were more than 

 15 inches in total length — the minimum legal size 

 in New York. The stomach content of the 13 

 legal-sized trout, and of 1 1 others of legal size 

 gathered from anglers, was 100 percent alewives 

 {Pomolobus psevdoharengus) or unidentifiable fish, 

 probably of the same species (anglers report 

 finding practically nothing but alewives in lake- 

 trout stomachs). 



The lengths and stomach contents of the sublegal 

 specimens are listed in table 7. Of the 16 speci- 

 mens between 10 and 15 inches in length, only one 

 had eaten arthropods, while the principal food of 

 those between 6 and 10 inches was arthropods, 

 mostly Mysis relicta. 



Table 7. 



-Food of lake trout less than 15 inches long from 

 Keuka Lake, 1940 



Summary: Of lake trout 10 to 15 inches in total length, 14 stomachs con- 

 tained fish remains and 1 stomach contained arthropod remains. Of lake 

 trout 6 to 10 inches in total length, 4 stomachs contained fish remains and 10 

 stomachs contained arthropod remains. 



In most cases capture of the lake trout was 

 very erratic. The 10 small specimens taken May 

 1 1 were found in the same place at very nearly the 

 same depth of 100 feet. Nets set there on follow- 

 ing nights caught nothing. The other small 



specimens taken during May and June and all the 

 larger lake trout were caught, one or two at a time, 

 in different places but almost entirely at depths 

 of 80 to 120 feet. 



Some consistency was found, however, in the 

 capture of the young lake trout caught September 

 11 to 16, 1940. These were taken, two or three 

 a rtight, in %- to K-inch bar gill nets set in one 

 restricted location off the southern tip of Bluff 

 Point, a very rocky, steep underwater slope, 

 between depths of 40 and 70 feet. Nets of the 

 same mesh set at the same depths in the vicinity 

 on mLxed mud and rubble bottom failed to catch 

 any trout. As large lake trout were taken in 

 larger-mesh nets in the same area, it seems that the 

 juveniles must have been relying on the shelter 

 of the rocks for protection from their voracious 

 elders. 



Scale examination indicated that these 6}i- to 10- 

 inch trout were yearlings and 2-year-olds. Since 

 the lake trout of Keuka Lake spawn in late 

 November and probably hatch in late April 

 (see p. 64, table 5), a rate of growth comparable 

 to hatchery growth would allow them to reach 

 only 2 or 3 inches by the first September. Possibly 

 these fingerling fish could be found in the same 

 location as the yearlings were found. Lack 

 of time and equipment prevented any further 

 effort in this direction but it is a good stage at 

 which to resume the search in the future. 



SUMMARY 



Lake trout were observed during their spawning 

 season in 1939, 1940, and 1941 in several lakes in 

 New York State, and actual spawning was seen 

 in Otsego Lake, N. Y. Extensive data on spawn- 

 taking operations were obtained from the New 

 York State Conservation Department, and exist- 

 ing literature on the subject was reviewed. 



It was found that, except for a striking color 

 change in the males while on the spawning area, 

 lake trout lack sexual dimorphism. They mature 

 in about their sixth year at lengths varying from 

 15 to 30 inches in the different lakes. 



Spawning occurs once each year, during the 

 autumn. The date varies from late September 

 to early December depending on the race of trout, 

 the amount of sunlight, the autumnal drop in 

 temperature, and the depth of the lake. 



In the deep water of Seneca Lake, one race 



