LAKE TROUT BREEDING HABITS 



61 



The latter have stronger colors, and the sexual 

 differences are a little more pronounced; the males 

 tend to have more brilliant yellow, orange, and 

 black in the paired fins than the females. But 

 even in these lake trout it is not always possible 

 to distinguish the sexes on the basis of external 

 differences. 



This normal coloration is considerably changed 

 when the male lake trout are excited on the spawn- 

 ing area. While they are courting, the chromato- 

 phores on their backs contract, making the backs 

 appear decidedly light colored, while the sides, 

 flooded with pigment, become very lustrous and 

 almost black (fig. 1). Merriman (1935) observed 

 this condition in the lake trout of Squani Lake, N . H. , 

 and it was seen by the writer in Otsego Lake, 

 N. Y., in 1940 and 1941, when selected fish were 

 speared and the brilliant coloration was found to 

 be restricted to the males. Striking as this colora- 

 tion was during the courting or spawning, the colors 

 were most ephemeral. After the fish were netted 

 or speared, color differences between the sexes 

 could not be detected. 



SPAWNING HABITS 

 AGE AND SIZE AT MATURITY 



The age analysis, by means of scales, of 33 

 mature lake trout caught by gill net on the spawn- 

 ing area oft' Peach Orchard Point in Seneca Lake, 

 N. Y., showed that 13 had 5 annuli and the remain- 

 ing 20 had 6 annuli. Comparison of the lengths 

 of the lake trout in this sample with the length 

 frequency of 424 lake trout taken during the 

 spawning season in 1941 showed that these age 

 groups comprised tlie bulk of the catch, but 

 probably an appreciable quantity of older fish 

 wiere taken. 



Data collected during 1940 by J. R. Westman 

 on the lake trout of Lake Simcoe, Ontario, showed 

 that 13 out of 20 five-year-old and 16 out of 17 

 six-year-old lake trout were mature. Samples from 

 Keuka Lake, N. Y., in the same year showed 

 similar results: 15 out of 18 five-year-old and 5 out 

 of 6 six-year-old trout were mature. There was 

 a shght tendency for the greater proportion of 

 the young males to be mature in these two lakes, 

 as well as in Seneca Lake. 



Fry and Kennedy (1937) estimated, by means 

 of the modes of a length frequency distribution, 

 that the lake trout of Lake Opeongo, Algonquin 

 Park, Canada, reached the minimum age at 



maturity in their fifth year of life (corresponding, 

 presumably, to four annuli). Inasmuch as they 

 had only five lake trout less than 13 inches long, 

 and as my observations indicate very small 

 growth of lake trout in the first year, I believe 

 that they assigned to each mode an age 1 year 

 less than it should have been. 



These data are substantiated by studies made 

 on the growth of hatchery-reared trout. Surbcr 

 (1933) secured eggs from female lake trout, aged 

 4 years 6 months, whose lengths varied from 18 

 to 26 inches; but at this time only 10 females 

 out of somewhat less than 2,000 males and females 

 spawned, producing an average of only 962 eggs 

 per female. No data on subsequent spawning 

 were presented, but certainly the majority of these 

 fish did not spawn before their sixth year. Surber 

 considered that this age at maturity was com- 

 parable to that attained by wild fish. He gave 

 the length of the trout at the end of their first, 

 second, third, and fourth years of life as 10, 14, 

 16 to 18, and 18 to 26 inches, respectively. This 

 rate of growth in the fii-st and second years of life 

 is markedly greater than that existing in Keuka 

 Lake. With this start it is possible that the 

 hatchery fish spawned earlier than they would in 

 the wild, which is known to be true of some other 

 species of hatchery-reared trout, especially brook 

 trout. 



The rapidly growing lake trout of Seneca Lake, 

 whatever their age, do not mature until they are 

 26 to 30 inches in total length; those of Keuka 

 Lake mature at a total length of 18 to 24 inches. 

 In Skaneateles Lake, N. Y., however, Rayner 

 (1941) captured many mature lake trout of 15 

 and 16 inches total length. Fry (1939) reported 

 that the minimum size at maturity in some lakes 

 of Algonquin Park, Canada, varied from 14 to 18 

 inches according to the lake. 



Obviously with this variation in size at maturity, 

 a uniform minimum legal-size hmit of 15 inches, 

 such as exists in New York State, may permit 

 the taking of many immature, rapidly growing 

 fish in some lakes while providing entirely too 

 much protection in other lakes. It would appear 

 necessary to consider the growth rate and fishing 

 pressure in each lake in setting a mmimum size 

 limit. 



Slowly growing lake trout may be subject to 

 senility at a small size. Fry and Kennedy (1937) 

 reported that none of the lake trout of more than 



