62 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



22 inches fork length in Lake Opeongo, Algonquin 

 Park, Ontario, were capable of spawning. Such 

 widespread inipotency was not observed in any 

 of the New York lake trout. The conservation 

 department employees engaged in spawn-taking 

 operations on the Adirondack and Finger Lakes 

 reported that only occasionally would an impotent 

 fish be found. The more limited observations I 

 made also failed to show any impotency, and it 

 is quite likely that after the lake trout in New 

 York State lakes are mature they may spawn 

 several times before succumbing to the infirmities 

 of age. 



TIME OF SPAWNING * 



The available information shows that lake trout, 

 and most other trout, spawn once a year in the 

 fall when the temperature is dropping and the 

 days are becoming shorter. Among different races 

 of lake trout, small variations in the spawning 

 date are found. This is true also of the same 

 race of lake trout in different lakes, and of the 

 same race in the same lake in different years. 

 It appears probable that fluctuations in light and 

 temperature, in the physical characteristics of 

 different lakes, and in the responses of different 

 races are the determining factors. 



These factors have proved important in in- 

 fluencing the spawning time of other species. 

 Hoover and Hubbard (1937) have shown that 

 brook trout which normally spawned in Decem- 

 ber could be induced to spawn in late August 

 and early September by increasing the amount 

 of light in early spring and decreasing it in late 

 summer. Bissonette and Burger (1940) state 

 that "there is no uniform control of the sexual 

 cycle applicable to all fish. In some fish, tem- 

 perature seems to be the major factor; in others, 

 light and temperature play cooperative roles; 

 while in still others, light appears to be the most 

 important factor." 



Merriman and Schedl (1941), on the basis of 

 laboratory experiments on the four-spined stickle- 

 back, Apeltes guadracus (Mitchill), concluded that 

 light influenced oogenesis but not spermato- 

 genesis, while temperature somewhat unequally 

 affected the maturation of the gonads of both 

 sexes. McCay et al. (1930) concluded on the 

 basis of feeding experiments that the spawning 

 time of brook trout could be influenced by the 

 food supply. They found that the age at ma- 



turity could be advanced or postponed by in- 

 creasing or decreasing the amount of food fed 

 to the hatchery trout, but the question of chang- 

 ing the spawning date of mature trout was not 

 clarified. 



After several years of netting lake trout in 

 Raquette Lake for spawn taking, the hatchery 

 men of the New York Conservation Department 

 have observed that the lake trout run earlier 

 after a sudden drop in temperature. The exten- 

 sive data on their operations were made avail- 

 able to me, and weather data were obtained 

 from the United States Weather Bureau (table 1). 



Table 1. — Weather conditions in relation to peak of lake- 

 trout egg take at Raquette Lake, 1933-41 



' Average air temperature for the month of September at nearby Indian 

 Lake. 



' Number of cloudy days in July, August, and September in the northern 

 plateau region of New York. 



3 No eggs taken. 



The average air temperature for September 

 reported by the Indian Lake weather station was 

 used because it was the nearest station to 

 Raquette Lake, with complete weather records for 

 the 8 years of spawning data. The average 

 number of cloudy days for the entire northern 

 plateau region of New York was selected because 

 many of the smaller stations had no automatic 

 sunshine recorders and their estimates of cloudi- 

 ness varied considerably. The number of cloudy 

 days in July, August, and September was used 

 because the work of Hoover and Hubbard (1937) 

 indicated that changes in the light required a 

 considerable time to influence the development 

 of the eggs, and these 3 months were the ones 

 preceding the spawning season which had 

 decreasing amounts of daylight. 



The analysis of these data by multiple regres- 

 sion (table 2) indicated that the date of spawning 

 was advanced by lower temperatures or a greater 

 number of cloudy days and retarded by warmer 

 weather or fewer cloudy days. However, neither 

 on air temperature alone nor on cloudiness alone 



