ROGERS: JUVENILE SOCKEYE SALMON 



stickleback (age I), ninespine stickleback, and 

 sculiHn(;/ = 10,)' = 0.80, 0.84, andO. 76, respective- 

 ly); (2) significant correlation between apparent 

 mortality rates of ninespine stickleback and 

 sculpin (r = 0.86); and (3) lack of significant 

 correlations involving sockeye salmon fry. The 

 correlations between water temperature and 

 apparent mortality rate suggest that ninespine 

 stickleback and sculpin populations (which do 

 not become pelagic) experience higher mortality 

 rates at higher water tem])eratures. The higher 

 mortality may be the result of increased spawn- 

 ing rate and/or rate of predation. Since sockeye 

 salmon fry constitute a major portion of the 

 inshore fish community and exhibit greater 

 annual variation in abundance than the rest, 



Figure 5. — Length-frequency distributions (mm) of three- 

 spine stickleback, 1966. 



Figure 6. — Length-frequency distributions (mm) of three- 

 spine stickleback, 1968. 



they would appear to have the greatest potential 

 for affecting the abundance of fish of other 

 species. The depressing effect of high abundance 

 of sockeye salmon fry on the abundance of other 

 species was suggested by Parr (1972), but such 

 an effect may be observable only after a time 

 lapse and would be detectable only with obser- 

 vations from a greater number of years. No 

 significant correlation was detected between 

 the catches of sockeye salmon fry and the 

 catches of other species in the same year or in 

 the following year. 



A significant, although highly variable, re- 

 lationship was apparent between the abundance 

 of parent spawners and mean catch of sockeye 

 salmon fry in Lake Aleknagik (r = 0.62, ii — 11). 

 A comparison of the density of sockeye salmon 

 spawners with mean catch of sockeye salmon 

 fry in the Nushagak District is given in Table 8. 

 A positive relation between density of adult 



1071 



