FISHERY BULLETIN: VOL. 71, NO. 4 



Figure 7.^- Length-frequency distributions (mm) of nine- 

 spine stickleback, 1968. 



spawners and density of fry progeny among 

 years and lakes is indicated. The relation be- 

 tween the abundance of fry and the abundance 

 of returning adults is of primary interest be- 

 cause of the possible value in forecasting the 

 magnitude of adult runs. More years of observa- 

 tions are necessary, however, before this relation 

 can be adequately defined. 



Annual Variation in Length 



Estimates of the average size of the fish in 

 Lake Aleknagik are more precise than estimates 

 of abundance from catches. The annual relative 

 variation in mean length is much less, moreover, 

 than the relative variation in catch. For ex- 

 ample, the coefficients of variation in annual 

 mean catches and mean lengths (20 July) for 

 sockeye salmon fry were 67 and 9% , respectively. 



The annual estimates of mean length on 20 



June and 20 July, which represent the sizes of 

 the fish at the beginning and end of early sum- 

 mer, were examined for determination of the 

 major factors regulating growth. Annual mean 

 lengths of sockeye salmon fry, threespine stickle- 

 back (age I), and char fry on 20 June were not 

 significantly correlated. A significant part of 

 the annual variation in lengths of sockeye salm- 

 on fry and char fry at this time was explained 

 by the surface water temperatures on 20-24 

 June (Figure 9). Water temperature on 20 June 

 is largely a function of the date of ice breakup 

 and amount of solar radiation. Thus the annual 

 growth attained in the spring by sockeye salmon 

 fry and char fry is primarily a function of cli- 

 matological conditions. The mean length of age 

 I threespine stickleback was most closely corre- 

 lated, however, with the abundance of sockeye 

 salmon fry in the previous year. The best rela- 



10 20 30 40 SO 60 70 80 90 



LENGTH 



Figure 8. — Length-frequency distributions (mm) of slimy 

 sculpin, 1968. 



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