ROGERS: JUVENILE SOCKEYE SALMON 



Table 4. — Geometric mean beach seine catches in Lake Aleknagik by area and year for the period 



21 July-5 August, 1962 through 1972. 



those of the other species caught by beach sein- 

 ing because this species moves offshore to the 

 pelagic region in midsummer. 



Threespine Stickleback 



Threespine stickleback were of ages to III 

 and perhaps age IV. They ranged in length from 

 6 to 81 mm. In years of poor growth, the three 

 major age groups had distinctive length fre- 

 quencies (Figure 5), whereas in years of good 

 growth, age groups II and III overlapped great- 

 ly in length distribution (Figure 6). When, also, 

 ice broke up earlier and water temperatures 



were higher than average, age fish appeared 

 in the catches before mid-July; threespine 

 stickleback spawn in June and July. 



Age I threespine stickleback were usually 

 easy to separate from other age groups from 

 their length, especially within a given lake 

 area. The mean lengths of age I threespine 

 stickleback were greater in area C at both the 

 beginning and end of early summer than in the 

 two other areas (Table 6), but growth rates 

 were similar among the three lake areas. 



Threespine stickleback were more abundant 

 along the north shore of the lake than the south. 

 This shore is shallower and has more aquatic 



1067 



