OUTLET 

 (KVICHAK RIVER) 



FISH PER TOW 



I 1 0-25 



26-100 

 vmm 101-300 

 (Z~] > 300 



Figure 9. — Abundance and distribution of threespine sticklebacks in Iliamna Lake, 1962, as 

 indicated by avei'age catches in tow nets. Catches in A (upper) made June 15 to July 

 31; in B (lower) August 1 to September 15. 



of juvenile salmon. The smaller size of threespine 

 sticklebacks and the juvenile sockeye salmon in 

 the western ends of the lakes of the Wood system 

 suggests that the same factors influence the 

 growth of both species. 



Kvichak system. — The abundance and distri- 

 bution of threespine sticklebacks in Iliamna 

 Lake in tow net catches in 1962 before and after 

 August 1 are shown in figure 9. The abundance 

 contours of figure 9 are intended only to indicate 

 the general situation in the pelagic areas. 



Threespine sticklebacks were most abundant 

 in the pelagic areas before August 1 in the upper 

 bays of Iliamna Lake and in an area west of but 

 adjacent to the Kakhonak-Intricate Bay complex 

 (fig. 9A). After August 1, threespine stickle- 

 backs were abundant over a much larger area 



(fig. 9B). The increased abundance in a larger 

 area must be caused by a seasonal movement of 

 sticklebacks from the littoral zone. Comparisons 

 of the seasonal distribution of threespine stickle- 

 backs and of age and age I sockeye salmon 

 suggest that competition could be greater be- 

 tween sticklebacks and age salmon than 

 between sticklebacks and age I salmon. 



No threespine sticklebacks were caught in the 

 limited tow net sampling in Lake Clark in 1962 

 or 1963. 



Naknek system. — The species and abundance 

 of fish caught in the Naknek system in tow nets 

 with juvenile sockeye salmon varied among the 

 lakes (table 25). Threespine sticklebacks were 

 caught in tow nets in all of the lakes and were 

 more abundant than all of the other species, 



SOCKEYE SALMON IN MAJOR RIVER SYSTEMS IN SOUTHWESTERN ALASKA 



437 



