Table 25. — Weighted mean catch per standard tow (surface 

 and deep tows combined) of species associated with juvenile 

 sockeye salmon, August 16-31, in lakes of the Naknek and 

 Karluk systems, 1961-62 



Fish per tow 



Species, system, and lake 



Number 

 Threespine sticklebacks 

 Naknek system 



Coville Lake 8.0 



Grosvenor Lake , 2 



Naknek Lake 



North Arm .1 



liiuk Arm 3.4 



South Bay 9.3 



West End 647.8 



Brooks Lake i.O 



Karluk system 



Karluk Lake 63.9 



Ninespine sticklebacks 

 Naknek system 



Coville Lake_.. 8.8 



Grosvenor Lake .1 



Naknek Lake 



North Arm .0 



Iliuk Arm .2 



South Bay.._ .9 



West End 65.0 



Brooks Lake .1 



Karluk system 



Karluk Lake .0 



Pond smelt 



Naknek system 



Coville Lake 91.0 



Grosvenor Lake 2 



Naknek Lake 



North Arm __ .0 



Iliuk Arm .0 



South Bay ,1 



West End .1 



Brooks Lake .0 



Karluk system 



Karluk Lake 



Pygmy whitefish 

 Naknek system 



Coville Lake .0 



Grosvenor Lake .0 



Naknek Lake 



North Arm ,0 



Iliuk Arm .0 



South Bay .5 



West End .0 



Brooks Lake .3 



Karluk system 



Karluk Lake .0 



' Less than 0.06. 



except pond smelt in Coville Lake. Although 

 ninespine sticklebacks were distributed the same 

 as threespine sticklebacks, they were generally 

 less abundant. Pond smelt were taken in tow nets 

 in all basins of the Naknek system except Brooks 

 Lake but were abundant only in Coville Lake. 

 Pygmy whitefish, which are basically benthic, 

 were rarely taken in the tow net catches but were 

 highly abundant in trawl catches from Brooks 

 Lake. Areas of the Naknek system that yielded 

 the largest catches of juvenile sockeye salmon 



34.4 

 



.2 



8 



15.0 



29.3 



2 



.0 



49 5 

 



.1 

 4 

 1 



.6 

 



or the fastest growing juveniles or both also 

 yielded the largest catches of associated species. 



Chignik system. — In the Chignik system, 

 threespine sticklebacks were about 30 times as 

 abundant in tow net catches in Black Lake as in 

 Chignik Lake (table 24). The sticklebacks may 

 be unable to compete successfully with the large 

 populations of young sockeye salmon that often 

 occur in Chignik Lake. Ninespine sticklebacks 

 were slightly more abundant than threespine 

 sticklebacks in Chignik Lake but were less abun- 

 dant in Black Lake (table 24) . Pond smelt were 

 not as abundant as sticklebacks but occurred 

 frequently in tow net catches in both lakes. Other 

 species were seldom taken. 



Karluk system. — The threespine stickleback 

 was the only species other than juvenile sockeye 

 salmon captured in tow nets at Karluk Lake 

 (table 25), and sticklebacks were much more 

 abundant than juvenile salmon in all sampling 

 with all gear. 



PREDATION ON JUVENILE SOCKE'i E SALMON 



Predation on juvenile sockeye salmon in fresh 

 water occurs during their emergence, migration 

 from the spawning areas, and residence in and 

 migration from the nursery lakes. Predation by 

 birds and fish is often very obvious and dramatic 

 in southwestern Alaska, 



A few studies and many general observations 

 have been made of the relative intensity of pre- 

 dation by various animals in several systems. 

 Most of the predators to be mentioned are pres- 

 ent in all the sockeye salmon systems in south- 

 western Alaska. 



In the Mainland Systems the Arctic char is the 

 most significant predator on sockeye salmon, but 

 many others do occur. 



In the Igushik, Snake, Wood, and Kvichak 

 systems the Arctic char is the fish that eats the 

 most sockeye salmon juveniles — as migrating 

 fry, as residents in the lakes, and as migrating 

 smolts. In the Nuyakuk system, lake trout are 

 more abundant than Arctic char and consume 

 more young sockeye salmon. Other fish predators 

 observed to eat young sockeye salmon in these 

 lake systems are juvenile coho salmon, northern 

 pike, grayling, and rainbow trout. During the 

 smolt migrations, Arctic Terns (Sterna para- 

 disaea) and Bonaparte's Gulls (Larus Philadel- 

 phia) prey on sockeye salmon in the rivers con- 

 necting lakes and in the trunk river. 



U.S. FISH AND WILDLIFE SERVICE 



