SOUTH BAY 

 AUG.3I,I964,N=I9 



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FORK LENGTH (MM) 



Figure 26. — Length frequency distributions of four samples of ninespine sticklebacks captured in tow nets of 

 lakes of the Naknek River system, 1961, 1963, and 1964. 



Wallace (1969) presented more data on this species 

 in the Naknek system and concluded from analysis of 

 otoliths that as many as six age classes are present in 

 the lakes, but that broad overlap of lengths for each 

 age prevents separation of age I and older fish by 

 length. 



Pygmy whitefish and least cisco.— Pygmy whitefish 

 and least cisco were seldom captured in tow nets, but 

 were frequently taken in gear that sampled near shore 

 or close to the bottom. The life history of the pygmy 

 whitefish in the Naknek system was described by 

 Heard and Hartman (1966) who found populations of 

 large and small types of pygmy whitefish in the sys- 

 tem. The maximum ages and sizes reported by Heard 

 and Hartman were age III and 84 mm for the small 

 type and age V and 163 mm for the large type. 



Information on the life history of the least cisco in 

 the Naknek system was compiled by Wallace (1969). 

 The range in ages and sizes he encountered were age 

 to VI and length 61 mm to 336 mm. The largest and 

 oldest individuals came from Coville Lake. 



PREDATION ON JUVENILE 

 SOCKEYE SALMON 



Predators have been considered to be both signifi- 

 cant in determining the abundance of juvenile sockeye 

 salmon (Foerster and Ricker, 1942; Rounsefell, 1958) 

 and not significant (DeLacy and Morton, 1943; Roos, 

 1959). During the present study it became obvious that 

 the Naknek system contained many potential sockeye 

 salmon predators and. although no specific studies of 



predation were made, data and observations were col- 

 lected incidentally. This information is included here 

 to add to the overall knowledge of the biology of the 

 system and to aid in the planning for future studies. In 

 the apparent general order of importance, the fish that 

 prey on sockeye salmon in the Naknek system are: 

 lake trout, Arctic char, Dolly Varden, rainbow trout, 

 northern pike, and juvenile coho salmon. The burbot 

 and humpback whitefish are probable predators. Arc- 

 tic terns. Sterna paradisaea, and Bonaparte's gulls. 

 Lams philadephia, appear in large numbers and feed 

 actively at the mouth of Coville River during the 

 summer migration of age sockeye salmon. Mergan- 

 sers and other fish-eating ducks occur throughout the 

 system. 



Lake Trout 



Many studies have shown that fish frequently con- 

 stitute the major portion of the diet of lake trout. Van 

 Oosten and Deason (1938) present a summary of ear- 

 lier literature on food habits and present additional 

 data. More recent studies were done by Miller and 

 Kennedy (1948) and Rawson (1951). Lake trout are 

 often found in deep cool water, but have been ob- 

 served in shallow water when water temperatures 

 permit (Rawson, 1951; Connecticut State Board of 

 Fisheries and Game, 1942). Lake trout occur in most 

 of the Naknek system (Table 3), but information on 

 their food habits is available only for a group occurring 

 in shallow water at or near the outlet of Coville River 

 in Grosvenor Lake. 



Lake trout feed voraciously near the mouth of 



46 



