the South Bay and Iliuk Arm samples, while, 

 crustacean zooplankton dominated samples from 

 Brooks Lake. Stomach samples from Brooks 

 River fish contained predominantly insects, while 

 samples from North Arm and Hammersly and 

 Grosvenor Lakes fish contained about equal 

 amounts of insects and zooplankton. 



Larvae, pupae, and adult dipteran and plecop- 

 teran nymphs were the main insects eaten by Nak- 

 nek system pygmy whitefish. Dipteran larvae and 

 pupae (chiefly Chironomidae) accounted for 68, 

 50, 33, and 88 percent of the food volume from the 

 four South Bay collections (table 8) . Forty-seven 

 percent of the volume of stomachs examined from 

 Iliuk Arm consisted of dipteran adults. In all 

 other samples, adult insects accounted for 5 percent 

 or less of the volume. Plecopteran nymphs were 

 the second most important insects eaten, account- 

 ing for 32 percent of the volume from a South Bay 



sample and 40 percent from a Brooks River sam- 

 ple. Five additional orders of insects were occa- 

 sionally eaten by pygmy whitefish, but these never 

 accounted for more than 5 percent of the volume 

 of any sample. 



The principal crustacean foods eaten were the 

 cladocerans Daphnia, Bosmina, and Holopedium 

 and the copepods Cyclops and Diaptomus (table 

 8). The crustacean percentage of total volume 

 varied from a trace (South Bay, August 24, 1962) 

 to 100 percent (Brooks Lake, November 7, 1962). 

 Ostracods and amphipods, which were the prin- 

 cipal foods eaten by pygmy whitefish in Lake 

 Superior (Eschmeyer and Bailey, 1955), were 

 minor items in the diet of Naknek system fish, 

 occurring in only 8 of 13 samples and never ac- 

 counting for more than 6 percent of the sample 

 volume. 



Table 7. — Length frequencies of -pygmy whitefish age 1+ and older collected from various areas in the Naknek system, 1961-63 



[M represents males; F, females; C, sexes combined) 



PYGMY WHITEFISH OF SOUTHWEST ALASKA 



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