Table 8. — Percentage of total volume ' of different food items in stomachs and (in parentheses) percent frequency occurrence 2 

 for 13 samples of age I + and older pygmy whilefish taken with seines, gill nets, and otter trawls from various parts of the 

 Naknek system 



[T represents Trace] 



1 Based on aggregate contents of all stomachs in each sample. 

 1 Based only on stomachs containing food. 



3 Tricopteran adults, coleopteran adults and larvae, hemipteran 

 nopteran, and collembolan adults. 



4 Daphnia lonqiremis, D. rosea, Bosmina coregoni, Holopedium gibberum 



s Cyclops strenuus and Diaptomus gracilis. 

 fl Pisidium. 

 hyme- 7 Diatoms and filamentous algae. 



8 Small sticks, bits of wood, seeds, and leaves. 



DIET OF AGE 0+ FISH 



Crustacean zooplankton was the major food in 

 two samples of age 0+ fish — one from South Bay, 

 July 11, 1963, and one from Brooks Lake, August 

 14, 1962. Insects and zooplankton were about 

 equal in volume in the September 26, 1962, South 

 Bay and August 19, 1963, Grosvenor Lake sam- 

 ples (fig. 9). It appears that in those areas where 

 insects are heavily utilized by older pygmy white- 

 fish, the diet shift of fish from zooplankton to in- 

 sects occurs late during the first summer of life. 

 Eschmeyer and Bailey (1955) found copepods to 



be the dominant food of age 0+ pygmy whitefish 

 from Lake Superior in September. 



DIEL VARIATIONS IN DIET 



The sample of age 1+ and older fish from 

 Brooks River on August 24-25, 1963 (table 8), 

 was collected from the same riffle area at four ad- 

 jacent 6-hour intervals to determine diel differ- 

 ences in quantity and quality of foods eaten. No 

 significant difference in the composition of diet 

 items was found throughout the 24-hour period; 

 however, the average volume of food material per 



570 



U.S. FISH AND WILDLIFE SERVICE 



