SOUTH BAY. NAKNEK LAKE 



KEWEENAW BAY. 

 LAKE SUPERIOR 



SISKIWIT BAY. 

 LAKE SUPERIOR 



BROOKS LAKE 



260 



240 



220 



200 



180 



160 



140 



120 



100 



80 



60 



40 



20 







YEAR OF LIFE 



Figure 6. — Calculated growth of female pygmy whitefish 

 from Brooks Lake and South Bay. Naknek River sys- 

 tem, compared with data from Lake Superior, Mich., 

 and Lake McDonald and Bull Lake, Mont., ( Eschmeyer 

 and Bailey, 1955) and MacLure, McLeese, Cluculz, and 

 Tacheeda Lakes, British Columbia (McCart, 1963). 

 Data from Eschmeyer and Bailey were converted from 

 total to fork length. 



fish in MacLure Lake is by far the greatest, known 

 for this species. 



EMPIRICAL GROWTH 



Although the average annual growth was not 

 calculated for all lakes in the Naknek system, 

 length frequency distributions of collections from 

 six areas (table 7) provide a basis for growth com- 

 parison. The broad range of length frequencies 

 suggests differences in growth rates that reflect 

 the ecological differences in various lakes and 

 basins in the system. The oldest pygmy whitefish 

 collected from Grosvenor Lake, Hammersly Lake, 

 and North Arm were age III+ females 95, 96, 

 and 100 mm. 4 long, suggesting growth rates inter- 

 mediate between those from Brooks Lake and 



South Bay. In Iliuk Arm the length of the larg- 

 est pygmy whitefish, a 132-mm. age IV+ female, 

 is comparable with the average calculated length 

 of the same age fish in South Bay. 



The striking difference in growth of pygmy 

 whitefish in Brooks Lake and South Bay is ap- 

 parent during the first summer. The earliest col- 

 lections of age 0+ pygmy whitefish were made 

 there in late June and early July. In early July, 

 age 0+ pygmy whitefish were about equal in 

 length in the two areas, averaging between 20 and 

 23 mm. long. By late August, however, age + 

 pygmy whitefish from South Bay were almost 10 

 mm. longer than fish from Brooks Lake (fig. 7). 

 Based on the average calculated growth rates, 

 South Bay pygmy whitefish are about 20 mm. 

 longer than Brooks Lake fish at the end of the first 

 growing season ( fig. 6 ) . There was little difference 

 in the lengths of age 0+ fish taken in mid- July 

 from Brooks River, North Arm, South Bay, and 

 Brooks Lake. A sample of age 0+ pygmy white- 

 fish from Grosvenor Lake in mid- August indicated 

 an average length similar to that in Brooks Lake in 

 mid-August. 



An interesting comparison of the first year 

 growth of pygmy whitefish with that of its close 

 relative, round whitefish (fig. 8), indicates that 

 age 0+ samples of both species collected in the 

 same seine haul from Brooks Lake on August 10, 

 1962, had no overlap in lengths and round white- 

 fish were considerably larger. 



FOOD HABITS 



Stomach contents were examined from 62 age 

 0+ and 396 age 1+ and older pygmy whitefish. 

 The age 0+ fish were from South Bay and Brooks 

 and Grosvenor Lakes, while the older fish were 

 from Brooks, Grosvenor, and Hammersly Lakes, 

 South Bay, North Arm, Iliuk Arm, and Brooks 

 River. These fish were collected with seines, otter 

 trawls, and gill nets. 



DIET OF AGE 1+ AND OLDER FISH 



Insects and zooplankton were the two principal 

 groups of food in the diet, of age 1+ and older 

 pygmy whitefish in the Naknek system (table 8). 

 The relative importance of these two foods varied 

 greatly between lakes. I )ipteran insects dominated 



'Two larger females, 102 and 115 mm. long were collected In 

 North Arm with (rill nets on Aug. 9. 11HVJ. Both specimens were 

 mutilated, however, and no scales were available for aging. 



566 



U.S. FISH AND WILDLIFE SERVICE 



