until late August. Some age 0+ fish may have 

 been present in limnetic areas before this time, 

 although they probably would have been too small 

 to capture in the available gear. Few tow net 

 hauls were made in September, except in Brooks 

 Lake in 1961. 



Although no permanent stream populations of 

 pygmy whitefish are known to exist in the Naknek 

 system, large numbers seasonally occupy the lower 

 100 to 400 m. of Brooks River. These fish are part 

 of the South Bay population (area 8, fig. 1) and 

 do not go above a rapids area below Brooks River 

 falls. They occupy lower Brooks River from late 

 June to early September for feeding and from 

 mid-November to mid-December for spawning. 

 Feeding pygmy whitefish in Brooks River char- 

 acteristically occupy neither the fastest moving 

 nor the slowest moving water, but seem to prefer 

 a moderate current adjacent to a faster one. 



A few pygmy whitefish have been collected or 

 observed in other streams in the system. With the 

 possible exception of an annual downstream drift 

 of spent fish in midwinter, these collections ap- 

 parently represent only sporadic downstream 

 movements of fish from Brooks, Coville, and 

 Grosvenor Lakes. LJnderwater surveys of upper 

 Brooks River from May through November and 

 of Coville River from May through August re- 

 vealed that pygmy whitefish did not occupy these 

 streams during this period. 



ASSOCIATED FISHES 



Nineteen species of fishes were collected with 

 pygmy whitefish in various parts of the system. 



The percent frequency occurrence of these species 

 (table 4) provides a basis for discussing associated 

 species. Throughout the system the cottids Coitus 

 aleuticus Gilbert and C. cognatus Richardson 

 were the most frequent associates, occurring in 55 

 percent of all sampling efforts that yielded pygmy 

 whitefish (table 4) . Juvenile sockeye salmon were 

 the second most frequent associates, occuring in 42 

 percent of the samples. Next in frequency of 

 association with pygmy whitefish were ninespine 

 sticklebacks, threespine sticklebacks, round white- 

 fish, and least cisco (table 4). The greatest num- 

 ber of sympatric associates in a specific area was 

 17 species in South Bay. 



Certain fishes in the Naknek system were not 

 caught with pygmy whitefish in all lake areas. 

 Least cisco, humpback whitefish, pond smelt, and 

 longnose sucker, were collected widely in other 

 parts of the system but not in Brooks Lake. 

 Alaska blackfish, abundant in Brooks Lake, were 

 not collected in South Bay or Iliuk Arm. Dif- 

 ferences in sampling gear and effort may account 

 for species not being caught in certain areas. 



The two most common associates of pygmy 

 whitefish in Lake Superior were cottids and nine- 

 spine sticklebacks (Eschmeyer and Bailey, 1955). 

 Round whitefish, which were never collected in 

 association with pygmy whitefish in Lake Su- 

 perior, occurred in 17 percent of the Naknek sys- 

 tem samples yielding pygmy whitefish. These 

 whitefishes were collected together in six of eight 

 major lakes, basins, or streams (table 4). This 

 apparent difference in association between pygmy 

 whitefish and its closest relative in Lake Superior 



Table 4. — Percent frequency occurrence of associated fishes in sampling efforts ' that yielded pygmy whitefish 



1 Sampling efforts of all gears were combined (or each area, then for all areas; see table 1 for total sampling effort by gear and area. 



2 Juveniles only. 



PYGMY WHITEFISH OF SOUTHWEST ALASKA 



563 



