then. 1 Beginning in 1961 and continuing through 

 1963, observations were extended throughout the 

 Naknek system. More than 10,000 specimens have 

 been collected by various methods since 1961. 



The present study was undertaken to investigate 

 the distribution, age and growth, food habits, re- 

 production, and general life history of pygmy 

 whitefish in the Naknek system. Emphasis was 

 placed on determining the relation of pygmy white- 

 fish biology to that of other fishes in the system, 

 particularly the sockeye salmon. 



STUDY AREA 



The Naknek River system, much of which lies 

 within Katmai National Monument, consists of 

 seven interconnecting lakes : Hammersly, Murray, 

 Coville, Grosvenor, Brooks, Idavain, and Naknek. 

 These lakes drain into the northeast side of Bristol 

 Bay through the Naknek River (fig. 1). All are 

 glacial in origin, dating from Wisconsin times 

 (Midler, 1952; and Karlstrom, 1957). Naknek 

 Lake comprises three major basins and a shallow 

 outwash plain. The basins, Iliuk Ann, North 

 Arm, and South Bay, and the outwash plain, West 

 End, will be referred to hereafter without refer- 

 ence to Naknek Lake. The maximum depths are 

 not known for Murray, Idavain, or Hammersly 

 Lakes. The other lakes vary between a maximum 

 depth of 53 m. in Coville Lake and 173 m. in Iliuk 

 Arm. 



The lakes and basins of the Naknek system in- 

 clude a broad range of environmental types. Most 

 of them are oligotrophic and usually have ice 

 cover from December through early May. Iliuk 

 Ann frequently does not freeze over completely, 

 probably because of its depth and excessive tur- 

 bidity, which is due to glacial melt water and 

 volcanic ash. In Iliuk Arm, Secchi disk visibility 

 is generally less than 0.5 m., while in the other 

 basins and lakes it ranges between 3 and 12 m. A 

 horizontal turbidity gradient occurs in South Bay, 

 increasing in intensity toward Iliuk Arm. Ther- 

 mal gradients commonly exist, although classical 

 thermoclines develop only occasionally and are un- 

 stable. The waters are slightly alkaline, and oxy- 

 gen levels remain at or near saturation at all 

 depths measured throughout the year. The basic 



limnology of lakes in the Naknek River system is 

 described in detail elsewhere. 2 



MATERIALS AND METHODS 



Most pygmy whitefish were collected in the 

 Naknek system with small otter trawls, tow nets, 

 beach seines, and small-meshed gill nets. A few 

 specimens were collected with fyke nets and float- 

 ing lake traps and by divers using hand nets. 

 These same methods were used to sample juvenile 

 sockeye salmon in various stages of their fresh- 

 water life. Heard (1962) described the small- 

 meshed gill nets, and the three other principal 

 types of gear are described below. All mesh sizes 

 are given in stretch measure. 



The otter trawls were Gulf Coast shrimp try- 

 trawls about 6 m. long, 2.6 m. wide, and 0.6 m. 

 deep. The cotton webbing varied from 50.8-mm. 

 mesh in the front section to 25.4-mm. in the cod 

 section, with a 13-mm. mesh cod liner. The foot- 

 rope was weighted with a 19-mm. mesh chain, and 

 the otter doors were 30.5 by 45.7 cm. Except for 

 use of a tow cable guide ring on the transom, our 

 use of these trawls behind an outboard skiff was 

 basically the same as described by Baldwin (1961) . 



Trawl drags varied in time, in length of drag, 

 and in depth. Generally they were between 8 and 

 15 minutes long and covered from 325 to 1,000 m. 

 The trawls were fished effectively for pygmy 

 whitefish to depths of 79 m. 



The tow nets were 3.1 m. in diameter and 6.9 

 m. long, and they were used generally at night in 

 limnetic (offshore or open water) portions of the 

 lakes. They were towed behind two outboard 

 skiffs with the. top of the net at the surface or 3.1 

 m. deep. A standard tow was 492 m. Mesh sizes 

 of nylon webbing varied from 38 mm. at the net 

 opening to 3 mm. in the cod end. Burgner (1960) 

 describes the construction and general use of this 

 net. A 1-m. tow net such as that described by . 

 Johnson (1956) was used to collect one sample of 

 pygmy whitefish in Brooks Lake. 



Three types of beach seines were used. The two 

 principal types, which were set in a semicircular 

 pattern from shore with an outboard skiff, were 

 3.1 m. deep and 32.8 or 42.6 m. long. The 32.8-m. 

 seine consisted solely of 3 mm. webbing, and the 



1 The annual field reports of the research operations at Brooks 

 Lake (1957-62) are on file at the Bureau of Commercial Fish- 

 eries Biological Laboratory. Auke Bay, Alaska. 



PYGMY WHITEFISH OF SOUTHWEST ALASKA 

 7195-358 O — 66 3 



'Hartman, Wilbur L.. and Robert L. Burgner. The limnology 

 of sockeye salmon nursery lakes in southwest Alaska. The 

 manuscript is filed in the U.S. Bureau of Commercial Fisheries 

 Biological Laboratory, Auke Bay, Alaska. 



557 



