Table 3. — Occurrence of fishes in the major lakes and basin complexes in the Naknek River system 



of southwest Alaska 



[surface elevations in meters above sea level for each basin are in parentheses] 



the earliest of which was probably pre -Wis- 

 consin, The present lakes and basins in the 

 Naknek system were formed by glacial activity 

 during Wisconsin times, which MuUer (1952) 

 called the Brooks Lake glaciation. This glacial 

 episode consisted of one main glacier--Naknek 

 Glacier--which occupied all the present basins 

 of Naknek Lake and had prominent tongues 

 projecting through the present Coville -Gros - 

 venor and Brooks Lake basins. The last major 

 glaciation in the Naknek system probably 

 ended about 8,000 B.C.; a minor readvance 

 into Iliuk Arnn of Naknek Lake ended about 

 4,000 B.C. (Karlstrom, 1957). 



Invasion of fish in the Naknek system prob- 

 ably began with the initial glacial recession 

 and the first development of postglacial drain- 

 age systems. At various times the entire sys- 

 tem, including Naknek River, was covered 

 with ice, so the fresh-water fishes invading 

 the system would have conne directly or in- 

 directly from the Bering Refugeum. Anad- 

 romous and salinity-tolerant forms could 

 have come from the Bering Sea or Pacific 

 Ocean. 



Although Brooks Lake drains directly into 

 Naknek Lake, four species in Naknek Lake-- 

 humpback whitefish, least cisco, longnose 

 sucker, and burbot --apparently do not occur 

 in Brooks Lake. These fishes probably were 

 barred from Brooks Lake by a 1.5- to 2-m. 

 falls that developed on Brooks River. These 

 species may have been late invaders of the 

 Naknek system. During certain phases of the 

 postglacial development of the system. Brooks 

 and Naknek Lakes were one lake, but con- 

 tinued downcutting of end nnoraines on Naknek 

 Lake subsequently lowered the lake level, sepa- 

 rated Brooks and Naknek Lakes, and developed 

 Brooks River. The time of sufficient separa- 

 tion of the two lakes to allow the formation of 

 Brooks Falls has been suggested at 2,000 

 B.C. Many species now in Brooks Lake, 



such as pygmy whitefish, pond snnelt, black- 

 fish, sticklebacks, and sculpins, probably could 

 not surmount Brooks Falls as it now exists; 



^°D. E. Dumond, Department of Anthropology, Univer- 

 sity of Oregon, Eugene, Oregon. Personal communication, 

 1965. 



17 



