these species probably were present when 

 Brooks and Naknek Lakes were continuous. 



Only one species in Naknek Lake, Arctic 

 grayling, does not occur in the Coville-Gros- 

 venor Lakes connplex (table 3). Three anad- 

 romous fishes, pink, chum, and chinook 

 salmon, occur only rarely in this area. The 

 absence of grayling in these lakes is puzzling 

 because no major physical barriers exist 

 between Grosvenor and Naknek Lakes, and the 

 Grosvenor River and lower American Creek 

 appear to be excellent grayling habitat. If gray- 

 ling are a relatively late arrival and still in 

 the process of dispersal in the system, cau- 

 tious speculation suggests that their dispersal 

 may be limited by the extreme turbidity of 

 Iliuk Arm and Savonoski River, The general 

 distribution and abundance of grayling in the 

 system are limited, and no large numbers of 

 this species are available to probe routinely 

 through adverse environments. Other more 

 complex environmental factors may be limiting 

 grayling distribution in the system. 



We know of only two fishes, Arctic char and 

 slimy sculpin, that inhabit Idavain Lake, which 

 drains into Naknek Lake through the 26-km,- 

 long Bay of Islands Creek, Two series of falls, 

 about 4,8 and 16,1 km. below the lake, have 

 probably prevented access to the lake by other 

 fishes since anearly stage of glacial recession, 

 Arctic char and slimy sculpin are the only 

 species common to all of the major basin 



complexes (table 3) and were probably among 

 the earliest fishes to invade the Naknek system. 



Hammersly and Murray Lakes, the highest 

 lakes in the Naknek River system (about 

 488 m.) have only six species (table 3), These 

 lakes drain into Coville Lake through 87-km.- 

 long American Creek. This creek has no com- 

 plete barriers, and anadromous sockeye salmon 

 annually spawn at the outlet of Hamnnersly 

 Lake. A series of precipitous rapids in Ameri- 

 can Creek, however, probably forms an effec- 

 tive barrier to many species in Coville Lake 

 and lower American Creek that do not occur in 

 Hammersly and Murray Lakes, 



Hammersly and Murray Lakes and upper 

 American Creek at one time may have drained 

 north into the present Alagnak River system 

 (fig, 1), The Coville -Grosvenor tongue of the 

 main Naknek Glacier pushed north alnnost to 

 the Alagnak River (Keller and Reiser, 1959, 

 plate 29) and coalesced with ice from the basin 

 of Nonvianuk Lake (Muller, 1952, p, 62). Drain- 

 age diversions associated with the retreat of 

 glaciers in this area may have caused the 

 headwaters of what is now American Creek to 

 flow north into the Alagnak River, Certain 

 physiographic features of the area suggest 

 this possibility (see footnote 19). If this diver- 

 sion did occur some of the fishes now in 

 Hammersly and Murray Lakes could have 

 invaded the lake via the Alagnak River system 

 rather than the Naknek River system. 



SUMMARY 



1. Katmai National Monument is divided by 

 the Aleutian Mountain Range into two princi- 

 pal drainage areas: (1) streams flowing into 

 Bristol Bay of the Bering Sea (dominated by 

 the multilake Naknek River s y s t e nn) and 

 (2) streanns flowing into Shelikof Strait of the 

 North Pacific Ocean (characterized by many 

 short streams and rivers and a few small 

 lakes). 



2. Twenty-four species of fresh-water 

 fishes, many of which are or can be anad- 

 ronnous, occur in the monument. All 24 spe- 

 cies occur in the Naknek system, at least 

 eight of them occur in the King Salmon River 

 system, and at least eight of them occur col- 

 lectively in the 18 to 20 systems draining into 

 Shelikof Strait. 



3. Four nnarine fishes, all known euryha- 

 line forms, occur in fresh water in or near 

 the monument. 



4. The Aleutian Range has been a barrier 

 to the southeastward movement of fresh-water 

 fishes within the monument area. All species 

 in Shelikof Strait drainages are capable of 

 dispersal through salt water, whereas many 

 forms in Bristol Bay drainages require fresh 

 water for dispersal, 



5. Dolly Varden occur, apparently through 

 natural dispersion, in the crater lake in the 

 c alder a of Kaguyak Volcano, 



6, The last major glaciation of the Naknek 

 system ended about 10,000 years ago. Sequen- 

 tial timing of species invasion and the post- 

 glacial development of barriers have strongly 

 influenced the present distribution of fishes in 

 this system. All upstream lakes in the Naknek 

 system have fewer species than the lakes 

 below them, and barriers exist between each 

 upstream and downstream lake, 



7, Arctic char and slimy sculpin, the only 

 species common to all basin complexes of the 

 Naknek system, were apparently early in- 

 vaders. Lake trout, pygmy whitefish, rainbow 

 trout, and sockeye salmon are present in all 

 basins except Idavain Lake. 



8, Least cisco, hunnpback whitefish, and 

 longnose suckers could have been late invaders 

 of the Naknek system because these fish ap- 

 parently are restricted from Brooks Lake by 

 a falls on Brooks River. Sufficient separation 

 of Brooks and Naknek Lakes to allow the de- 

 velopment of Brooks Falls is estinnated to 

 have occurred around 4,000 years ago. 



9, Hammersly and Murray Lakes, although 

 not in the monument, are important in the 

 distribution of fishes in the Naknek system. 

 These lakes and the upper portion of Ameri- 

 can Creek may have drained north into the 

 Alagnak River system during early post- 

 glacial drainage development. 



18 



