these fishes now live in brackish waters in 

 the vicinity of Katmai National Monument, and 

 assume their dispersal in southwest Alaska 

 was essentially by fresh-water pathways or 

 via bridges of low salinity during early post, 

 glacial stages. 



The presence of pygnny whitefish (Kendall, 

 1917), pond smelt (Narver, 1966), and black - 

 fish (Roos, 1959) in the Chignik River system 

 supports the concept of the Aleutian Range 

 barrier. This system is about 274 km. south- 

 west of the nnonument at a point on the Alaska 

 Peninsula where the mountains become dis- 

 continuous. It drains into the Pacific Ocean 

 southwest of Shelikof Strait, but the headwaters 

 are flat, low in elevation, and only slightly 

 separated from other streams that flow north- 

 west into Bristol Bay. Headwater streann trans - 

 fer, which in the Chignik system would amount 

 to a lowlands transfer, or flooding as discussed 

 by Walters (1955, pp. 329-330), could easily 

 account for the occurrence of these fresh- 

 water fishes in the systen-i, illustrating that 

 where the Aleutian Range breaks down the 

 fishes from Bristol Bay drainages are dis- 

 persed southward. 



That pygnny whitefish, pond smelt, and 

 blackfish occur in the Chignik system and 

 apparently in no other drainages flowing into 

 the Pacific Ocean side of the Alaska Peninsula 

 illustrates that most Shelikof Strait drainages 

 are isolated not only from fresh-water areas 

 north of the Aleutian Range but also from 

 each other. Adjacent drainages along Shelikof 

 Strait, particularly in much of the monument, 

 flow parallel to each other but are separated 

 and isolated by buttress ranges and deep fiords. 

 It seems unlikely that species incapable of 

 tolerating high salinity would be dispersed 

 along the Shelikof Strait coastline. 



Similarities in the ichthyofauna of Shelikof 

 Strait drainages and nearby Kodiak Island 

 emphasize the isolation of these areas from 

 continental sources of fresh-water fishes. 

 The only fishes reported from Karluk or Bare 

 Lakes on Kodiak Island (Greenbank and Nel- 

 son, 1959) that were not found in fresh waters 

 along Shelikof Strait of the nnonument were 

 Chinook salmon, Arctic char, and rainbow 

 trout. Each of these species could occur in 

 Shelikof Strait drainages because they com- 

 monly live in the sea during part of their 

 life cycle. 



The scarcity of species in the King Salmon 

 River system portion of the monument may be 

 related to the limited diversity of habitat in 

 the headwaters. Although we collected only 

 eight species inthis system, zoogeographically 

 it has the same potential for fresh-water 

 fishes as the Naknek system because it lies 

 north of the Aleutian Range barrier and ad- 

 jacent to the Naknek systenn. The collections 

 in the King Salnnon River system were ad- 

 mittedly small, but this systenn probably does 

 not have all of the fishes that occur in the 



Naknek system because it is a stream environ- 

 nnent without the ecological diversity of a 

 multilake -streann connplex. 



The Naknek River system has by far the 

 most diverse ecological habitats of the drain- 

 ages in Katmai National Monument. This 

 interconnecting stream-lake connplex has also 

 been open to invasion by fresh-water fishes 

 from the Bering Refugeunn (see McPhail, 1963, 

 and Flint, 1945) without significant barriers 

 since early postglacial times. It has the 

 largest number of fishes (24 species) of the 

 major drainages in the monument, and in- 

 cludes all species found in the other drainages 

 (table 2). 



We believe that open avenues of fresh- water 

 dispersal account for the principal differences 

 in fishes in the Naknek system and Shelikof 

 Strait drainages. Although no single Shelikof 

 Strait drainage approaches the ecological di- 

 versity of habitats in the Naknek system, they 

 afford a variety of stream and lake environ- 

 ments. These environments along the Shelikof 

 Strait side of Katmai National Monument sug- 

 gest that many (though probably not all) fishes 

 in the Naknek system could survive in various 

 parts of the Shelikof Strait systems if given 

 access to them. Differences between fishes in 

 the Naknek and King Salmon River systenns, 

 on the other hand, appear mostly related to 

 the lack of a diverse habitat in the King Salnnon 

 River system. This lack is particularly note- 

 worthy in that portion of the King Salmon 

 River systenn that lies within the monument. 

 Additional collections in the King Salmon 

 River downstream from the nnonument should 

 help clarify this point. 



The number of species in various lakes of 

 the Naknek system differed considerably. All 

 24 known species in the Naknek system occur 

 in Naknek Lake (table 3). Naknek Lake as the 

 downstream ternninus of the multilake system 

 is the first area to be invaded by fish through 

 existing drainage patterns. All upstreann lakes 

 that drain directly or indirectly into Naknek 

 Lake have fewer species than Naknek Lake, 

 and in each upstream lake a barrier or poten- 

 tially adverse environment now exists between 

 it and Naknek Lake. 



The heterogeneity of species in different 

 lakes of the Naknek system appears to be re- 

 lated to the development of barriers and the 

 sequential timing of the invasion of species 

 into the system. Physical barriers such as 

 falls or rapids or ecological barriers such as 

 unfavorable environments may have prevented 

 dispersal of certain species within the system. 

 Developnnent of barriers before the invasion 

 of species would prevent dispersal beyond 

 the barriers, whereas earlier invasion before 

 barriers formed could allow nnore extensive 

 dispersal. 



The Naknek system has been extensively 

 glaciated. Muller (1952) discussed at least 

 four major glacial episodes in the systenn. 



16 



