recent years of 14,000 adults per square kilo- 

 meter. 



Karluk System 



The Karluk River sockeye salmon run has been 

 historically among the more valuable in Alaska. 

 Commercial fishing began at Karluk in 1882. 

 Several million fish were harvested annually in 

 the early years of the fishery (1885-95), but a 

 long-term decline began after the turn of the 

 century. This declining trend continued in spite 

 of attempts to maintain escapement levels ; in re- 

 cent years, the total run seldom has exceeded 1 

 million fish. 



The timing of the run of adult sockeye salmon 

 to the Karluk system is similar to that of the 

 Chignik system in that it extends 4 to 5 months. 

 The Karluk run has late spring and fall peaks. 

 Beach spawning is insignificant in most years, 

 and most of the spawners are dispersed over the 

 lateral and terminal tributaries and the outlet, 

 Karluk River. Occasionally, however, as much as 

 25 percent of the escapement may use beach 

 areas. Certain terminal streams and beach areas 

 are used by both spring and fall spawners. The 

 lateral tributaries, however, are used almost 

 exclusively by spring spawners. 



The individual spawning areas in the Karluk 

 system are occupied continuously for about 5 

 weeks to 5 months by a succession of spawners, 

 with the result that many more spawners are 

 accommodated than could be if they all spawned 

 in 2 or 3 weeks. This occupation by successive 

 waves of spawners introduces questions as to the 

 effect of superimposition of redd sites on the 

 success of spawning. We do not know the 

 answers. 



The Karluk Lake watershed is composed of 

 sedimentary rock and is so situated as to be 

 strongly influenced by the oceanic climate. The 

 lake waters originate from snowmelt and sur- 

 face runoff. Two small lakes, Thumb and O'Mal- 

 ley, drain into separate arms of Karluk Lake. 



The concentrations of most of the chemical 

 constituents in Karluk Lake are similar to those 

 of lakes of the Alaska Peninsula, particularly the 

 high concentration of sodium and the low levels 

 of nitrate nitrogen and total alkalinity. Of all the 

 lakes studied, however, Karluk Lake is second 

 only to those of the Chignik system in produc- 

 tivity as measured by rate of carbon fixation and 

 content of chlorophyll a. The very high produc- 



tivity is paralleled by the rank of the Karluk 

 system as first in density of spawners per unit 

 lake area. 



The growth of juvenile sockeye salmon was 

 correlated positively with changes in lake pro- 

 ductivity and negatively with the abundance of 

 juveniles in 1961 and 1962. Because of varying 

 numerical strength of young from a protracted 

 period of fry emergence and migration, growth 

 data are difficult to interpret. 



The only abundant potential competitor with 

 juvenile sockeye salmon for food in Karluk Lake 

 is the threespine stickleback. Arctic char and 

 Dolly Varden are the most abundant predators. 



The estimate of numbers of smolts produced 

 in Karluk Lake each year in 1961-63 was about 

 1.5 million. Numbers of smolts and numbers of 

 adults in the parent escapements were not re- 

 lated; the parent escapements ranged from 

 210,000 to 435,000 fish. 



Data on fluctuations in abundance of sockeye 

 salmon in Karluk Lake have been analyzed in 

 some detail by Barnaby (1944) and Rounsefell 

 (1958) . Portions of these data that deal specifi- 

 cally with the return-escapement relation have 

 been reported in a bulletin of the International 

 North Pacific Fisheries Commission (1962), 

 where it is concluded that in the past, escape- 

 ments of about 750,000 fish have produced the 

 largest surplus of return over escapement. The 

 expanded research in 1961 and 1962 did not 

 yield new information that would alter this con- 

 clusion. Recent work serves, however, to empha- 

 size that restoration of the Karluk runs to 

 former high levels will require considerably 

 more than mere manipulation of numbers of 

 spawners in the escapement. Evidence suggests 

 that the average reproductive capacity of the 

 sockeye salmon in the Karluk system was re- 

 duced while the run was in decline. Current re- 

 search at Karluk is directed toward determina- 

 tion of the cause of this reduction. 



ACKNOWLEDGMENTS 



The salmon canning industry made substan- 

 tial contributions of additional operating funds 

 for FRI programs, which it had been supporting 

 partially, and provided funds for equipment, 

 camp, and laboratory facilities in the Nushagak, 

 Kvichak, and Chignik areas. This support made 

 possible a larger and more detailed program of 

 research. 



SOCKEYE SALMON IN MAJOR RIVER SYSTEMS IN SOUTHWESTERN ALASKA 



457 



