negative linear relation between the average 

 length of smolts produced and the escapement 

 level — that is, growth is retarded through intra- 

 specific competition for food when the popula- 

 tion of juvenile salmon is too great. It is known 

 that ocean survival is generally positively corre- 

 lated with size of smolts at migration, although 

 data do not exist to calculate the differences in 

 survival rates for the Kvichak system. 



Whether the progeny of large escapements 

 migrate at age I or age II in the Kvichak system 

 is probably determined by the size they attain 

 during their first year in fresh water. The per- 

 centage of young salmon that migrate as age II 

 increases as the population of young salmon in 

 the nursery areas increases, although the per- 

 centage holdover to age II can be modified by the 

 environment. Any extension of the average 

 length of the fresh-water life in the Kvichak 

 system will also extend the length of the repro- 

 ductive cycle. 



In assessing the optimum escapement for the 

 Kvichak system, we must consider production in 

 an entire cycle and not for just one outstanding 

 year such as 1956. Before 1942, the returns of 

 the peak years contained progeny of at least two 

 (and usually three) escapements. 



If we accept the thesis that the carrying ca- 

 pacity of the nursery areas limits the production 

 of sockeye salmon in the Kvichak system, a ra- 

 tional approach to regulation would be to utilize 

 the nursery areas to the fullest every year. This 

 approach would require the presence of age I 

 juveniles (fish that will migrate as age II 

 smolts) in addition to the young-of-the-year, 

 because only age I and older fish use the larger 

 downlake portion of the nursery area. Histori- 

 cally, fish that went to the ocean as age II smolts 

 made up almost 60 percent of the catches in the 

 Naknek-Kvichak district (fish from the Kvichak 

 system constituted the greater share of the catch 

 in peak years) . 



If we also assume that the historical sequence 

 of large and small escapements of the Kvichak 

 cycle is the one which will yield the greatest re- 

 turn over many years, the following conclusion 

 is unavoidable. The Kvichak system must be 

 managed so as to provide at least two, and prefer- 

 ably three, successive large escapements pre- 

 ceded and followed by smaller escapements. The 

 relative abundance of fish in the successive years 

 of large escapements may be manipulated in such 



a manner as to provide about the same potential 

 egg deposition each year. Because of the present 

 conditions of the stocks, it may take two or more 

 cycles to reestablish this pattern. Only after the 

 historical pattern has been restored will it be 

 possible to define an optimum escapement for the 

 peak years, which may well be higher than that 

 desirable during the present transition period. 

 Collection of vital statistics must be improved 

 substantially to define the optimum escapement 

 of sockeye salmon for the Kvichak system. To 

 clarify the known vagaries of cycles of abun- 

 dance and reproductive capacity, not only must 

 better methods be devised to assess the escape- 

 ment, the standing crop of young salmon in the 

 lakes, and the smolt migration but many other 

 factors must be evaluated. 



Naknek System 



The Naknek system consists of a series of in- 

 terconnected lakes totaling 790 km.= Drainage to 

 Bristol Bay is via the Naknek River into the 

 Naknek-Kvichak fishing district. Adult sockeye 

 salmon returning to the Naknek system mingle 

 in the fishing area in Bristol Bay with others 

 bound for the Kvichak and Alagnak systems. 

 Catches were reported for the Naknek-Kvichak 

 district as a whole until recent years, when por- 

 tions of the catch were assigned to the respective 

 river systems of the district on the basis of age 

 composition and escapement. Since 1957 the run 

 to the Naknek River has averaged 1.6 million 

 fish — the commercial catch averaged 760,000 

 and the escapement 840,000. 



The escapement of sockeye salmon to the Nak- 

 nek system is composed mainly of 2- and 3-ocean 

 fish, the relative strength of the groups varies 

 widely from year to year. Fresh-water and ocean 

 ages and numerical strength of the various 

 spawning units within the system fluctuate some- 

 what independently of each other. The various 

 spawning units seem to pass through the trunk 

 river at about the same time. 



Estimates of the total capacity of the potential 

 spawning areas of the system are in excess of the 

 average escapement for the past 10 years. Only 

 limited data are available on the escapement of 

 sockeye salmon per unit lake area for each lake, 

 but great variations are known to exist among 

 the lakes of the system. In 1961 Coville Lake re- 

 ceived 6,600 spawners per square kilometer of 

 lake. This density of spawners produced a catch 



SOCKEYE SALMON IN MAJOR RIVER SYSTEMS IN SOUTHWESTERN ALASKA 



463 



