Chignik system has been able to produce large 

 numbers of sockeye salmon per unit lake area. 



Although spawning in the Chignik system is 

 primarily in streams, about one-third of the 

 spawning in Chignik Lake is on the beaches. 

 Most of the stream spawning is in the longer 

 streams. No estimates have been made of poten- 

 tial spawning area, but the level of sockeye salm- 

 on production by the Chignik system does not 

 appear to be controlled by the capacity of the 

 spawning grounds. 



The runs to Black and Chignik Lakes are 

 segregated in time of passage through the fish- 

 ery. This segregation is significant because it 

 permits control of the escapement to each lake 

 by regulation of the fishery. 



The adults returning to the Chignik system 

 are predominantly 3-ocean fish. 



The average time juvenile sockeye salmon re- 

 main in fresh water is different in the two lakes ; 

 the smolts from Black Lake are mostly age I, 

 and those from Chignik Lake are mostly age IL 



Age sockeye salmon are reared in three 

 major areas in the Chignik system — Black Lake, 

 Chignik Lake, and Chignik Lagoon. Most of the 

 juvenile sockeye salmon that originate in Black 

 Lake remain there to the smolt stage, although 

 some age fish migrate into Chignik Lake. The 

 brackish water of Chignik Lagoon is the rearing 

 area for a significant part of the Chignik Lake 

 progeny. 



The growth of juvenile sockeye salmon is in- 

 versely related to the density of the parent popu- 

 lation within each of the two lakes. Accurate 

 indexing of the abundance of migrating smolts 

 has not been achieved in the Chignik system, but 

 studies of the size and age composition of the 

 smolts and of abundance and growth of juveniles 

 in the lakes are in agreement. Both studies indi- 

 cate an increase in abundance, a reduction in 

 growth rate, and an increase in average length 

 of fresh-water residence for progeny of larger 

 escapements. Also, the density of spawners is 

 generally lower, and the juveniles grow faster 

 in Black Lake than in Chignik Lake. 



The juvenile sockeye salmon produced by the 

 Chignik system are larger than those of the 

 Wood system at comparable parent population 

 densities — an indication that growing conditions 

 are more favorable in the Chignik system. 



Several species of fish other than sockeye salm- 

 on are also present in the system. Threespine 



and ninespine sticklebacks and pond smelt are 

 present and are potential competitors of sockeye 

 salmon for food; they also may act as buffer 

 species between sockeye salmon and predators. 

 The potential competitors are much more abun- 

 dant in Black than in Chignik Lake; possibly 

 they are held in check in Chignik Lake by the 

 great abundance of young sockeye salmon. 

 Young coho salmon and Dolly Varden, also 

 present, are the system's principal predators on 

 juvenile sockeye salmon. Arctic char and lake 

 trout are not present. 



The abundance of associated species and the 

 growth of juvenile sockeye salmon indicate that 

 recent escapements in the Chignik system as a 

 whole have been adequate, but apportionment of 

 the escapement to the two lakes must be con- 

 sidered. Low escapements to Black Lake and the 

 resultant underutilization of its nursery areas 

 by juvenile sockeye salmon may be one reason 

 for the large populations of potential competi- 

 tors in this lake. In contrast, the relatively high 

 escapements to Chignik Lake have resulted in 

 a shortage of food that has undoubtedly led to 

 the reduced growth and survival of juvenile 

 sockeye salmon and perhaps kept the populations 

 of potential competitors low. The optimum es- 

 capement to Black Lake, therefore, is greater 

 than the present level of escapement ; to Chignik 

 Lake it is considerably less than the larger es- 

 capements of recent years. 



Suggested target escapements for each lake 

 are based on the relative success of recent es- 

 capements and the effective rearing areas of the 

 lakes. Although the total area of Black Lake is 

 39 km.-, the effective rearing area is only about 

 30 km.- because of extensive shoals not utilized 

 by juvenile salmon. We recommend that escape- 

 ments to Black Lake should be increased from 

 the recent average of 4,600 per square kilometer 

 of effective rearing area to 6,000 to 8,000, or a 

 total of 180,000 to 240,000 fish.'* The effective 

 rearing area of Chignik Lake as determined 

 from tow net catches includes the entire surface 

 area of 22 km.- The suggested escapement to 

 Chignik Lake is 8,000 to 10,000 per square kilo- 

 meter or a total of 180,000 to 220,000 fish. This 

 escapement is a reduction from the average in 



'* Recent studies of distribution and growth of species which com- 

 pete with juvenile sockeye salmon for food and space in the Chignik 

 system suggest that the populations of competitors would be reduced 

 by larger populations of juvenile salmon. Therefore, the attainment of 

 the recommended escapements might make it possible to increase 

 escapementa considerably above 240.000. 



456 



U.S. FISH AND WILDLIFE SERVICE 



