348,000 adults. This estimate is only approxi- 

 mate — the situation in the Karluk system is 

 complicated by the occurrence of successive 

 waves of spawners in most streams and incom- 

 plete information on the amount of potential 

 spawning ground, especially on lake beaches. Es- 

 capements to Karluk neared or exceeded 1 mil- 

 lion fish for many years during the early 1900's. 



SPAWNING AREA AS THE LIMITING FACTOR IN 

 PRODUCTION 



An excessive density of spawners may cause 

 increased retention of egfes, loss of eggs because 

 of dislodgment from gravel during spawning, 

 and increased mortality of eggs because of 

 crowding of eggs in the gravel. We do not know 

 the relation between these variables and density 

 of spawners. 



With the possible exception of the Karluk sys- 

 tem, the tentative data on potential spawning 

 areas indicate that the major lake systems could 

 accommodate spawning populations consider- 

 ably in excess of average present-day escape- 

 ments. Full use of potential spawning grounds 

 would, however, require a distribution of spawn- 

 ers strictly in proportion to the capacity of each 

 ground. Such a distribution has never been ob- 

 served. 



CAPACITY OF REARING AREAS 



Young sockeye salmon usually emerge from 

 the spawning gravels in the spring to begin their 

 stay in the rearing areas of the lakes. Here they 

 remain 1 or 2 years (occasionally 3, as at Kar- 

 luk) before they migrate seaward in May, June, 

 and July as smolts. The abundance and growth 

 of juvenile sockeye salmon and the age and size 

 of smolts produced in each system were deter- 

 mined and were examined in relation to several 

 physical and biological factors of the rearing 

 areas : ( 1 ) number of spawning sockeye salmon 

 per unit of rearing area ; (2) relative numbers 

 of other fish species in each system, both possible 

 competitors and predators; (3) movement of 

 presmolt sockeye salmon within and between 

 lakesof a system ; (4) basic biological productiv- 

 ity of the waters ; and (5) innate characteristics 

 of the various stocks of sockeye salmon. 



Because long-term observations were not 

 available for most individual systems, the carry- 

 ing capacity of each system was judged by means 



of comparisons among the several systems of the 

 biological and physical characteristics of the 

 rearing areas. 



RELATION BETWEEN NUMBERS OF SPAWNERS 

 AND SIZE OF REARING AREAS 



In the systems of southwestern Alaska the 

 capacity of the rearing areas to support sockeye 

 salmon is, in general, reflected in the number of 

 adults returning to each system. The most exten- 

 sive data on the comparative numbers of fish in 

 the returns are found in the escapement records ; 

 the escapement is also generally a good indicator 

 of the magnitude of the total return. Because the 

 size of the lakes and systems considered varies 

 widely, the escapements and other measures of 

 productivity are frequently expressed as inim- 

 bers i)er square kilometer of lake area. Table 15 

 gives the average number of adults in the escape- 

 ments in 1955-62, the area of the lakes, and the 

 numbers of spawners per square kilometer of 

 lake for the major systems in southwestern 

 Alaska. 



The systems fall into four general levels of 

 escapement per unit area (table 15) : (1) es- 

 capements that averaged about 8,000 spawners 

 per square kilometer (Karluk and Chignik) ; (2) 

 escapements of about 2,300 to 4,400 spawners 

 per square kilometer (Igushik and Wood) ; (3) 

 escapements between 1,100 and 1,500 spawners 

 per square kilometer (Kvichak, Alagnak, Nak- 

 nek, and Ugashik) : and (4) escapements less 

 than 800 spawners per square kilometer (Ege- 

 gik. Snake, and Nuyakuk) . 



For some systems data are available for ex- 

 amining variation in productivity between lakes 

 (in terms of numbers of adults in the escape- 

 ments to individual lakes) and between years 

 within lakes. 



Table 15. — Aiwrage sockeye nalmon escapemenlt^, area of 

 lakes, and spairners per square kilometer of lake bij siislcm in 

 southwestern Alaska, 1955-62 



System 



Fish in 

 fscappmcnt 



Lako 



Spawners per 

 square kilometer 



Thousands 



Igushik 323 



Snake 2fi 



Wood H!)6 



Nuyakuk (Tikchik) 78 



Kvichak 4,334 



Alagnak (Branch) 428 



Naknck 886 



Egegik 826 



Ugashik 615 



Chignik 492 



Karluk 334 



426 



U.S. FISH AND WILDLIFE SERVICE 



