Table 29. — Number ofsockeye salmon in each escapement and 

 number of smolis produced, by year of spawning, Uyashik 

 system, 1956-60 



Smolts 

 Year of Fish in 



spawning escapement Age I Ago II Age III Total 



Thousands Millions Millions Millions Millions 



1956 425 11.43 37 06 11.86 



1957 215 2.52 2.16 Trace 4.68 



1958 280 3.28 3 03 6 31 



1959 219 78 3 22 Trace 4 00 



1960 2.294 13 47 18 12 (■) 31 59 



' Age III smolts will migrate seaward in the spring of 1964. 



32p 



30 - 

 28- 

 26 - 

 24 - 

 22- 

 20 - 



18 - 



16 - 



14 - 



12 - 



10 - 



/ REPLACEMENT LINE ALLOWING - 

 FOR 84 7% OCEAN MORTALITY 



«-56 



0.25 0.50 75 1.00 I 25 1,50 I 75 2.00 2.25 2.50 

 FISH IN PARENT ESCAPEMENT ( MILLIONS) 



Figure 14. — Relation between numbers of smolts pro- 

 duced and number of sockeye salmon in parent escape- 

 ment in the Ugashik system for the escapements of 

 1956-60. The number beside each point indicates the 

 escapement year. A broken line is used to connect 

 the values for 1956 and 1960 because the escapements 

 were so different that the probable shape of the curve 

 between them is not apparent. 



Ugashik system should probably be greater than 

 one-half million. 



Karluk System 



Estimates have been made of the numbers of 

 sockeye salmon smolts produced by the Karluk 

 River system for 3 years (1961-63). About 

 1.5 million smolts were produced each year, 

 although parent escapements varied from 

 210,000 to 435,000. Within this range of es- 

 capements, the relation between numbers of 

 smolts produced and numbers of parents is not 

 definable. 



RELATION BETWEEN LENGTH OF SMOLTS AND 

 NUMBERS OF ADULTS IN PARENT ESCAPE.MENT 



Small smolts would be expected to have greater 

 ocean mortality than large smolts. Indeed, Kick- 



er's (1962) compilation and analysis of return- 

 per-smolt data from six sockeye salmon systems 

 outside Bristol Bay confirmed this general rela- 

 tion. Burgner (1962) determined that a group 

 of age I smolts that migrated from Wood River 

 in 1955 at an average length of about 72 mm. 

 suffered about twice the ocean mortality of a 

 group of age I smolts 90 mm. long that migrated 

 in the .same year. This influence of size on sur- 

 vival agrees well with the data shown in Ricker's 

 figure 1 ( 1962) . We, therefore, consider the rela- 

 tion of length of smolts to numbers of adults in 

 the parent escapement and discuss the effects of 

 size of smolts on their survival in the ocean. 



Wood System 



The relation between the mean length of age I 

 smolts and numbers of adults in the parent es- 

 capements in the Wood system is presented in 

 figure 15, where a regression line has been fitted. 

 The equation for the regression of length of age I 

 smolts on number of spawners in the parent 

 escapement is 



L, = 87.86 -4.4X 



where L, is the average fork length in milli- 

 meters of age I smolts, and X is the parent 

 escapement in millions of spawners. The corre- 

 lation is significant at the 98-percent level. Thus, 

 the mean length of age I smolts (the dominant 

 age group) is inversely related to the number of 

 parent spawners. 



On the basis of this equation, age I smolts from 

 an escapement of 2 million spawners would be 

 expected to have an average length of about 79 

 mm. and those from 500,000 spawners, about 

 86 mm. 



05 1.0 1.5 2.0 



FISH IN PARENT ESCAPEMENT (MILLIONS) 



Figure 15. — Relation between growth of progeny (as 

 indicated by mean length of age I smolts) and number 

 of adults in the parent escapement, 1949-60, Wood 

 system. The number beside each point indicates the 

 escapement year. 



SOCKEYE SALMON IN MA.JOR RIVER SYSTEMS IN SOUTHWESTERN ALASKA 



443 



