Within the Kvichak system there are many 

 spawning groups of sockeye salmon. Adult fish of 

 the different spawning groups are not segregated 

 by time of passage into Iliamna Lake. The re- 

 turnees generally have spent 1 or 2 years in fresh 

 water and 2 or 3 years in the ocean ; four prin- 

 cipal age groups result. The age composition of 

 the adults differs among the spawning grounds. 

 In 1962, streams, with one major exception, con- 

 tained significantly higher proportions of 2- 

 ocean spawners than did beaches. It is not known 

 if the relative proportion of 2- and 3-ocean fish 

 is genetic. Fresh-water age, however, is prob- 

 ably determined more by the environment than 

 by genetic factors. 



Sockeye salmon generally spawn within the 

 Kvichak system from early August to mid- 

 October — a time span that probably reflects the 

 adaptation of the various spawning populations 

 to the different types of environments. Fry also 

 emerge over an extended period. An indirect 

 measure of the relative time of emergence is the 

 size of juveniles during their first summer. The 

 greatest range in time of emergence in the Kvi- 

 chak system is in Lake Clark, where age sock- 

 eye salmon in August range from 32 to more 

 than 60 mm. 



Although estimates of the amount of potential 

 spawning area in the Kvichak system are incom- 

 plete, the available data indicate that the carry- 

 ing capacity for this system is about 20.5 million 

 spawners. Even the largest recorded escapement 

 — 14.6 million spawners in 1960 — did not ap- 

 proach this figure (footnote 10). Between 1955 

 and 1963, the escapements in terms of number 

 of adults per squai'e kilometer of lake ranged 

 from 84 in 1955 to 11,890 in 1960. The escape- 

 ments to Lake Clark have not been well docu- 

 mented but are thought to be somewhat less than 

 10 percent of the total for the Kvichak system. 



The greatest abundance of age sockeye 

 salmon in Iliamna Lake is in the vicinity of the 

 heaviest spawning — in the east half of the lake. 

 As the age and size of young fish increase they 

 spread over the whole lake, and the largest fish 

 are found in the western part. 



Our knowledge of predators and potential food 

 competitors in the Kvichak system is scanty. We 

 do know that the distribution of threespine 

 sticklebacks, the main potential competitor with 

 juvenile sockeye salmon for food, is similar to 

 that of age salmon. Large populations of lake 



trout, Dolly Varden, Arctic char, and rainbow 

 trout are also present. We suspect that competi- 

 tion for food and predation are important fac- 

 tors in the production of juvenile sockeye salmon 

 in Iliamna Lake. The effect of predation would be 

 much heavier in years of low abundance of juve- 

 niles and, thus, would tend to maintain the cyclic 

 pattern of the Kvichak run. 



Lakes of the Kvichak system are generally 

 similar limnologically to lakes of the other 

 Mainland Systems. The values for pH and con- 

 centrations of total dissolved solids and total 

 alkalinity are intermediate among all systems. 

 The rates of carbon fixation in Iliamna Lake 

 were near the lower end of the range for main- 

 land lakes, but in Lake Clark the rates were 

 much reduced, probably because of the opacity 

 of the water. The Kvichak system ranks in the 

 same general position in numbers of spawners 

 per lake area and in rate of carbon fixation per 

 square meter, i.e., in the low range of the inter- 

 mediate values. 



Limnological studies in the Kvichak system 

 span too short a time to permit comparisons 

 between years. Future studies will determine 

 whether dissolved minerals differ between off 

 and peak years of the cycle ; such differences 

 could cause cyclic manifestations or, conversely, 

 be caused by them. 



Observations span too few yeai's to indicate 

 the relation between production of fry and par- 

 ent escapement. 



The relation between production of smelts and 

 parent escapement varies, depending on whether 

 we consider peak years or low years. The prog- 

 eny of the 2 peak years studied, 1956 and 1960, 

 had production indices of sniolts of 181 and 150, 

 respectively, although the escapement was al- 

 mo.st 50 percent greater in 1960 than 1956. In 

 both years, 2-ocean fish were dominant in the 

 escapement — 98 percent in 1956 and 99 percent 

 in 1960. The maximum number of smolts is 

 apparently produced at escapements below the 

 1960 level of 14.6 million (based on data col- 

 lected through 1963). A reproduction curve 

 based on the data of the 2 peak years 1956 and 

 1960 indicates that a range of escapements of 

 5 to 12 million will not drastically change the 

 number of smolts produced. 



A target escapement for peak years must be 

 based on several factors in addition to the num- 

 ber of smolts produced. The data clearly show a 



U.S. FISH AND WILDLIFE SERVICE 



