ABUNDANCE AND AGE OF KVICHAK RIVER RED SALMON SMOLTS 



Bv Orra E. Kerns, Jr., Senior Fisheries Biologist 

 University of Washington 



Two essentials to managing a fishery for red 

 .salmon, Oncorhijnchus nerka (Walbaum), are 

 knowledge of the abundance and of the ages of 

 the smolts as they leave a river system on their 

 way to the sea. When the abundance and ages 

 of the smolts are related for a number of years 

 to the number and ages of the returning adults, 

 predictions can be made of the size of subse- 

 quent adult returns. These data are particu- 

 larly important in the Kvichak River, since it is 

 the largest red salmon producing system in 

 Alaska. 



Specific objectives of red salmon smolt studies 

 in the Kvichak River system were (1) an index 

 of the abundance, and (2) the age composition 

 of the entire migration. 



Our method of assessing smolt abundance is 

 based on the catch of a single fyke net. Gear 

 and fishing effort expended are kept constant, 

 but the fishing site is changed slightly to pro- 

 vide uniform water depth and velocity. Com- 

 bined daily fyke-net catches for the season pro- 

 vide an index of total smolt migration (Burgner, 

 1958). 



An index of abundance is not as desirable as 

 an enumeration of the total migration, which 

 has been explained by Foerster (1929), Krogius 

 and Krokhin (1948), and the International Pa- 

 cific Salmon Fisheries Commission (1955), but 

 a total enumeration in the Kvichak River sys- 

 tem has not been practical. Suitable gear has 

 not been developed to cope with the width, 

 depth, and velocity of the river. Therefore, we 

 have located and operated the fyke net in 

 such a manner that we think it reasonable to 



Note. — The author is presently with the Fisheries Research Insti- 

 tute. Collesre of Fisheries. University of WashinKton, Seattle 5, 

 Washington. 



Approved for publication, April 5. 19G1. Fishery Bulletin 189. 



assume a con.stant (but unknown) ratio of the 

 fyke-net catch to the total migration. 



Samples for the determination of age com- 

 position of the smolt migrations were taken 

 from the fyke-net catches. Age composition has 

 been based on smolt length-frequency and scale 

 studies. 



The Kvichak River drainage basin covers 

 nearly 8,000 square miles. Included are two 

 major lakes, Iliamna Lake, which is 80 miles 

 long, 20 miles wide, and 1,115 square miles in 

 area ; and Lake Clark, which is 50 miles long, 4 

 miles wide, and 143 square miles in area (fig. 

 1). Iliamna Lake is about 50 feet above sea 

 level and Lake Clark is about 220 feet above sea 

 level (U.S. Army Corps of Engineers, 1957). 



From 1947 through 1954 studies of age com- 

 position and sex ratio of the Naknek-Kvichak 

 commercial catch and spawning-ground escape- 

 ments were conducted annually by staff mem- 

 bers of the Fisheries Research Institute, Uni- 

 versity of Washington. In the spring of 1955, at 

 the request of Alaska Salmon Industry, Inc., 

 systematic observations of red salmon runs in 

 the Kvichak River system were initiated by the 

 Institute under contract with the U.S. Bureau 

 of Commercial Fisheries. Expanded investiga- 

 tions since 1955 were designed to measure mor- 

 talities at various points in the red salmon life 

 history (Thompson, 1953). 



The Kvichak River program began under the 

 general direction of Dr. W. F. Thompson ; 

 project leader since 1956 has been H. D. Smith. 

 The smolt enumeration program was supervised 

 in 1955 by Dr. R. L. Burgner, in 1956 and 1957 

 by D. W. Linn, and in 1958 and 1959 by the 

 author. Records and preliminary unpublished 



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