tinuation of studies of smolts, catch, and escape- 

 ment, and analysis of data previously collected. 



Commercial fishing began in the Ugashik dis- 

 trict in 1889 when several small salteries were 

 established. Unlike the other districts of Bristol 

 Bay, the Ugashik fishery developed rapidly and 

 experienced a decline in the catch several years 

 before peak production was achieved in the Ege- 

 gik and Naknek-Kvichak districts. 



The Ugashik also differs from the other Bris- 

 tol Bay systems in that it has had several periods 

 of peak production of sockeye salmon. The first 

 was early — from 1899 to 1903 — when the an- 

 nual catch averaged 1,114,400 fi.sh. A period of 

 gradual decline followed, and in 1911 the catch 

 reached its lowest point — about 113,000 fish. Be- 

 tween 1904 and 1916 the annual catch averaged 

 368,400; from 1917 to 1923, it rose to about 

 882,000. The 1924-42 period was characterized 

 by generally low catches. A regulatory closure 

 of the fishery occurred in 1935. Fishing effort in 

 the district was greatly curtailed in 1940 and 

 1941 because of the war. Annual catches in 1942- 

 48 averaged nearly 1 million fish. Since 1949, 

 with a few exceptions (1953, 1954, and 1960) 

 the annual catch has averaged less than 500,000. 



Escapement counts were obtained for the 

 Ugashik system in 1925-32 and 1949-63. Escape- 

 ments during the earlier period ranged from 

 149,000 in 1929 to 1,380.000 in 1931 and aver- 

 aged about 533,000 fish ; escapements in the later 

 period varied from 77,000 to 2,294,000 and aver- 

 aged about 574,000. 



The Ugashik system, in common with other 

 Peninsula Systems, is currently supporting es- 

 capement densities that average about 1,300 

 sockeye salmon per square kilometer of lake. 

 This density is about one-sixth of that observed 

 in the Chignik and Karluk systems and about 

 one-half of that of the Wood system. Most of 

 the sockeye salmon of the Ugashik system spawn 

 in tributary streams that drain the foothills of 

 the Aleutian Range. 



Limnological observations, though not as ex- 

 tensive as those made in other systems, indicate 

 that the Ugashik lakes rank low in total dis- 

 solved solids, phytoplankton abundance, and 

 primary productivity. 



Estimates of the numbers, ages, and sizes of 

 smolts have been obtained annually since 1058. 

 We cannot see a relation between the size of 

 smolts and parent escapement nor between the 



proportions of each year's progeny that migrate 

 seaward at age II and escapement. It is possible 

 that relationships are masked by year-to-year 

 variations in environmental conditions. 



Although the size of smolts in the Ugashik 

 system apparently is not related to escapement, 

 the number of smolts produced is. The greatest 

 recorded escapement (2.3 million fish in 1960) 

 produced the greatest recorded smolt migration 

 (31.40 million). Low escapements of 215,000 in 

 1957 and 219,000 in 1959 resulted in 4.33 million 

 and 4.08 million smolts, respectively. The es- 

 capement of 425,000 fish in 1956 produced about 

 12 million smolts. Because no escapements have 

 been of intermediate size, it is not possible to de- 

 fine precisely the smolt-escapement relation over 

 the entire range. All that can be determined now 

 is that smolt production increases markedly with 

 increasing escapement up to about one-half mil- 

 lion. The results from the large 1960 escapement 

 show only that increases in numbers of smolts 

 can be realized from escapements greater than 

 one-half million. 



The best that can be inferred from the sug- 

 gested form of the smolt-escapement relation is 

 that the target escapement should be at least 

 500,000. 



Chignik System 



The history of the fishery on sockeye salmon 

 runs of the Chignik system is similar to that of 

 the Nushagak district in that the catch remained 

 high until the 1920's, then dropped to a lower 

 level from which it has never recovered. 



The two lakes in the Chignik system — Black 

 and Chignik — have dissimilar physical charac- 

 teristics. Black Lake (mean depth, 3 m.) is the 

 shallowest of the lakes we studied. Chignik Lake 

 has less area than Black Lake but has six times 

 the volume. The total area of the two lakes is 

 61 km.^ 



Chignik Lake supports an unusually large es- 

 capement of sockeye salmon per unit lake area. 

 The average escapement of 14,000 per square 

 kilometer of lake for 1955-62 is the highest for 

 the lakes studied. Black Lake had an average 

 escapement of about 4,600 per square kilometer 

 over the same period. 



Chignik and Black Lakes had the highest 

 primary productivity and chlorophyll a concen- 

 trations of the lakes studied. The richness of 

 the lakes is undoubtedly the main reason that the 



SOCKEYE SALMON IN MAJOR RIVER SYSTEMS IN SOUTHWESTERN ALASKA 



455 



