As mentioned earlier, the Naknek River sockeye 

 salmon run is of relatively short duration when 

 compared with rivers like the Fraser and Karluk. 

 The total spawning escapement enters the Naknek 

 system during a 4- to 6-week period, and normally 

 over half the total escapement occurs in a period 

 of 3 to 5 days (table 1). Spawning activity, how- 

 ever, occurs over a period of 2% months, although 

 the period and duration of spawning are quite 

 different for the various grounds used. Time of 

 spawning apparently has little effect in producing 

 segregation. Regardless of the characteristics of 

 spawning activity, most grounds seem to receive 

 their escapement proportionately from all parts 

 of the run. 



It seems apparent that the short duration of 

 the Naknek run is not an adaptation to a single 

 optimum spawning period for the Naknek system 

 as a whole, and it is probable that the conditions 

 responsible for the compressed nature of the run 

 occur in the ocean before Naknek salmon reach 

 Bristol Bay. Regardless of the cause, it is likely 

 that the short duration of the run is responsible 

 for the significant lack of segregation. The 

 result is, of necessity, a more or less complete 

 intermingling of the spawning populations com- 

 posing the Naknek sockeye salmon run in the 

 trunk stream and, therefore, in the fishery. In 

 view of this, it seems impossible now to manage 

 in the fishery the individual spawning groups 

 composing the run. 



AGE SEGREGATION BY TIME OF OCCURRENCE 

 IN THE RUN 



The daily percentages of the four dominant age 

 groups (4 2 , 5 2 , 5 3 , and 6 3 ) in the 1962 escapement 

 were determined from samples of fish taken at 

 the tagging site. Little difference was noted 

 between the daily age composition of males and 

 females. Both sexes showed similar daily fluctu- 

 ations in abundance. The age data for males and 

 females were, therefore, combined (fig. 8). 



Although daily fluctuations in age composition 

 of the escapement did occur, there were no marked 

 changes in age composition during the run. Only 

 the 5 3 age group appeared to increase in relative 

 abundance toward the end of the run. During 

 the peak escapement period of July 5-7 (table 1), 

 the proportion of the 5 2 age group was somewhat 

 higher and the 5 3 group lower than the overall 

 seasonal average for these groups. Except for 

 daily fluctuations, there appears to be little change 



Figure 8. — Percent contribution of four dominant age 

 groups of sockeye salmon by day of tagging in Naknek 

 River escapement, 1962. 



in the age composition of the escapement with the 

 passage of time. Segregation on the basis of age 

 groups appears to have been minimal in the 1962 

 Naknek escapement. 



In figure 9 the daily age composition of the 

 escapement is replotted by fresh-water and ocean 

 age. When examined from this standpoint, only 

 minor changes in age composition appear to occur 

 during the run. The proportion of 3-fresh-water 

 fish increases, while the 2-fresh-water group 

 decreases slightly after the peak escapement 

 period of July 5-7. Also, the proportion of 3- 

 ocean fish is somewhat higher and that of 2- 

 ocean fish lower during the peak escapement period. 

 There is, however, no marked change in the pro- 

 portion of any age category during the run. 

 Segregation in time by ocean and fresh-water age 

 appears to have been limited in the 1962 

 escapement. 



To what extent the daily age composition of the 

 Naknek escapement is altered by effects of the 

 fishery is unknown. It is known, however, that 

 the Bristol Bay gill net fishery tends to be selective 

 for the larger or 3-ocean fish (i.e., the 5 2 and 6 3 

 age groups). It is possible that the fishery could 

 account for the marked day-to-day fluctuations 



SALMON SPAWNING POPULATIONS IN NAKNEK RIVER 



473 



