FISHERY BULLETIN: VOL. 71, NO. 3 



JUNE JULY 



1955 



1959 



AUG. SEPT. OCT. 



JUNE JULY 



AUG. 



SEPT. 



OCT. 



Figure 5. — Karluk district fishing season, 1941-72. Open 

 seasons shown in black. 



Of course other factors such as too heavy 

 sampling on the spawning grounds, the presence 

 of the weir or other activities which might have 

 interfered with the free movement and migra- 

 tion of adult or young sockeye salmon in the 

 Karluk watershed may have added to the effect 

 of the fishery. Moveover varying numbers of 

 Karluk adults were also taken in the Uyak ex- 

 tension of the Karluk district which was left 



open in 1953 and 1954 and probably also in 

 other years after the Karluk district had been 

 closed. 



Nevertheless the fact that the size of the re- 

 turns from individual spawning years as well 

 as the total size of runs responded to the added 

 protection afforded them in 1951 through 1956 

 in July and August supports the hypothesis of 

 the greater productivity of the races which pass 

 through the fishery during these months. 



Moreover the continued decline after the 1957 

 spawning (total run size in 1962) indicates that 

 regulation by weekly closed periods in the Kar- 

 luk district is not sufficient alone to cause re- 

 covery of the runs. 



The Karluk weir with heavy fishing on those 

 races must therefore have reduced those seg- 

 ments of the Karluk run, which in former years 

 migrated into the lake and when ready to spawn 

 dropped downstream below the lake and below 

 the present location of the weir to spawn. It 

 could also have imposed an additional mortality 

 on adults headed for some of the spawning 

 grounds above the weir by delaying them and 

 by preventing the free movement of adults which 

 overshoot their spawning area and wish to move 

 downstream. This would be especially true for 

 those which were ready to spawn when they 

 reached the weir and had little margin of time 

 to avoid physical deterioration characteristic 

 of this period of sockeye salmon life history. 



Another important effect was indicated by 

 the observations of Walker (see footnote 7) 

 quoted above which indicated that the weir must 

 take an unknown toll of sockeye salmon fry by 

 blocking their movement up the Karluk River 

 into the lake and by injuring those that try to 

 fight their way through it. In 1950 M. C. Bell 

 of the College of Fisheries, University of Wash- 

 ington designed a small Denil type fishway 

 which Bevan and Walker constructed out of 

 corrugated galvanized roofing to help the sock- 

 eye salmon fry surmount the barrier presented 

 by the weir. Bevan also persuaded those respon- 

 sible for the weir to modify the shape of the weir 

 pickets to create a more favorable flow pattern 

 to induce the smoits to move downstream more 

 quickly. As far as can be determined, however, 

 no effort has been made to improve the move- 

 ment of sockeye salmon fry upstream through 



642 



