MATHISEN: NUSHAGAK SOCKEYE SALMON FISHERY 



exploitation rates. This situation is in contrast 

 to the situation in the Fraser River, where the 

 removal of the Hell's Gate blockade and increased 

 escapements initiated almost an immediate in- 

 crease in the returns in some river systems. 



Therefore, it remains for us to explore if any 

 changes have occurred in the Nushagak runs that 

 can explain the described reduction in reproduc- 

 tive potential. 



DISCUSSION 



No visible changes have taken place in the 

 Nushagak environment since fishing commenced 

 there before the turn of the century. Even today 

 there are no dams or any other obstruction to 

 the migrating salmon. The resident population 

 still remains so low that pollution problems or 

 any form of industrial waste are nonexistent. 

 Neither has the subsistence fishery increased in 

 volume and an estimated 30,000 or more of all 

 species are harvested today. Other freshwater 

 fishes were not or were lightly harvested until 

 recent years, when a recreational fishery for 

 trout and char has developed. 



A sockeye salmon run to a watershed such as 

 the Nushagak District is made up of a great 

 number of races that difl'er in morphological 

 features, age structure, time and place of spawn- 

 ing, and reproductive rate. The most direct ef- 

 fect of overfishing would be the disappearance 

 of certain races, or at least a reduction in their 

 numerical size to the point where they cease 

 to be important contributors to the commercial 

 catches. If this were true, it could manifest it- 

 self on the spawning grounds after the various 

 races have segregated. The number of spawners 

 per unit of nursery area reflects the stock 

 strength on a spatial basis. 



There are some river systems within the 

 Nushagak District with low spawning density 

 relative to that of others. For 1955-1962 the 

 average number of spawners per square kilom- 

 eter of lake rearing area in the Tikchik Lakes 

 was 280 and in Lake Nunavaugaluk 290. In 

 contrast, the spawning density in the Wood River 

 lakes was 2,340 fish per square kilometer of lake 

 rearing area and 4,360 fish in the Igushik system 

 (Burgner et al., 1969). There is no evidence 



available to indicate that this was different in 

 the early history of the Nushagak fishery. While 

 there are relatively more 3-ocean fish in the 

 Tikchik runs than elsewhere in the Nushagak 

 system and hence a higher fishing mortality, the 

 scarcity of spawning beaches and streams pre- 

 cludes both here and in the Nunavagaluk system 

 the possibility of a large population prior to com- 

 mercial exploitation. 



The possibility still remains that the individual 

 races may pass through the fishery at diff'erent 

 times and thereby be exposed to diff"erent fishing 

 rates. If this were so, one might expect to see 

 some shift in time when peak abundance oc- 

 curred. This was studied by plotting the dates 

 when 10, 50, and 90 ""^ of the commercial catches 

 were made (Figure 5). From 1895 to 1947, the 

 two first points were reached at the same time 

 aside from simultaneous year-to-year variations. 

 There are some indications in Figure 5 that 

 salmon were present longer in Nushagak Bay 

 in years prior to 1920, but when one considers 

 the exponential rate of departure to the spawning 

 streams from the fishing grounds, the larger total 

 runs dui'ing these years would account for such 

 a prolongation of the fishing season. Added to 

 this consideration is the fact that the canneries 



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Year 



Figure 5. — Data on which 10, 50, and 90% of the Nu- 

 shagak catch was made, 1895-1947. (Subsequent years 

 omitted since a progressively stricter curtailment of fish- 

 ing time prevented direct comparison with forrner years.) 



759 



