60 



BULLETIN OF THE BUREAU OF FISHERIES 



The trends in all four districts show a constant and fairly regular rise during 

 the first 10 years or so (up to 1903 or 1904), which is indicative of the gradual develop- 

 ment of the fishery during that period. In the Nushagak district the trend remained 

 generally high (near the 5,000,000 level) for the next 15 years (1902 to 1916) then 

 fell off sharply. Since 1920 it has remained at about the 3,000,000 level. This 

 drop was even more sharply marked than shown by the trend, as may be seen by 

 reference to Figure 3. This shows that the change to a lower level came very sud- 

 denly and without warning in 1919. In this case the process of smoothing, by 

 which the trend was obtained, has obscured the very sharp drop in the general level. 

 It is of the greatest importance to those interested in conservation to note the sud- 

 denness with which the catch sank to this lower level. It seems impossible to 

 ascribe this phenomenon to any cause other than depletion — to overfishing in the 

 15 years or more that preceded the drop. This is exactly the sort of thing that 

 biologists have warned could be expected, the logical explanation being that the 

 catch was held up, in spite of real depletion, by an increased intensity in fishing, 

 until finally the break came and severe depletion became apparent all at once. It 

 is interesting to note, in accordance with the hypothesis advanced above that wide 

 fluctuations are a mark of a too intensive fishery, the decade and more that preceded 

 the year 1919 was marked by wide fluctuations in the total catch. The question 

 immediately arises, is the present intensity of fishing on the Nushagak side too 

 great for the lowered level of abundance that is now established? Unfortunately 

 the problem is complicated by a number of factors, which it is impossible to evaluate 

 with the available data. During the period of heavy catches (from 1902 to 1918) 

 there was a considerable increase in the number of gill nets but a decrease in the 

 number of traps, and to what extent one offset the effect of the other we can not 

 linow. Neither do we know how the intensity of fishing has been modified by changes 

 in the length of gill nets and the length of time each giU net was actually in 

 the water. It would appear that a reduction in gear from 8 traps and over 1,000 

 gill nets to no traps and about 500 giU nets was more of a change than that of a 

 catch of approximately 5,000,000 to one of approximately 3,000,000, but this is by 

 no means ^certain. Furthermore, the former intensity of fishing was unquestion- 

 ably too great, but just how excessive it was we have no way of telling. With the 

 greatly decreased abundance it may well be that the present intensity is still too 

 great and that further depletion will result. The extremely poor catch of 1927 

 certainly would indicate that the intensity of fishing had not been reduced suffi- 

 ciently in 1921, 1922, and 1923 to permit an adequate escapement, as the red salmon 

 of Bristol Bay are largely 4, 5, and 6 years old; and even though the reduction in 

 gear has been sufficient to permit the maintenance of the catch at the 3,000,000 

 level, should there not be a sufficient reduction in the catch to permit the runs to 

 increase to something approaching their former abundance? Unquestionably the 

 general tendency on the Niishagak has been downward, and if the depletion should 

 continue at the present rate we may anticipate that within the next two or three 

 decades the formerly magnificent runs here wiU be so reduced as to be worthless 

 commercially. 



None of the other districts of Bristol Bay show such sudden and serious depletion 

 as does the Nushagak. While the Nushagak catch reached its taaxiTnum size about 



