FISHERIES OF ALASKA, 1908. 



47 



and important character. One may see in the figures cited some 

 intimation of the breeding quota necessary to maintain a supply of 

 salmon in the Nushagak region. It is plain that in the years of 

 lighter runs a smaller number escaped than during the season of 1908, 

 and probably a very much smaller number, since a heavy run favors 

 the escape of salmon. Of a smaller run a larger fraction is caught 

 by the fishermen. There has probably been but one larger run since 

 the salmon industry on Nushagak Bay became extensive than that of 

 1908, if one takes the catch as the index of abundance, and no better 

 criterion is at hand. This was in 1905, when almost 7,000,000 red 

 salmon were taken. The progeny of the 1905 run, however, can 

 hardly be expected to have contributed to the run of 1908, which 

 according to the present evidence of the age of red salmon at maturity 

 is based on the runs of 1902, 1903, and 1904. The following table 

 gives the catch for Nushagak Bay and its tributaries since 1900: 



Even though the larger catches are taken to signify a correspond- 

 ing large escape to the spawning grounds, this run of 1908 and the 

 present potential abimdance of red salmon have probably resulted 

 from a smaller breeding quota than that escaping in 1908, certainly 

 fewer than 7,200,000, perhaps fewer than 3,700,000, and possibly 

 very many fewer than the latter number. 



It is futile, of course, to expect to deduce from the available figures 

 the rate of increment numerically. Any calculation of this rate at 

 present involves some important assumptions. It is nevertheless of 

 interest, if not of importance, to see what follows these assumptions. 

 If the maximum estimate of escaping salmon is correct and this num- 

 ber is enough to re-create a run as large as that of 1908, then 6,400,000 

 is the increase, or mcrement, and the rate of increase is 88.8 per 

 cent. For the 7,200,000 going to the spawning grounds die imme- 

 diately after spawning, and they must therefore replace themselves, 

 and 6,400,000 in addition for the fishermen to catch. In this view 

 every salmon leaves finally in its place very nearly two others. In 

 case the minimum estimate is true and the other assumption remains 

 the same, then the relative increment or rate of increase is much 

 higher. 



