BRISTOL BAY AND ALASKA PENINSULA SALMON STATISTICS 



77 



disadvantages of using the total catch as a measure of abundance and have suggested 

 that some measure of the yield per unit of gear or per unit of fishing effort would bo 

 more satisfactory. Such measures of abundance have been used with marked 

 success in various recent fishery investigations, notably those conducted by W. F. 

 Thompson and his associates for the California Fish and Game Commission and the 

 International Fisheries Commission. 



Table 7. — Salmon caught and finhing appliances used in Nelson Lagoon, 1906 to t927 



Note. 

 no record. 



-No catch reported in 1910. Cobb (loc. cit.) states that a saltery was operated also in 1902 and 1903 but of this we have 



As fishing in Nelson Lagoon has been conducted so largely with traps, it has been 

 possible to analyze the data, and while the results are not entirely satisfactory they 

 have proved suggestive enough to warrant inclusion m this report. 



It is apparent from Figure 12 that the rise in the catch, which culminated in 

 1915 and 1916, was accompanied by an increase in gear from one to six traps, and 

 similarly the later reduction in the catch accompanied a decrease in gear. Further- 

 more, the intensity of fishing has been affected by the increase in the weeldy closed 

 period, which has been in effect from 1924 to 1927, inclusive. This has reduced the 

 weekly open period from 132 to 84 hours. In other words, the present time available 

 for fishing is only seven-elevenths (63.6 per cent) of the time available previous to 

 1924. It is pertinent to inquire how much of the reduction in the total catch is due 

 to the decreased intensity of fishing and how much to depletion. 



In order to answer this question, it is essential to have some measure of the 

 fishing effort maintained from year to year, and this is by no means simple, as there 

 are various complicating factors. In the first place, we have to consider the fact 

 that the multiplication of gear, beyond a certain point at least, will, even with a 

 constant supply of fish, tend to reduce the catch per unit of gear solely as a result of 

 what may be called competition between the units of gear. Thus, in the case of 

 Nelson Lagoon an increase in the number of traps in all probability would tend to 



