340 U. S. BUREAU OF FISHERIES 



the marketable population. The number of boats on which the 1934 

 catch analysis is based was reduced to about one-half of the large 

 otter trawlers, a reduction made necessary by a much curtailed staff. 

 This reduction was made reluctantly after a careful analysis had 

 demonstrated that during 1932 and 1933 the fluctuations in the aver- 

 age catch per day of the smaller group were representative of the 

 entire fleet. But during 1934 the principal activities of the large 

 trawlers were transferred to the Nova Scotian banks and the boats 

 in question remained on Georges Bank only when fishing was rela- 

 tively good. If catches were poor, the boats moved to the more 

 distant banks. Consequently, the higher 1934 catch per day may be 

 due partly to this selective fishery and not represent an equally great 

 increase in abundance. Limited facilities have not yet permitted us 

 to examine this possibility through the analysis of records of the 

 smaller boats which regularly fish on Georges Bank. 



There seems little doubt but that the size of the marketable stock 

 of haddock on Georges Bank was somewhat greater in 1934 than in 

 1933, even though the increase was not as great as indicated by the 

 catch-per-day figures. This improvement was due partly to the fairly 

 good 1931 class which reached commercial size during the winter of 

 1933-34 and sipring of 1934, and partly to the great decrease in the 

 strain imposed on the stock by the reduced commercial catch. With 

 only about half as much haddock caught out during 1934 as in the 

 several preceding years, the population level was maintained and 

 even somewhat increased with only moderate additions of young fish. 



The success of the fishery on Georges Bank during any year — that 

 is, the return for a given unit of fishing effort — is primarily de- 

 pendent on two factors: (1) The rate at which the connnercial stock 

 declines as the result of catch and natural mortality (this is largely 

 determined by the intensity of the fishery) ; and (2) the contribution 

 to the commercial stock from the young haddock spawned 3 years 

 earlier. Thus, the 1929 class boosted the catch in 1932 ; and the 1931 

 class, in 1934. 



To make accurate forecasts for the fishery 1 or 2 years in advance 

 it is necessary that the above-mentioned factors be known. With 

 present facilities for observation it is possible to determine the rate 

 of decline of a stock of fish once it has reached commercial size, pro- 

 viding it is possible to estimate the amount of fishing effort that will 

 be expended in that area. However, we now have no means of deter- 

 mining how much an incoming year class will affect the commercial 

 catch, for we have no observations by which we can evaluate the 

 abundance of such year classes until they achieve commercial size 

 and have been represented in the commercial landings for a period 

 of nearly a year. Inasmuch as there are great fluctuations in the 

 abundance of the different year classes, the annual contribution from 

 this source is highly variable and is the most important factor in 

 determining the fluctuating level of the fishery. The relative level of 

 abundance in two general areas such as Georges Bank and the Nova 

 Scotian Banks largely determines where the fishing fleet will expend 

 their major efforts; consequently, it determines the intensity of the 

 fishery in either area. Therefore, it follows that the level of abun- 

 dance of the marketable stock during the course of any year is 

 affected both directly and indirectly by the contribution of young 



