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II I.e. Current Evaluation of Stocks and the Fishery 



Based upon the production model analyses, it does not appear that 

 increasing the effort on yellowfin within the CYRA will result in an 

 increased yield. Depending upon the shape of the right hand side of the 

 production curve, the catch can remain constant as effort increases or it 

 can decline. 



If CPSDF indices accurately reflect trends in yellowfin abundance, 

 the population is currently at its lowest known level. It appears then 

 that caution should be exercised in increasing the catch beyond the current 

 best estimate of AMSY (159,000 mt) . 



In 1978 concern was expressed over the changing size composition 

 of the CYRA yellowfin catch. It was noted that the recruitment of 

 yellowfin is variable and that this variability, coupled with a shift of 

 fishing mortality to the younger age groups, could lead to reduced catches 

 of yellowfin in years of below-average recruitment. 



If the number of larger fish in the ETP yellowfin population is to 

 be increased, the fishery should be less dependent upon 1 year-old fish. 

 As pointed out in the 1978 lATTC Annual Report, however, while protecting 

 the young yellowfin would eventually bring substantial benefits to the 

 fishery, this reduction in catch would be difficult to accomplish. 



IV. STATUS OF CURRENT RESEARCH NEEDS AND EFFORTS 

 IV. A. Major Research Problems 



The immediate biological problem facing the ETP yellowfin fishery 

 concerns its growing dependence on 1 year-old fish. The increase in 1 

 year-old catches and concurrent decreases in yield-per-recruit results in a 

 diminished potential yield and dependence of fishing success on recruit 

 class strength. In addition, heavy fishing on a succession of poor recruit 

 classes could reduce the adult population to a level such that recruitment 

 failure may occur. Analyses of management measures designed to reverse 

 this trend, such as time/area/gear closures, could be undertaken to assess 

 not only the biological impact on the resource itself, but also the socio- 

 economic impacts on the resource constituency. 



The failure to implement a yellowfin conservation program in the 

 ETP for 1980 strongly suggests that the biological condition of the fishery 

 cannot be managed unless there is some acceptable mechanism for resolving 

 conflicts related to the distribution of resource- related benefits among 

 active and potential participants in the fishery. Evaluation of potential 

 management actions should therefore be made with regard to the diversity in 

 resource strengths, fishery interests, and national priorities of those 

 affected by such actions. 



