62 



II. CATCH AND EFFORT STATISTICS 



Assessments must address the potential yields available from selected 

 fisheries on a year-to-year basis. Present theory holds that the health of 

 a chosen stock can only be determined through analysis of catch and effort 

 data; as long as effort increases produce yield increases, the stock is 

 considered robust and underutilized. 



As indicated in Part I of this report, sophisticated methods have been 

 developed to convert the landed weight of dressed fish into "round" weight 

 figures, as well as sophisticated estimates of fishing effort. Particularly 

 in recent years, however, technological changes in fishing fleets have com- 

 plicated effort calculations. Vessels from different nations must be 

 standardized according to chosen effort coefficients. It has been extremely 

 difficult to develop a basis for comparing, for example, the effort pro- 

 duced by an American seventy-foot side trawler with a Soviet Atlantik Class 

 stern trawler. 



Historically, ICNAF figures for both landings and effort have been re- 

 ported to the Dartmouth headquarters in Nova Scotia on a piece-meal basis. 

 Assessment had to be undertaken with a clear awareness that such figures 

 were often inaccurate or missing. While landings of species from American 

 vessels were gathered by NMFS with a high degree of accuracy, particularly for 

 groundfish species,^ ^ figures for foreign fleets were often guesses. 



Thus, while abundance surveys were relatively accurate, even with the 

 limitations outlined previously, possible yield estimates in relation to 

 potential effects on stocks were not. Theoretically, continual surveys 



