O'BRIEN AND MAYO CPUE OF YELLOWTAIL FLOUNDER 



In our study, factors were selected for inclusion 

 in the model based on prior knowledge of fleet 

 characteristics and seasonal and spatial distribu- 

 tion patterns of the species. Despite this, the 

 three attributes incorporated in the final model 

 accounted for 15-25% of the total variation in 

 CPUE, depending on the stock. Undoubtedly, 

 other factors such as experience of the captain, 

 net design and rigging, and variation in local fish 

 abundance contribute substantially to overall 

 variation in catch rates. 



Differences between the annual CPUE esti- 

 mates based on Lux's original fishing power coef- 

 ficients and the recalculated indices occur in 

 many cases because of shifts in the vessel compo- 

 sition of the fleet over the past 20 years. The in- 

 clusion of larger vessels in the more recent years, 

 particularly on Georges Bank and Southern New 

 England grounds, may account for the consis- 

 tently higher CPUE estimates obtained for these 

 areas since the mid-1970's. On Cape Cod grounds, 

 CPUE estimates differ substantially prior to this 

 time. Lux (1964) has stated that a relatively low 

 proportion of the landings from this area were 

 used in his CPUE computations and, conse- 

 quently, the indices were not considered to be as 

 valid a measure of relative abundance as those 

 obtained for Georges Bank and Southern New 

 England. Our analyses for Cape Cod grounds, 

 based on data for the period since 1964, are sub- 

 ject to the same concerns since a large proportion 

 of the yellowtail flounder landings continues to be 

 taken incidentally. 



Although the revised standardized CPUE esti- 

 mates presented in this paper are based on a dif- 

 ferent standardization technique, trends are gen- 

 erally similar to those obtained previously. The 

 revised procedure, however, accounts for seasonal 

 and technological influences and insures com- 

 plete representation of all vessel classes engaged 

 in the yellowtail fishery. 



ACKNOWLEDGMENTS 



We wish to sincerely thank Stephen H. Clark 

 for his advice throughout this study, and for crit- 

 ically reviewing the manuscript. Michael J. Fo- 

 garty reviewed the final draft and advised on 

 statistical procedures. We are also grateful for the 

 suggestions provided by two anonymous referees. 



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