Punsly et al.: Potential non-dolphin-associated tuna catches in the eastern Pacific Ocean 133 



some purse-seine fishermen 

 may decide to move to other 

 oceans or retire, which would 

 reduce total fishing effort and 

 hence the catch. 

 6 Since skipjack tuna (Katsuwo- 

 nus pelamis), the only other 

 primary target species in the 

 fishery, seldom associate with 

 dolphins, their catch may in- 

 crease if effort remains at 

 1980-88 levels and is directed 

 only toward tuna schools not 

 associated with dolphins. 



Because no relation between 

 spawners and recruitment of yel- 

 lowfin has been established 

 (Bayliff, 1992, p. 62), the possible 

 effects of reduced recruitment 

 were not addressed in this study. 

 Also, since the authors cannot 

 predict how many seiners would 

 leave the EPO, or how much the 

 fishery would contract, these two 

 factors were not considered. In 

 other words, this study only at- 

 tempted to estimate how much 

 tuna catches might change due to 

 changes in yellowfin catchability, 

 yield per recruit, total biomass, 

 and age structure. 



To measure the possible effects 

 of changing the mode of fishing 

 from being directed toward prima- 

 rily dolphin-associated schools of 

 tuna ("dolphin sets," Allen, 1981) 

 to one directed at exclusively free- 

 swimming schools ("school sets") 

 and floating-object-associated 

 schools ("log sets," Greenblatt, 

 1979), we first estimated what the 

 tuna catches would have been in 

 previous years if dolphin sets had 

 been replaced by non-dolphin 

 sets. Then the estimates were 

 compared with actual catches. 

 Our method used non-dolphin-set 

 catchability coefficients and total 

 effort to estimate what the 

 catches would have been during 

 1980-88 if there had been a mora- 

 torium on dolphin sets beginning 

 in 1980. Other works in which 

 catches were estimated for alter- 



Figure 1 



(A) Geographic distribution of average yellowfin tuna (Thunnus 

 albacares) catch by purse seiners, during 1980-88, from schools associ- 

 ated with dolphins (Delphinidae). Catches are expressed in metric tons 

 by 2.5-degree quadrangles. (B) Geographic distribution of average yel- 

 lowfin catch by purse seiners, during 1980-88, from schools not associ- 

 ated with dolphins. Catches are expressed in metric tons by 2.5-degree 

 quadrangles. 



