AN ATTEMPT TO MODIFY CREATING PROCEDURE OF CATCH-AT-SIZE OF YELLOWFIN TUNA CAUGHT BY THE JAPANESE LONGLINE TUNA FISHERY IN THE ATLANTIC OCEAN

SUMMARY The catch-at-size of yellowfin tuna of the Japanese longline in the Atlantic Ocean has been updated with a modification in the compiling procedure. In the last yellowfin assessment (Brazil, 2008), it was noted that the annual average weight of yellowfin tuna based on catch-at-size was different from that based on total catch number and total catch weight after 1995. We made two modifications in creating the catch-at-size method. Firstly, in order to reduce the room for substitution, the two trigger criteria for substitution were changed. The criteria were changed that the specimen number is 100, the coverage is 3%. Secondly, we did not use substitution among quarters. The estimated catch-at-size using these new criteria showed that the discrepancies between two average weights were reduced. Although the effect of modifications applied in this study is clear, the annual average weights from catch-at-size are consistently larger than the average weight from total weight/total number as of now. RESUME