Assessing the misidentification rate for bigeye and yellowfin juveniles in brine sampled at Port Victoria (Indian Ocean): consequences for the species composition estimates of landings

It is widely accepted that the identification of small to medium sizes of frozen bigeye (Thunnus obesus, BET) and yellowfin (Thunnus albacares, YFT) tunas is an especially difficult task, mainly at fork lengths (FL) under 50 cm. This is due to the fin damage, discoloration, skin abrasion and distortion of crushing during the storage process. For this reason, certain level of misidentification would be expected. The main aim of the current study is to analyze the potential misidentification rates of small YFT and BET during purse seiners sampling at port, in Port Victoria (Seychelles). Our results suggest that Error observed for YFT was almost negligible. However, certain level of misidentification was observed in the case of BET, with about 10% error. Unfortunately, the low number of BETs obtained in sample (3 BET vs. 97 YFT), makes it difficult to draw conclusions. We believe that this type of exercise should be repeated on a larger scale, and with more means for which greater economic investment is required.