Incidental catch of dolphinfish (Coryphaena spp.) reported by the Mexican tuna purse seiners in the eastern Pacific Ocean

Abstract

In the eastern Pacific Ocean (EPO), dolphinfish (Coryphaena spp.) are caught incidentally by the tunapurse-seine fishery; therefore, the records of this fishery are a good source of information to analyzethe distribution of dolphinfish. To determine the spatiotemporal distribution of dolphinfish and catchvariability in the three types of tuna-fishing sets (on schools associated with dolphins or with floatingobjects, or on unassociated schools), statistical analyses were made of the 1998–2005 records takenby scientific observers on board tuna-fishing vessels. The incidental catch did not show a well-definedannual or seasonal distribution pattern. Two high catch areas were observed, the first located in Mexicanoffshore waters (15–25◦N), with 15% of the total catch, and the second located in offshore watersof the central EPO (0–10◦N), with almost 60% of the total catch. The incidental catch was significantlydifferent among years and seasons (H7,780 = 54.6, p < 0.05 for years, and H3,780 = 42.7, p < 0.05 for seasons),the greatest catch being recorded during 1999 and the first two quarters, respectively. Sets on floatingobjects recorded most of the incidental catch of dolphinfish, followed by unassociated sets, whiledolphin-associated sets recorded the lowest catch. Almost 80% of the total catch was fished in waterswith sea-surface temperatures between 25 ◦C and 28 ◦C. The mean size of dolphinfish was significantlydifferent (H2,777 = 12.8, p < 0.05) by set type, but the smallest specimens caughtwere associated with floatingobjects. Among sets associated with floating objects, the incidental catch of dolphinfish was greatestin sets on logs, branches, etc. (PALO sets), though those on FADs (fish-aggregating devices)were the mostnumerous in the central EPO.