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

In the eastern Pacific Ocean (EPO), dolphinfish (Coryphaena spp.) are caught incidentally by the tuna purse-seine fishery; therefore, the records of this fishery are a good source of information to analyze the distribution of dolphinfish. To determine the spatiotemporal distribution of dolphinfish and catch variability in the three types of tuna-fishing sets (on schools associated with dolphins or with floating objects, or on unassociated schools), statistical analyses were made of the 1998-2005 records taken by scientific observers on board tuna-fishing vessels. The incidental catch did not show a well-defined annual or seasonal distribution pattern. Two high catch areas were observed, the first located in Mexican offshore waters (15-25°N), with 15% of the total catch, and the second located in offshore waters of the central EPO (0-10°N), with almost 60% of the total catch. The incidental catch was significantly different among years and seasons (H_7,780 = 54.6, p < 0.05 for years, and H_3,780 = 42.7, p < 0.05 for seasons), the greatest catch being recorded during 1999 and the first two quarters, respectively. Sets on floating objects recorded most of the incidental catch of dolphinfish, followed by unassociated sets, while dolphin-associated sets recorded the lowest catch. Almost 80% of the total catch was fished in waters with sea-surface temperatures between 25 °C and 28 °C. The mean size of dolphinfish was significantly different (H_2,777 = 12.8, p < 0.05) by set type, but the smallest specimens caught were associated with floating objects. Among sets associated with floating objects, the incidental catch of dolphinfish was greatest in sets on logs, branches, etc. (PALO sets), though those on FADs (fish-aggregating devices) were the most numerous in the central EPO.