Environmental and spatial preferences of dolphinfish (Coryphaena spp.) in the eastern Pacific Ocean off the coast of Mexico

The main objective for this study was to provide information on the relationship between dolphinfish (Coryphaena spp.) catches and the environmental conditions, which could help to explain dolphinfish movements in the eastern tropical Pacific Ocean off the coast of Mexico-a topic that is still under debate. We analyzed a 10-year (2004-2013) database of estimated incidental catch from the Inter-American Tropical Tuna Commission, reported by observers on board tuna purse-seine ships. Significant seasonal and interannual differences were found in the incidental catch. No segregation due to size was apparent. Two areas of high catch were present in the study zone: one near the Baja California Peninsula that is especially productive during summer, and a second in an oceanic area (similar to 15 degrees N, 120 degrees W), which is present all year long but becomes more important during May-June. Using satellite images, we found that the 2 species of dolphinfish preferred warm waters (24-28 degrees C) with low concentrations of chlorophyll-a (<0.02 mg/m(3)), and mainly positive values of sea-surface height, all of which suggested that dolphinfish spp. associate with oceanographic features, such as anticyclonic eddies. There was a seasonal SE-NW-NE movement of high incidental catch across survey quadrants (1 degrees x1 degrees), movement that is closely related to the latitudinal displacement of the 25 degrees C isotherm.