Search

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 (~15°N, 120°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°C) with low concentrations of chlorophyll-a (<0.02 mg/m3), 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°×1°), movement that is closely related to the latitudinal displacement of the 25°C isotherm. [ABSTRACT FROM AUTHOR]

Dolphinfish are little known migratory fish targeted by sport, artisanal and commercial fleets. In this study, we analyzed a 10 year database of incidental catches of the tuna purse seine fleet in the Pacific Ocean off Mexico with the aim to understand the environmental determinants of the spatial distribution and seasonal migration patterns of dolphinfish. We modeled the probability of occurrence of dolphinfish as a function of spatial (geographical coordinates), temporal (month/year) and environmental variables (sea surface temperature [ SST], chlorophyll [ CHL] and sea surface height [ SSH], inferred from satellites) using logistic Generalized Additive Models. Dolphinfish preferred waters with SST values from 23 to 28°C, low (<0.2 mg/m3) CHL values, and primarily positive SSH values. Two dolphinfish hot spots were found in the study area: one in an oceanic zone (10°-15°N, 120°-125°W), which was more defined during spring, and one on the Pacific side of the Baja California Peninsula, which became important during summer. Models suggested that dolphinfish migrated through the study area following a 'corridor' that ran from the Gulf of Tehuantepec along the Equatorial Upwelling zone to the oceanic hot spot zone, which in turn connected with the hot spot off the BCP. This 'migratory corridor' went around the Eastern Pacific Warm Pool, which suggested that dolphinfish avoided this high temperature-low production zone. Dolphinfish occupied zones close to certain oceanic features, such as eddies and thermal fronts. Results suggested that the primary cause of the biological hot spots was wind-driven upwelling, because the hot spots became more important 3-4 months after the peak in upwelling activity. [ABSTRACT FROM AUTHOR]