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]

Fishery catch data on yellowfin tuna (Thunnus albacares) were examined to study the effects of El Niño events between 1990 and 1999 for an area in the northeastern tropical Pacific (18-24°N, 112-104°W). The data were extracted from a database of logbook records from the Mexican tuna purse-seine fleet. Latitudinal distribution of the catches increased from south to north for the 10-year period. Highest catches and effort were concentrated between 22°N and 23°N. This area accumulated 48% of the total catch over the 10 year period. It was strongly correlated with El Niño-Southern Oscillation (ENSO) events. At least two periods of exceptionally high catches occurred following El Niño events in 1991 and 1997. Peaks of catches were triggered by the arrival of positive anomalies of sea surface temperature (SST) to the area. A delay of two to four months was observed between the occurrence of maximum SST anomalies at the equator and peaks of catch. Prior to these two events, negative SST anomalies were the dominant feature in the study area and catch was extremely low. This trend of negative SST anomalies with low catches followed by positive SST anomalies and high catches may be attributed to northward yellowfin tuna migration patterns driven by El Niño forcing, a result that contrasts with the known behavior of decreasing relative abundance of these tuna after El Niño events in the eastern Pacific. However, this decrease in relative abundance may be the result of a local or subregional effect. [ABSTRACT FROM AUTHOR]

Presents a study that examined the occurrence of yellowfin tuna at Espiritu Santo Seamount in the Gulf of California. Methods; Results; Discussion.