Resumen del producto

Blue marlin are large, tropical pelagic fish that are capable of making long distance migrations. It is considered the most tropical of all billfish, and its abundance and distribution is affected by variations in Sea Surface Temperature, because they inhabit mainly in the mixed layer. In this paper, we analyzed a historic (1959 – 2015) database of blue marlin catch, reported by the industrial longline fleet that operated in the Eastern Pacific Ocean. We modelled the time series of blue marlin Catch-per-unit-effort (CPUE) as a function of temporal (month, year) and environmental (ONI, PDO) variables using Generalized Additive Mixed Models (GAMMs). Results suggested that most of the fishing effort was distributed near the equator. The majority of blue marlin CPUE was also distributed near the equator during boreal winter, spring and autumn, with a shift towards the north during the boreal summer. Two events of high CPUE were found, one in the early 60s and another one in the early 90s. A notorious decline of CPUE started at the late 90s and remained until the end of the time series. The final GAMM explained 61% of the total variance of the CPUE time series. Only a small percentage of total deviance was explained by the environmental variables, so we propose that changes in targeting practices of the longline fleet are the main cause of the large variability of the time series. We also propose that overfishing is the main cause of the decrease of blue marlin CPUE. Our final GAMM can be used to predict blue marlin CPUE as a function of month, year, PDO and Oni. Predictions for 2015 – 2016, where no fishery data was available, suggested that blue marlin CPUE is likely to remain low for the next years.

Palabras clave: Blue marlin; Environmental variability; Generalized Additive Mixed Models; Fisheries Oceanography.

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