Movements of blue shark (<i>Prionace glauca</i>) inferred from oceanographic conditions in the northeastern Pacific using conventional tagging

Godínez-Padilla CJ, Castillo-Géniz JL (2024) Movements of blue shark (Prionace glauca) inferred from oceanographic conditions in the northeastern Pacific using conventional tagging. Marine Environmental Research pre-proof:106555.

Given that blue shark (Prionace glauca) is the most caught species in Northeast Pacific by the Mexican fleet in target and bycatch fisheries, it is essential to understand its movement behavior under mesoscale oceanographic conditions to maintain a sustainable fishery. Through the initiative of the conventional shark tagging program in the artisanal fleet for research purposes in the region, this program is being expanded to cover a larger area in the Northeast Pacific Ocean through the support of the industrial fleet. Therefore, the objective of the present study is to verify the differences in size and sex of conventionally tagged blue sharks with respect to the type of hooks where they were caught. The horizontal distribution and effect of environmental-oceanographic variables on the yield of conventional tagging using the generalized additive model (GAM) were also examined. In the 2010-2018 period, 870 blue sharks were tagged by the artisanal and industrial fleets, of which 8.4% were recovered, showing that the size of the sharks is conditioned to the fishing area of each fleet, but not to the type of hook used. Their movements reflected a horizontal distribution with no fixed course but preferring temperate anomaly waters, mainly near cyclonic eddies. Assessing that the best tagging yield was proportional to the abundance, the GAM confirmed that the explanatory variables (Lat-Long, Year, Curl, Lunar Index, SSTa and Douglas sea scale) have explained 41.9% of the total deviance, whereof spatial interaction with both fleets was the main predictor followed by Year which was influenced by climatic events.