Analysis of the effect of atmospheric oscillations on physical condition of pre–reproductive bluefin tuna from the Strait of Gibraltar

Abstract

The aim of this study was to explore the possible effects of atmospheric oscillations: North Atlantic Oscillation (NAO) and Arctic Oscillation (AO), on the physical condition of bluefin tuna (Thunnus thynnus). We estimated a fitness ratio from 3,501 pairs of length–weight data based on bluefin tuna caught in bait–boat fisheries before the spawning season (January, February and March), for each length class and year. In order to obtain a single fitness ratio (K–mean) per year we determined the average for all length classes. We also evaluated Le Cren’s condition index (KLC). We observed significant positive correlations between the atmospheric oscillations and both physical condition indexes. In the case of K–mean, the AO explained 75% of the observed variability. Regarding KLC, the NAO explained approximately 73% of the observed variability, while the AO explained 70% of the observed variability. The increase in physical conditions of bluefin tuna in association with positive atmospheric oscillations could be mediated by the increase in the prevalence of strong trade winds. We concluded that the increase in the prevalence of strong westerly winds, mediated by a positive AO or NAO, favours the trip from the Atlantic to the Mediterranean by reducing energy costs due to migration and by increasing the supply of nutrients at the surface by the mixing of deep water and surface water in local areas such as the Strait of Gibraltar.

Effect of climatic oscillations on small pelagic fisheries and its economic profit in the Gulf of Cadiz

“…Atmospheric disturbances affect marine sedimentation by a transfer of energy from the air to the sea, and from it to the seabed (De Luque 2008 ). This energy agitates the waters favouring the mixing of deep and superficial waters, increasing the contribution of nutrients to the surface (Báez et al 2013b ), affecting primary production positively, and this in turn affects the abundance of European sardine (Vargas-Yáñez et al 2020 ). The increase in precipitation by the negative NAO also leads to an increase in runoff from the Iberian Peninsula (Trigo et al 2004 ; Báez et al 2013a ).…”

Assessing the influence of the North Atlantic Oscillation on a migratory demersal predator in the Alboran Sea

“…Suárez Sánchez et al ., 2004; Báez et al ., 2011b) and their physical condition (e.g. Golet et al ., 2007; Báez et al ., 2013b).…”