Sustainability of tunas and swordfish exploitation in the equatorial tropical Atlantic Ocean

Abstract

Fishing is important as it generates employment, income, high-quality food and livelihoods for native communities in many parts of the world. However, when poorly managed, it can cause irreversible overfishing impacts on the ecology of communities. The present study aimed to construct models to estimate the presence probability of young specimens of Thunnus albacares, Thunnus obesus and Xiphias gladius in the Western Equatorial Tropical Atlantic Ocean (WETA) using oceanographic, temporal, and spatial variables. The data used were generated by monitoring the fishing operations of vessels of the pelagic longline fleet in the extreme northeast of Brazil. The Generalized Additive Model was used to estimate the effect of different factors and covariates (oceanographic, temporal, and spatial variables) on the juvenile probability of the presence of the species T. albacares, T. obesus and X. gladius. The capture of juveniles becomes graver in the results obtained annually, for T. albacares ranged between 12.4% and 50.5%, T. obesus ranging from 27.5% to 36.4% and X. gladius from 0% to 13.8% immatures. Models established indicated that water temperature, year, longitude, chlorophyll-a and the interactions between moon phases and latitude, as well as the interactions between quarters and latitude, are statistically significant, influencing the distribution of juveniles of these resources. More efforts and attention should be directed to investigating the distribution of juvenile presence in the WETA, mainly in the southern hemisphere. We want to initiate here a broad discussion and campaign for establishing studies aiming at the constant monitoring of juvenile levels captured.