Effects of environmental factors on the historical time serie of blackspot seabream commercial landings (1983 to 2015) in the strait of Gibraltar: A shared marine resource between the Spanish and Moroccan fleets

Abstract

In the Strait of Gibraltar, the Blackspot Seabream (Pagellus bogaraveo, Brünnich 1768) is an economic resource of great commercial importance for the Spanish and Moroccan artisanal and Moroccan longline fleets. Given the great interest of the species for the fleets, it is of vital importance to know the dynamics of landings and how this can be influenced by environmental variability. From this arises the hypothesis of the present study: environmental mechanisms cause forcings in the dynamics of landings. To this end, we analysed the average annual dynamics of the time series of commercial landings of the Blackspot Seabream from 1983 to 2015 from a multivariate perspective. We applied trend, principal component (PCA) and time series clustering analyses to determine patterns and relationships between the fishery series and different oceanographic variables and climatic indices. In addition, we determined the influence of this set of variables on landings from a linear approach based on multiple linear regressions (MLRs) and generalized linear models (GLMs) and non-linear determined by generalized additive models (GAMs). The results obtained indicated the presence of common temporal patterns and the existence of significant influence between landings and ocean temperature with the current velocity modulus in specific layers and heat flux, causing lower fishing yields as we get colder waters with less intense currents. Such studies are of vital importance for the application of an ecosystem approach to the management of this resource by understanding the effect and influence of the environment on the dynamics of landings from the fishery.