Climatic and oceanographic variability associated with historical landings of blackspot seabream in the Strait of Gibraltar: Wavelet-based analysis

Abstract

Blackspot seabream [Pagellus bogaraveo (Brünnich, 1768)] is a demersal fish species of great commercial value for Spanish and Moroccan fleets operating in the zone of the Strait of Gibraltar. The influence of environmental and climatic effects on commercial landings of this species are not fully understood. The aim of this paper is to explore, analysis and identify potential relationships between climate and oceanographic forcing and fishery production. For this purpose, we use wavelet analysis, time domain and time-frequency domain. Monthly landings of this transboundary resource at the Spanish ports of Algeciras, Ceuta, Conil and Tarifa and the Moroccan port of Tangier between 1983 and 2015 have been characterised by two main cycles, from 1990 to 2000 and 2005 to 2015, and marked seasonality, with landings being larger between April and July and smaller in January, February and September. Time-frequency analysis found that fish landings series had high variance (high energy fluctuations) during two cycles with dominant 6- and 12- month periodicities. Further, bivariate time-frequency analysis exploring the relationship of fish landings with a wide range of climate indices and oceanographic variables suggest that the dynamics of the landings are associated with climatic and oceanographic variability. Given this, larger fish landings may be attributable to environmental conditions favouring both population reproduction and fishing success.