Historical changes of Blackspot seabream (Pagellus bogaraveo) landing patterns in the Strait of Gibraltar from 1983 to 2016: Environmental and legislation effects

Abstract

The Blackspot seabream (Pagellus bogaraveo) is one of the most important fishery resources in the region of the Strait of Gibraltar. The fishery of this demersal species, carried out by the Spanish and Moroccan artisanal fleets, is highly vulnerable to overexploitation whose effects can be enhanced by environmental and regulatory changes. This study evaluates from a univariate perspective the variation patterns of Blackspot seabream landings (from 1983 to 2016) in the Strait of Gibraltar and investigates the effects environmental factors (sea temperature anomaly and NAO index) and regulatory changes on the landings. For this purpose, we used a wide set of univariate seanonal and non-seasonal approaches like Holt-Winters, autoregressive integrated moving average (ARIMA) models and generalized autoregressive conditional heteroscedasticity (GARCH) models and submodels. The Holt-Winters, autoregressive and ARIMA models were able to detect a strong linear dependence between current landings and previous landings as well as seasonal effects, while the GARCH models indicated the presence of intense uncertainty or volatility around two periods (1993-1998 and 2007-2011), associated to possible effects of underlying biological, environmental-climatic and regulatory factors. Therefore, the use of a combination of univariate modelling techniques has enabled us to establish potential factors associated with the variability in the landings, which could significantly help move the management of this fishery towards an ecosystem-based approach.