The Spanish purse-seine fishery targeting small pelagic species in the Bay of Biscay: Landings, discards and interactions with protected species

Abstract

Ecosystem-based fishery management (EBFM) is based on a holistic approach, recognising all the interactions within an ecosystem rather than considering single species or issues in isolation. Studies of catch profiles of target and bycatch species for different fleets and metiers are necessary for successful management of target species. Such studies are also needed for the assessment of the interactions and evaluation of the impact on the ecosystems. This paper presents a study of the Spanish purse-seine fleet operating in the Bay of Biscay during the years 2016–2019. It considers the species selectivity and the effect of fishing activities on the pelagic community by assessing the interactions with the endangered, threatened and protected (ETP) species and estimating the discard sizes. For the purpose of this study, the metiers were defined by grouping similar catch profiles, using hierarchical agglomerative cluster analysis. This definition of metier goes beyond the Data Collection Framework (DCF) concepts; it includes specific target species, thus increasing the accuracy. Sampling conducted at sea during the four years of the study demonstrated that; 1) the discards were scarce both in terms of overall values and the proportion of the catch (below 1% for almost all metiers and years); 2) The studied purse-seine fishery is one of the most selective among those harvesting the pelagic domain in the Bay of Biscay; 3) The results also showed that the fleet avoided the unwanted catches, mostly by practising slipping;4) The interaction with the ETPs was almost non-existent. Only a single case of a yellow-legged gull entanglement was recorded, and the bird was released alive. Notably, more than 7500 individuals of 16 species of seabirds and marine mammals were recorded in the vicinity of the fishing grounds. Thus, we conclude that this purse-seine fishery has only a slight impact on the main species of the pelagic ecosystem, due to the purse-seine slipping practices.