Elasmobranch species richness, fisheries, abundance and size composition in the Azores archipelago (NE Atlantic)

ABSTRACT

Elasmobranchs are a vulnerable resource, more susceptible to overfishing than most teleosts, and their assessment is complicated due to a general lack of information about their fisheries, biology and ecology. This study aimed to analyse all fishery and survey data available for elasmobranchs caught over the past c. 25 years around the Azores (NE Atlantic) to provide a baseline information, which can be used to inform stock assessment and management strategies. Elasmobranch species covered pelagic, benthopelagic and demersal habitats, from shallow to deep-water strata in areas around the islands and seamounts. These species are taken accidentally as by-catch of three main fisheries: swordfish fishery, black scabbardfish fishery and demersal bottom longline fishery. The latter represents one of the most important fishing activities in the Azores, and frequent elasmobranch by-catches include Raja clavata, Galeorhinus galeus, Deania calcea, D. profundorum, Etmopterus pusillus and E. spinax. A slight reduction in the abundance indices of these species was observed, despite the implemented technical measures (e.g. minimum size, zero catch). Little is known about resource dynamics for the Azorean region and no analytical assessments have been conducted. This study highlights the vulnerability to overfishing of these resources and the urgent need to develop management strategies.

KEYWORDS:

• Sharks
• skates and rays
• long-term changes
• Azores EEZ
• ICES Subdivision 10.a.2

Acknowledgements

The authors thank all who participated in field surveys and sampling processing onboard the R/V ‘Arquipélago’. Ricardo Medeiros (ImagDOP/UAz) is thanked for the generation of the map. An early version of this paper was presented at ICES Annual Science Conference, held at Hamburg, Germany between 24 and 27 September 2018.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Régis Santos http://orcid.org/0000-0002-4167-3573

Ana Novoa-Pabon http://orcid.org/0000-0002-7194-7176

Hélder Silva http://orcid.org/0000-0001-7181-1976

Mário Pinho http://orcid.org/0000-0002-8045-2546

Additional information

Funding

This study was funded by the Azorean Government under the European Commission’s Data Collection Framework and the DEMERSAIS project. Régis Santos was funded by the IMAR Instituto do Mar, through a Post-doc fellowship [ref. IMAR/DEMERSAIS/001-2018]. Ana Novoa-Pabon was funded by a FCT Ph .D. fellowship [ref. SFRH/BD/124720/2016].