The estimated survival of species of skates after being captured by mixed fisheries using trammel nets in Peniche, Portuguese coast, and kept in captive

• Autor(a) principal: Castelo, João André Correia
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
• Texto Completo: http://hdl.handle.net/10400.12/8663
• topic: Landing obligation; High survival exemption; Trammel nets; Survival; Rajiforms; Obrigação de Desembarque; LO; Sobrevivência; Rajiformes

By-catch fisheries are a large problem nowadays, affecting marine populations that are a non-target for world fisheries. The creation of the Landing Obligation (LO) was an important law introduced in the management and control of European fisheries, by aiming for more sustainable fisheries and promoting the bycatch reduction of species managed by quotas. Yet, a stock can be exempted from the LO if scientific studies support a high survivability to a given fishing gear. This means that with this exemption, based on high survivability, the bycatch of a stock if discarded can be delivered alive to the sea, promoting the recuperation of the stock. Currently, there is already a provisional exemption by high survival for most skate and ray species (Rajiformes) caught in European waters, yet the European Commission will only grant a definitive exemption of member states provide sufficient scientific evidence to support it. Therefore, the present study aims to gather scientific information on the survivability after capture of Rajiformes species caught in the polyvalent fleet operating with trammel nets off Peniche, central Portugal, which are the main fishing gears and area where Rajiformes are caught in mainland Portugal. For this study a holding tank with 1000 L was prepared for the individuals and weekly they were tested with CVA – Categorical Vitality Assessments, RAMP tests and lesion coverage. The results were utilized to evaluate discard survival for this two species, using a non-parametric Kaplan-Meier it was observed that R. brachyura species had 76% survival probability and R. montagui species had 54% survival probability, also it was observed that their vitality status influence the survival probability.