Percorrer por autor "Marsili, Tiago"
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- New insights on the ecology and biology of the rare shark species Oxynotus paradoxus from recent recordsPublication . Graça Aranha Carvalho Ramos, Sofia; Dias, Ester; Marsili, Tiago; Pires da Rocha, Pedro; Teodosio, Maria; Figueiredo, IvoneOxynotus paradoxus, documented in the Eastern Atlantic Ocean from Senegal to Scotland at depths ranging between 92 and 1044 m, has been a subject of limited scientific attention in Portugal. Despite its presence in various Portuguese occurrence checklists, only two scientific studies have reported O. paradoxus, one off the mainland and the other off the Azores islands. In this study, conducted during fishing campaigns, four O. paradoxus specimens were caught off the southwest coast of Portugal (SW Iberian Peninsula) at depths ranging between 742 and 1238 m. Notably, an adult female achieved a new maximum depth record for this species, measuring 650 mm in total length. By examining this adult female, we provide novel insights into the ecology and biology of O. paradoxus. Morphometric measurements are compared with previous studies, revealing some intra-specific variability. The observed low hepato-, gonadosomatic, and ecophysiological indices suggest that the adult female had refrained from feeding for some time before collection. This individual-focused approach contributes significantly to the understanding of this poorly known species, especially considering its rarity. This study marks a noteworthy effort to enhance knowledge and emphasizes the importance of individual-based investigations when targeting rare species.
- Under pressure: deep-sea elasmobranchs experience high mortality and stress in a crustacean trawling fisheryPublication . Graça Aranha Carvalho Ramos, Sofia; Teodosio, Maria; Marsili, Tiago; Pires da Rocha, Pedro; Modesto, Teresa; Guerreiro, Pedro Miguel; Tambutte, Aurélien; Carvalho Alves, Alexandra; Relvas, Paulo; Dias, EsterCrustacean bottom trawling in southern Portugal is an economic and culturally important fishing activity but may result in considerable bycatch of deep-sea elasmobranchs (DSE). Due to DSE life-history strategies, at-vessel mortality (AVM) rates in crustacean bottom trawl fisheries are expectedly high but require further investigations. This study assessed the at-vessel condition of 18 species of DSE, and AVM rates and stress of four deep-sea shark species (Etmopterus pusillus, E. spinax, Galeus melastomus, and Scymnodon ringens), to understand the impact of bottom trawling on these animals. Opportunistic sampling on a crustacean trawler in the southern Portuguese coast, revealed that 95% of specimens were either dead (n = 1,258) or in poor condition (n = 224) upon collection, underscoring their minimal chance of post-release survival. General linear model analyses showed that AVM was species-specific and highest in smaller sharks, as well as in those from hauls that exhibited larger temperature dierences between bottom and surface waters, and those caught in hauls with heavier codend weight using a 55 mm codend mesh (targeting shrimp and prawns) instead of those caught in hauls using a 70 mm codend mesh (targeting Norway lobster). Stress, evaluated through metabolites and electrolytes levels in sharks’ plasma, indicated significant dierences in potassium, urea, and magnesium levels between live and deceased specimens of E. pusillus and G. melastomus, suggesting these as reliable mortality markers. Elevated lactate levels in G. melastomus further pointed to high post-release mortality risk. These findings highlight an urgent need to find solutions to mitigate the impacts of bottom trawling on those DSE, which are thoroughly discussed. A coordinated, multi-stakeholder approach involving researchers, the fishing industry, and regulatory bodies is crucial for developing and implementing eective, and more sustainable fisheries management and protection of DSE populations.
- Unravelling the deep: assessing the bycatch of deep-sea elasmobranchs in crustacean bottom trawl fisheries in PortugalPublication . Dias, Ester; Marsili, Tiago; Barkai, Amos; Queiroz, Nuno; Graça Aranha Carvalho Ramos, Sofia; Pires da Rocha, Pedro; Teodosio, MariaDeep-sea elasmobranchs (DSE) play a crucial role in marine ecosystems. However, they are poorly studied and face threats from overfishing, emphasizing an urgent need for improved scientific information, monitoring, and management strategies to reduce their bycatch. This study aimed to assess DSE bycatch from crustacean bottom trawling in southern Portugal, considering depths above and below 800 m (Regulation 2016/2336). Potential bycatch of deep-sea sharks was evaluated using in situ observations from the months of February and March and extrapolated for the fishing ban period (2017–2022). A total of 1559 specimens belonging to 18 DSE species were collected from 77 hauls between June 2020 and May 2022. Despite trawlers preferences for fishing above 800 m in the South, fishing below 800 m in the Southwest resulted in increased bycatch of DSE, including protected, uncommon, and endangered species such as Deania calceus, Mitsukurina owstoni, and Centroscymnus coelolepis. Furthermore, the areas and depth strata occupied by species like Galeus melastomus and Scymnodon ringens, suggested habitat flexibility, while others showed an apparent preference for specific depths and areas. These findings highlight the complexity of managing DSE populations amidst fishing pressures and depth restrictions. Despite the ban imposed to fishing below 800 m, bottom trawling persisted, leading to a potential elevated bycatch of deep-sea sharks for the months of February and March. This study emphasizes the urgency for improved enforcement of regulations in Portuguese waters and calls for the implementation of effective bycatch mitigation and fisheries management practices to safeguard DSE populations.