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Carvalho, Flávia

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  • Seasonal variation in seabird abundance and bycatch at artisanal bottom-set net fisheries in the southern Iberian Atlantic coast
    Publication . Pereira, Jorge M.; Ramos, Jaime A.; Almeida, Ana; Marçalo, Ana; Carvalho, Flávia; Fagundes, Isabel; Gonçalves, Jorge Manuel Santos; Frade, Magda; Oliveira, Nuno; Nascimento, Tânia; Paiva, Vitor H.
    Bycatch is a major cause of seabird mortality, yet most studies focus on industrial fisheries, with limited knowledge on artisanal fisheries. This study investigates the seasonal abundance of seabirds off the southern-eastern coast of mainland Portugal, their attendance at artisanal bottom-set net fisheries, and observed bycatch, using onboard observations and fishermen interviews. From March 2020 to November 2022, 24,643 seabirds were observed attending fishing vessels in 183 daily fishing trips (98.4 % of 186 trips), spanning 20 species across 7 families, with 25 seabirds recorded as bycatch. Lesser black-backed and Yellow-legged gulls (Larus fuscus and Larus michahellis) were the most abundant species, followed by Audouin's gulls (Ichthyaetus audouinii), Great shearwaters (Ardenna gravis), and Northern gannets (Morus bassanus). During summer, the abundance of Yellow-legged and Audouin's gulls (local breeders) and Lesser black-backed gulls (non-breeding species) increased with fishery catch per unit effort. Great shearwaters were more affected by gear type, exhibiting higher attendance and bycatch in trammel nets during autumn. 65 % of Great shearwater bycatch occurred during a single fishing event, probably from fishermen cleaning nets and discarding fish and viscera during net setting. Fishermen interviews identified Northern gannets and Great cormorants (Phalacrocorax carbo) as the most frequently bycaught species, particularly in winter when onboard observations were limited. These findings underscore the impact of artisanal fisheries on seabird populations and highlight the importance of combining onboard data with fishermen interviews to improve bycatch estimates and inform conservation efforts. Our study also suggests that fishermen behaviour during fishery operations significantly influence seabird bycatch.
  • Reducing cetacean interactions with bottom set‐nets and purse seining using acoustic deterrent devices in Southern Iberia
    Publication . Marçalo, Ana; Carvalho, Flávia; Frade, Magda; Bentes, Luis; Monteiro, Pedro; Pontes, João; Ferreira Alexandre, Teresa Sofia; Oliveira, Frederico; Kingston, Allen; Erzini, Karim; Gonçalves, Jorge Manuel Santos
    In southern Iberia (NE Atlantic), cetacean bycatch is reported in several fisheries, whereas depredation by bottlenose dolphin (Tursiops truncatus) is commonly observed in bottom set-net fisheries. This study tested the effectiveness of acoustic deterrent devices in discouraging small cetaceans from approaching bottom set-nets and purse seine to reduce interactions. The acoustic deterrent devices used in the study were dolphin deterrent devices and dolphin interactive devices for the bottom set-net fishery to reduce dolphin bycatch and depredation and dolphin deterrent devices in the purse seine fishery to reduce common dolphin (Delphinus delphis) bycatch. Data collection was carried out by at-sea observers and trained fishing vessel crew observers. Hauls with and without acoustic deterrent devices were compared and analysed to investigate differences in catch per unit effort, factors affecting the interaction, probability of interaction and habituation (in bottom set-nets only). In bottom set-nets, the depredation rate was significantly lower and reduced by about 50% in hauls using acoustic deterrent devices. Habituation of the bottlenose dolphins to the devices was observed but was gradual. In the purse seine fishery, common dolphin bycatch was reduced by 100% when using the acoustic deterrent devices. Overall, the results are promising, but the different interaction reduction efficiencies observed between gear types indicate that the potential application of acoustic deterrent devices should be considered on a m & eacute;tier-by-m & eacute;tier basis. Other mitigation measures should be developed, especially for static gears, in collaboration with the fishing sector in an inclusive management approach to reduce direct interactions between fisheries and cetaceans.
  • Circannual prevalence of tetrodotoxins in trumpet shells: sea stars as a possible source of contamination and Implications for food safety
    Publication . Pais, Maria; Carvalho, Flávia; Frade, Magda; Reis Costa, Pedro; Silva, José Paulo da; Marçalo, Ana; Canario, Adelino; Lage, Sandra
    Tetrodotoxin (TTX) is a potent neurotoxin, first identified in fish from the Tetraodontidae family but also detected in marine invertebrates. A Human poisoning episode after consumption of trumpet shell Charonia lampas, likely caught off the Portuguese mainland southern coast - Algarve, together with the increasing reports of TTX in European waters, led the European Food Safety Authority (EFSA) to recommend maximum safe limits for Human consumption of shellfish meat. However, data on temporal and species incidence of TTX are lacking. In the present study, TTX and its analogues were analysed by liquid chromatography-high resolution mass spectrometry (LC-HRMS) in trumpet shells and in one of their potential prey sources of TTX, the sea star Astropecten aranciacus. The estimated toxicity, based on a Toxicity Equivalency Factors approach, of non-edible trumpet shell tissues consistently surpassed EFSA limits (44 mu g TTX equivalent (eq.) kg(-1)) over the studied year. A correlation between TTX concentration and bottom seawater temperature suggests a possible role of this parameter in TTX uptake. TTX levels in edible trumpet shell tissues and all but one sea star individual were below quantification limits. However, several TTX analogues were quantified in the sea stars, resulting in estimated toxicities (monthly averages) ranging from 7 to 64 mu g TTX eq kg(-1) in the digestive glands and from 0.3 to 27 mu g TTX eq. kg(-1) in the stomachs. Therefore, the sea star is a possible TTX source for trumpet shells. Despite the absence of TTX in common edible parts of trumpet shells, whole-shell sales in markets pose a consumer risk, highlighting the need for TTX monitoring and public awareness programs to prevent poisoning.
  • Mitigation measures to reduce seabird's interactions with bottom-set nets in southern Iberia
    Publication . Frade, Magda; Carvalho, Flávia; Samel, Vighnesh Nilesh; Oliveira, Nuno; Andrade, Joana; Gonçalves, Jorge Manuel Santos; Marçalo, Ana
    Bycatch poses a significant threat to seabird populations globally. On the southern coast of mainland Portugal, mitigation measures were tested to reduce seabird interactions with fishing vessels. Between 2021 and 2023, this study evaluated the effectiveness of a visual deterrent (a ’scarybird’ device), an acoustic deterrent (megaphone broadcasts), alongside modification in fisher’s behaviour discard management— avoiding discards during fishing operations to minimize seabird interactions. Observers monitored 166 fishing events, comparing control and experimental treatments. Discard management was the most effective deterrent, significantly reducing seabird abundance, particularly gulls (Larus spp.) and northern gannets (Morus bassanus). Model predictions indicated a 37 % and a 47 % reduction in the abundance of gulls and northern gannets, respectively, around commercial fishing vessels when discard management was used. This practice effectively kept a substantial proportion of birds away from the vessel during operations, thereby reducing their vulnerability to bycatch. The megaphone showed limited efficacy, with higher seabird abundance in treatment groups compared to controls. The scarybird device was largely ineffective in deterring gulls unless combined with discard management but showed potential in reducing interactions with northern gannets. Importantly, all mitigation measures did not negatively impact Landings Per Unit Effort (LPUE), which facilitated their acceptance among fishers. Our findings suggest that simple modifications in the fisher’s behaviour, such as retaining fish discards and viscera onboard, could serve as a promising bycatch mitigation measure, potentially eliminating the need for additional less effective mitigation devices that fishers may be reluctant to adopt.