Departamento de Ciências Agrárias
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Browsing Departamento de Ciências Agrárias by Author "Afonso, Pedro"
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- Coastal marine fishes of São Tomé Island (Gulf of Guinea).Publication . Afonso, Pedro; Porteiro, Filipe M.; Santos, Ricardo S.; Barreiros, João P.; Worms, Jean; Wirtz, PeterSince the early works of Balthazar Osório, at the turn of the century, only few papers have been published on the ichthyofauna of São Tomé island. The papers dealing with these fishes were compilations of previous works or the results of a few scientific expeditions (e.g. "Galathea" and "Calypso"). In this paper, we present the results of several surveys carried out from the island over the last decade, together with an annotated revision of the known bibliography for the area. The result is an inventory of the coastal fish of São Tomé island. Our records (124 species belonging to 59 families) are based on fish captured, photographed or observed whilst diving and also on those landed by local artisanal fishermen. In this paper we report a total of 185 confirmed coastal species and 67 families. Twenty-seven of these are reported for the first time for the area, and three other unidentified species may represent new species to science. The best represented families are Carangidae (14 species), Serranidae (11 species), Gobiidae and Scombridae (8 species each). Despite its proximity to the African Continent, it is clear that these islands harbour a particular fish fauna, including several amphiatlantic species, which, in the eastern Atlantic, occur only around oceanic islands (e.g., Epinephelus ascencionis, Paranthias furcifer, Mulloidychtis martinicus, Bodianus pulchellus, Chromis multilineata, Gnatholepis thomsoni, Melychthis niger). The coastal ichthyodiversity of São Tomé is apparently poorer than that of the adjacent coasts, showing a significant influence of the islands further west, St. Helena and Ascencion.
- Feeding ecology of the white sea bream, Diplodus sargus cadenati (Perciformes: Sparidae) and the ballan wrasse, Labrus bergylta (Perciformes: Labridae), from Faial Island – AzoresPublication . Figueiredo, Miguel; Morato, Telmo; Barreiros, João P.; Afonso, Pedro; Santos, Ricardo S.To make a first approach in the assessment of the sea urchin predators in the Azores, the diet of white seabream (Diplodus sargus) and ballan wrasse (Labrus bergylta), were studied by the analyses of their stomach contents. The white seabream is a diurnal omnivore, feeding on algae, sea-urchins, worms, gastropods and amphipods, while ballan wrasse fed mainly on echinoderms (sea-urchins), gastropods and decapods. Both species tended to feed on harder prey, such as echinoderms and gastropods, as they grew. Although both species feed upon similar resources, the diet overlap was low. This study shows that the white seabream and the ballan wrasse are important predators of sea-urchins in Azorean coastal habitats. Furthermore, larger fish account for most of the predation on sea-urchins. Thus, a reduction in the abundance and mean size of fishes, which is a typical consequence of fishing, may significantly decrease predation on sea-urchins and could thus facilitate their proliferation.
- Length-weight relationships for 21 coastal fish species of the Azores, north-eastern AtlanticPublication . Morato, Telmo; Afonso, Pedro; Lourinho, Paula; Barreiros, João P.; Santos, Ricardo S.; Nash, Richard D.Length–weight relationships were estimated for 21 coastal fish species of the Azores, namely Abudefduf luridus, Bothus podas, Chromis limbata, Coris julis, Diplodus sargus, Echiichthys vipera, Gaidropsarus guttatus, Labrus bergylta, Mullus surmuletus, Phycis phycis, Pomatomus saltator, Sarda sarda, Scorpaena maderensis, Scorpaena notata, Seriola rivoliana, Serranus atricauda, Sparisoma cretense, Sphyraena viridensis, Synodus saurus, Thalassoma pavo and Trachinotus ovatus. Significant length–weight relationships were found for all species. Sexual dimorphism did not affect the length–weight relationships, except in the cases of S. cretense and C. julis. Length–length equations for converting size measurements (standard length (SL) and fork length (FL) to total length (TL)) are also presented for all fish species.
- Plataformas de petróleo – Pontos de encontro de peixes em alto-marPublication . Hostim-Silva, Maurício; Fontes, Jorge; Afonso, Pedro; Serpa, Norberto; Sazima, Cristina; Barreiros, João P.; Sazima, IvanAlém da sua importância econômica, as plataformas marítimas de prospecção e extração de petróleo desempenham uma função ecológica pouco conhecida do público: em alto-mar, suas estruturas submersas, que chegam a dezenas de metros de profundidade, servem como locais de abrigo, alimentação e reprodução de peixes. Também constituem um hábitat para organismos que vivem fixos ou junto a algum substrato, como corais, algas, moluscos e crustáceos, fontes de alimentação para diversas espécies de peixes. […].
- Valuable but vulnerable : Over-fishing and under-management continue to threaten groupers so what now?Publication . Mitcheson, Yvonne Sadovy de; Linardich, Christi; Barreiros, João P.; Ralph, Gina M.; Aguilar-Perera, Alfonso; Afonso, Pedro; Erisman, Brad E.; Pollard, David A.; Fennessy, Sean T.; Bertoncini, Áthila A.; Nair, Rekha J.; Rhodes, Kevin L.; Francour, Patrice; Brulé, Thierry; Samoilys, Melita A.; Ferreira, Beatrice P.; Craig, MatthewAmong threats to marine species, overfishing has often been highlighted as a major contributor to population declines and yet fishing effort has increased globally over the past decade. This paper discusses the decadal reassessment of groupers (family Epinephelidae), an important and valuable group of marine fishes subjected to high market demand and intense fishing effort, based on IUCN criteria. Allowing for uncertainty in the status of species listed as Data Deficient, 19 species (11.4%) are currently assigned to a “threatened” category. This first reassessment for a large marine fish taxon permits an evaluation of changes following the original assessments, provides a profile of the current conservation condition of species, identifies the challenges of assessing conservation status, and highlights current and emerging threats. Measures needed to reduce threats and lessons learned from conservation efforts are highlighted. Present threats include intensifying fishing effort in the face of absent or insufficient fishery management or monitoring, growing pressures from international trade, and an inadequate coverage in effectively managed, sized, or located protected areas. Emerging threats involve expansion of fishing effort into deeper waters and more remote locations, shifts to previously non-targeted species, increases in the capture, marketing and use of juveniles, growing demands for domestic and international trade, and, potentially, climate change. Those species most threatened are larger-bodied, longer-lived groupers, most of which reproduce in spawning aggregations.