Browsing by Author "Ribeiro, Filipe"
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- Análise preliminar da pesca ao sável (Alosa alosa) e à savelha (Alosa fallax) na aldeia das Caneiras – SantarémPublication . Gago, João; Colaço, Sérgio; Ribeiro, FilipeO sável, Alosa alosa (Linnaeus, 1758), e a savelha, Alosa fallax (Lacépède, 1803), são dois clupeídeos anádromos e importantes recursos para a pesca nas águas interiores de Portugal. Apesar da recente recuperação de algumas populações destas espécies, nas últimas décadas foram observadas fortes quedas nas suas capturas. No entanto, a informação disponível sobre a pesca destes peixes é escassa, dificultando a implementação de medidas de gestão adequadas. Neste trabalho apresentamos dados sobre a pesca na Aldeia das Caneiras (Santarém) (rio Tejo), entre março e maio de 2014. A maioria das capturas pertenceram ao género Alosa (36,4% para o sável e 21,0% para a savelha), e espécies secundárias como o barbo-comum (Luciobarbus bocagei) com 23.5%, a lampreia- marinha (Petromyzon marinus) e tainhas (Mugilidae) também foram capturadas. O valor económico do sável e da savelha variou entre 10 €/kg (preço de venda nos pescadores) até 20 €/kg (preço praticado no mercado local). Neste trabalho são apresentados dados sobre a estrutura populacional de sável e savelha com base no tamanho, idade, sexo e estádio de maturação dos exemplares capturados. Estes dados constituem a primeira informação sobre as populações destes clupeídeos no baixo Tejo, sendo ferramentas importantes na avaliação do impacto da pesca e das tendências populacionais, podendo ser usadas na definição de medidas de gestão sustentável compatíveis com a manutenção da cultura avieira.
- Diet of European Catfish in a Newly Invaded RegionPublication . Ferreira, Marco; Gago, João; Ribeiro, FilipeBiological invasions are considered to be one of the leading causes of biodiversity loss worldwide. Freshwater ecosystems are amongst the most biodiverse, containing about 50% of the world’s known fish species but, ironically, are the most invaded ecosystems. In Portuguese freshwaters, there are currently 20 identified non-native fishes, arriving at an unprecedented rate of a new species every two years. A recent non-native is the European catfish Silurus glanis, a top predator native to Central and Eastern Europe, that arrived at the Lower Tagus (Portugal) circa 2006. This study compares the dietary habits of this top predator in two di erent habitats of the Lower Tagus in order to evaluate its potential impact. The stomach contents of 96 individuals were analyzed, 61 from the lotic environment and 35 from the lentic systems. A total of 66 stomachs contained prey items, 38 from the lotic and 28 from the lentic. Diet varied considerably between habitats, with shrimp and crayfish being the most abundant prey items in the lentic systems and shrimp and fish the most abundant prey items in the lotic section. Tendency to piscivory was observed in large-sized individuals. Overall, the findings in this study provide the first evidence of the potential impacts of European catfish through predation on the fish communities.
- Fish communities in the lower Tagus inland wetlands: from anthropogenic pressures to conservation managementPublication . Ribeiro, Diogo; Dias, Diogo; Santos, Gil; Gago, João; Serrano, Beatriz; Almeida, Luís; Martelo, Joana; Costa, Luís M.; Ribeiro, Filipe; Catalão, João; Magalhães, M. F.Inland wetlands are important biodiversity hotspots and amongst the most impacted ecosystems worldwide. Conservation management and restauration actions in wetlands are thus urgently needed to reverse trends in species loss and habitat degradation, particularly in regions harbouring already endangered endemic species. Inland wetlands may play an important role in supporting endemic endangered fishes in the Lower Tagus basin, where anthropogenic pressures have been increasing, but there is a lack of studies on fish communities, and few areas are identified as inland wetlands. Here, we aim to identify small inland wetlands in the Lower Tagus River and their potential role in supporting fish species, constituting the first study to identify and evaluate the most important fish communities. Inland wetlands were identified through the usage of remote sensing techniques and the calculation of a Normalized Difference Water Index (NDWI) with Sentinel-2 imagery for the Lower Tagus region. From a total of 486 locations identified, 31 were recognized as wetlands as having potential to host fish communities, with 11 being selected for sampling after in loco assessment. Fish sampling was conducted between 6 May and 11 June 2021. Furthermore, for each wetland, we evaluated anthropogenic stressors and land use changes between 2007 and 2018, using national land use data (i.e., Carta de Uso e Ocupação do Solo). A total of 7727 fishes from eight non-native and five native species were captured. Overall, fish communities were dominated by non-native species (97% catches), but both European eel (Anguilla anguilla) and Lisbon arched-mouth nase (Iberochondrostoma olisiponense), which are globally classified as critically endangered (CR), were found in at least two wetlands. Our results suggest that, over the last 10 years, intensive agriculture decreased (on average ≈ 3%) in the areas surrounding these wetlands, being replaced by extensive agriculture or natural uses. Despite non-native fish prevalence, some wetlands may act as refuge habitats for CR fish species. These results are important for guiding the restoration of inland wetlands and promoting conservation management actions to help reverse fish diversity loss.
- Historical food-web changes in invaded fish communities in the lower Guadiana basinPublication . Gkenas, Christos; Martelo, Joana; Cucherousset, Julien; Ribeiro, Filipe; Gago, João; Alves, Maria Judite; Ribeiro, Diogo; Cheoo, Gisela; Magalhães, M. F.Freshwater ecosystems are increasingly being reshaped by biological invasions, leading to biotic homogenization and biodiversity loss. However, the extent to which novel species may drive changes in food-web structure over time remains poorly understood. Clarifying changes in historical ecological processes is critical to inform conservation and restoration efforts in recipient ecosystems. Here, we address food-web changes associated with fish invasions in the Lower Guadiana Basin (LGB) over the past 40 years, by contrasting feeding relationships between museum-archived and contemporary specimens, using stable carbon (δ13C) and nitrogen (δ15N) ratios. Specifically, trophic niches of museum-archived fishes sampled throughout 1978–1987 and 1999–2004 corresponding to the initial establishment and spread of non-native fishes, respectively, were compared with those of fishes sampled in 2019, characterizing the integration of non-native species in the recipient ecosystem. We focused on five native species (Anaecypris hispanica, Cobitis paludica, Iberochondrostoma lemmingii, Squalius pyrenaicus and Squalius alburnoides) and four non-native species (Lepomis gibbosus, Australo heros facetus, Micropterus salmoides and Gambusia holbrooki) with potential to cover multiple trophic positions in the food-webs. We approached historical baseline resources using prey items in gut con tents of the museum-archived fishes and characterized primary producers and macroinvertebrates in 2019. Prior to analysis, samples were normalized for high lipid content and corrected for preservation. We found considerable asymmetries in niche partitioning among species as invasion progressed. Over time, native species tended to be displaced to lower trophic levels, while non-native species showed significantly higher trophic niches, driven mainly by increases in trophic (δ15N) range. Our study highlights that stable isotopes may provide important insights on historical food-web structure and particularly on processes underpinning ecological changes associated with anthropogenetic pressures on freshwater ecosystems.