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- 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.
- 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.
- 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.
- Angler’s preferences, perceptions and practices regarding non-native freshwater fishPublication . Banha, F.; Gago, João; Margalejo, D.; Feijão, J.; Casals, F.; Anastácio, P.M.; Ribeiro, F.It is globally recognized that freshwater anglers can have a decisive role in promoting fish introductions. The aim of this study was to analyze fresh water anglers’ actions and perceptions regarding fish introductions, comparing two distinct situations, one with recently arrived non-natives fishes and another with older fish introductions, using the Iberian Peninsula as a case study. To achieve this goal, a bilingual survey was implemented on-line in Portugal and Spain and in person (direct inquiries) in two Iberian regions: Lower Ebro (older fsh introductions) in Spain; and Lower Tagus (recent fish introductions) in Portugal. Results showed spatial diferences in perceptions and actions, namely about the target species, awareness of the impact of non-native fishes, fish introductions reported and proportion of anglers that wanted new fish species. In the Ebro river there is a high percentage of foreign anglers, higher awareness of fish introduction impact and lower introduction rates reported than in the Tagus river. However, popularity of non-native species like European catfish, was higher in the Ebro. In general, although risk behaviors such as use of fish as life bait was of low prevalence for both countries (approx. 5%), it corresponds to large numbers of fish being introduced. Our conservative estimates revealed 273,600 events of bait discharge per year. Regarding the intentional introductions, we estimated a total of 140,000 intentional introduction (illegal) events per year. These findings may help to improve monitoring, awareness and fisheries management programs led by governmental agencies.
- First record of Silurus glanis Linnaeus, 1758 in Portugal (Iberian Peninsula)Publication . Gkenas, C.; Gago, João; Mesquita, N.; Alves, M. J.; Ribeiro, F.
- Condition and size of the non-native pikeperch Sander lucioperca (Linnaeus, 1758) in Portuguese river basinsPublication . Gago, João; Neves, A.; Gkenas, C.; Ribeiro, D.; Ribeiro, F.We studied life-history traits focusing on the growth and condition of the pikeperch Sander lucioperca to evaluate its phenotypic plasticity when introduced to new environments. Pikeperch is a non-native fish introduced to Iberian freshwater fauna in 1998 that quickly spread to other river basins through human-mediated activities, occupying now a wide variety of habitats along mainland Portugal. Condition (K and SMI), fork length at age, and length-weight relationships were studied for Portuguese populations. Pikeperch fork length for ages 1, 2, 3, and 4 was different between several populations. We applied generalized linear models (GLM) to study the influence of habitat type, latitude, altitude, time after first detection, and fish prey richness on pikeperch populations size at age 4 and condition. We observed higher condition values on populations from lower altitudes at lentic systems more recently introduced. But higher fork length at age 4 was found in populations from higher altitudes, on older populations with higher prey richness. Habitat type, time since first detection, and fish fauna composition are discussed as the main environmental factors explaining the observed phenotypic plasticity with concerns on predatory impact on native fauna.
- Variation in diet patterns of the invasive top predator Sander lucioperca (Linnaeus, 1758) across portuguese basinsPublication . Ribeiro, D.; Gkenas, C.; Gago, João; Ribeiro, F.The introduction of non-native species is recognized as a major threat to biodiversity, particularly in freshwater ecosystems. Pikeperch Sander lucioperca, is a recent invader to Portugal, primarily providing commercial and angling interest. The aim of this work was to study the diet of this top predator across Portuguese basins and to evaluate its potential impact on recipient ecosystems. In total, 256 pikeperch stomachs from seven basins were examined, of which 88 (n = 34%) were empty. Pikeperch diet was dominated by R. rutilus, M. salmoides and Diptera in northern populations, while A. alburnus, P. clarkii and Atyidae were important prey in more humid highlands. Variation in diet was most strongly linked to latitude and ontogeny, with both size classes showing signs of cannibalism. The population niche breadth remained low and was accompanied by higher individual diet specialization, particularly in northern populations. Pikeperch dietary patterns denoted an opportunistic ability to use locally abundant prey in each ecosystem, and was size dependent, with larger individuals becoming more piscivores, causing a higher impact in the lotic systems. This first perspective about the pikeperch diet presents a very broad view of the feeding traits of this non-native predator across Portugal, being very important to deepen our knowledge about the impact of these introduced piscivores.
- Protecção biológica de conservação e gestão de largadas de auxiliaresPublication . Figueiredo, E.; Martins, J.; Godinho, Maria; Mateus, C.; Valério, E.; Silva, E. B.; Silva, R.; Gago, João; Seabra, S.; Rebelo, M.; Mexia, A.Os complexos de espécies de parasitóides e predadores que limitam as populações das principais pragas de culturas hortícolas protegidas, mosquinhas brancas, larvas mineiras, lagartas, afídeos e tripes, têm vindo a ser estudados na região Oeste desde há mais de 25 anos. A riqueza específica encontrada nestes complexos é elevada. Algumas das espécies identificadas são comercializadas para largadas. Estas largadas podem afectar as populações dos agentes de luta biológica presentes nas culturas, ao nível da composição específica dos complexos, da abundância populacional de cada espécie e na proporção relativa dos vários genótipos presentes nas populações. Está a decorrer uma operação/projecto ProDeR, medida 4.1, promovida por duas empresas agrícolas e três instituições de ensino superior público, que pretende definir regras de actuação no combate às pragas destas culturas face à intensidade de ataque observada e aos auxiliares autóctones presentes e sua abundância, com o objectivo de definir regras para eventuais tratamentos biológicos e analisar as consequências destes, de forma a melhor adequar as estratégias de protecção a adoptar.-------The species complexes of parasitoids and predators which control populations of the main pests of vegetable protected crops have been studied for the last 25 years in the Oeste region. Species richness found in the complexes which prey or parasitize the main pests found in these crops, such as whiteflies, leafminers, caterpillars, aphids and thrips is high. Some of the identified species are commercialized for biological control releases. These releases can affect populations of the naturally occurring biological control agents, regarding species composition of the complexes, species abundance and representativeness of the genotypes present in the populations. A ProDeR - measure 4.1 operation/project promoted by two enterprises and three higher education institutions is ongoing. The aim of this project is to define decision rules to control pests of protected crops taking into account pest attack severity, beneficial arthropod species present and their abundance, and through this to define rules for eventual commercial releases of beneficial arthropods and to analyse their consequences. This will lead to the adoption of more adequate plant protection control measures.
- Spatial distribution patterns of the non-native European catfish, Silurus glanis, from multiple onlinesources : a case study for the River Tagus (IberianPeninsula)Publication . Gago, João; Anastácio, P.; Gkenas, C.; Banha, F.; Ribeiro, F.Effective management of invasive fishes depends on the availability of updated information about their distribution and spatial dispersion. Forensic analysis was performed using online and published data on the European catfish, Silurus glanis L., a recent invader in the Tagus catchment (Iberian Peninsula). Eighty records were obtained mainly from anglers’ fora and blogs, and more recently from www.youtube.com. Since the first record in 1998, S. glanis expanded its geographic range by ≈700 km of river network, occurring mainly in reservoirs and in high-order reaches. Human-mediated and natural dispersal events were identified, with the former occurring during the first years of invasion and involving movements of >50 km. Downstream dispersal directionality was predominant. The analysis of online data from anglers was found to provide useful information on the distribution and dispersal patterns of this non-native fish, and is potentially applicable as a preliminary, exploratory assessment tool for other non-native fishes.
- Avaliação da toxicidade das lamas de cal sobre o ouriço-do-mar Paracentrotus lividus (Lamark, 1816). Perspetivas para novas aplicações destes resíduos industriaisPublication . Gaspar, N.; Gago, João; Repolho, T.; Luís, O.Através da utilização do ouriço-do-mar Paracentrotus lividus como bioindicador, neste estudo avaliou-se a potencialidade de utilização de um resíduo das indústrias do papel, as lamas de cal, em duas vertentes. A primeira consistia em aproveitar a característica alcalina das lamas de cal como redutiva da crescente acidificação dos oceanos. Nos bioensaios realizados obteve-se um aumento significativo na percentagem de malformações das larvas pluteus de P. lividus que foram cultivadas em águas com concentrações superiores a 0,1 mg/L de lamas de cal, o que coloca em causa esta primeira potencialidade. A segunda baseava-se no elevado teor em cálcio presente nas lamas de cal que desta forma poderiam servir como matéria-prima deste macronutriente em rações para adultos P. lividus. Após 6 meses de cultivo em que os ouriços-do-mar foram alimentados com 4 rações diferentes que diferiam na concentração de lamas de cal utilizadas, os resultados obtidos para as variáveis biométricas analisadas, para o índice gonadossomático, para a concentração de Ca, Hg, Pb e Cd nas gónadas e parede do corpo, e para os ensaios ecotoxicológicos, parecem viabilizar esta segunda potencialidade.Through the use of the sea urchin Paracentrotus lividus as bioindicator, this study evaluated the potential to use the waste of paper mills, lime sludge, on two perspectives. The first was to take advantage of the lime sludge alkaline character as a deterrent of increasing ocean acidification. In bioassay testing, a significant increase in the percentage of plutei larvae malformations was obtained when they were cultured at lime sludge concentrations above 0.1 mg/L. This result undermines this first perspective. The second relied on the lime sludge high calcium concentration which could thereby serve as raw material for P. lividus feeds. After 6 months of captive period in which adult sea urchins were fed 4 diets that differed in lime sludge addition, the results obtained for the biometric variables analyzed, for the GSI, for the concentration of Ca, Hg, Pb and Cd in the gonads and in the body wall, and for larvae ecotoxicological testing, appear to support this second potential.