Browsing by Author "Bruxelas, S."
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- Coexistência de duas espécies exóticas de lagostins (Pacifastacus leniusculus e Procambarus clarkii) na bacia hidrográfica do rio Sabor (NE Portugal)Publication . Costa, A.M.; Bruxelas, S.; Bernardo, J.M.; Teixeira, AmílcarEm Portugal existia uma única espécie europeia de lagostim de água doce, Austropotamobius pallipes, o lagostim-de-patas-brancas, que se considera actualmente extinta no país. No nordeste de Portugal continental onde anteriormente ocorria esta espécie, os cursos de água estão actualmente a ser colonizados por duas espécies de lagostins norte americanos. Na década de 70, proveniente de Espanha onde foi intencionalmente introduzido, o lagostim-vermelho-da-Luisiana, Procambarus clarkii, colonizou rapidamente os rios do sul de Portugal, propagando-se depois por todas as massas hídricas do país. Em 1994, as autoridades espanholas introduziram uma outra espécie, o lagostim sinal, Pacifastacus leniusculus, na província de Zamora, que foi detectada em Portugal, no rio Maçãs (Bacia do Sabor) três anos depois. A propagação e evolução das populações destas espécies no rio Maçãs têm sido seguidas anualmente desde 2000. P. clarkii, espécie sub-tropical, nunca atingiu neste curso abundâncias muito elevados. Pelo contrário, P. leniusculus, espécie de águas mais frias, apresenta valores mais elevados, cerca de seis vezes superiores aos de P.clarkii. O lagostim sinal encontra-se bem adaptado, continuando a sua expansão neste rio e prevendo-se que venha a colonizar outras massas hídricas adjacentes. A expansão do lagostim vermelho de jusante para montante parece ser menos efectiva, não tendo, desde 2005, sido observado em novos locais deste rio. A coexistência das duas espécies verifica-se actualmente num troço fluvial de cerca de 45 km de extensão, apesar das diferenças notórias ao nível das características dos seus habitats.
- Colonization and dispersal rates of two non-native crayfish species (Pacifastacus leniusculus and Procambarus clarkii) in NE PortugalPublication . Bernardo, J.M.; Costa, A.M.; Bruxelas, S.; Teixeira, AmílcarIn Europe, a generalized regression of the native crayfish was observed during the past decades. Simultaneously, several non-native species spread in most countries. In Portugal, the red swamp crayfish, Procambarus clarkii, is now occurring in most inland waters. The NE Portugal is one of the most isolated and low populated regions of Western Europe. Most rivers in these region present low levels of human impact and some are actually pristine. Recently, two American crayfish species reached the area: signal crayfish (Pacfastacus leniusculus) coming from Spain and red swamp crayfish. The isolation and the natural conditions of these rivers make them particularly valuable for the study of crayfish colonization and spreading. The colonization by both species was followed throughout the last decade in the Maçãs river (Douro catchment). Sampling was undertaken every year with baited traps. The average dispersal rate of signal crayfish was approximately 2 km/year, although a great variability among sectors was observed. Coexistence of signal and red swamp crayfish was detected in a large part of the river system. Signal crayfish developed well adapted and persistent populations. The lower abundance of red swamp crayfish is apparently caused by the low winter temperatures.
- Colonization of Rio Maçãs (North Portugal) by two exotic crayfish, Pacifastacus leniusculus and Procambarus clarkiiPublication . Costa, A.M.; Bruxelas, S.; Bernardo, J.M.; Teixeira, AmílcarIn Portugal there was only one European crayfish species, the white clawed Austropotamobius pallipes. During the last decades, a sharp regression of these populations took place and the species is presently considered extinct in Portugal. Coming from Spain, two American species invaded the Portuguese freshwaters. The red swamp crayfish, Procambarus clarkii, a sub-tropical species, extremely resistant to severe climatic conditions, is actually present in almost inland waters. The signal crayfish, Pacifastacus leniusculus, a cold-water crayfish, reached recently the streams of NE Portugal and presently occurs in a sector of Rio Maçãs with approximately 43 km length. Progression of the two exotic species in Rio Maçãs was followed every year since 2000. The average velocity of propagation of signal crayfish from dispersion point is 2 km/year, although a great variability between sampling points was observed. Signal crayfish is well adapted to local stream conditions. Coexistence of signal and red swamp crayfish was detected in part of the river system.
- Dispersal and coexistence of two non-native crayfish species (Pacifastacus leniusculus and Procambarus clarkii ) in NE Portugal over a 10-year periodPublication . Bernardo, J.M.; Costa, A.M.; Bruxelas, S.; Teixeira, AmílcarNE Portugal is one of the most isolated and low populated regions of Western Europe. Recently, two American crayfish species reached this area: signal crayfish Pacifastacus leniusculus coming from Spain and red swamp crayfish Procambarus clarkii in its northward expansion. The dispersion of both species was followed throughout the last decade in river Maçãs (Douro catchment). Our results support the hypothesis of faster downstream colonisation. The mean spread rate of signal crayfish was faster for the downstream expansion, 2.8 km·yr-1, while the upstream rate was 1.7 km·yr-1. Exceptionally, in one period, the rate of spread reached 6.7 km·yr-1, which was apparently caused by downstream washing in extreme conditions of flow. The mean rate of spread is higher than the observed in other studies which may also be related to the low current velocity of late spring and summer that provides favourable conditions for a fast upstream colonisation. Coexistence of signal and red swamp crayfish was detected in a large river sector. Signal crayfish strongly dominates in the upper and intermediate sectors which are the colder part of the river and in the lower sectors, species abundances are not significantly different. Winter temperature in the higher altitude reaches seems to moderate the competitive abilities of P. clarkii.
- Indicators of movement and space use for two co-occurring invasive crayfish speciesPublication . Anastácio, P.M.; Banha, Filipe; Capinha, C.; Bernardo, J.M.; Costa, A.M.; Teixeira, Amílcar; Bruxelas, S.Red swamp crayfish (Procambarus clarkii) and signal crayfish (Pacifastacus leniusculus) are two invasive freshwater species with a worldwide distribution. The objective of this work was to investigate how the two species move and use space in an area of recent coexistence. Simultaneously, we test the use of new tools and indices to describe their movement patterns. To accomplish this we performed a radio-tracking program within a river-type habitat during two different periods (September/October 2010 and June/July 2013). We used spatial analysis tools to map crayfish radio-location data with and without accounting for the curvature of the river. To assess the consistency of the direction of movement and of the distances traveled by crayfish, two indices were developed. To assess the habitat preferences of each species we applied Ivlev’s Electivity Index and the Standardized Forage Ratio. Movement of P. clarkii and P. leniusculus differed. The average detected movement was 8.8 m day−1for P. clarkii and 17.5 m day−1forP. leniusculus. However, crayfish behavior ranged from almost complete immobility – sometimes during several days – to large movements, in half a day, up to a maximum of 255 m for P. clarkii and 461 m for P. leniusculus. The proportion of upstream or downstream movements was independent of the speciesand both species displayed no preference for either direction. The indices of consistency of movement showed a large interindividual variation. Species and period (2010 or 2013) affected the mean daily distance traveled, maximum observed distance from location of release and percentage of observations under vegetation cover. The Ivlev’s Electivity Index and the Standardized Forage Ratio presented similar results. P. clarkii showed a preference for pool areas with riparian vegetation cover while P. Leniusculus preferred riffle and pool areas with riparian vegetation cover. Our work provided new and valuable data for modelling the active dispersal of these two problematic invaders in a context of coexistence.
- Interacção entre duas espécies exóticas de lagostins (pacifastacus leniusculus e procambarus clarkii): estudo experimental com recurso à PIT-telemetriaPublication . Teixeira, Amílcar; Costa, A.M.; Bernardo, J.M.; Bruxelas, S.; Nogueira, Mónica Sofia ReisNo rio Maçãs (bacia do Rio Douro), no Nordeste de Portugal, coexistem duas espécies de lagostins exóticos, o lagostim vermelho da Louisiana (Procambarus clarkii) e o lagostim sinal (Pacifastacus leniusculus). Para estudar o movimento e padrão de actividade de ambas as espécies foi desenvolvida uma experiência num espaço confinado (300 x 100 cm) e aplicada a técnica da PIT-telemetria (Passive Integrated Technology, UKID Systems, U.K.), com recurso a um MPD (Data-logger) e oito antenas circulares de detecção de transmissores (PIT-tags). Seleccionou-se um local de alimentação e alguns refúgios capazes de fornecer isolamento visual entre lagostins. Foram implantados PIT-tags, com identificação individual, em 5 machos e 5 fêmeas de cada espécie e monitorizado o seu comportamento de forma contínua (dia e noite) ao longo de 15 dias, durante o período estival de dois anos consecutivos. Obtiveram-se cerca de 30 000 dados, diferenciados em termos de frequência de dados repetidos (registos contínuos na mesma antena) e não repetidos por cada animal. A análise dos dados sugere um comportamento diferenciado entre espécies e sexos com dominância do lagostim vermelho relativamente ao lagostim sinal e dos machos sobre as fêmeas. As interacções entre espécies podem estar na origem do afastamento e menor actividade de P. leniusculus dos locais mais próximos da área de alimentação. Por outro lado, as fêmeas de ambas as espécies demonstraram ser menos activas do que os machos.
- Movement and interaction of two exotic crayfish (Pacifastacus leniusculus and Procambarus clarkii) using PIT telemetry in experimental conditionsPublication . Teixeira, Amílcar; Costa, A.M.; Bernardo, J.M.; Bruxelas, S.The coexistence of two exotic crayfish species (Procambarus clarkii and Pacifastacus leniusculus) was observed in a stretch of Rio Maçãs (Douro basin, Northeast of Portugal). The red swamp crayfish, P. clarkii, a sub-tropical species, was first detected in 1979 in Rio Caia (Alentejo) and from there rapidly spread through most freshwater bodies. This species is extremely resistant to severe climatic conditions, living in such contrasting environments as South or Northeast streams of Portugal. The signal crayfish, Pacifastacus leniusculus, a cold-water crayfish recently reached Portuguese waters and is now spreading in Rio Maçãs. To characterise movements, activity patterns and interactions of both species an experiment was developed in a confined area using PIT telemetry equipment with a multi-point decoder unit connected to eight circular panel antennae. Data were collected from sympatric tagged populations monitored during several days, to detect interactions between individuals during night and day.