Behavioral interactions and trophic overlap between invasive signal crayfish Pacifastacus leniusculus (Decapoda, Astacidae) and native fishes in iberian rivers

The signal crayfish Pacifastacus leniusculus Dana, 1852 is a successful invasive species in the Iberian Peninsula. This is of particular conservation concern, as fish fauna is highly endemic and also threatened within this ecoregion. The aim of this study was to analyze behavioral interactions and trophic overlap between signal crayfish and native fishes in Iberian rivers (northern Spain). Video cameras were used to record fish "dominance/evasion" after spatial encounters with crayfish. Diet composition and isotopic signatures (¿13C and ¿15N) were compared to evaluate the niche overlap. Fish were dominant in 25% of the encounters with juvenile crayfish, whereas this percentage was only 4% with adult crayfish. Observations showed a high fish "evasion" response for Pyrenean stone loach Barbatula quignardi (B¿cescu-Me¿ter, 1967) (>30%). Dietary results showed a high trophic overlap between signal crayfish with the pelagic Pyrenean minnow Phoxinus bigerri Kottelat, 2007 and the benthic loach. However, the isotopic niche overlap was low, with brown trout Salmo trutta L., 1758 showing the highest area (only 0.1 ¿2). Overall, our findings suggest that interferences may occur with native species for food (i.e., benthic invertebrates). Consequently, measures should be applied to control invasive crayfish in Iberian rivers

Caracterización estacional del hábitat fluvial del río Erro (Navarra)

Se presenta la descripción de catorce tramos representativos del río Erro (Navarra) a partir de la caracterización del hábitat fluvial llevada a cabo en invierno, verano y otoño de 2002. Para este estudio se han considerado parámetros tanto del hábitat físico (profundidad, anchura del cauce, pendiente de las orillas, velocidad del agua, tipo de sustrato, vegetación acuática y sombreado) como físico-químicos del agua (temperatura, pH, conductividad, sólicos disueltos y oxigeno disuelto). El análisis de las caracteristicas del rio Erro permite considerar su estado general como bueno, aunque se detecta la presencia de un tramo sensible aguas abajo de la localidad de Erro. Si bien este tramo sensible presenta niveles de conservación aceptables, es susceptible de deteriorarse si no de adoptan las medidas oportunas para su conservación. Se sugiere su inclusión en el Lugar de Interés Comunitario (Red Natura 2000 de Navarra) de los "Sistemas Fluviales de lis Ríos Irati, Urrobi y Erro"

Contribución al conocimiento de los heteróptros (Insecta) de ríos de Navarra

Se pesentan los resultados de las capturas de heterópteros (Gerromorpha y Nepomorpha) en cinco ríos de Navarra. Se han identificado un total de 91 heterópteros pertenecientes a cuatro especies (Aquarius najas, Aquarius paludum, Hydrometra stagnorum y Nepa cinerea). Cabe destacar la captura de A. paludum, primera cita de esta especie en Navarr

Influencia del régimen de caudales en los movimientos reproductivos de la trucha común en la Península Ibérica

Brown trout (Salmo trutta) is a worldwide distributed species with a great social and economic importance. Its reproductive migration is generally triggered by the decrease in water temperature and the increase in flow rate. Therefore, anthropogenic alterations in these factors may cause negative impacts on its populations. The main goal of this study is to understand the consequences on brown trout migration caused by artificial alterations in the flow regimen. To achieve this, brown trout captures in two fishways (mandatory pass points during migration) located in two rivers of the Iberian Peninsula with different flow regimens and under two different regulation scenarios (regulated and non-regulated) are analyzed. Results show that the increase in flow rate triggers the movement and significantly influences the onset and maintenance of reproductive migration. In addition, the different flow regimens situated migration peaks in different dates. The knowledge about the factors that influence the brown trout migration is crucial to define conservation and management strategies for this species (e.g. definition of environmental flows, fishways operation dates or fishing periods and quotas).La trucha común (Salmo trutta) es una especie ampliamente distribuida a lo largo del mundo y de gran importancia social y económica. En general, el descenso de la temperatura del agua y el aumento de caudal estimulan su migración reproductiva. Por lo tanto, alteraciones antropogénicas de estos factores pueden causar impactos negativos en sus poblaciones. El objetivo de este trabajo es entender las consecuencias de alteraciones artificiales en el régimen de caudales sobre la migración de la trucha común. Para ello, se comparan las capturas de trucha en escalas para peces (puntos obligatorios de paso para la migración) en dos ríos de la Península Ibérica sometidos a diferentes regímenes hidrológicos (atlántico y mediterráneo) y bajo diferentes escenarios de regulación de caudales. Los resultados de este trabajo muestran que el aumento del caudal estimula los movimientos e influye significativamente en el inicio y mantenimiento de la migración reproductora. Además, los diferentes regímenes de caudales provocan diferencias en las fechas medias de migración. Conocer los factores que influyen en la migración de la trucha común será muy útil para definir estrategias para su conservación y manejo (e.g. definición de caudales ecológicos, funcionamiento de pasos para peces, períodos y cupos de pesca, etc.)

Behavioral interactions and trophic overlap between invasive signal crayfish Pacifastacus leniusculus (Decapoda, Astacidae) and native fishes in iberian rivers

The signal crayfish Pacifastacus leniusculus Dana, 1852 is a successful invasive species in the Iberian Peninsula. This is of particular conservation concern, as fish fauna is highly endemic and also threatened within this ecoregion. The aim of this study was to analyze behavioral interactions and trophic overlap between signal crayfish and native fishes in Iberian rivers (northern Spain). Video cameras were used to record fish "dominance/evasion" after spatial encounters with crayfish. Diet composition and isotopic signatures (¿13C and ¿15N) were compared to evaluate the niche overlap. Fish were dominant in 25% of the encounters with juvenile crayfish, whereas this percentage was only 4% with adult crayfish. Observations showed a high fish "evasion" response for Pyrenean stone loach Barbatula quignardi (B¿cescu-Me¿ter, 1967) (>30%). Dietary results showed a high trophic overlap between signal crayfish with the pelagic Pyrenean minnow Phoxinus bigerri Kottelat, 2007 and the benthic loach. However, the isotopic niche overlap was low, with brown trout Salmo trutta L., 1758 showing the highest area (only 0.1 ¿2). Overall, our findings suggest that interferences may occur with native species for food (i.e., benthic invertebrates). Consequently, measures should be applied to control invasive crayfish in Iberian rivers