Environmental influences on fish assemblage distribution of an estuarine coastal lagoon, Ria de Aveiro (Portugal)

Abstract

SUMMARY: Fish assemblage was examined for patterns in spatial and seasonal structure within an estuarine coastal lagoon, Ria de Aveiro. Two years of variation in abiotic conditions were recorded to identify factors responsible for maintaining the structure of fish assemblages. Nine sites were sampled monthly with a traditional "chincha" beach-seine net between November 1998 and October 2000. Fish abundance and biomass changed significantly between sites. Temperature was found to be the most important abiotic factor affecting the abundance (number of fish) distribution of fish assemblage, which is more related to seasonal migrations than to spatial migrations. Salinity was the most important abiotic factor affecting the fish biomass, with temperature also having a major influence. The other abiotic parameters analysed also showed some influence on the distribution of fish, although, isolated from the other controlled and/or uncontrolled factors, they could not fully explain all the differences between assemblages. Feeding analysis indicates that fish assemblage is mostly dependent on small benthic and pelagic crustaceans and/or detritus, although they can feed opportunistically on other prey. The low spatial segregation of fish in relation to feeding preference indicates that, in a food-rich lagoon such as Ria de Aveiro, the environmental-biological interactions appear to have a greater effect on fish distribution than do biological interactions.Key words: fish fauna, diversity, environmental factors, Ria de Aveiro. RESUMEN: INFLUENCIAS AMBIENTALES EN LA DISTRIBUCIÓN DE LA COMUNIDAD DE PECES EN UNA LAGUNA COSTERA ESTUÁRI-CA, RIA DE AVEIRO (PORTUGAL). -La estructura espacial y estacional de la comunidad de peces fue examinada en una laguna costera estuárica, la Ria de Aveiro. La variación de las condiciones abióticas fue registrada durante dos años para identificar los factores responsables de mantener la estructura de las comunidades de peces. Nueve estaciones fueron muestreadas mensualmente con una red tradicional de arrastre tipo "chincha", entre noviembre 1998 y octubre de 2000. La abundancia y la biomasa variaron perceptiblemente entre las estaciones. La temperatura fue el factor abiótico más importante que afectó la distribución de la abundancia (número de individuos) de la comunidad de peces, fenómeno que se relaciona más con las migraciones estacionales que con las migraciones espaciales. La salinidad fue el siguiente factor abiótico más importante que afecta la biomasa de peces. Los otros parámetros abióticos analizados también demostraron una cierta influencia en la distribución de los peces, aunque, aislados de los otros factores controlados e incontrolados, no podrían explicar completamente todas las diferencias halladas en la comunidad. Los análisis de alimentación indican que la comunidad de peces es principalmente dependiente de los crustáceos de pequeño tamaño así como de detritos bentónicos y pelágicos, aunque pueden alimentarse de forma oportunística de otras presas. La baja segregación espacial ...

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