Desenvolvimento do método hidro-acústico como ferramenta de gestão piscicola e da qualidade ecológica em albufeiras: aplicação à Albufeira do Maranhão

Mestrado em Gestão e Conservação de Recursos Naturais - Instituto Superior de Agronomia / Universidade de ÉvoraFisheries acoustics is a methodology of quantitative assessment of the fish populations, which, besides being efficient is simultaneously fast and non-intrusive, enabling access to information on the fish density, biomass and size distribution. This method, except for an essay from the 80’s (Brabrand et al. 1986, 1989), has never been used in Portuguese reservoirs. The objective of this work was the development of fisheries acoustics as a tool for fisheries management and ecological quality evaluation in the Maranhão reservoir. A methodology of successive optimization was defined, comprising 7 stages which included: selection and acquisition of the scientific echosounder and transducer, optimizing the operation of the echosounder/boat set; vertical and horizontal, diurnal and nocturnal surveys, during the thermal stratification and mix of the reservoir and assessment of the fish population with multimesh gillnets. It was observed a strong variability of the fish density, whether in spatial or in bathymetric axis, according to the time of day and season, associated with fish detection by horizontal and vertical, diurnal and nocturnal echosounding. The results obtained foresee an important role of fisheries acoustics for fisheries management and ecological quality evaluation in Portuguese reservoirs