Fisheries artisanal diagnosis in the Machadinho reservoir in the upper Uruguay River, Brazil

Abstract

Machadinho reservoir, formed in 2001, is located in the upper Uruguay River. Aiming to diagnose fish production in this reservoir, as well as fisheries composition along the years after its formation, surveys of catches were taken from fishermen that represent the fishing activity in this reservoir between 2003 and 2009. A total of 81 fishermen took part in these surveys, totalizing 1,907 fishing days during the study period. The analysis of fisheries showed an annual average CPUE, based on the biomass of capture of each morphospecies registered per each fisherman per day (kg fisherman1 day^-1), of 9.60 (± 3.27) kg fisherman^-1 day^-1, in 2003, and 18.28 (± 8.57) kg fisherman^-1 day^-1 in 2006, with a subsequent fall over time, reaching 8.65 (± 2.92) kg fisherman^-1 day^-1 in 2009. Twenty-six morphospecies were recorded during the studied period, with emphasis on biomass for the catfish, lambari, mandi, suruvi, carpa, cascudo and traira, being the last three the most captured fishes between 2003 and 2009. Among migratory species, stood out curimba (Prochilodus lineatus) and dourado (Salminus brasiliensis), species which were targeted by experimental storage actions. CPUE values estimated to Machadinho reservoir were relatively low when compared to those of other reservoirs. The observed decline of fisheries in Machadinho reservoir over the years may be related to sedimentation process, increase in fishing effort and to the reduction of nutrients in the reservoir, which are released through spillways.