Seasonal dynamics of fishery at the Piracicaba River (Brazil)

This study describes and analyses the small-scale fishery in the Piracicaba River, located at the southeastern Brazil, with regard to the diversity, quantity and composition of fish catches both by seasons and gillnets mesh sizes. We recorded fish landings monthly during a year. collecting data on the weight of fish caught (kg per species) and on the quantity of nets utilized ton square meters). During the study period the fishermen used gillnets, capturing 8382 kg of fish from 43 species. Of these, only 22 fish species were of commercial value, and six dominated the catches year round (90% of total weight). The species composition and quantity of fish caught varied between seasons and gillnets mesh sizes. During the autumn and winter, fishermen relied more on the medium sized mesh gillnets, exploiting closer fishing grounds and capturing a greater diversity of fish, including those of low commercial value. In the spring and summer, catches were of lower diversity, and more specialized large mesh gillnets were used, harvesting large and more desired fish in more distant fishing grounds. Such seasonal variation in fishing strategy reduces fishing pressure among several fish species along the year, and should be important in reducing fish stock depletion at the Piracicaba and at other impounded and altered tropical river basins. (C) 2001 Elsevier Science B.V. All rights reserved.