The artisanal fishery of the River Piracicaba (Sao Paulo, Brazil): fish landing composition and environmental alterations

Large reservoirs are increasing in number in South America and Brazil, and are exploited by fishers. The River Piracicaba receives several pollutants discharged from industries and residences, and had its downstream portion d ammed in 1962. This study is about the gillnet fishery located at the impou nded portion of the River Piracicaba, and the possible influences of habita t alterations on the fish catch composition. Fish landings were recorded th ree days each month between October 1994 and September 1995. Data on the we ight of fishes caught (kg per species) in 248 fish landings were collected. The catch of the large migratory catfishes (Siluriformes) decreased in the last 10 years, probably because of the interruption of their migratory rou te by the impoundment. Migratory Characiforms, on the other hand, have incr eased in the fishery. The river organic pollution probably favoured the spr ead of fishes that can adapt to low oxygen conditions. Forest clearance, wh ich reduces forestry food resource availability, could be decreasing omnivo rous fishes in the fishery. Fish landings in the River Piracicaba fishery s uffered change in its composition in the past 11 years. Thr environmental a lterations that had occurred in the Piracicaba River basin, like impoundmen t, pollution, and deforestation, can be important factors influencing such changes.