Artisanal fisheries in urban reservoirs: a case study from Brazil (Billings Reservoir, Sao Paulo Metropolitan Region)

Billings Reservoir is an urban reservoir located in the Sao Paulo Metropoli tan Region. Tt supports 101 active artisanal fishermen. To describe this fi shery, landings were recorded daily between February 1996 and January 1997 at Colonia (23 degrees 50' 57" S; 46 degrees 40' 02" W). In every landing, a data collector recorded catch, effort, fishing gears and fishing grounds. A total of 147 593 kg of fish were recorded in 3515 fishing trips. The exo tic Nile tilapia, Oreochromis niloticus (L.), was the main species exploite d (81.4% of the annual catches). Five other species were also targeted: the characid Astyanax eigenmaniorum (Cope) (13.0% of the annual catches); the erythrinid Hoplias aff malabaricus (Block) (2.1%); the exotic cyprinid Cypr inus carpio L. (Campos & Fernandez-Yepez) (2.4%); the curimatid Cyphocharax modestus L. (1.1%); and the pimelodid Rhamdia sp. (0.1%). Two main groups of fishermen were discriminated using Principal Components Analysis; these were associated with the type of fishing gear and fishing strategies, i.e. those who exploited Nile tilapia with cast nets and beating gill nets, and those who exploited other species with set gill nets. Management and mainte nance of this fishery should consider the positive top-down effects that Ni le tilapia could have in controlling eutrophication and also the social ben efits.