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

Abstract

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 dammed in 1962. This study is about the giilnet fishery located at the impounded portion of the River Piracicaba, and the possible influences of habitat alterations on the fish catch composition. Fish landings were recorded three days each month between October 1994 and September 1995. Data on the weight 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 route by the impoundment. Migratory Characiforms, on the other hand, have increased in the fishery. The river organic pollution probably favoured the spread of fishes that can adapt to low oxygen conditions. Forest clearance, which reduces forestry food resource availability, could be decreasing omnivorous fishes in the fishery. Fish landings in the River Piracicaba fishery suffered change in its composition in the past 11 years. The environmental alterations that had occurred in the Piracicaba River basin, like impoundment, pollution, and deforestation, can be important factors influencing such changes.

O que dizem as pesquisas acadêmicas sobre os impactos das hidrelétricas na pesca artesanal?

“…Somente três dos estudos se deram nos períodos pré e pós barragem (BAISRE;ARBOLEYA, 2006;COSTA et al, 2012;BHAUMIK et. al., 2017 (BERKES, 1982;COSTA-PIERCE, 1997;SILVANO;BEGOSSI, 1998;SANTOS;OLIVEIRA, 1999;AVAKYAN et al, 2002;BAIRD et al, 2004;AGOSTINHO et al, 2004;TORDECILHA-PETRO et al, 2005;ANGELINE et al, 2006;BAISRE;ARBOLEYA, 2006;JIMÉNEZ-BADILLO, 2006;AGOSTINHO et al, 2007;ARAYA et al, 2008;BARAN;MYSCHOWODA, 2009;SHORK et al, 2009;GARAVELLO et al, 2010;KANTOUSSAN et al, 2010;QUARCOOPONE et al, 2011;COSTA et al, 2012;DORIA et al, 2012;GÓRSKI et al, 2012;ORR et al, 2012;DEINES et al, 2013;USUNOVA et al, 2015;COOPER et al, 2016;DUPONCHELLE et al, 2016;GREEN et al, 2016;KANO et al, 2016;BHAUMIK et al, 2017). , 1998;AGOSTINHO et al, 2004;AGOSTINHO et al, 2007;KANTOUSSAN et al, 2009;SCHORK et al, 2009;MARUYAMA et al, 2009;HALLWASS et al, 2011;…”

“…Outro tema importante abordado em parte dos estudos foi sobre introdução / manutenção de espécies exóticas nos reservatórios e seus efeitos nas espécies nativas (AGOSTINHO et al, 2004;CARVALHO, 2011A;CARVALHO, 2011B;CARVALHO, 2013;SCHORK et al, 2013;DAVID et al, 2016;SANTA-FÉ et al, 2016 , 1998;BAIRD et al, 2004;TOS et al, 2009;DORIA et al, 2012;HEGG et al, 2015;DUPONCHELLE et al, 2016;SIDDONS et al, 2017). No caso de Tucuruí, os grandes bagres migradores podem ter sido os mais prejudicados com a interrupção do fluxo migratório promovido pela barragem (GARAVELLO et al, 2010).…”

Fish Biodiversity and Fishing Activities at Njoboliyo Lake, Adamawa State, Nigeria

“…These lacks of high availability of other commercially valued species may be caused by overfishing or alterations in the environmental conditions of the lakes, like persistence seasonal flooding from Lagdo dam which negatively will affect the reproductive ecology of the various fish species in the lakes [16,22,28,29]. Study also shows that Hydrocynus, L. niloticus, Protopterus and Heterotis were seen rarely at Njoboliyo, confirm the characteristics of those fish adaptive to where there are macrophytes acting as shelter and provide available food generated by the decaying vegetation [25].…”

“…The 29% and 25% of Drag and Cast nets usage at Njoboliyo is recorded due to the concentrated large surface area of water free from vegetation that allows easy operations of these gears. The low percentages usage of gill net is because of the fact that no enough space to operate it due to disturbances from the fishers throwing Cast Nets and Drag Nets, and mostly the recommended mesh size to be used as promulgated by , should not less than 76 millimeters and thus the fishers cannot adopt the use of the gear since it will give low yield or no catch at all due to presence of smaller fishes at the lakes due to overfishing [4,24,25] thus most fishers react by reducing their fishing net mesh size by moving into other like, Drag net, Set net, Traps, where the fishers use less smaller mesh size to construct [26][27][28].…”

“…The conditions responsible for these threatened species may vary either as a result of overfishing due to the demand or affected by macrophytes due to ecosystem degradation cause by the persistent floods from Lagdo dam yearly [16,25,28].…”