Mudanças a longo prazo na comunidade de peixes de uma baía tropical do sudeste do Brasil (1987-2013): perda gradativa da biodiversidade da zona interna para zona externa

Abstract

Fish communities in developing countries have, in many cases, showed a decrease in the species richness and abundance over time as a result of anthropogenic impacts. We analyzed fish communities of three zones (inner, middle and outer) of the Sepetiba Bay (Southeastern Brazil) using identical sampling methods (bottom trawl) during four different time periods: 1987–1988; 1993–1995; 1998–2001 and 2012–2013. A total of 33,140 fish representing 127 species in 88 genera and 41 families were recorded. Our results revealed highly significant and consistent differences in the fish community structure among the bay zones, and a decreased in the fish richness and abundance over the time period. Changes in fish richness and abundance were related mostly to a sharp decrease that occurred in the inner bay zone, the most impacted bay area, and, to a lesser extent, in the middle zone between the two first (1987–1988 and 1993–1995) and the two latter time periods (1998–2001 and 2012–2013), whereas the outer zone remained comparatively stable over time. Spatial changes in the fish community structure among the bay zones were related to differences in salinity, transparency and depth with this latter variable, together with other factors, acting as a buffer for stabalizing community changes; however, these environmental variables explained little of the variation in the temporal changes. The most important changes over time in abundant species were the numerical decreases of the Ariid Cathorops spixii, the serranid Diplectrum radiale and sciaenid Cynoscion leiarchus, and increases of the sciaenid Micropogonias furnieri and the marine catfish Genidens genidens, with this latter species restricted to the inner and middle zones. This study adds long-term information on gradual fish community changes along spatial gradients of environmental and anthropogenic influences in embayment systems. It is perhaps timely to link conservation and management planning with historical information to protect fish biodiversity in tropical developing countries