Ecological and economic impacts of exotic fish species on fisheries in the Pearl River basin.
The Pearl River basin has the highest fish diversity in China and has been identified as a global hotspot of fish biodiversity. Twenty-three exotic fish species are distributed in the Pearl River basin, tilapias, North African catfish, roho labeo, and mrigal carp have become important exotic species to the local fisheries economy. We investigated catches in the Pearl River basin using an isometric random sampling method and analyzed the ecological and economic impacts of exotic species. The results show that the biomass percentage of exotic species in the upper reaches of the Pearl River basin was higher than that in other regions, and was higher in the drought season than in the flood season. Pearson correlation analysis indicated that the abundances of exotic species were significantly positively correlated, which indicates that they might have joint impacts. Although exotic species enhance fishing production, they decrease the income of fishermen. A multiple linear model indicated that as the biomass percentage of exotic species increased by one percent, the income decreased by 20.19 RMB/vessel/month (RMB, Ren Min Bi, Chinese currency) at a given site. This inevitably caused the fishermen to catch more fish to increase their income. It is urgent to assess the invasion potential of introduced species in southern China and limit both the biomass and spread of exotic species.