Assessing commercial fishery impacts on Amazonian floodplain lakes: taxonomic and functional diversity

The Amazon Basin has a history of overexploitation of fish stocks and conflicts between users of the resource. The negative impact of overfishing generally is measured as a decline in the number and relative abundance of fish species, i.e., taxonomic diversity measured as various indices. To date studies have not examined the impacts on functional diversity, i.e., attributes such as trophic position, migration behavior, and life cycle. Co-management initiatives have emerged in this region, aimed at zoning and restricting areas for fishing. We conducted the first study to compare taxonomic and functional diversity of fish assemblages between two floodplain lakes in the Central Amazon, one managed by restricted access by and the other open to commercial fishing, over eight consecutive years. Sampled fish were almost twice as abundant in the restricted lake as in the open access lake. Taxonomic diversity measured as Shannon’s H’ declined in the unrestricted lake but increased in the managed lake. The index of functional divergence (FDiv) remained stable in the restricted lake over the course of the study, while increasing over time in the unrestricted lake. Composition of species differed widely between lakes, which provided a comprehensive picture of the differences between lakes.