Caroline ARANTES

Fish Biomass and Functional Diversity Are Positively Associated with Forest Cover in the Amazon River Floodplains

Authors:

Caroline ARANTES, Kirk WINEMILLER

Texas A&M University, United States of America

Abstract

Floodplains are among the most biologically productive, but also threatened ecosystems in the world with global loss exceeding 60%. Floodplain forests have been severely impacted by the development of hydropower and agriculture, but the extent to which floodplain forest loss affects fish biomass, and consequently fishery production, remains unknown. Here, we used fisheries data and descriptions of satellite-mapped landscape features to test the extent to which fish biomass in the lower Amazon River floodplains is related to forest cover. Fish stocks were surveyed in 462 floodplain habitats distributed along a gradient of land cover, ranging from nearly pristine to severely deforested. We modeled total fish biomass in each habitat plus subsets of species possessing different functional traits and relative importance in the fishery as functions of forest cover. Resulting estimates were used to infer fish production and vulnerability of fish stocks in relation to forest loss. Forest cover generally was associated with greater fish biomass and the strength of this relationship varied according to functional group. Habitats within catchment areas with greater forest coverage had significantly greater total fish biomass. Forest also had positive and relatively strong relationship with the biomass of species important in local fisheries, and with several functional groups defined by life history, trophic ecology, migratory behavior, and body shape and microhabitat use. Other species, including some that would be considered habitat generalists and species directly dependent on autochthonous resources (e.g., planktivores), did not vary significantly in relation to forest cover. These results suggest that forest loss in the lower Amazon decreases fishery production and alters the biomass distribution of functional groups.