Baited remote underwater video as a promising nondestructive tool to assess fish assemblages in clearwater Amazonian rivers: testing the effect of bait and habitat type

Abstract

Baited remote underwater video (BRUV) systems are being used in marine ecosystems as a nonextractive, cost-effective method of assessing the fish fauna with minimal species bias. This technique has had limited applications in freshwater ecosystems. Rheophilic fish assemblages of the Xingu River, a clearwater Amazonian river in Northern Brazil, were sampled with BRUV systems. Two-hour video recordings were collected using five different bait treatments (sardine, croaker, cat food, sweet corn, and no bait) in two lotic habitat categories (rocky and sandy bottoms). A total of 2460 fish from 56 taxa and 13 families were recorded from the 80 BRUV deployments. Significantly different fish assemblages, species richness, and abundance were detected between habitat types and among treatments. Our results suggest that the use of crushed sardines as a standardized bait optimizes the sampling recording the highest species richness, relative abundance, and number of exclusive species of rheophilic fish in clearwater Amazonian rivers. The data also highlight the unique fish diversity of the Xingu River prior to the expected large-scale environmental degradation resulting from the forthcoming operation of the Belo Monte hydroelectric power plant.