Colonization, diversity, and seasonality of fishes at pelagic fish aggregating devices (FADs).

The pelagic zone of the ocean can be a challenging environment to conduct research in, and as a result we lack robust baseline abundance and diversity data, compared to what is available in more accessible coastal habitats, to be able to track changes or stressors to the biota in this environment. Many large-scale fisheries target pelagic fish, and much of the information available on these species is based on fisheries-dependent data that may be biased towards hotspots and commercially valuable fishes. Here, a long-term video and visual fish survey was conducted on two subsurface moored FADs in the pelagic waters of the central Bahamas to determine the feasibility of using moored pelagic FADs as tools for collecting fish abundance and diversity data. A wide range of species were documented, including large migratory fish that are the focus of commercial and recreational fisheries, and smaller often overlooked species on which little abundance or seasonality information exists. We found that FADs colonize quickly and reach a peak stable (albeit seasonally cyclical) abundance and diversity within the first several months after deployment. Species richness was higher in video surveys, but abundance was found to be higher in visual surveys except in sharks. Our results highlight the need to tailor survey methods to fit the context and study objective and provide further evidence for the importance of fisheries-independent data in monitoring pelagic species. This article is protected by copyright. All rights reserved.