Abstract

Mesophotic coral ecosystems (MCEs) are challenging to assess due to both depth and geomorphology, but their characteriza-tion is important for the assessment of fisheries resources habitat health and threatened species. Surveys based on rebreather and mixed-gas diving are costly and limited in bottom time. Patchy distributions and depth variations further complicate MCE assessments. We report on use of small Remotely Operated Vehicles (ROVs) to characterize habitats and resources to depths of 130 m, primarily off La Parguera and Ponce, Puerto Rico. The ROV is equipped with parallel laser beams for size estimation, and a sampling claw, and it can be deployed off of small boats using a portable generator. Preparation times for ROV dives are shorter than other methods. All video images are recorded on digital tape using a camcorder, which provides a permanent record and allows for subsequent analyses by experts in various taxonomic or scientific disciplines. These surveys allow for baseline observations of fish communities and benthic cover, habitat use (including nursery areas) and behavior. Results to date include (1) the documenta-tion of new areas of MCE development, (2) the abundance and distribution of threatened species, (3) the deep occurrence of commercially shallow species, (4) documenting the depth and spatial extent of spawning aggregations, (5) the apparent deep refugia for overfished shallow species, (6) the occurrence of deeper commercially important species, (5) the impacts of sedimentation on MCEs, and the colonization of MCEs by invasive lionfish. ROVs are excellent companions to any mesophotic research diving program.

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