Abstract

The Deep Coral Reef Monitoring Program (DCRMP) was recently implemented to provide reef fish quantity (i.e., abundance, density) and size (i.e., length frequency) data for the mesophotic reefs off St. Thomas and St. John, US Virgin Islands. DCRMP surveys from 30 to 50m use the same survey design and Reef Visual Census methodology as NOAA’s National Coral Reef Monitoring Program (NCRMP) that survey from 0 to 30m. Combined DCRMP and NCRMP fishery-independent surveys encompass the majority of the regional reef tract shelf (0 - 60m) and DCRMP surveys provide data from the portion of the reef tract commonly targeted by commercial fishers. Deeper surveys (n=162) occurred over three years and were compared to one year of NCRMP data (n=262). Of the 20 fishery target species tested, 40% (8 out of 20) of mature fish had significantly higher densities in the deeper surveys suggesting that for some species these deeper reefs may offer a potential refuge. Size distributions varied by species and survey depth, with some species such as yellowtail snapper (Ocyurus chrysurus), red hind (Epinephelus guttatus), and queen triggerfish (Balistes vetula) showing larger sizes more frequently in the DCMRP surveys, although, largest sizes classes were observed in both DCRMP and NCRMP surveys. Together DCRMP and NCRMP data can be used to provide accurate and unbiased information on fish sizes, densities, and habitat preferences to better inform U.S. Caribbean island-based fishery management actions.

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