Remote Video Technology Allows Survey of Jacks and Sharks in Deeper Coral Reef Habitat

During a recent research mission to the Northwestern Hawaiian Islands, scientists in the PIFSC Coral Reef Ecosystem Division (CRED) used video cameras to observe and quantify fish populations in coral reef habitat previously unexplored, waters too deep for the usual scuba diver surveys. During May 19–31, 2014, a team led by CRED scientist Jacob Asher of the University of Hawaii Joint Institute for Marine and Atmospheric Research surveyed reefs at French Frigate Shoals using baited and unbaited remote underwater video systems (BRUVs) in waters up to 100 m in depth, well below depths comfortably reached by scuba divers (<30 m). Also involved in the BRUV operations were Biological Science Tech Jamie Barlow of PIFSC and Fishery Policy Analyst Emily Crigler from the NOAA Fisheries Pacific Islands Regional Office (PIRO).

A BRUV is a rudimentary metal frame placed on the seafloor and enclosing two stereo video cameras that simultaneously film fishes as they swim in front of the cameras' lenses. By synchronizing the images from each camera and using special software, the scientists can accurately identify and enumerate fishes that pass in front of the BRUV and estimate their size and position. The BRUV was deployed from a small rigid inflatable boat launched from the Honolulu-based research vessel Searcher.

JIMAR scientist Jake Asher (left) and PIRO policy analyst Emily Crigler (right) prepare to deploy BRUV underwater video camera 
        systems on the seafloor at French Frigate Shoals in the Northwestern Hawaiian Islands.
JIMAR scientist Jake Asher (left) and PIRO policy analyst Emily Crigler (right) prepare to deploy BRUV underwater video camera systems on the seafloor at French Frigate Shoals in the Northwestern Hawaiian Islands.

Data collected during this mission and from another NHWI survey planned for September 2014 will be used to assess the abundance and distribution of roving piscivores, particularly sharks and jacks. Data from the NHWI will be compared with BRUV data gathered in the main Hawaiian Islands in recent years. A core goal of CRED's work with diver-independent BRUV technology is to augment the findings from CRED's routine coral reef surveys—conducted by scuba divers in waters of depths <30 m. By combining results of the two survey methods, we can achieve a better understanding of coral reef fish communities over a much broader depth range, from shallow reefs down to depths of 100m.