Research Seeks Fishery-independent Methods to Assess Reef Fish Stocks in the Main Hawaiian Islands

BRUVS are stereo-video samplers that can provide estimates of fish abundance and size structure.
BRUVS are stereo-video samplers that can provide estimates of fish abundance and size structure.

PIFSC researchers are pressing forward to develop fishery-independent methods for assessing coral reef fish stocks. During an expedition from September 1 to September 13, 2012, aboard the NOAA Ship Oscar Elton Sette and the chartered M/V Huki Pono, PIFSC researchers and collaborating investigators conducted surveys of coral reef fish assemblages in the main Hawaiian Islands to compare the performance of two fishery-independent methods at two depth ranges. The paired operations involved stationary point counts conducted by scuba divers at depths of 0–30 m and deployment of BRUVS (baited and unbaited remote underwater video stations) at depths of 1–100 m in waters around Oahu, Maui, Lanai, and Molokai.

Participants in the research included staff from the Coral Reef Ecosystem Division (CRED), the Fisheries Research and Monitoring Division, the Joint Institute for Marine and Atmospheric Research of the University of Hawaii at Manoa, the Hawaii Department of Land and Natural Resources, and the University of Western Australia.

Visual survey data gathered on the expedition will supplement data gathered by CRED scientists and partners as part of the Pacific Reef Assessment and Monitoring Program. At some study locations, the shallow-water (< 30 m) survey design involved use of both survey methods. Comparison of data from each method will lead to a better understand the strengths and weaknesses of different of survey approaches.

This expedition was among the first to survey the entire depth range of inshore reef fishes from the maximum safe diving limit of 30 m for scuba divers down to 100 m. A similar coordinated study using scuba diver surveys and remote video technology was conducted around Tutuila, American Samoa, in April 2012. In addition to extending the depth range over which coral reef fish assemblages can be surveyed, remote video deployments potentially can enable the study of behavioral responses of reef fish— particularly large, roving predatory fish— in the presence of divers. There is particular interest in using these fishery-independent methods to assess differences in fish stocks between fished and un-fished locations.