Expedition in Maui Triangle Evaluates Methods for Next-Generation Assessment of Hawaii Bottomfish Stock

April 5, 2014

Researchers from the NOAA Pacific Islands Fisheries Science Center (PIFSC) are leading an expedition to develop fishery-independent methods of assessing the abundance of deepwater bottomfish around the main Hawaiian Islands. The bottomfish population supports important commercial and recreational fisheries in Hawaii.

The research expedition is being carried out by a team of PIFSC scientists on the NOAA Ship Oscar Elton Sette in collaboration with colleagues from the Northwest Fisheries Science Center, University of Hawaii at Manoa (UHM), Joint Institute for Marine and Atmospheric Research at the University of Hawaii at Manoa, and the Pacific Islands Fisheries Group (PIFG). The Sette departed her home port at Ford Island, Pearl Harbor, on April 5, 2014, for the study area in waters of the Maui Triangle, an ocean region delineated by the islands of Maui, Molokai, Lanai, and Kahoolawe. Joining the Sette in the expedition will be the chartered research vessel Huki Pono and 3 PIFG cooperative research bottomfish fishing vessels. Working together, the vessels will collect information on the abundance of bottomfish in the study area using hook-and-line fishing as well as stationary and mobile stereo-underwater video camera gear.

LT Faith Knighton is leading the 15-day expedition, with Dr. Ben Richards serving as Science Advisor. The expedition objective will be to accomplish a near-simultaneous survey of deepwater bottomfish in the Maui Triangle region using 3 fishery-independent methods, or gears: an autonomous underwater vehicle (AUV) stereo-video camera system (deployed from the Sette), baited underwater stereo-video camera systems (or BotCam, deployed by a UHM team aboard the Huki Pono), and cooperative research hook-and-line fishing from the PIFG vessels.

The three survey gears will be intensively deployed within a stratified-random survey grid in the Maui Triangle region. Survey grids 500 m x 500 m and were chosen at random in proportion the prevalence of their habitat type in the overall survey domain and taking into account the variation in the data from each habitat stratum as sampled during prior research missions. Survey grids were selected shortly before project mobilization to best allow for prevailing weather conditions, proximity to ports, and patterns of fish abundance, and to mitigate impacts of the fishing operations on activities of local fishermen and management regions.

Each survey method will provide information helping to assess bottomfish abundance within the survey area and the resultant data will enable researchers to better understand variability in the measures of bottomfish abundance both within each gear as well as among the different gears and habitats.

The results of this portion of the project will be used by the PIFSC Stock Assessment Program to evaluate the potential future development of an operational, fishery-independent, non-extractive, non-lethal survey methodology to estimate size-structured abundance within the Hawaii Deep 7 Bottomfish assemblage. The fishery-independent approach can supplement the standard method presently used for measuring changes in bottomfish abundance, catch-per-unit-of-fishing-effort (CPUE) derived from commercial bottomfish hook-and-line fishery data.

Bottomfish assessment research will be carried out at numerous locations on soft-bottom and hard-bottom habitats in the Maui 
        Triangle area. Colored squares indicate the locations of sampling grids in different types of habitat.
Bottomfish assessment research will be carried out at numerous locations on soft-bottom and hard-bottom habitats in the Maui Triangle area. Colored squares indicate the locations of sampling grids in different types of habitat.