Research Aims to Advance Bottomfish Stock Assessment in Main Hawaiian Islands

September 22, 2012
NOAA Ship Oscar Elton Sette. NOAA photo by Benjamin Richards.
NOAA Ship Oscar Elton Sette. NOAA photo by Benjamin Richards.

Since 2011, the NOAA Pacific Islands Fisheries Science Center has been engaged in a quantitative comparison of fishery-independent methods for sampling bottomfish stocks in the main Hawaiian Islands (MHI) with a view to improving our understanding of MHI bottomfish assemblages and our ability to assess these populations. The studies are part of a key PIFSC mission to improve scientific understanding of fish resources and related ecosystems and improve assessments of regional fish stocks.

On September 22, the NOAA Ship Oscar Elton Sette embarked on a 12-day research expedition to assess the strengths and weaknesses of these bottomfish sampling methods and the types of data that can be collected with each method. The data will be compared quantitatively and used in concert to develop ways to improve the accuracy of bottomfish stock assessments. Better assessments will enable improved management of these important resources.

At any point in time, in a given area of bottomfish habitat there is a certain true, but unknown assemblage of bottomfishes. Each sampling method gives a different "picture" of that true assemblage and their abundance. By conducting designed experiments comparing sampling methods and by appropriately combining and calibrating the results from the various methods, stock assessment scientists are able to improve the measures of abundance they use in quantitative assessment models.

From September 22 to October 3, a team of scientists on the Sette will be engaged in bottomfish sampling experiments under the leadership of PIFSC biologist Dr. Benjamin Richards. The research will focus on designated sampling areas leeward of the island of Maui and will be conducted in water depths of 100 to 400 meters. The research team on the Sette includes scientists from PIFSC and colleagues from the Alaska Fisheries Science Center, the University of Hawaii's Joint Institute for Marine and Atmospheric Research, and the University of Miami Rosenstiel School for Marine and Atmospheric Science. This group will carry out bottomfish sampling using baited remote underwater video stations (BRUVS, deployed using the Sette's 19-ft SafeBoat), EK60 active acoustics (echosounder), and a towed stereo-video camera system (TOAD) used to optically validate EK60 results. As part of the designed experiments, other types of fishery-independent sampling will be conducted concurrently. Baited stereo-video camera stations (BotCams) will be deployed by collaborating University of Hawaii scientists on the R/V Huki Pono and handline fishing for bottomfish will be conducted from small commercial fishing vessels by contracted members of the Pacific Island Fisheries Group.

Surveys using alternative sampling methods will be generally be focused in the boxes labeled B, D and E in waters leeward 
                 of the island of Maui.  Exact deployment locations for the BRUVS and BotCam and survey track lines for the EK60 will be 
                 determined by weather conditions.
Surveys using alternative sampling methods will be generally be focused in the boxes labeled B, D and E in waters leeward of the island of Maui. Exact deployment locations for the BRUVS and BotCam and survey track lines for the EK60 will be determined by weather conditions.