Researchers Study Biology and Habitat of Deepwater Bottomfish in American Samoa

March 12, 2012

A research team from the NOAA Pacific Islands Fisheries Science Center has embarked on a 15-day study to better understand the life history of bottomfish species in deepwater bank habitats of American Samoa and describe oceanographic characteristics of the area. The investigation is being conducted from the NOAA Ship Oscar Elton Sette. The team is made up of PIFSC staff and collaborators from the University of Hawaii Department of Oceanography and Joint Institute for Marine Atmospheric Research, the American Museum of Natural History, the American Samoa Department of Marine and Wildlife Resources, and NOAA's Teacher at Sea Program.

The NOAA Ship Oscar Elton Sette is named for the founding Director of the Honolulu Laboratory, which became the NOAA 
        Pacific Islands Fisheries Science Center in 2003.  Dr. Sette was a pioneer in the development of fisheries oceanography. NOAA photo
        by Benjamin Richards.
The NOAA Ship Oscar Elton Sette is named for the founding Director of the Honolulu Laboratory, which became the NOAA Pacific Islands Fisheries Science Center in 2003. Dr. Sette was a pioneer in the development of fisheries oceanography. NOAA photo by Benjamin Richards.

Under the leadership of PIFSC scientist Dr. Donald Kobayashi, the research team will use a variety of methods to collect critical biological and oceanographic data. To learn more about rates of growth and ages of bottomfish, the team will catch bottomfish specimens using hook-and-line gear, operating from small boats launched off the Sette. They will collect biological tissue samples from each fish specimen, including fin spines and otoliths (ear bones) that will later be examined in the laboratory to reveal information on the fish's age and growth. Other samples will support studies of bottomfish maturity and diet. Results of the research will help PIFSC better assess the status of the bottomfish population and improve scientific advice to managers responsible for ensuring sustainable use of the bottomfish resource.

Across the bottomfish fishing grounds, oceanographers will conduct surveys to measure physical, chemical and biological characteristics of the water column. At designated locations, they will lower a CTD instrument into the water to collect measurements of salinity, temperature, oxygen content, and concentration of chlorophyll and nutrients at various depths. They will also tow a Cobb midwater trawl and several smaller sampling nets through the water to sample nektonic fish, plankton, and neustonic organisms in the area. Analysis of these data will provide insights on the biological productivity of the area and geographic patterns of the forage organisms available to larger fish and other marine life at upper levels of the food chain, including species that are commercially and ecologically important.

The bottomfish research will focus on 3 offshore banks of American Samoa (Northeast Bank, Two Percent Bank, and South 
                Bank). In the event of inclement weather, 2 backup study locations have been designated (Tutuila and Manua).
The bottomfish research will focus on 3 offshore banks of American Samoa (Northeast Bank, Two Percent Bank, and South Bank). In the event of inclement weather, 2 backup study locations have been designated (Tutuila and Manua).

Besides the primary mission objectives, the research team will carry out several ancillary projects. One will be a study to measure the "catchability" of deepwater bottomfish associated with hook-and-line fishing. To do this, the research team will deploy a baited video camera (BotCam) just above the seafloor. The camera has low-light-level capabilities that allow it to record video of fish attracted to bait released from a canister attached to the camera frame. The captured video footage will be analyzed along with data from hook-and-line fishing conducted by the research team simultaneously at the BotCam location. From this analysis, scientists will learn more about the attraction and capture characteristics of deepwater hook-and-line fishing gear, and the interspecific and size-specific behavioral interactions of fish. This knowledge will add to an understanding of the linkage between fish catch statistics and fish abundance.

In a second ancillary study, the research team will document patterns in the abundance of microplastic debris in the water column. Neuston nets and subsurface plankton nets will be used to quantify distribution of the debris. Stomachs from fish specimens captured by hook-and-line and in the Cobb midwater trawl hauls will also be collected and later examined to learn about the presence of microplastic debris in the gut contents.