Main Hawaiian Islands Deep 7 Bottomfish

Much of the biology of the Deep 7 bottomfish is either not known or was only recently investigated. Age, growth, longevity, and maturity are important biological parameters for understanding the life history of these species.

‘Ōpakapaka—one of the snappers of this group—has set the stage for studies currently underway for the other Deep 7 members. The ‘ōpakapaka was once thought to be a short-lived species that didn’t live longer than 20 years. But several age estimation and validation techniques have revealed that the species can live more than 40 years. This biological information, when combined with an assessment of the fish’s reproduction, make the life history of ‘ōpakapaka the most well understood of the Deep 7 bottomfish.

Scientists have investigated the other Deep 7 snappers to a more limited extent. These fish may grow in a similar manner to ‘ōpakapaka, but there is evidence to support faster growth for ehu, gindai, and lehi. In contrast to the Deep 7 snappers, Hawaiian grouper was recently shown to have quite complex biological characteristics. This species changes sex (female to male) at bigger sizes and older ages and can live longer than 50 years.

NOAA's Pacific Islands Fisheries Science Center is responsible for conducting assessments of the Deep 7 bottomfish stock, used by managers such as the Western Pacific Regional Fishery Management Council to develop annual commercial fishery catch limits. The stock assessment process requires reliable sources of data on catch, fishing effort, biology, and abundance.

Research, Surveys, and Data

NOAA researchers monitor the seven species of bottomfish in Hawai‘i by working with local fishermen and deploying underwater camera technology as part of the Bottomfish Fishery-Independent Survey in Hawaiʻi (BFISH). These annual surveys assess the numbers and sizes of bottomfish around the main Hawaiian Islands.

We collect data at various scientifically selected sites around all eight of the islands by working with local fishermen through the Pacific Islands Fisheries Group. At sea, our researchers also collect video footage of bottomfish in their deepwater habitat using an underwater camera system called MOUSS (modular optical underwater survey system). We are committed to cooperative research with local fishermen to build relationships with the community and continually improve the collection of scientific information. Data collected on BFISH surveys guides sustainable fisheries and resource management for the Deep 7 species in Hawai‘i and the overall ecosystem.

The more details we know about a fish species, the more the Council can accurately manage it. We estimate deep 7 bottomfish biological and life history information using biological samples of fish collected during research cruises, as well as samples purchased from and donated by local fishermen. After we identify the species and measure and weigh all the fish, we extract fish gonads to reveal information on sex and reproductive status. We also extract otoliths (ear bones), which display annual rings similar to tree rings and are used to estimate age by counting these rings. Bomb radiocarbon dating of otoliths validates the age estimates from counting otolith rings. After we estimate the fish’s individual age and reproductive status, the next step is to examine growth rates and mortality rates.

NOAA scientists combine data from the annual BFISH surveys and biological information, along with data reported by bottomfish fishers on catch and effort, into an analysis called a stock assessment. The stock assessment estimates the total number of Deep 7 bottomfish around Hawaiʻi and how many can be sustainably harvested into the future, and the assessment forms the basis for federal management regulations recommended by the Council.