Unsupported Browser Detected

Internet Explorer lacks support for the features of this website. For the best experience, please use a modern browser such as Chrome, Firefox, or Edge.

Developing a Management Area for Hawaiʻi Pelagic False Killer Whales

November 06, 2023

Defining a new management area that accounts for what is known about the distribution of Hawaiʻi pelagic false killer whales outside the Hawaiian Islands EEZ.

Most species of cetaceans in the central Pacific Ocean are thought to have extensive open-ocean distributions, both within and beyond the boundaries of the U.S. Exclusive Economic Zone (EEZ).

Stocks assessed and managed under the U.S. Marine Mammal Protection Act (MMPA) are generally designated following identification and delineation of demographically independent populations (DIPs) within species (NMFS 2021). Although, within vast open ocean areas, the number and range of DIPs is often unknown and very difficult to assess without extensive telemetry, genetic, distribution, or habitat datasets (Martien et al. 2019a).

Most large-scale assessment surveys for cetaceans are conducted within the U.S. EEZ, leading to an incomplete assessment of abundance and status across the full ocean-basin range of these species. In Hawaiʻi, NOAA Fisheries recognizes most cetacean stocks with pelagic distribution as transboundary with ranges including, and extending beyond the EEZ, around the Hawaiian Islands (Hawaiian Islands EEZ); however, the formal assessment of these stocks is based on the Hawaiian islands EEZ, since it is within this space that we can often best estimate both abundance and removals from fisheries or other human-caused impacts.

Defaulting to an EEZ area is not necessarily aligned with current assessment guidance (NMFS 2023) and other options for designating management units should be considered, particularly when high rates of human-caused mortality and serious injury (MSI) may be adversely impacting animals outside of the U.S. EEZ.

In 2010, NMFS convened the False Killer Whale Take Reduction Team (FKW TRT) as a response to unsustainable levels of bycatch of the Hawaiʻi pelagic stock of false killer whales by the Hawaiʻi-based deep-set longline fishery.

Since that time, with an assessment based on the Hawaian Islands EEZ only, there has been a notable spatial mismatch in the assessment approach for this stock. The Hawaiʻi-based deep-set fishery area has been expanding to the northeast on the high seas (outside of the Hawaiian Islands EEZ) over the last two decades (Woodworth-Jefcoats et al. 2018).

Following the implementation of the Take Reduction Plan in 2012, this fishing area shift has also been accompanied by an increase in MSI on the high seas (Carretta et al 2023, Appendix). With an assessment approach currently based on the Hawaiian Islands EEZ, the impact of the deep-set fishery on the portion of the stock outside of U.S. waters cannot be assessed or managed effectively.

Therefore, we have defined a new management area that accounts for what is known about the distribution of Hawaiʻi pelagic false killer whales outside the Hawaiian Islands EEZ. This report serves to provide the rationale for the proposed management area along with additional information about the datasets available to support this boundary choice and other management areas that were considered.


The Pacific Islands Fisheries Science Center of NOAA’s National Marine Fisheries Service uses the NOAA Technical Memorandum NMFS-PIFSC series to disseminate scientific and technical information that has been scientifically reviewed and edited. Documents within this series reflect sound professional work and may be referenced in the formal scientific and technical literature.

Oleson, EM, Bradford, AL, Martien, KM 2023. Developing a management area for Hawai'i pelagic false killer whales U.S. Dept. of Commerce, NOAA Technical Memorandum NOAA-TM-NMFS-PIFSC-150, 25p.


Last updated by Pacific Islands Fisheries Science Center on 12/04/2023

Cetacean Surveys