Estimating the Winter Abundance of Cetaceans Around the Main Hawaiian Islands
November 04, 2022
A winter HICEAS (WHICEAS) was conducted in Jan−Mar 2020 to estimate the abundance and distribution of cetaceans around the main Hawaiian Islands during winter.
Twenty-four cetacean species (18 odontocetes and 6 mysticetes) regularly occur in the waters around the Hawaiian Islands. Abundance estimates are needed to evaluate the impacts of human activities on these species in population assessments and management plans.
Most ship-based, line-transect surveys for cetaceans in Hawaiian waters have occurred during the summer−fall period, including the recurring Hawaiian Islands Cetacean and Ecosystem Assessment Survey (HICEAS) that took place in 2002, 2010, and 2017. There are no recent abundance estimates of cetaceans in Hawaiian waters during winter, when seasonally-migrating baleen whales are at peak abundance.
A winter HICEAS (WHICEAS) was conducted in Jan−Mar 2020 to estimate the abundance and distribution of cetaceans around the main Hawaiian Islands during winter. An established multiple-covariate approach, which involves pooling data from previous line-transect surveys to estimate detection functions and using trackline detection probabilities that consider the effect of survey sighting conditions, was used to produce design-based abundance estimates for 17 species (14 odontocetes and 3 mysticetes).
This study represents the first multi-species assessment of winter abundance around the main Hawaiian Islands. Model-based density estimation incorporating the WHICEAS 2020 data provides finer-scale seasonal and spatial inference for 9 species (8 odontocetes and humpback whales). Additional winter survey effort beyond the main Hawaiian Islands and other types of data collection (e.g., satellite tagging) may be needed to more fully evaluate seasonal differences in the abundance and distribution of cetaceans in Hawaiian waters.
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.
Bradford AL, Yano KM, Oleson EM. 2022. Estimating the Winter Abundance of Cetaceans around the Main Hawaiian Islands. U.S. Dept. of Commerce, NOAA Technical Memorandum NOAA-TM-NMFS-PIFSC-135, 46 p. https://doi.org/10.25923/801q-ke40.