Biologically Important Areas II for cetaceans within U.S. and adjacent waters – Hawaiʻi Region

Abstract

In this assessment we incorporated published and unpublished information to delineate and score Biologically Important Areas (BIAs) for cetaceans in the Hawaiʻi region following standardized criteria. Twenty-six cetacean species have been documented in Hawaiʻi. Eleven odontocete species have distinct small populations resident to one or more island areas: rough-toothed dolphins, pantropical spotted dolphins, common bottlenose dolphins, spinner dolphins, short-finned pilot whales, false killer whales, pygmy killer whales, melon-headed whales, Blainville’s beaked whales, Cuvier’s beaked whales, and dwarf sperm whales. Eight species of mysticetes have been documented, although their occurrence and behavior are poorly understood, with the exception of breeding humpback whales and, more recently, common minke whales. Thirty-five BIAs were delineated or revised from the initial 2015 effort: 33 for small and resident odontocete populations and two for humpback whale reproductive areas. Hierarchical BIAs reflecting core areas of use or population-specific ranges were delineated for nine species. Reproductive watch list areas were designated for common minke whales in the main Hawaiian Islands (MHI) and humpback whales in the Northwestern Hawaiian Islands (NWHI); these areas did not meet the criteria for a BIA due to limited supporting information. All but three BIAs were in the MHI, reflecting the disparities in research effort between this region and the NWHI. Spatial extents of BIA boundaries ranged from 457 km2 to 138,001 km2 (median = 8,299 km2). Scores (range: 1-3) for Data Support and Boundary Certainty were moderate to high (mean = 2.40 and 2.43, respectively), while Intensity and Importance scores were slightly lower (mean = 1.94 and 1.89, respectively). Many of the Hawaiʻi species have been extensively studied over several decades; accordingly, this region ranks among the highest in terms of Data Support relative to other regions. BIAs presented here describe known ranges of small resident populations, intensities of use, and uncertainties in important areas for cetaceans in Hawaiʻi based on the best available data, and have also revealed knowledge gaps to guide future research efforts.

Priorities for ecological research on cetaceans in the Galápagos Islands

“…Admittedly, cetacean research is comparatively more expensive and more logistically demanding. However, at present, the study of cetaceans in Galaṕagos lags other tropical and subtropical oceanic insular ecosystems around the world, especially the Hawaiian (e.g., Baird et al, 2013b;Baird, 2016;Kratofil et al, 2023) and Macaronesian (e.g., Silva et al, 2014;Hartman et al, 2015;Fais et al, 2016;Tobeña et al, 2016;Alves et al, 2018;Alves et al, 2019;Romagosa et al, 2020;Dinis et al, 2021;Ferreira et al, 2021;Herrera et al, 2021) archipelagoes, where long-term studies have been generating significant new information in recent years. We acknowledge that, being located in the global north, the latter two ecosystems have benefited from established expertise, access to financial resources, and robust legislation mandating marine mammal research and protection that are generally not available in the global south.…”

Identifying and Comparing Important Areas for Marine Sustainable Use and Conservation

“…The best estimates of abundance for the small and resident populations identified across all regions range from 10 (beluga whales (Delphinapterus leucas) in Yakutat Bay, Gulf of Alaska; Wild et al, In Review) to ~4,250 (harbor porpoise (Phocoena phocoena) in Morro Bay; the coefficient of variation values associated with this estimate encompass the largest abundance bin size). The spatial extent of the small and resident populations were as small as 45 km 2 for the Gulf of Mexico bottlenose dolphin stock mentioned above and as large as 138,000 km 2 for the Northwestern Hawaiian Islands false killer whale (Pseudorca crassidens) insular stock (see Kratofil et al, 2023).…”

“…The region codes are EC = East Coast, GOM = Gulf of Mexico, WC = West Coast, HI = Hawai'i, GOA = Gulf of Alaska, ABS = Aleutian Islands and Bering Sea, and ARC = Arctic. For example, a BIA with "R-BIA3-s-b2" at the beginning of the label refers to a Reproductive (R) BIA with the highest (3) of three possible Importance scores, generally static (s) in nature, with medium confidence (b2) in the accuracy of the Example of hierarchical small and resident BIA for Hawai'i Island dwarf sperm whale (Kogia sima) (from Kratofil et al, 2023). Parent BIA boundary (blue polygon) for the Hawai'i Island dwarf sperm whale population represented as a minimum convex polygon (MCP) encompassing all sighting locations in less than 2,000 m water depth (yellow circles), and child BIA boundary (core range; purple polygon) represented as the area between the 500-m and 1,000-m isobaths within the parent BIA.…”

“…A core BIA was delineated for SRKWs with the intent of highlighting areas of intensified use within their overall range. The basis of the core BIA was a combination of NOAA's Critical Habitat core area (around the San Juan Islands, extended across the U.S./Canada border) and high-density areas identified through kernel density analyses of satellite tag data (details on satellite tag data methods are described in Supplementary File A, Section S2.3 and follow those used by the Hawai'i region (Kratofil et al, 2023;Figure 11). While NOAA's Critical Habitat core range is designated as a "summer core range", SRKW occurrence in this region during summer months has declined considerably over recent years; the importance of this area for SRKWs may not be as strongly associated with this particular season as has been the case historically (Shields et al, 2018;Hanson et al, 2021;Ettinger et al, 2022).…”

Biologically Important Areas II for cetaceans within U.S. and adjacent waters - West Coast Region

“…A core BIA was delineated for SRKWs with the intent of highlighting areas of intensified use within their overall range. The basis of the core BIA was a combination of NOAA's Critical Habitat core area (around the San Juan Islands, extended across the U.S./Canada border) and high-density areas identified through kernel density analyses of satellite tag data (details on satellite tag data methods are described in Supplementary File A, Section S2.3 and follow those used by the Hawai'i region (Kratofil et al, 2023; Figure 11). While NOAA's Critical Habitat core range is designated as a "summer core range", SRKW occurrence in this region during summer months has declined considerably over recent years; the importance of this area for SRKWs may not be as strongly associated with this particular season as has been the case historically (Shields et al, 2018;Hanson et al, 2021;Ettinger et al, 2022).…”