Odontocete Detections Are Linked to Oceanographic Conditions in the Hawaiian Archipelago

The Hawaiian Archipelago provides a unique study site for toothed whales (odontocetes), with at least 18 species of odontocetes residing in the region². The archipelago consists of volcanic islands, separated into the Northwestern Hawaiian Islands (NWHI, older islands) and the Main Hawaiian Islands (MHI, newer islands).

Oceanographic conditions in these regions differ significantly, with the MHI experiencing high nearshore upwelling, regional fronts and leeward eddies, and increased mixing and turbulence in channels between islands that encourage relatively high primary productivity³.

This subsequently supports a variety of odontocete prey species (e.g., myctophids, shrimp, squids, cephalopods, and demersal and mesopelagic fishes). Nutrient input along coastal areas from frequent rainfall and steep island slopes also promotes the flourishing of odontocete prey; this effect is concentrated nearshore on the windward side of the islands but more dispersed and diluted in the islands’ lees due to westerly winds. 

In the NWHI, the contrast between inshore and offshore production is less marked because of eddies and a lack of above-water land mass. However, proximity to the transition zone chlorophyll front (TZCF) near the Subtropical Convergence Zone also results in higher productivity and increased abundance of odontocete prey species compared to the surrounding gyre.

The heightened production supported by these processes provides prime habitat for many odontocete species and results in numerous island-associated populations of various species.

Ziegenhorn, M.A., Hildebrand, J.A., Oleson, E.M. et al 2023. Odontocete detections are linked to oceanographic conditions in the Hawaiian Archipelago Commun Earth Environ 4, 423.
https://doi.org/10.1038/s43247-023-01088-7