Co-occurrence between cetaceans and fisheries can result in competition for resources or conflicts such as depredation and bycatch. Developing effective mitigation strategies, therefore, requires understanding the ecological factors that promote co-occurrence. However, obtaining such information is challenging in the open ocean where resources are highly ephemeral and both cetaceans and fishing vessels move over extremely large scales, as in the case of pelagic false killer whales (Pseudorca crassidens) and Hawaiʻi’s commercial longline fleet. Using data from satellite-tagged false killer whales (n=19 whales/11 groups; 864 combined days tracked; 2013-2025) and vessel logbooks (n=170 vessels; 53,220 sets), we quantified spatial behavior relative to oceanographic features at multiple scales to identify the ecological contexts that underlie co-occurrence and potentially conflicts. Habitat selection models show high similarity between whales and longliners in their range-wide selection for increased sea surface height—indicative of anticyclonic eddies—but also some differences. Specifically, whales selected for metrics reflective of submesoscale features (e.g., meanders, fronts) compared to longliners, who consistently selected for areas with more seamounts. These findings point to differences between the two competitors’ abilities to detect features supporting prey aggregations. False killer whale habitat selection models did not improve with the addition of longline covariates, suggesting that broad scale habitat selection patterns are not driven by attraction to longline fishing activity. At finer scales, whales were infrequently within 50km of longliners (mean percent of locations=6.7%). These closer proximities were predominant in low eddy kinetic energy (EKE) conditions, but whales were no farther than 200km from longliners during the highest EKE conditions (compared to a maximum of 2,153km across all conditions). Together, these findings suggest that shared affinities for mesoscale eddies can result in broad co-occurrence of whales and longliners. However, fine-scale interactions between these competitors more likely occur under ecologically poor conditions.
Citation:
Kratofil, M.A., R.W. Baird, C.J. Cornforth, A.L. Bradford, and M. Cantor. 2026. Dynamic, Scale-Dependent Oceanographic Features Structure Co-Occurrence Between Hawai’i’s Pelagic False Killer Whales and Longline Fishing Vessels. Presentation at the 26th Biennial Conference on the Biology of Marine Mammals, San Juan, Puerto Rice, 19-23 October 2026.
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