August 15, 2025 — Three false killer whale populations occur in the waters of Hawaiʻi. There are two island-associated populations—one around the main Hawaiian islands and another around the Northwestern Hawaiian Islands—and a broadly ranging pelagic population. The small main Hawaiian Islands insular distinct population segment of false killer whales was listed as endangered in 2012 and faces multiple ongoing threats. Evidence suggests—based on high rates of dorsal fin and mouthline injuries—that fisheries interactions represent one of the most significant threats to this population. This threat may also act synergistically with other threats, such as exposure to pollutants and reduced genetic diversity, on the insular population. Scientists at the Pacific Islands Fisheries Science Center led the development of a new method to more accurately estimate the size of the main Hawaiian Islands insular false killer whale population by incorporating animal movement.
We analyzed photos of dorsal fins of 202 main Hawaiian Islands insular false killer whales encountered over 20 years (1999–2022) and movements from 53 satellite tags deployed from 2007–2022. We found that the population numbered 139 whales in 2022 and declined by 3.5 percent per year during the last 10 years of the study. Our findings provide the first reliable trend estimate for the population since it was listed as endangered and suggest the population will number fewer than 100 individuals within 10 years.