August 12, 2026 — A new study from the Hawai’i Institute of Marine Biology at the University of Hawaiʻi Mānoa has found that the population of spinner dolphins off the Kona Coast is in decline. And disruption caused by people is likely to blame.
The study used 3D digital models created using drone photography taken in 2021 and 2022 to determine the ages of the dolphins that live along the coast. It found that the number of calves was just 9% of the total — a notable drop from 17%, the number that scientists expect to see under stable conditions.
“This study is really eye-opening,” said Lars Bejder, director of HIMB’s Marine Mammal Research Program. “Over the last 25 to 30 years there’s been a lot of concern from NOAA, from the general community, from Hawaiian practitioners and from some commercial operators that the pressure on these animals is pretty severe.”
Spinner dolphins live for 20 to 25 years and reproduce slowly; getting a clear population count has long been a challenge. But this study adds a new form of evidence to the existing science. Fewer calves will most likely lead to fewer mature dolphins over time, and that “raises concerns about the long-term viability” of the dolphins off the Big Island, the scientists said.
The researchers added that the evidence is a clear call for further protection for the dolphins at a time when the existing protection may be lacking enforcement.