A rare dolphin found dead on a remote Hawaii beach earlier this month swallowed five fish hooks, but they apparently didn’t cause its death.
A necropsy of the dolphin — called a false killer whale — showed the hooks were floating in its stomach along with the partially digested remains of a large marlin, some tuna and several types of squid.
The hooks weren’t embedded in the stomach lining and there’s no evidence they caused the dolphin’s death, Kristi West, the Hawaii Pacific University professor who led the necropsy, said Thursday.
Scientists are still trying to determine how the false killer whale died.
The adult male, which was more than 14 feet long, was one of a small population of false killer whales living near Hawaii that was declared endangered last year.
It was found Oct. 5 at South Point on Hawaii island. Its white blubber was showing through his skin in some areas, most likely because its body was scraped while waves washed it onto the rocky shore.
Several kinds of hooks use by commercial and recreational fishermen were found in its stomach.
Some were shiny and appeared to be new, while others looked like they were eaten away by stomach acid and were ingested a while ago.
None were circle hooks recently adopted by Hawaii longline fishermen, under a rule issued last year by the National Marine Fisheries Service, to prevent the accidental snagging of dolphins.
Hawaii’s longline fishermen have been inadvertently hooking the dolphins at high rates, in part because the animals like to eat ahi, mahimahi and many other fish caught on fishing lines.
The new circle hooks are designed to hook fish on the mouth, making it less likely false killer whales will get caught when they steal fish. The hooks are also weaker, making it easier for dolphins that get caught to wiggle free.
Robin Baird, a research biologist with Cascadia Research Collective, said the discovery of the hooks in this animal’s stomach indicates the population is still interacting with fisheries — perhaps fisheries other than the longline fishery.
Baird said this raises the question about whether other fisheries in Hawaii should adopt similar rules to the longline fishery to protect the animals. The shortline fishery and the troll fishery are also believed to accidentally snag the dolphins.
The National Marine Fisheries Service last year listed false killer whales found in and around the waters of Hawaii’s eight main islands as endangered. There are just 150 to 200 of these dolphins remaining.