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 why 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.
He was found Oct. 5 at South Point on the Big Island. His white blubber was showing through his skin in some areas, most likely because his body was scraped while waves washed him on to 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 tuna, 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.
Baird said this raises the question about whether other Hawaii fisheries should adopt similar rules as 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 considers hook ingestion a serious injury, Baird said. Marine mammals have died trying to regurgitate fish hooks.
The agency 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 the dolphins remaining.
A Hawaii Pacific University team removes and conducts necropsies on marine mammals stranded in the islands. But the program lost $100,000 in grant money this fiscal year amid federal budget cuts, forcing it to scramble for alternative funding.
West doubts people want dead marine mammals to stay on Hawaii’s beaches.
“They stink and they’re a human health hazard and we lose valuable information, so it pains me to think that they could be sitting on beaches in the future,” she said.