A newly published eight-year tiger shark study has found a significant number of sharks with stainless-steel fishing hooks lodged in their jaws.

“We were surprised so many sharks were swimming around with the same hooks for years,” said University of Hawaii shark researcher Carl Meyer with the Hawaii Institute of Marine Biology.

Meyer, one of the authors of the study published in the journal Fisheries Research, urged commercial and recreational fishermen to reject stainless-steel fishing hooks and instead use carbon steel hooks, which break down and exit the sharks much faster.

Many kinds of sharks become collateral damage for hook-and-line fisheries tolling for high-value food species around the world. Millions of sharks are accidentally hooked and bite through fishing lines or are set free with hooks dangling from their jaws.

Meyer and three Tahiti- based researchers took eight years of observations and photos of tiger sharks at diving sites off Tahiti’s northwest coast and identified 55 individual sharks in an attempt to estimate the impacts of hooks and trailing fishing line.

Some 38% of the sharks had some form of fishing gear attached, and 20% of those had multiple hooks — up to seven — embedded around their jaws. Other sharks showed scars characteristic of previous hooking.

Some of the tigers wore their hooks for nearly the length of the study, and the scientists said it is possible the hooks would remain a burden for an entire lifetime.

The tiger shark is renowned as a robust creature, and the researchers didn’t see any obvious debilitating affects on the hooked tigers over the years, according to the study.

But Meyer said many other types of warm-water sharks aren’t nearly as stout, and the hooks likely have profound long-term consequences.

“They have been known to impact feeding, impact the ability to swim. They can affect energy balance and they probably slowly starve,” he said.

Meyer said it’s virtually impossible to follow a shark once it’s been hooked to determine how long that hook remains attached. He said the researchers were able to take advantage of a trove of photos and information taken by “citizen scientists” who recorded tiger sharks at Tahitian eco-tourism diving sites, many of the animals returning year after year.

While firmly embedded stainless-steel hooks persisted for at least 7-1/2 years, according to the study, all corrodible carbon steel hooks were shed within 2-1/2 years.

Stainless-steel hooks are no longer permitted by longline fisheries in Australia and in various areas of the U.S., including fisheries in the Atlantic, off Florida and in the Gulf of Mexico.

Stainless-steel hooks are still commonly used in the pelagic longline fishery in Polynesia, and there is no mandate for fishermen in Hawaii, both commercial and recreational.

Meyer is well aware of their use in Hawaii. Within a few weeks at the end of 2019, he managed to remove four hooks from sharks off Oahu. Three of them were stainless steel.

“It’s happening right in our backyards,” he said.

Sharks sit at the top of the food chain and play an important role in the balance of the marine ecosystem, he said. And studies have shown that high-value species are more abundant when ecosystems are healthy.

“These fisheries are increasingly aware that they need to reduce their impacts,” Meyer said. “It’s a relatively small price to pay, switching away from stainless steel. It’s a relatively small tweak to benefit the shark population.”