Eight years ago a female Hawaiian monk seal struck its head and died on a rocky shelf in Hanauma Bay in a struggle with researchers who were trying to tag her, an incident that led to new stringent capture protocols designed to avoid such deaths in the future.

Those protocols help to explain why National Oceanic and Atmospheric Administration officials didn’t rush to dislodge a fishhook from the mouth of a seal at rocky Kaena Point a couple of weeks ago as some were urging.

As it turns out, the 9-year-old monk seal was able to shake the hook from its lip a week and a half later, and the animal doesn’t appear to be any worse for the wear.

Other seals haven’t been so lucky in their interaction with fishhooks. Five seals have died because of swallowed fishhooks since 2010, according to NOAA.

While fishhooks are not considered the greatest threat to the Hawaiian monk seal, officials said, they do represent a growing problem as the critically endangered marine mammal becomes more common in the main Hawaiian Islands.

Since 1988 there have been 132 instances of monk seal hookings in the main isles, involving 26 percent of the seals NOAA tracks. However, more than half of those incidents occurred in just the past five years, averaging about 13 annually.

The Hawaiian monk seal is one of the rarest marine mammals in the world, numbering fewer than 1,100 and estimated to be declining in population size by 3 percent per year.

Most Hawaiian monk seals live in the remote Northwestern Hawaiian Islands, but some 150 to 200 animals live in the main isles and the population here has been growing at about 5 percent a year. The consequence is more interactions with set nets, traps, spearfishing and shoreline fishing.

The National Marine Fisheries Service has intervened to remove hooks in roughly 40 percent of the incidents since 2010 — 29 of 70 — while seals have lost hooks on their own just over 50 percent of the time (36 of the 70 hookings), according to NOAA.

In January a 12-year-old Hawaiian monk seal was returned to White Plains Beach after a two-week recovery from lifesaving surgery that removed a 4-inch fishhook embedded deep within its stomach wall. A steel wire leader connected to the hook extended through its esophagus and up to its mouth.

Last month a young seal was flown back to Kauai after it had swallowed a fishhook and was taken to Oahu for emergency surgery at NOAA’s facility on Ford Island.

On May 27 the 9-year-old adult male known as Kaena, or RO40, showed up at Kaena Point with an ulua hook in his lower jaw and monofilament line trailing from the hook. The next day the monofilament line disappeared, but the hook and the metal leader were still dangling from the seal.

NOAA was called for help, but after an evaluation a decision was made to wait until the animal moved to a location, such as a sandy beach, where it would be safer to intervene.

Zeenat Mian, a Hawaiian monk seal advocate who had called NOAA, said she was extremely disappointed by NOAA’s response.

“I strongly believe NOAA is acting in an incredible irresponsible and lazy manner,” she said a few days after RO40 was hooked. “The hooked monk seal was incredibly distressed and in pain.”

But Charles Littnan, lead scientist with NOAA’s Hawaiian Monk Seal Research Program, said his staff and volunteers monitored the seal and would have intervened in an attempt to take off the hook if a safe opportunity had presented itself. That likely would have meant the seal moved to a beach.

Littnan, who was a witness to the Hanauma Bay seal death, said his agency now has robust protocols that focus first and foremost on the safety of both the animals and the captors.

Kaena Point is a notoriously difficult area for capturing a seal, he said, and the hook was in a spot on the seal’s lower jaw that made the incident superficial.

David Schofield, NOAA’s marine mammal health program coordinator, said staffers and volunteers report that even with the hook attached and causing some irritation, the animal was generally acting normally, even showing interest in a female.

“We’re very happy he shook the hook on his own,” Schofield said.

Only a relative few seals get hooked multiple times, but RO40 is a notable exception. In fact, this particular animal may be the most “hooked” Hawaiian monk seal in history, according to NOAA records, which show he has been hooked five other times since 2009. Only on one occasion, in 2009, did RO40 receive assistance, and that was while he had hauled out on the nice sandy beach at Yoko­hama Bay.

According to NOAA records, RO40 has been seen mostly on lava platforms, making for a difficult capture.

“So unless it’s life or death, we will not endanger the animal,” Littnan said, adding that crew members will take the risk only if there are indications of infection or any other signs of life-threatening conditions.

Littnan added that all of the recent seal deaths from hooks were a result of an ingested hook — not from hookings similar to RO40’s situation.

Littnan, acting deputy director of NOAA’s Ino­uye Regional Center, said he’s proud of NOAA’s record of care for the Hawaiian monk seal.

“This is all we do. It is our bread and butter. We have a fiercely dedicated staff who works hard,” he said.

In 2004 several scientists at the Pacific Islands Fisheries Science Center began the Barbless Circle Hook Project to encourage the use of fishhooks without a barb. Barbless circle hooks are just as effective at catching fish as barbed hooks but allow seals and other sea creatures to more easily shake them off.

The program has been a big success due to the enthusiastic support and active participation of the fishing community, according to John Henderson of the Hawaiian Monk Seal Research Program.