A Hawaiian monk seal that died Friday likely swallowed back in August the fish hook that caused its death, a National Oceanic and Atmospheric Administration official said.
Charles Littnan, lead scientist with NOAA’s Hawaiian Monk Seal Recovery Program, said someone in August reported seeing a monk seal that matched the description of seal RK68, in an area the seal was known to frequent on Hawaii Island, with what appeared to be fishing line hanging from its mouth.
Volunteers and a Hawaiian Islands Humpback Whale National Marine Sanctuary employee went looking for the seal, but couldn’t locate it, Littnan said. A week later, someone spotted RK68. The fishing line was no longer visible and the seal appeared to be fine, Littnan said. Through December, observers reported RK68 appeared to be in good health.
What observers couldn’t see — and what didn’t become clear until a Waikiki Aquarium employee performed a necropsy on the animal after its death on Friday — was the damage a hook was doing to the animal’s esophagus, trachea and lungs. Over the last six months, the hook sank through the esophagus into the trachea, Littnan said.
“The body tried to wall off the hook with scar tissue,” he added. “It basically became quite a large obstacle to breathing. It is a pretty excruciating way to die.”
Someone reported seeing a monk seal that sounded like it was suffering from breathing difficulties in early January. NOAA officials gave the woman instructions to return to the area where she saw the seal, giving her a few things to look for, to assess the seal’s condition. Littnan said when the woman returned, the seal again appeared to be fine.
In late January, someone again saw the monk seal and again heard labored breathing.
“The problems really accelerated in the last week to 10 days,” after which, RK68’s condition “rapidly deteriorated,” Littnan said.
The monk seal likely bit bait on a hook and swallowed the bait. A fisherman feeling the line tug would have pulled the line and set the hook, Littnan said. Hooks being swallowed and catching in the esophagus or stomach are not as common, and are more difficult to diagnose early or treat, than hooks in the tongue or face, he added.
The veterinarian performing the necropsy on the seal told NOAA officials by the time the seal was captured on Thursday, no surgery would have saved its life.
NOAA officials ask anyone who sees a hooked monk seal, or who hooks one while fishing, to call a toll-free, around-the-clock reporting hot line for any fishery interactions and other marine mammal incidents. The number is (888) 256-9840. National Marine Fisheries Service Marine Mammal Branch Chief Jeff Walters said fishermen often have concerns about reporting such incidents.
“There may be an investigation from law enforcement, but the fact that they self-reported is — it’s working in their favor — a mitigating circumstance,” Walters said.
When fishermen have reported the hookings, and when the incidents happened in a way that was not reckless, no one has been charged, Walters said.
The number of monk seals being caught by hooks appears to be increasing, NOAA officials said. Nine such hookings were reported in 2011, none of which resulted in an animal’s death. In 2012, 15 animals were hooked and three died. Already this year, a second seal was hooked, on Monday on Kauai.