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Killing 18 galapagos sharks near the remote French Frigate Shoals in seven weeks isn’t the easiest of tasks, especially when you’re casting a fishing line from shore that’s baited with a large tuna head. You never know what you might get.
And it wasn’t galapagos sharks.
Eleven researchers with the National Oceanic and Atmospheric Administration spent part of their summer in the nature preserve trying to kill the species they say is the main culprit in the demise of baby monk seals. They did catch some tiger and white tip sharks, which they threw back.
NOAA’s shark eradication program, with this year’s 18-shark target, was approved in March by state officials.
“You can look at it two ways,” said Sam Gon, a senior scientist and cultural advisor at Hawaii’s Nature Conservancy. “Either they aren’t very good at getting sharks or they are being very careful about which sharks they pursue. It’s probably a little bit of both.”
Shark killers might not be the term that comes to mind when you think of NOAA scientists, whose task it is to protect and conserve marine life. And the practice that dates back to 2000, has raised concerns locally.
“It’s complex, it’s not comfortable and you are pitting one native species against another,” said Gon.
He is a member of the state land board which approved NOAA’s application to conduct the killings this year. He said he was disturbed by the practice, but also saw the rationale.
“I wish there would never be any take of one thing for another,” he said. “But in the case of monk seals, they’re a resource I believe strongly are native and therefore important to protect. The fact that marine life is taken every day for food and various other purposes, sharks included, makes it so it’s not a black and white matter.”
The endangered mammals only exist in Hawaii waters and have declined since the 1950s. They now number about 1,060. The vast majority live in the Northwest Hawaiian Islands, though they are increasingly showing up around the main Hawaiian Islands. Currently, the seals are declining at a rate of about 4 percent a year, according to NOAA.
NOAA scientists have been working to rid the nearshore waters of the galapagos sharks around main pupping areas on the islets of Trig, Round and Gin in the French Frigate Shoals since 2000. The atoll, part of the Papahānaumokuākea Marine National Monument, is about 550 miles from Oahu.
NOAA came up with the strategy of killing the sharks — officials call it culling — after a rash of shark attacks on pups in the late 1990s. About 70 pups were killed or injured, according to agency data.
“What happened was we had a peak in shark predation in 1997 and 1998,” Kathleen Gobush, a research ecologist at NOAA’s Hawaiian monk seal program, explained. “Prior to that there was only one pup per year at most being lost. Historically it was a non-issue.”
Since then, the number of baby monk seals being killed or maimed by sharks has remained relatively high, ranging from 6 to 17 per year, according to NOAA.
There are other reasons for the decline in the monk seal population, according to scientists, including limited food sources due to increases in more dominant predators, entanglement in fishing gear and nets, habitat loss due to rising sea levels and rogue male seals attacking female seals and pups.
But ensuring the survival of seals when they are juveniles is a critical part of NOAA’s recovery plan. Only one in five seals survives to reproductive age, after which their survival rates increase significantly, according to NOAA.
“If we can’t even get them to weaning then we are really hamstrung,” said Gobush.
The shark removal is just one aspect of the monk seal recovery plan, and it’s not clear if it’s effective, in part because officials haven’t been very good at killing the sharks.
They only killed one shark a year in 2010 and 2011. Since 2000, the total take has been 14 sharks. This year’s goal of 18 was based on previous research that had been conducted on the number of sharks that were entering the shallow waters around the islets.
This year, budget cuts were a problem. NOAA’s $5.7 million budget for monk seal research and recovery was cut by 40 percent for fiscal year 2011 and 2012, according to Charles Littnan, lead scientist for NOAA’s monk seal research program.
Usually a team of about 15 researchers spend three to five months camped out in the Northwest Hawaiian Islands. But this year, funding only allowed 11 staff to spend seven weeks there, he said.
In addition to the short season this year, NOAA officials also have to be careful not to harm other marine life in their quest to snag the galapagos sharks, which can grow to 12 feet long.
“We don’t want to have a large impact on the shark population out there,” said Gobush. “We’re just trying to get these pups to weaning. It’s a pretty conservative endeavor.”
In June, the scientists headed to the French Frigate Shoals. The plan was to catch a shark, pull it into shore or along a boat, tail rope it and kill it with a bangstick, or underwater gun, according to NOAA’s permit application.
“We are very conservative, very selective and very humane about what we do out there,” said Gobush.
She said that most galapagos sharks stay in deep water and so aren’t a threat to nursing pups. And if NOAA can remove the sharks that do come close to shore there is a chance that, based on their behavior characteristics, they won’t be replaced by more sharks.
“The idea is if we did remove the handful coming into pupping sites, they might not necessarily be replaced,” she said. “So few come in and and other sharks are not going to be traveling around filling spots.”
If NOAA can save pups from the sharks, it could be a big boost to survival rates. The baby seals nurse for about 35 days before being abandoned by their mother to fend for themselves. NOAA researchers have been transporting the seals to less sharky waters, mainly the islet of Trig two miles away, and where they have a better chance of surviving.
This year, they moved 10 pups. But because of the shortened trip, they had to leave 10 others that were still nursing.
As part of NOAA’s recovery plan, scientists are required to mitigate shark predation.
The shark culling is not their only attempt to fend off the predators. In 2008 and 2009, researchers instead tried to trick the sharks into thinking that humans were lurking in the nearshore waters or on the beaches.
Past research suggested that when officials intensified their monitoring activities, sharks fed less on the seals, and there seemed to be fewer attacks when there were people on the beach near pupping sites, said Gobush.
So, officials tested devices that mimicked the sights and sounds of human activity. They continuously played boat sounds underwater and left a boat moored offshore. They had staff camp out on the beach around the clock and tried setting up an underwater electric field that sharks can sense.
It was difficult to maintain and in the end proved ineffective. It was hard to keep electronic devices charged in the remote islands and come up with sounds that wouldn’t disturb other marine life.
“It all sounded nice on paper, but when we tested it out there it proved to be hard to do continuously,” said Gobush.
The electronic field was particularly tough.
“The impact zone of the devices was too small to feasibly use in the environment at French Frigate Shoals,” she said. “We would have needed a lot of those to even test it and it would impact other marine life having all these devices everywhere in the water.”
While shark deterrence may not be NOAA’s strong suit, there’s a lot more that the agency is doing to try to save the seals from extinction. In addition to relocating the pups to less sharky waters, scientists deworm juvenile pups, treat infections, re-unite mother-pup pairs that have become separated, clean-up marine debris and disentangle seals that have been caught in the refuse, such as fishing nets. They have also removed aggressive male seals that are harming or drowning other seals.
Overall, their efforts have found success, according to Littnan, who noted that 18 percent of the monk seal population is alive today because of NOAA’s efforts.
“So, even though the population is in trouble, it is in a far better state than if we hadn’t been working on these issues.”
Video shows shark attacking monk seal pup in Northwest Hawaiian Islands, courtesy NOAA.
NOAA photos show monk seals and sharks in the French Frigate Shoals, as well as the shark fishing gear: