Pacific reef sharks will swim into oblivion without more regulation and effective enforcement, the latest science says.

But a federal agency that could recommend changes to turn this trend around by closing certain fishing areas or pushing for ways to reduce bycatch is dismissing the findings as overblown.

“What would you rather see, lots of people swimming in the water or lots of sharks?” said Paul Dalzell, a senior scientist with the Western Pacific Regional Fishery Management Council. “Sharks don’t spend any money. Isn’t it great that millions upon millions upon millions of people have been able to swim at Waikiki with impunity?”

But the sharks are important as the top natural predators on the nearshore reefs, said Andrew Rossiter, who heads Waikiki Aquarium.

“The role they play there is to selectively remove weak, old, sick or injured fishes, thus ensuring that those fish populations living there are, ecologically speaking, in top condition,” he said. “It is somewhat akin to an arborist removing stunted branches and dead limbs from a tree to promote the vigor and productivity of a tree or forest.”

Marine scientist Marc Nadon of the Joint Institute for Marine and Atmospheric Research at the University of Hawaii and his colleagues estimate that the number of Pacific reef sharks has plummeted 90 percent.

“Our results suggest humans now exert a stronger influence on the abundance of reef sharks than either habitat quality or oceanographic factors,” Nadon wrote in a scientific paper published in April.

“Possible explanations for the reduced abundance of reef sharks near human populations include fishing and a reduction of the sharks’ prey base,” he said. “Although there are currently no active commercial reef shark fisheries around any U.S. Pacific island, reef sharks may be fished recreationally, taken incidentally, killed because they are perceived as a nuisance, and possibly taken illegally for their fins.”

The plight of the reef sharks was a topic of contention at a recent meeting of Wespac, a federal board that works with the National Oceanic and Atmospheric Administration on ocean issues. Wespac could restrict fishing in favor of reef sharks.

But that doesn’t seem likely, at least for now.

Wespac’s Dalzell called Nadon’s paper “a good piece of work,” but rejected the conclusions.

“Any discussion in the Nadon paper that fishing is the cause of shark population decline around inhabited islands is simply wrong and illustrates that scientists need to think more broadly about their results than just grasp for the easiest explanation,” he said recently. “We have replaced sharks, as humans. We have not fished the sharks down, they’re simply outcompeted so they bugger off somewhere else where they can get a feed.”

This inverse relationship is not necessarily a bad thing, Dalzell said.

He compared it to the monk seals doing well in the populous main Hawaiian Islands compared to the remote Northwestern Hawaiian Islands. Scientists have started bringing the seals to the main Hawaiian Islands where there are fewer sharks and less competition for pups learning to forage for food.

Michael Seki of the National Oceanic and Atmospheric Administration’s Pacific Islands Fisheries Science Center, which partners with JIMAR, shared the study with the Western Pacific Regional Fishery Management Council at its June meeting. The council advises NOAA on a variety of things, such as setting tuna quotas and closing fisheries to protect certain species.

Wespac Executive Director Kitty Simonds, Chair Manny Duenas and other members peppered Seki with questions about the implications the science could have on a billion-plus-dollar fishing industry. Hawaii’s commercial fishing industry alone generates roughly $500 million in sales annually and provides 11,000 jobs, a recent report states.

People Or Sharks?

Fewer sharks is a good thing economically, Dalzell said, noting the impact on tourism.

“We drive the population down by fishing. We play the same apex predator role as the shark,” Dalzell said. “Three cheers for the fishermen!”

Duenas, the Wespac chair, challenged reports of shark depletion and the overall accuracy of the science.

“I don’t know where you guys are getting your information,” he told Seki. “It seems like an attack on the local fishing community. We eat sharks, but we’re not targeting sharks.”

In Nadon’s study, divers towed behind a boat counted sharks in more than 1,600 surveys throughout 46 Pacific islands and atolls.

The study concluded that reef shark populations are likely in decline not just due to the illegal and incidental catch by commercial fishermen, but also a 70 percent decline in reef fish biomass caused by recreational nearshore fishing and environmental factors like polluted runoff. If the sharks don’t have enough food to eat, Nadon said, their populations can’t be supported.

Another significant factor is the “slow life history” of reef sharks, he said. Many reef sharks simply don’t reproduce quickly, so even a small amount of fishing pressure can slowly lead to a decline in population.

Duenas, an avid diver and fisherman from Guam, said the surveys should have been done at night as well as during the day because he sees some sharks more often at night.

Councilman McGrew Rice, a charter fisherman from Hawaii, agreed. He said the study should have been a “24-hour thing.”

Nadon said the scientific team may be able to confirm the data by following up using survey techniques that involve baited underwater cameras.

He declined to speculate on what he thought the council should do, if anything, to help reef sharks recover. NOAA tries to keep the science separate from resource management, he said.

Nadon suggested in his paper there may be insufficient scientific research yet to make recommendations on what conservation measures should be implemented.

“Although our baseline estimates may provide an impetus for shark conservation, they are likely to be less useful for setting specific management targets until ecological and physical controls on carrying capacity are better understood,” he said.

Designating certain waters as protected marine areas would not be enough to stop the bleeding of reef shark stocks, Nadon said.

“The recent implementation of marine national monuments at most isolated U.S. Pacific islands may substantially increase the probability of persistence of reef shark populations, but effective enforcement and additional fishing regulations elsewhere would also be necessary to slow the decline of these species,” he said.

Department of Land and Natural Resources Chair William Aila, an avid diver and fisherman who is one of the Hawaii’s representatives on the council, said he would find it hard to believe only 10 percent of the anticipated number of Pacific reef sharks are left.

Hawaii passed a law in 2010 banning shark fins, but the state still lets people fish for sharks if the whole animal is utilized. However, Aila said unless sharks are prepared well, it’s not very good eating so he doesn’t see people targeting them.

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