Friday | May 26, 2017
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NOAA: Carcharodon carcharias not at risk for extinction

Federal officials say studies of white shark populations along the West Coast show no need to list the animal as threatened or endangered.

National Oceanic and Atmospheric Administration scientists began investigating white shark populations in the northeastern Pacific Ocean in October, after two environmental groups filed petitions asking to give the shark Endangered Species Act protections, scientist Heidi Dewar said. The goal of the study, which wrapped up in May and was published in the federal register last week, wasn’t to get a complete census on white shark populations, but to see if the populations exceeded a threshold at which scientists believed the species wasn’t in danger of extinction.

“All the available evidence supports a population that was at least stable or increasing,” Dewar said.

That evidence included increasing reports of white sharks biting or killing sea lions and sea otters along the California coast, increased bycatch of smaller white sharks in Pacific fisheries and photographic evidence of population growth near Guadalupe Island, Mexico.

A biological review team of scientists from the National Marine Fisheries’ Southwest Fisheries Science Center with expertise in shark biology and ecology, genetics, population estimation and modeling, fisheries management and conservation biology. In addition to ascertaining at least some of the population level, the scientists also assessed threats against the white shark.

The white shark, Carcharodon carcharias, also known as the great white shark, lives in coastal and open ocean areas. Sharks in their first year of life and juvenile white sharks in the northeastern Pacific are most commonly observed in shallow coastal waters, mainly in the southern California and west coast of Baja California regions, the NOAA report said.

Dewar said the study raised questions for future research into the sharks’ habits.

“It was really interesting to take a look at the demographics of the sharks visiting the near shore areas,” she said. “One big question is what is going on with the females? There’s more to be discovered.”

Other shark species show large disparities in where males and females tend to congregate, so it wouldn’t be surprising to find male and female white sharks in different areas, too, Dewar said.

The report listed several potential threats to the sharks, including pollution, depletion of white shark prey species, ocean acidification, and ocean warming associated with climate change.

“Although legacy pollutants remain in the (areas sharks frequented), pollutant inputs to this area have decreased since the 1970s as a result of improved discharge management,” the report said. “White shark prey resources have substantially increased in abundance over the last several decades due to protections for marine mammals and improved fisheries management. The effects of ocean acidification and climate change now and in the foreseeable future remain highly uncertain, but the best available information indicates that habitat used by the Northeastern Pacific white shark population is not likely to be substantially impacted or that the white shark population will be able to compensate for any habitat changes.”

The westernmost reaches of white shark’s range seems to be the Hawaiian Islands, the report said. A study released earlier this year noted increasing sightings of the shark in the islands. Kevin Weng, manager of the Pelagic Fisheries Research Program, a collaboration between the University of Hawaii and NOAA’s Pacific Islands Fisheries Science Center, who worked on that study, said in an email Wednesday he has another study currently under peer review that supports NOAA’s findings of stable or even growing white shark populations.

“We concluded that there are more than 2,000 white sharks in the (Northeast Pacific) region, and that the population is growing,” Weng wrote. “One of the greatest challenges for white sharks was the decimation of their prey in the 19th and 20th centuries — human exploitation of seals, sea lions and whales. Sea lion and seal populations have rebounded in recent decades, bringing back a key food source for white sharks, and likely allowing their populations to slowly recover.”

Oceana, one of the environmental groups seeking to add the white shark to the Endangered Species Act listings, gave several reasons on its website to protect the species.

“Recent scientific studies provided the first ever population estimate, concluding that there are only a few hundred adults swimming off the Pacific coast of California and Mexico, far fewer than anyone expected,” organization officials said. “And those that are left face deadly dangers from commercial gillnet fishing nets. … Newborn great whites from this area are regularly killed by commercial fishing gear off southern California and Baja California in offshore gillnet fisheries targeting halibut, white seabass, and swordfish.”

Oceana officials also described the white shark as “one of the most iconic ocean animals.”

Other groups joining the petition to list the shark were the Center for Biological Diversity, Shark Stewards, and WildEarth Guardians.

“The federal government simply made the wrong decision in the face of the best available science,” California Program Director for Oceana Geoff Shester said in a written statement after NOAA announced it was recommending not to list the shark. “However, our efforts have demonstrated the dire need for more research on West Coast white sharks, and we should all agree that steps need to be taken immediately to start managing the white shark bycatch problem in gillnet fisheries.”