August 14, 2012
Conservation Groups Want Protection For California Sharks
Brett Smith for redOrbit.com - Your Universe Online
As the Discovery Channel kicks off its annual Shark Week, conservation groups are petitioning the government to protect the ferocious ocean predators living off the coast of California.Citing a declining population, Oceana, The Center for Biological Diversity, and SharkStewards filed a scientific petition with the National Marine Fisheries Service seeking to protect great white sharks living off the West Coast under the Endangered Species Act.
"There could be fewer than 100 breeding females left," said Geoff Shester, a director for Oceana, an international group focused on ocean conservation. "Numbers in this range are lower than most species currently listed as endangered."
According to Oceana, great white sharks found in the northeastern Pacific are genetically distinct and isolated from all other great whites around the world.
A statement on the group´s website also points to a recent study that pegged the West Coast population of adult and sub-adult great white sharks at fewer than 350 sharks. In the study, Stanford scientists tracked the giant predators between 2000 and 2008 from San Diego to Hawaii and back as they followed a regular, exacting route with occasional detours under the Golden Gate Bridge and into San Francisco Bay.
Fishing for great white sharks is illegal in Mexico and California, where capture or possession of the animal is considered a misdemeanor. The biggest threat to the shark comes from gillnet fisheries that target halibut, swordfish, and white sea bass. The nets used by these fisheries often entangle and kill great white pups.
Mercury and other pollutant levels are also considered a threat to the shark population, according to the Center for Biological Diversity. A group statement said the West Coast sharks suffered from disproportionately high exposure rates.
“Young great white sharks off the Southern California coast are also found to have the second-highest mercury level on record for any sharks worldwide – six times higher than levels shown to cause physiological harm to other ocean fish species,” the statement read. “In addition, these sharks had the highest levels of the contaminants PCB and DDT in liver tissue observed in any shark species reported to date globally."
The petition filed by the groups also points to widespread hunting and subsequent decimation of the sharks´ primary food sources, elephant seals and sea lions, as a threat to the health of the shark population.
“Since prey is a critical component of white shark habitat, northeastern Pacific white sharks have suffered a serious curtailment of their habitat, and hence carrying capacity, at the locations in which their adult populations are most concentrated with high levels of site fidelity,” the petition said. “Therefore, although the current northeastern Pacific white shark population is being quantified, the history of human exploitation, both indirectly through killing prey and directly through capture, has likely resulted in a heavily depleted white shark population, which would comport with declining trends in most other large shark species worldwide for which long-term population data exist.”
The groups mentioned other factors that also play into the predator´s population woes, including a low reproductive output, late maturity, and high mortality rates during the shark pups´ first year.