Conservation groups Oceana, Center for Biological Diversity, and Shark Stewards filed a petition to the California Fish and Game Commission today seeking to protect the US West Coast population of great white sharks, throughout their California range, under the state's Endangered Species Act. The legal filing comes on the heels of a similar petition submitted to the National Marine Fisheries Service on August 10, 2012 seeking federal Endangered Species Act protection for this unique population of great white sharks.
California Endangered Species Act listing will provide the sharks with protections from key threats and funding for research to better understand the status and threats to this distinct population. New findings show that numbers of adult great white sharks off the coast of California and Baja California, Mexico are alarmingly low.
"California's iconic ocean predator, the great white shark, is in trouble and there must be action taken," said Oceana California Program Director Geoff Shester. "Letting great whites disappear would be like taking lions out of the Serengeti â€" it just wouldn't be the same."
In the past two years, new scientific studies by Taylor Chapple et al[1] and Oscar Sosa-Nishizaki et al[2] produced the first population estimates of West Coast adult and sub-adult great white sharks, together totaling fewer than 350 sharks â€" far fewer than researchers expected, presenting an inherently high extinction risk. New genetic studies have confirmed that this population is isolated and distinct from all other great white shark populations worldwide. The population is unique to the West Coast, although it makes yearly trips on the "Great White Highway" to Hawaii and the "White Shark Café." The café is a remote mid-Pacific Ocean area noted as a winter and spring habitat of otherwise coastal great white sharks.
While their direct capture for sale is prohibited off the coasts of California and Mexico, young great white sharks are killed as incidental bycatch in commercial fishing. Set and drift gillnets â€" which together target California halibut, white seabass, yellowtail, thresher sharks and swordfish â€" are responsible for more than 80 percent of the reported young white sharks caught in their nursery grounds off Southern California. Bycatch in these fisheries has averaged more than 10 sharks per year since the 1980s, but as there are few independent observers, the actual number of great white shark bycatch could be much higher. If the state wildlife commission advances this species to "candidacy" this fall, there could be interim measures put in place, such as full observer coverage in these gillnet fisheries, while the full listing determination is considered.
"As a surfer, I've learned a cautious respect for great white sharks. Sharks are part of California's ocean ecosystem â€" even predators need protection against deadly gillnets that could wipe them out," said Miyoko Sakashita, oceans director at the Center for Biological Diversity.
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 â€" six times higher than levels shown to cause physiological harm to other ocean fish species. In addition, these sharks had the highest levels of PCB and DDT in their liver tissue of any observed shark species in the world.
"With a population numbering in the low hundreds, we need to be cautious and learn more about the population and population dynamics of these enigmatic predators," said David McGuire, Director of Shark Stewards.
Great white sharks are a critical part of California's ocean ecosystem, playing an important top-down role in structuring the ecosystem by keeping prey populations in check, like California sea lions and northern elephant seals. The presence of great white sharks ultimately increases species stability and the diversity of the overall ecosystem.
[1] Chapple, T., S. Jorgensen, S. Andersen, P. Kanive, P. Klimley, L. Botsford and B. Block (2011). A first estimate of white shark, Carcharodon carcharias, abundance off Central California Biology Letters 7(4): 581-583. [2] Sosa-Nishizaki, O., E. Morales-Bojorquez, N. Nasby-Lucas, E. Onate-Gonzalez and M. Domeier, (2012). Problems with Photo Identification as a Method of Estimating Abundance of White Sharks, Carcharodon carcharias: An Example from Guadalupe Island, Mexico. Global Perspectives on the Biology and Life History of the White Shark. M. Domeier (ed.). CRC Press.