March 3, 2013
Approximately 100 Million Sharks Illegally Killed Each Year
redOrbit Staff & Wire Reports - Your Universe Online
Overfishing kills an average of 100 million sharks worldwide each year, according to new research highlighting the dangers faced by many different species of fish as they attempt to avoid possible extinction.According to Dan Stone of National Geographic Magazine, biologists from Dalhousie University in Canada and colleagues used data obtained from global shark catch reports and nearly 100 past research papers to estimate the total number of unreported shark deaths that occur annually.
In research published in the journal Marine Policy, they estimated “catch and mortality of sharks from reported and unreported landings, discards, and shark finning” at 1.44 million metric tons during the year 2000 and 1.41 million tons for the year 2010. Converting those figures based on the average weight of shark species, the researchers report an estimated mortality rate of 100 million for 2000 and 97 million for 2010, with an total range of possible values between 63 million and 273 million sharks annually during that time frame.
“Further, the exploitation rate for sharks as a group was calculated by dividing two independent mortality estimates by an estimate of total global biomass,” the Dalhousie University-led team explained. “As an alternative approach, exploitation rates for individual shark populations were compiled and averaged from stock assessments and other published sources. The resulting three independent estimates of the average exploitation rate ranged between 6.4% and 7.9% of sharks killed per year.”
“This exceeds the average rebound rate for many shark populations, estimated from the life history information on 62 shark species (rebound rates averaged 4.9% per year), and explains the ongoing declines in most populations for which data exist,” they added. “The consequences of these unsustainable catch and mortality rates for marine ecosystems could be substantial. Global total shark mortality, therefore, needs to be reduced drastically in order to rebuild depleted populations and restore marine ecosystems with functional top predators.”
According to the Washington Post, these latest shark mortality figures are “substantially higher” than those presented in past studies, partially because the US and Canadian biologists, marine scientists and environmentalists are the first to account for the effects of illegal catches and discarded sharks. It was released just one day before international negotiators were expected to meet in China to discuss possible new trade restrictions on select endangered shark species, the newspaper added.
“It is not sustainable,” lead author Dr. Boris Worm told the Washington Post. “Imagine we still had 500 species of dinosaurs around — every form and color from tiny critters to huge, whalelike creatures. Once they were everywhere, but then we started to chop off their tails to make soup from it, and now they are going extinct — not because a meteorite hit the planet, but because we ate their tails.”
"Biologically, sharks simply can't keep up with the current rate of exploitation and demand. Protective measures must be scaled up significantly in order to avoid further depletion and the possible extinction of many shark species in our lifetime,” he added in a separate interview with the UK Press Association.
In addition to Worm, other credited authors of the report include Brendal Davis, Lisa Kettemer, and Christine A. Ward-Paige, all of Dalhousie University´s Biology Department; Demian Chapman of the Institute for Ocean Conservation Science, School of Marine and Atmospheric Sciences at Stony Brook University in New York; Michael R. Heithaus at Florida International University´s Department of Biological Sciences; Steven T. Kessel at the University of Windsor´s Great Lakes Institute for Environmental Research; and Samuel H. Gruber from the Bimini Biological Field Station at the University of Miami.