March 3rd, 2013 by James Ayre
Sharks may become extinct within only the next few decades as a result of the significant declines they are experiencing, new research has found. Shark populations have been declining at a rapid rate as a result of the booming trade in their fins, recreational fishing, and being caught as by-catch in other forms of fishing. The current rate is at 100 million, or possibly more, sharks being killed every year. When this is combined with their very slow growth and reproduction rates, it’s having a devastating effect on the animals.
“Sharks have persisted for at least 400 million years and are one of the oldest vertebrate groups on the planet. However, these predators are experiencing population declines significant enough to cause global concern,” states lead author Boris Worm, professor of biology at Dalhousie.
The new study, titled, “Global Catches, Exploitation Rates and Rebuilding Options for Sharks,” features accurate calculations on total yearly shark death rates, and offers possible solutions, because of a collaboration between researchers at Dalhousie University, the University of Windsor, Stony Brook University, Florida International University and the University of Miami.
“This is a big concern because the loss of sharks can affect the wider ecosystem,” said Mike Heithaus, executive director of FIU’s School of Environment, Arts and Society and co-author of the new paper. “In working with tiger sharks, we’ve seen that if we don’t have enough of these predators around, it causes cascading changes in the ecosystem, that trickle all the way down to marine plants.” Such changes can harm other species, and may negatively affect commercial fisheries, Heithaus explains.
The data collected for the study shows that shark mortality was estimated to be about 100 million in 2000, and 97 million in 2010, with the possible range in the intervening years being between 63 and 273 million.
The main cause of these huge loss of sharks is as a result the huge global boom in shark fishing, especially that done specifically for only the fins. Because of how slowly they grow and reproduce, death rates that are this high for them are devastating. “Because adequate data of shark catches is lacking for most of the world, the wide range of possible mortality is based on available data of shark deaths and calculated projections for unreported, discarded and illegal catches.” Even if you are being very conservative with your estimates, there is no doubt that they are being caught at a much faster rate than they reproduce at.
“Sharks are similar to whales, and humans, in that they mature late in life and have few offspring’ said Boris Worm. “As such, they cannot sustain much additional mortality. Our analysis shows that about one in 15 sharks gets killed by fisheries every year. With an increasing demand for their fins, sharks are more vulnerable today than ever before.”
There are some shark species that in recent years have begun receiving some limited protection through national and international agreements, but according to the researchers these policies need to be expanded to a larger number of species and areas. “Imposing a tax on the export and import of shark fins could also help curb demand and generate income for domestic shark fisheries management.”
“The findings are alarming, but there is hope. Existing regulations are a great start but we must ensure they are adequately enforced,” said Samuel Gruber of the University of Miami. “In addition, more nations must invest in sustainable shark fisheries management. This means introducing catch limits, trade regulation and other protective measures for the most vulnerable species and those that move across international boundaries.”
The main point that the researchers are trying to make in their paper, is that without sharks, the sustainability of many marine ecosystems will be lost, with great consequences for those environments and for the fisheries associated with those areas. “Because of the role sharks play in the sustainability of marine ecosystems, the researchers insist that protective measures must be scaled up significantly to avoid further depletion and possible extinction of some of the world’s top predators.”
“The information from this report comes at a critical time, as 177 governments from around the world will attend the March 3-14 meeting of the Conference of the Parties to the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) in Bangkok. CITES is widely considered one of the best tools for protecting vulnerable species from extinction. Hammerheads, Oceanic whitetip, and porbeagle sharks are currently being considered for protection under CITES.”
The new research was just published in the journal Marine Policy.
Sharks are one of the oldest most-successful group of animals living on the planet currently. First appearing about 420 million years ago, most modern species date their origins back to about 100 million years ago during the time of the dinosaurs. Currently there are about 470 species of sharks in the world, of which many have been listed on on the IUCN’s Red List Of Threatened Species. Some species and populations have seen their overall numbers fall by 90% in the last 20-30 years.
Despite their depiction as being mindless predators, they actually possess a brain-to-body ratio similar to mammals and intelligent birds, and they can be quite social. There also are known to be curious animals that will investigate things that are clearly not food, and have been observed engaging in what could only be considered “play” in the wild.
They also possess an amazing set of predatory super-senses, such as electroreception, which allows them to sense electromagnetic fields, and to use them to locate prey and navigate. And they also possess a “stereo” sense of smell, a good sense of sight with good night vision, an incredible sense of hearing, and the “lateral line” system.
Source: Dalhousie University
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