Great White Shark On Historic Marathon Migration
Researchers from Ocearch use a hydraulic platform to safely tag sharks like Lydia.
Sept. 5, 2012
-- Five rays and sharks are receiving priority attention at this week's IUCN World Conservation Congress held in Jeju, Republic of Korea. The congress is the world's largest conservation event. One of the five sharks is the porbeagle, shown here. Porbeagles are vulnerable globally, and are classified as critically endangered in the Northeast Atlantic. Their low reproductive capacity combined with over-fishing has led to severe population declines over several parts of its range. "Sharks and rays have traveled the Earth for more than 400 million years," said Dr. Cristián Samper, president and CEO of the Wildlife Conservation Society and keynote speaker at the Jeju congress. "Yet, in only recent decades, many of these species have become threatened from overfishing and, in some instances, have disappeared entirely from major portions of their range." He added, "The potential loss of one of only two groups of the world's living fishes is a crisis the world community must take decisive action to address. We are calling for governments around the world to vigorously support CITES international trade regulations and strengthen fisheries management and protection measures for shark and ray species. We cannot continue to allow the destruction of these wonders of evolution."
Manta Rays Fate Worse Than Sharks
The oceanic whitetip shark is critically endangered in the Northwest and Central Atlantic Ocean. It's frequently sought after for its fins, used to make shark fin soup. Usually the rest of the dead or dying shark is then tossed back into the sea. Andrew Brierley, a University of St. Andrews marine ecologist, told Discovery News that when sharks like this die off, the deaths can cause a domino effect of other ecosystem losses. Shellfish, for example, may go into decline because they are consumed more by predators that the sharks would normally prey upon. "The trophic cascade brought about by the increasing demand for shark fin soup has not only left once economically valuable bivalve fisheries in crisis, but has precipitated an ecological and culinary bankruptcy," explained Brierley.
Scalloped hammerhead sharks are endangered all around the globe. This tropical species forms large migratory schools at certain times of the year. The aggregating behavior, distinct from that of other sharks, makes the shark particularly vulnerable to fishing. "We estimate that many millions of sharks are killed annually through both legal and illegal, unregulated and unreported fishing for the trade in fins, the prime ingredient in shark fin soup," said Dr. Rachel Graham, director of WCS's Gulf and Caribbean Sharks and Rays Program. "The high price for fins has caused the global shark fishery to expand far beyond what is sustainable. The need for international regulation and enforcement has never been greater."
Shark Paradise Found
Many rays, such as these, are also in peril. The Wildlife Conservation Society and over 35 government agencies and NGO partners at the congress additionally highlighted population loss problems associated with so-called "devil rays," which feed on planktonic crustaceans. Small schooling fishes become trapped on their specialized gill rakers. Rays are frequently captured in target fisheries and as bycatch across much of their range. One reason is that the gill rakers are dried and exported for the Asian medicinal market.
Dr. Dwayne Meadows, NOAA/NMFS/OPR
The reef manta ray, shown here, is among the world's largest fishes. Both it and the giant manta ray can grow several feet across. They are slow growing, however, typically giving birth to only one pup every two to three years. They are migratory and occur in small, highly fragmented populations that are sparsely distributed across the world’s tropics. Manta rays are captured in targeted fisheries and incidentally as bycatch. In addition, manta rays are used for human consumption, shark bait, and -- as for devil rays -- are increasingly sought for their gill rakers. "The international trade in shark and ray products, including fins, meat, and other body parts, is driving shark and ray fisheries around the world, and most of these are unmanaged or only minimally managed," said Dr. John Robinson, WCS's executive vice president for Conservation and Science. "Lack of controls on fisheries and international trade puts species at risk, but also jeopardizes sustainable fisheries, ecosystems, and food security." The Convention on International Trade in Endangered Species of Wild Fauna and Flora will meet in Thailand in March 2013.
PHOTOS:Shark Teeth Weapons Reveal Surprises
A great white shark called Lydia is set to make history. First tagged a year ago off the Florida coast, she's on her way to becoming the first tracked white shark to cross the Atlantic.
Lydia is being monitored by the marine nonprofit Ocearch as part of its ongoing project to help researchers and scientists gather previously unattainable data on shark movement, biology and health. The 14-foot-6-inch great white has migrated more than 19,000 miles since being tagged, and is about to cross the mid-Atlantic ridge -- closer to Europe than the United States.
Over time, Ocearch has collaborated with over 50 researchers from more than 20 institutions. The team that tagged Lydia included Massachusetts Division of Marine Fisheries senior scientist Greg Skomal. Tracking helps the scientists learn more about great white shark biology, he told me last summer. And that could mean providing beach managers with better information to keep both the sharks and the public safe.
The Ocearch team uses two different kinds of electronic tags, Skomal explained. One is a pop-up satellite tag that can archive data such as depth and light levels. The tag can be programmed to release from the shark and then float on the water surface to transmit data back to the scientists.
Another is a real-time satellite tag, which connects to a satellite whenever the shark comes to the surface, providing data about the shark's movements so scientists -- and the public -- can follow a shark's migration patterns over a long time. This is what Lydia has.
In order to tag a great white shark, the team first had to lure it to a smaller boat -- no easy task -- then catch the shark safely and transfer it to the main Ocearch vessel via hydraulic lift. The team only had 15 minutes to attach tracking tech, do scans, take a small sample and then release the shark. In August, they successfully tagged a 14-foot-2-inch great white named Katharine and followed her progress from Cape Cod to Daytona Beach, Florida.
In the future, an underwater robot could even track tagged great white sharks. Skomal, a Shark Week veteran (video), has been working on an autonomous underwater shark tracking robot that can compete with the robots that West Coast shark trackers Chris Lowe and Chris Clark are developing. "For science purposes it's great to know everything you possibly can about all the animals on Earth. White sharks are no exception," Skomal said.