Gray with dark vertical stripes that run along their topsides, tiger sharks can inspire fear in the minds of the masses. Data gathered from the International Shark Attack File shows that between 1580 and 2014 there were 111 attacks. That’s second to the great white, whose attacks number 314.
But human activity is hurting the tiger shark population. The species, according to the International Union for Conservation of Nature Red List of Threatened Species, is classified as “near threatened.” Major threats include fishing and human pollution, which tiger sharks have been known to eat, including garbage, such as tires and car license plates.
Researchers from the Univ. of Western Australia recently published a study regarding tiger shark movement and found the species has the ability to travel vast distances regardless of water temperature. One of the studied sharks, over a 517-day period, traveled 4,000 km.
“Tiger sharks are considered residents of tropical waters, however, we showed that these sharks can travel thousands of (kilometers) and go as far south as to the cold temperatures off Albany,” said study co-author Luciana Ferreira, of Univ. of Western Australia.
Common in tropical and sub-tropical waters throughout the world, tiger sharks can grow to between 10 and 14 ft and weigh between 850 and 1,400 lbs; but large specimens can grow between 20 and 25 ft, and weigh more than 1,900 lbs, according to National Geographic.
“We know relatively little of their patterns of residency and movement over large spatial and temporal scales,” write the researchers in PLOS One. “Given the anthropogenic threats to these apex predators, information on their movement behavior … is essential for the development of appropriate management and conservation strategies.”
The 11 sharks studied were caught off Ningaloo Reef in Western Australia in June 2007, August 2008 and May-June 2010. Satellite-linked transmitters were mounted on the sharks’ dorsal fins.
After being tagged, the 222 cm female, which traveled 4,000 km, moved 500 m “to the Rowley Shoals and Kimberley region. It then made a path to Sumba Island, Indonesia, and returned, crossing ocean depths of 5 km and covering a distance of more than 1,000 km in two weeks. In December 2008, the shark moved south, traveling to waters off Jurien Bay and Perth between January-February 2009. Between April and May 2009, the shark rounded Cape Leeuwin with transmissions clustering off Albany. After a period of no transmissions (118 days), the tag then started to transmit again in September, when the shark moved towards the north, returning again to Perth/Jurien Bay in January 2010,” the researchers write.
The sharks spent time in waters between 23 and 26 C, but also traveled in waters between six and 33 C.
“Our results showed that the regional marine reserves can only provide temporary protection to tiger sharks and their ability to move extensive distances will likely take them across national boundaries,” Ferreira said. “This means that any fishing pressure in parts of their distribution range may cause negative effects to the whole population, which will result in severe impacts to pristine environments.”
Due to the breadth of the species’ distribution, the researchers write conservation efforts will most likely require international cooperation.
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