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Mysterious Travels by Tagged Tigers

Werry and a colleague release a tiger shark that has been tagged with satellite and acoustic transmitters.

In Australia, the government has started to cull sharks of 3 meter or longer with baited drum lines. But these sharks are not Australian, they cross borders!

The tiger shark loves warm waters and is found in most tropical and temperate regions, both on the surface and in depths of up to 1,150 feet (350 meters), and often coastal murkey waters, where this species loves to hunt for a wide variety of prey. One study found that the tiger shark swam about 30 miles to 40 miles (48 km to 64 km) a day looking for food.

A shark knows no borders…

 

For example, it’s largely believed that tiger sharks migrate to warmer locations when it gets cold, but biologists aren’t sure if the tiger sharks are following their prey, or if they just prefer a warmer climate. The tiger shark is generally thought to be a nocturnal animal, but in some cases, it’s been spotted feeding during the day. In Hawaii for instance, tiger sharks are not nocturnal because they frequently eat monk seals, which are diurnal.

A research project led by Jonathan Werry, of Griffith University in Australia, examined the migration patterns of tiger sharks across the Coral Sea, which is located between the east coast of Australia and the Pacific island of New Caledonia.

Spatial patterns of tiger shark movements across the Coral Sea between 2008 and 2013.

 

The study tracked 33 tiger sharks (Galeocerdo cuvier) using satellite and acoustic transmitters. The sharks ranged in length from 5 feet (1.5 meters) to nearly 13 feet (4 m).

The researchers found that mature female sharks tend to be the ones making long-distance journeys across the Coral Sea — between the deep ocean and the more shallow, coastal waters — while adult males and younger females were found to linger in oceanic reefs away from the coasts.

Tiger shark migration off Bermuda between 2011 – 2013

A long-term project at the Guy Harvey Research Institute in Florida by Dr. Mahmood Shivji and his team followed tiger sharks, outfitted with satellite tags that provide remarkable and previously unknown information about  long-term movement behavior. The team was able to follow many of these tiger sharks for a long period of time (10-23 months and counting).

The results from long-term tracking of sharks tagged in Bermuda are showing that in the western North Atlantic, adult tiger sharks display detectable patterns of movements and clear evidence of residency “hot-spots” that appear to be seasonal. The overall patterns detected for adult sharks are that they migrate south along a broad corridor from Bermuda to the Bahamas (mainly) and some sections of the Antilles, where they overwinter. The sharks then migrate north during spring and summer months, spending 5-6 months in the open ocean, north of Bermuda and in many cases almost in the middle of the Atlantic Ocean!

Read the report Reef-Fidelity and Migration of Tiger Sharks, Galeocerdo cuvier, across the Coral Sea at Plos One:

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0083249

Read about tracking tiger sharks by Guy Harvey Research Institute:

http://www.nova.edu/ocean/ghri/tiger-sharks/index.html

See more images at

http://www.livescience.com/42427-photos-tracking-tiger-shark-migrations.html

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