Tagged tiger sharks to reveal travels

(CNS): Scientists will be following the travels of two tiger sharks tagged in local waters recently, with the hope of learning a bit more about these marine predators and assist in their conservation. Marine biologists working with the Department of Environment caught and tagged the sharks last week fitting each with two types of high-tech electronic tracking devices. The sharks, a ten feet female called Tina and a seven feet younger, immature female Luiza,will help the researchers understand their species’ migration patterns, movements and behaviour. Sharks are becoming increasingly endangered and scientists are in a race against time to protect them.

The technology used to track the sharks is expected to give more details on the life of the species. One type of tracking de vice being used is a satellite tag that includes a GPS receiver and transmitter, and signals via satellite the location of the shark. The other type is a small acoustic tag or pinger that transmits a signal that can be detected by a permanent or hand held receiver, so showing that the animal is near. The acoustic tags (pingers) can be used to detect movements on a finer scale, providing a more detailed picture of the behaviour and movement of the tiger sharks while they are in Cayman.

“Both of them seem to being doing fine. Tina has reported in several times a day while moving around the island; she seems to be deep during the day, coming into shallower water at night to look for the stingrays and turtles on which these species normally feed,” said lead researcher Dr. Mauvis Gore. “Tiger sharks like many other species are increasingly endangered, as a result of intense overfishing globally. In fact large shark species are becoming so scarce globally that in many countries they are either fully protected, or else their fishing quotas have been reduced to zero.”

Only in the last few years have scientists discovered that tiger sharks can make extensive annual migrations between countries or even across oceans. The tracks revealed by the satellite tags results will show whether the tiger sharks that are sometimes observed in the Cayman Islands move around or between the islands, and whether, as suspected, they are here for only part of the year, and then migrate elsewhere.

International efforts to protect dwindling shark populations have come to the fore in the last few years because of the dramatic crash in shark populations that has taken place globally. Unlike bony fish, sharks mature very slowly and reproduce only once every one to two years, producing only a small number of pups. Yet over the last decade or two 70 million sharks per year have been fished and killed, almost entirely for their fins that are in demand as a component of sharks’ fin soup.

“Even if we agree to exploit sharks,” said Dr. Gore. “We want to do it sustainably, not in this crazy way that will see the resource completely destroyed in another 10 years. As it is, sharks are now far more valuable in the sea, than in the fishing boat. Divers will pay good money to dive in places where they have a chance of seeing such iconic wildlife, and the same sharks can be seen over and over again – whereas once it’s dead that’s it, and it fetches very little in the market.”

Local artist, Guy Harvey, whose Ocean Foundation provided the satellite tags, and who helped the team catch Luiza said tiger sharks are one of his favourite animals.

“They are the most handsome of all the sharks, and I just love painting them. It’s just unfortunate they have these stripes that give rise to their name, making people think they are much more dangerous than they really are.”
Harvey has also assisted with tagging of tiger sharks in Bermuda and the Bahamas.
The tiger shark study is part of a project that is being undertaken by a team from Marine Conservation International led by Dr. Gore.

The project is funded by UK Overseas Territories Environment Programme (OTEP) together with the Cayman Islands Department of Environment, the Save Our Seas Foundation, and the Guy Harvey Ocean Foundation. The team have been working in the Cayman Islands over the past year and a half to assess the species and abundance of species of both sharks and rays as well as whales and dolphins.

“We are very pleased with the preliminary results of this work,” stated Gina Ebanks-Petrie, Director of the DoE, “It is our duty to manage our marine environment in the best interests of the people of the islands; it makes sense to find ways of managing our resources so they benefit us in the long-term, not destroy them; and we also have international obligations to protect these threatened species.”

Sharks, because of media “hype” and their “Jaws” image, often cause public concern. But shark attacks on man are in fact very rare, typically causing only 4 – 6 fatalities throughout the whole world per year.

The resident project officer Oliver Dubock explained that people’s fear of sharks was greatly exaggerated. “Of course they can be dangerous,” he said, “but no more than fierce dogs. You need to know how to behave and how to handle them. Just as an example, in Florida on average over 70 people per year die from boating accidents, but less than one every two years as a result of shark attack.”

Tim Austin, Deputy-Director at the DoE, added, “We plan to keep people informed about the behaviour of Tina and Luiza. We hope to be able to keep the press updated with maps of their migrations. Of course it is essential that they are not harmed. All past experience has shown that killing local tiger sharks does not get rid of them; others simply come in from elsewhere. We urge fishermen and divers to join this important conservation effort and help look after these two beautiful animals.”

According to surveys, less than 10 percent of the world’s shark populations remain and the decline is continuing. “This is extremely worrying as sharks are key components of marine biodiversity,” Gore said.

While they are here the scientist will also be collecting data on other shark species, dolphins and whales to help protect this often undervalued resource in local waters.

“Our only hope to save the ocean’s iconic species is to gather information to develop conservation plans that will safeguard their future. This in turn could translate into sustainable economic benefits for local tour operators, dive companies and sports fisherman,” Dr. Gore added.

The research project will run until April 2012 and scientists are encouraging residents to help in the understanding of Cayman’s seas by reporting any shark, whale or dolphin sightings to the DOE at DOE@GOV.KY or 949-8469.