Natural Environment Blog

Satellite tracking has revealed that Great White Sharks travel large distances to unlikely places. Photo: Terry Goss.

Two great white sharks have traveled 4,000 kilometers from the cold waters of southern New Zealand to the tropical waters of North East Australia.

The sharks began their journey in Stewart Island - 30 kilometers south of New Zealand’s South Island, and made their way to the Great Barrier Reef off the coast of the Australian state of Queensland.

The journey, of which one shark dived 1,000 meters, has surprised scientists who were studying the sharks. 

“We used to think great white sharks were shallow-water coastal species that lived in cold areas, where there were lots of seals to eat,” said Malcolm Francis, of the National Institute of Water and Atmospheric Research in Wellington.

“Now we have changed our impression of what they do.”

Possible World Record

Dr Francis added that the 1,000 meter dive could even be a world record for a great white shark.

Although various reports on the Internet claim that great whites have been known to dive to as much as 1,280 meters, great whites, which are known for swimming close to the surface, rarely dive to more than 800 meters below the surface. 

It’s likely that the shark was chasing a giant squid or phosphorescent fish at the time. Dr Francis says that at those depths, it would have been pitch black, and the shark would have been guided by the glow of the fish.

Great Whites “Know Where They’re Going”

National Institute of Water and Atmospheric Research (NIWA) and the Conservation Department have been attaching satellite tracking devices to great white sharks to measure position, depth and water temperature. After several months, the devices eventually detach themselves from the shark and float to the surface, where data is transmitted to a satellite.

Dr Francis was also surprised to learn that the sharks traveled in a straight line, and covered up to 120 kilometers per day. 

“They seem to know where they are going,” he said.

A million tonnes of fish and other marine life caught in the North Sea is thrown overboard every year, according to a new study by WWF-Germany.

The resulting report, entitled “Sea Creatures Are Not Rubbish”, says that one-third of all North Sea catch ends up back in the sea. In other words, for every tonne that ends up at the fishmonger, two tonnes were thrown back into the ocean. 

The discarded creatures are usually referred to as “bycatch”. Bycatch is any species caught in a fishery that wasn’t supposed to be - often because it’s the wrong species or it’s too small. 

The main problem with bycatch is that, most creatures are dead or close to death by the time they’re thrown back into the ocean. This represents a huge threat to marine life all over the world. Each year, millions of turtles, whales, dolphins, sharks, and seabirds, right through to juvenile fish, corals, crabs and starfish etc are killed and tossed back into the ocean.

And it’s not just a conservation problem. It’s also a problem for the fishers themselves.

“Bycatch costs fishers time and money,” says Amanda Nickson, Head of WWF’s Bycatch Initiative. “It contributes to the already critical problem of over-fishing, it jeopardizes future revenue, jobs and long-term food security.”

“It is also a major killer of marine wildlife. How many more reasons do you need to change the way we fish?” she adds.

Different target species result in different degrees of bycatch. For example, the report says that for every kilogram of Dover sole (Solea solea) that found its way to the fishmonger, six kilograms of bycatch had been thrown overboard. The study also found that every kilogram of Norwegian lobster or scampi results in five kilograms of bycatch.

WWF says that every year several million sharks and up to 250,000 sea turtles are killed in fishing operations designed to catch other species.

“Bycatch is an incredible waste and one of the largest threats to many sea creatures,” said Karoline Schacht, Fisheries Policy Officer, WWF-Germany. “The drama happens far away at sea but this unseen wastefulness must come to an end.”

WWF has been working on the bycatch issue arround the world, and currently has 70 bycatch projects in over 40 countries.

Here’s the full report (written in German): Sea Creatures Are Not Rubbish [PDF, 1.03 MB]

The Wildlife Trust of India (WTI) is about to implement a satellite tracking program for the whale shark (Rhincodon typus).

The program, believed to be the first of its kind in India, will involve monitoring of whale sharks along the Gujarat coast. The sharks will have a tag implanted in their dorsel fin, which will be able to rely important information to satellites about the movements of the fish.

In particular, the satellite tracking will provide scientists with information about the migration, breeding, water temperature and deep movement among other parameters of the fish and its habitat.

Often referred to as the "gentle giant", the whale shark can grow up to 12.2 m. (40 ft.) in length and can weigh up to 13.6 tonnes (15 short tons).

Although this is the first time satellite monitoring will be used for whale sharks in India, its not the first time the country has used satellite tracking on marine life. India has used satellite tracking on sea turtles and other marine species. 

“We do not have any population specific data about the species. One of the greatest constraints of the conservation of the fish is poor knowledge about the life and biological parameters such as growth, reproduction, distribution and movement,” coordinator of the project Dhiresh Joshi said.

The data provided by the program will help in designing conservation projects for the whale shark, which has been listed on the International Union for Conservation of Nature’s (IUCN) Red List as vulnerable since 2000.

The whale shark is often killed for meat, liver oils, fins, frozen meat that are in huge demand in the south Asian countries.

Previous Satellite Monitoring

The U.S. and China have already been tagging whale sharks, with some interesting results. Satellite monitoring in the U.S. and South China sea have revealed that whale sharks can travel thousands of kilometers over many years. 

About the Whale Shark

Often referred to as the “gentle giant”, the whale shark can grow up to 12.2 m. (40 ft.) in length and can weigh up to 13.6 tonnes (15 short tons). The giant fish can be found in warmer, tropical oceans, usually between latitudes 30°N and 35°S, and is often seen in the waters of Australia, India, the Maldives, South Africa, Belize, Mexico, the Galapagos Islands, Southeast Asia and Indonesia.

A whale shark can live for as long as 70 years (if its not hunted and killed beforehand).

Although the whale shark was first discovered in 1828, it is believed to have been around for at least 60 million years.