Shrinking Whale Sharks in Western Australia

Whale sharks are the biggest shark in the sea growing to 12 metres and weighing 13 tonnes. That’s a big fish! They live for 70 years and swim the earth’s tropical waters and warm oceans. Unlike the stereotypical shark, they eat plankton and don’t have sharp scary teeth. They swim gently near the surface, mouths wide open, straining the oceans of plankton.

They are spectacular. Dark blue on top , lighter underneath, and covered in white spots like a starry night. In fact, these starry patterns of spots are used to identify individual sharks with software developed by NASA to identify stars in the night sky.

Because they are beautiful animals and swim near the surface they have become a major tourist attraction in places like Belize, the Seychelles, and Ningaloo Reef in Western Australia. Unfortunately though and because they swim the oceans, they are easy targets for fishermen looking for the biggest shark fins in the world.

New research on Ningaloo Reef, Western Australia (Bradshaw et al 2008) has found that the sharks are getting shorter! The average length of the sharks that visit the reef is about 2 metres less than it was. There are also few sharks turning up each year, sightings have fallen by about 40%! This has happened despite a total ban on fishing for these sharks in Australian waters – no good for the tourism industry…and the sharks.

A decreasing size and abundance of a fished species is a classic signal for overfishing. Because this beautiful shark wanders the oceans of the world it is exposed to different fisheries regimes, some conservative and some totally unregulated. With shark fins being worth so much in the Asian markets, capturing a large whale shark is like a big Christmas bonus for fishermen. As human populations grow the pressure on these fish is only likely to increase.

Nemo’s home to be the world’s largest marine park

Everyone’s heard of the Great Barrier Reef, in the Coral Sea off the east coast of Australia. You know, the home of Nemo, that cute little clown fish with the odd shaped fin. Recently Australia’s best marine scientists together with the Pew Environment Group have called for the Coral Sea to be declared a marine protected area. A National Park in the sea.

That’s 400 000 square miles, even bigger than Texas!

Professor Terry Hughes from James Cook University (a man whose seen the Caribbean coral reefs fade away) said “There is overwhelming evidence the world's marine ecosystems have been seriously degraded by overfishing, pollution and global warming. These trends call for urgent, practical solutions”. The Coral Sea is a beautiful place and one of the last relatively unscathed warm water environments on Earth. The endangered Hawksbill and Green turtles call it their home as well as 25 species of whales and dolphins, countless species of fish, birds, invertebrates, and of course little old Nemo.

The large fish like sharks, tuna, marlin and sailfish are some of the fastest animals in the seas. They are targeted by fishers in all the oceans of the world because they are so valuable. Fishermen can get up to $110/ kg for shark fin making them well worth the hunt. The Coral Sea is one of the few places left on Earth where these large fish have not been overfished…yet.

With climate change on the way and an ever increasing human population, marine ecosystems need as much biodiversity and responsible management as they can get if they are to be resilient in the face of changing ocean currents, ocean acidification, and habitat loss. There are only a handful of places in the world where a large oceanic marine park could be made, and enforced, Australia and the Coral Sea is one of them.