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Saturday, October 11, 2008

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.

1 comment: said...

Shrinking Whale Sharks in Western Australia is a painful topic to talk about. and i think there is a need to look into the patterns that are causing the humans to damage the nature and its beauty.