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Jellyfish threaten to 'dominate' oceans

Monday, 8 June 2009 Anna Salleh
ABC
Giant jelly fish are taking over parts of the world's oceans due to overfishing and other human activities, say researchers.

Dr Anthony Richardson of CSIRO Marine & Atmospheric Research and colleagues, report their findings in the journal Trends in Ecology and Evolution.

"We need to take management action to avert the marine systems of the world flipping over to being jellyfish dominated," says Richardson, who is also a marine biologist at the University of Queensland.

Richardson says jellyfish numbers are increasing, particularly in Southeast Asia, the Black Sea, the Gulf of Mexico and the North Sea.

He says the Japanese have a real problem with giant jellyfish that burst through fishing nets.
. . .
Richardson says researchers are experimenting with different ways of controlling jellyfish.

Some methods involve sound waves to explode jellyfish, while others use special nets to try and cut them up.
Simple animals

Jellyfish are considered simple jelly-like sea animals, which are related to the microscopic animals that form coral.

They generally start their life as a plant-like polyp on the sea bed before budding off into the well-known bell-shaped medusa.

Jellyfish have tentacles containing pneumatocyst cells, which act like little harpoons that lodge in prey to sting and kill them.

The location and number of pneumatocysts dictate whether jellyfish are processed for human consumption.

While dried jellyfish with soya sauce is a delicacy served in Chinese weddings and banquets, not all kinds of jellyfish can be eaten, says Richardson.

According to Richardson, the species increasing in number aren't generally eaten.

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