From: Discovery News and ABC Science Online
Published June 9, 2009 07:20 AM

Overfishing, Other Factors Leading to Proliferation of Giant Jellyfish

Giant jellyfish are taking over parts of the world's oceans as overfishing and other human activities open windows of opportunity for them to prosper, say researchers.

Jellyfish are normally kept in check by fish, which eat small jellyfish and compete for jellyfish food such as zooplankton, researchers said. But, with overfishing, jellyfish numbers are increasing.

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These huge creatures can burst through fishing nets, as well as destroy local fisheries with their taste for fish eggs and larvae.

Anthony Richardson of CSIRO Marine & Atmospheric Research and colleagues reported their findings in the journal Trends in Ecology and Evolution to coincide with World Oceans Day.

They say climate change could also cause jellyfish populations to grow. The team believes that for the first time, water conditions could lead to what they call a "jellyfish stable state," in which jellyfish rule the oceans.

The combination of overfishing and high levels of nutrients in the water has been linked to jellyfish blooms. Nitrogen and phosphorous in run-off cause red phytoplankton blooms, which create low-oxygen dead zones where jellyfish survive, but fish can't, researchers said.

In the photo, a diver is attaching a sensor to track a monster Echizen jellyfish, which has a body almost 5 feet across, off the coast of northern Japan.

Article continues:  http://dsc.discovery.com/news/slideshows/monster-jellyfish.html

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