Miami, FL - Blobs of slimy jellyfish are taking over some beaches in the southern United States, the result of a shrinking fish population caused by humans, scientists claim.
"Now that fish are being overfished in a lot of ecosystems, it's providing an opportunity for jellyfish populations to explode," said Sean Colin, an associate professor of marine biology at Roger Williams University in Rhode Island.
"There's been evidence suggesting that there are more and more jellyfish blooms globally."
When there are fewer fish, the jellyfish are able to ingest more food as there is less competition for it.
Climate change is also a factor, Colin said in an interview, because fish higher up in the food chain are affected by changing water temperatures and the availability of their food sources.
For swimmers and fishermen in Florida, Alabama and Mississippi, the result is simple: more jellyfish, more problems.
"We've had a lot of trouble," Larry Scott, who shrimps in Mobile Bay, Ala., told the Press-Register.
"There were a couple of weeks before (Tropical Storm Lee) where we quit shrimping over around Tensaw (Ala.) because we couldn't even pick up the nets for all the jellies."
The "jellies" in question were of the moon variety, which have weak stings but can grow to the size of dinner plates, according to a New York Times report.
In Florida, moon jellyfish were found every 10 metres on beaches in Brevard County, southeast of Orlando, the local newspaper said.
Colin says during the past decade the number of jellyfish in some oceans around the world, including the Black Sea and the Bering Sea, has ballooned.
Other scientists agree. Lucas Brotz, who studies trends in jellyfish populations at the University of British Columbia, writes that anecdotal evidence points to a global increase in jellyfish.
"Fishing, pollution, aquaculture, global warming and coastal development can all create conditions which favour jellyfish over fish," he writes in his online biography.
"In addition to affecting tourism by stinging swimmers, jellyfish can interfere with fishing activities and clog industrial cooling intakes, resulting in significant economic losses."
Colin examined why the blind blobs are becoming good enough predators to compete with fish in a recent article published in Science Magazine.
"Being large has helped them ingest, or capture, more prey," he said. "In some ecosystems, definitely, they're taking over the role of fish."
The difference is, you can't really eat them.
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