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Thursday, 19 October, 2000, 16:21 GMT 17:21 UK
Shark deaths mystery
shark
An algal bloom may be to blame for the deaths
Biologists are baffled by a spate of shark deaths on the United States east coast.


"I've never seen anything like this

Biologist Dr Enric Cortes
About 300 decaying dead sharks have been washing up along a half-mile stretch of Florida beaches since Monday.

Traces of blood reported on nostrils and gills of some sharks suggest an infection might be the culprit.

But Dr Enric Cortes, a biologist for the National Marine Fisheries Service, said he had checked 100 carcasses and saw no blood.

Nor were there any signs the sharks had been injured by fishing nets or long-line gear.

Red tide

st petersburg
Samples have been sent to St Petersburg for analysis

"I've never seen anything like this," Dr Cortes said.

"Mass mortalities in sharks are very unusual."

About 85% of the sharks - up to 1.5 metres long - are blacktips and the rest Atlantic sharpnose.

An algae bloom known as red tide has been reported in the area, but it would have killed other fishes and sea life, and no other species was dead, Dr Cortes said.

He said the sharks may have died from a low level of oxygen in the shallow waters.

Biologists collected tissue samples to send to the Florida Marine Research Institute in St Petersburg to check for signs of red tide.

Red tide occurs when microalgae burst, releasing reddish brown toxins into the water. It can kill fish and cause respiratory irritations and watery eyes in humans.

No plans are being made to remove the carcasses because the area is not heavily frequented by people.

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See also:

06 Jul 00 | Sci/Tech
Soup threatens sharks' survival
12 Jul 99 | Sci/Tech
Protection call for 'gentle giant'
26 Sep 00 | Asia-Pacific
Sharks kill two surfers
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