Residents of the Florida Keys have spotted hundreds of sharks swimming along canals adjoining their properties as the fish attempt to escape a toxic red tide.
Bonnethead, black tip, nurse and lemon sharks have all been reported over the past month during the red tide, an overgrowth of microorganisms that can turn ocean water red, deplete oxygen levels and concentrate toxins in the water.
"You saw fins at first just like popping up and then you would look down the canal and with a little bit of the sun, you just saw more and more and you were like, 'Oh, that is not good'," said John Wagman, who lives in Longboat Key on Florida's west coast.
Longboat Key is a few kilometres from a breach at the abandoned Piney Point fertiliser plant in April that pumped tens of millions of litres of toxic discharge into Tampa Bay.
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Environmentalists are investigating the effect this had on red tide, which occurs naturally at this time of year, though not usually on this scale.
"You just don't normally see sharks piling up like that in these canals, they do go in there but not in the huge numbers that we're seeing reported," said Professor Mike Heithaus, a shark expert at Florida International University.
"It's not the kind of thing you would see if it wasn't a big red tide."