Fish dying in droves as red tide takes its toll

Shaun Gillham

THE toxic red tide which invaded Eastern Cape waters over the past four weeks has taken a deadly toll on Algoa Bay and its adjacent shore- lines where hundreds of dead fish and other marine life have washed up over the past few days.

Two leading marine experts said yesterday it was the first time so many fish and other Bay marine life had died as a result of a red tide.

Experienced Bayworld marine biologist Dr Malcolm Smale collected about 80kg of dead fish in the Sardinia Bay area on Saturday.

Marine and red tide expert Dr Tommy Bornman said dead fish had been washing up since the weekend between Woody Cape and the Sundays River Mouth, and on Port Elizabeth's "wild side" that extends from Cape Recife to the Maitlands River Mouth. A large number of dead fish had also washed up in the Alexandria dune field areas.

Bornman said samples from the dead fish were being sent for toxicity testing, but his initial evaluation indicated that the fish had died from a lack of oxygen rather than toxins.

"The red tide is dying off and decaying which results in oxygen loss in the water.

"The marine life affected is mostly reef fish, which are territorial, meaning that they stay in their territory despite diminishing oxygen."

The affected fish were mostly in-shore species and larger, more mobile fish and line-fish, as well as squid – which prefer clean water – would not be affected, he said.

A Herald photographer who visited Sardinia Bay on Tuesday found dead fish about every 10m along one stretch, including octopus, puffin fish and yellowtail.

The recent red tide was viewed as a unique red tide by marine experts. Their tests revealed that not only was some of the red tide toxic, but it also contained species of algae found in Algoa Bay for the first time. The red tide was also denser than ever experienced along the Eastern Cape coastline, with the tide up to 15m deep in places.

Bornman advised people not to eat any of the dead fish.

Smale said he had collected a variety of fish species, ranging from romans to bronze beam, black tail and zebra fish. "I can confirm that this event resulted in a fairly large mortality," he said.

Nelson Mandela Bay Municipality spokesman Mthubanzi Mniki said the municipality was still monitoring the red tide.