Knysna - Fishermen must not fish for shellfish and mussels in the Knysna estuary at the moment as a possible red tide is approaching, SA National Parks (SANParks) said on Tuesday.
“Common types of red tide can kill shellfish, abalone, white mussels and black oysters,” said Garden Route National Park Knysna section senior ranger Owen Govender.
“Other blooms can be stored in mussels until they become poisonous if eaten by humans,” he said.
“It is for this reason that we are cautioning against fishing mussels in the estuary until it is safe to do so.”
In a SANParks statement, local estuary expert Prof Brian Allanson said water samples collected from two key points in the estuary confirmed the presence of phytoplankton in the water.
While the low numbers were highly unlikely to cause a bloom, the authorities nonetheless cautioned against fishing there until it was declared safe.
According to Marine and Coastal Management guidelines, phytoplankton are microscopic, single-celled organisms that float in the sea.
One type lay dormant on the seabed until being lifted to the surface, where it germinated. It was associated with paralytic shellfish poisoning, which occurred one to five hours after eating contaminated seafood.