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Possible Red tide: no fishing for mussels for now

08 January 2014

He has found "low numbers that are highly unlikely to cause a bloom". Authorities have nonetheless cautioned against the fishing of shellfish/ mussels in the Knysna estuary until it is declared safe to do so.

"Common types of red tide can kill shellfish, abalone, white mussels and black oysters. Other blooms can be stored in mussels until they become poisonous if eaten by humans. It is for this reason that we are cautioning against fishing mussels in the estuary until it is safe to do so" says Owen Govender, Senior Section Ranger of the Knysna section of the Garden Route National Park.

What are these phytonplankton organisms?

According to a Marine and Coastal Management Guideline from the Department of Environmental Affairs, Phytonplankton are "microscopic, single-celled organisms that float in the sea. They are able to photosynthesise and form the basis of food chains in the oceans. There are three types of red tide organisms, dinoflagellates, diatoms and ciliates."

Dinoflagellates usually lie dormant on the seabed until they are lifted to the surface during upwelling where the ideal conditions of temperature and light trigger their germination.

Paralytic Shellfish Poisoning (PSP), which produces toxins that disrupt normal nerve functions, can be associated closely with dinoflagellate. Symptoms of PSP appear anytime between one and five hours after eating contaminated seafood.

Issued by:
South African National Parks (SANParks) Corporate Communications:
Tel: 044 302 5633

Nandi Mgwadlamba
Tel: 044 302 5633 Cell: 078 702 9663 or email:

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