Cape Town - There has been no new strandings of West Coast rock lobster since Saturday, January 16, according to the environment, forestry, and fisheries department.
"This is despite research findings indicating that the red tide stretched along the northern shores of St Helena Bay, from Dwarskersbos to north of Lambert’s Bay, and moved south and is now located off the Berg River [estuary]," the department said in a statement on Sunday.
On Friday, January 15, the red tide was responsible for marine mortalities, including about 1000 kg of West Coast rock lobster in the vicinity of Elands Bay, about 220 km north of Cape Town.
The flow of the algal bloom, or red tide, into the southern region of St Helena Bay meant that there was unlikely to be further lobster mortalities of significance, owing to the smaller lobster populations in that region.
Further mortalities of other marine life were possible, particularly at risk was the Berg River estuary.
"The public is warned not to consume any decayed fish and shellfish washed ashore as a result of the red tide which could pose a serious health hazard," the department said.
Last Sunday, the department said a red tide had been building up at Elands Bay and had resulted in several marine species washing up on the beach. These included rock lobster, octopus, white mussels, and some fish species.
"As is often the case in summer and late summer, there has been a build-up of large red tides in the greater St Helena Bay region over the past few weeks. These blooms of phytoplankton presently extend 50-60 km in the vicinity of Elands Bay, Lambert’s Bay, and Doring Bay," the department said at the time.
Red tides are a natural phenomenon in coastal waters caused by a dense accumulation of microscopic algae. Some of the algal species are harmful because they contain toxins, which are poisonous to humans.
Poisoning may either take place through the consumption of contaminated seafood or by toxic aerosols or water-bound compounds that cause respiratory and skin irritation.
Other red tides cause harm through the depletion of oxygen (anoxia), which affects all marine creatures, and can lead to mass mortalities of the entire marine communities or mass walkouts of rock lobsters that try to escape the anoxic conditions.
In the Benguela upwelling region off the West Coast of Southern Africa, red tides have periodically led to rock lobster strandings. The best known examples are the strandings of hundreds of tonnes of rock lobsters in Elands Bay in 1997 and 2000.
In 2014, an extensive and long-lasting red tide occurred for the first time along the South Coast, extending from Knysna to beyond Port Elizabeth and causing wide-scale mortalities of fish.
African News Agency (ANA)