Consuming red tide catch not worth risk

Reel Time, with Wayne Rudman

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KILLER TIDE: This dead poenskop washed up at Sardinia Bay

THE Eastern Cape has again experienced a red tide. I personally witnessed the reddish, oily slick (red tides are not only red in colour) that could be seen from the shore at the Noordhoek Ski Boat Club this month.

This has been widely reported in the media. It is caused by upwelling of concentrations of high nutrient warming water that triggers the germination of dinoflagellate cysts as the light and salinity influence them.

These lie dormant in the sediment of the sea floor. The rapid increase in dinoflagellate numbers, known as a “bloom” of phytoplankton, is the formation of the red tide.

The toxins produced by certain dinoflagellates are some of the most potent poisons known to man.

The most notorious of the dinoflagellate toxins are neurotoxins (there are other types of poisons which are found in different red tides), which disrupt normal nerve functions.

The consumption of shellfish during this period can be fatal.

The symptoms of such poisoning include a tingling, prickling, stinging or burning sensation within 30 minutes of consumption. This is followed by numbness of the arms, legs and neck, with dizziness, general muscle incoordination, headaches, vomiting and impaired respiration.

Death results as respiratory failure sets in within a matter of hours.

These red tides often kill fish directly or indirectly too, as experienced at Sardinia Bay, as the microscopic phytoplankton clog their gills, preventing the extraction of oxygen from the water.

Red tides also deplete the oxygen levels of the water. The fish are not necessarily poisonous if collected immediately as they wash ashore, however I would not take that chance.

This is the same phenomenon that drove the crayfish ashore in the Western Cape not long ago.

In the Western Cape, red tides are most toxic. It has been noted that there is a level of toxicity in the red tide along our shores – but that danger has not been determined yet.

What has been noted is that rare species are “blooming” and this can be from other regions where water has been carried in the hulls of fishing boats. The water is then expelled in our waters as the catches made replace the water that is used for ballast.

On to another matter, I was troubled to witness the abusive verbal conduct of a skipper of a recreational craft when being inspected at the harbour recently.

It was quite clear he had little or no regard for the law and the inspectors who are simply enforcing compliance. It was clear there was little compliance on his craft and thus the need for prosecution.

It is these unscrupulous individuals, who are also angling club members, who tarnish the image of sport and recreational angling.

The clubs and organisations that control angling in our province need to clean up their act. There were a number of summonses issued at the recreational slipway of the port that particular day and this for excess numbers of the daily quota, along with a lack of permits to angle.

For an electronic version of the angling brochure visit www.daff.gov.za

For more information on red tides visit www.botany.uwc.ac.za/envfacts/redtides

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