Update

MOSSEL BAY NEWS - Seeing a jellyfish in the water while you are swimming can make your knees turn to jelly, because they can sting you painfully.

Last week the Mossel Bay Advertiser reported on its website that there were jellyfish in the Poort - a favourite Mossel Bay swimming spot at the Point in town. The Poort was closed for swimming last week because of the jellyfish.

Photographs and a video were taken of the fascinating creatures which displayed luminous colours and graceful, flowing movements in the water. They are small and people wonder if they are juveniles or simply a small species of jellyfish.

Mossel Bay resident Kosie Gericke said on Tuesday, 4 February: "I swam in the Poort yesterday and did not see the jellyfish at first, but then realised they were under the waves, under the foam." Kosie said there were not as many jellyfish as there were last week.

Juanita Terblanche said: "I saw many jellyfish last week. There were also some dead ones. I think they were trapped in the Poort and could not get out." On 4 February, no jellyfish could be seen at the Poort. It was a sweltering 27C - good weather for swimming.

Municipal spokesperson Nickey le Roux still urged swimmers to be cautious: "Jellyfish - much like bluebottles - may be in the Poort at times because of rough seas and conditions on the open ocean. 

The Poort is a channel that is open to the sea, so there is no way of knowing whether there will be jellyfish or blue bottles in the swimming area.

"The Mossel Bay Municipality urges bathers to always be careful when swimming, especially during or after rough seas."

Night-light jellyfish
A jellyfish expert told the Advertiser: "Pelagia noctiluca (night-light jellyfish) can be found along the Mediterranean and the Atlantic Ocean, stretching from Namibia to False Bay."

The expert said the jellies were in the Poort, far from False Bay "possibly due to strong winds and currents and the sudden drop in sea water temperature (from 25 to 18 degrees Celsius), and or climate change".

He said: "They come in along the coast and wash up on beaches when strong oceanic currents and winds move in the direction of the coast. The fact that they are being washed out more regularly could be due to climate change and its effect on weather patterns.

"They eat mainly zoo-plankton and small crustaceans. Prey is caught using the eight mauve-coloured stinging tentacles (these are its identifying markers).

"The barbs or spines on the tentacles are sharp and can penetrate the shell of a crustacean, which is then paralysed by the venom and moved to the clumped tentacles. There are four oral tentacles located in the middle of the jellyfish. The head, or umbrella, of the jelly fish has eight lobes at its edge, where sense organs are located. Its umbrella is covered with wart-like nodules (another identifying marker). 

The expert said: "The sting can be painful and varies from person to person. Often a whip-like mark is left on the skin that can become red and swollen.

"It is not lethal to humans and there are very few people allergic to the venom. If allergic, the person can go into anaphylactic shock, which can cause death if not treated.

"The night-light jellyfish is often confused with compass jellyfish, but the identifying markers are what distinguishes the Pelagia noctiluca (night-light) from the Chrysaora fulgida (compass jellyfish). If they are seen in the water or on the beach it is best to avoid them."