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- Communities and fishermen along the eastern and southern coast of the Eastern Cape have reported rare species of fish arriving ashore.
- Experts say hundreds of fish died after sea temperatures dropped from 24 degrees Celsius to 12 degrees Celsius off the south and east coasts of South Africa last week.
- The first reports of dead fish in the province were made by the Morgan Bay community on Wednesday when a pregnant giant ocean stingray carrying a 60kg cub washed up on a rocky shore.
Communities and fishermen along the eastern and southern shores of the Eastern Cape have enjoyed the haunting sight of rare species of fish washed ashore.
Experts say the fish were killed by a temperature shock after sea temperatures suddenly dropped from 24 degrees Celsius to 12 degrees Celsius in South Africa last week.
East London Museum scientist Kevin Cole has been busy tending to species, including two giant oceanic manta rays, a pregnant one, a 3.1m sand shark, a 2.1m Carcharhinus, and a host of other unknown fish types. .
Sharks showed up at Gulu and Kidd beach over the weekend, while stingrays hit Morgan Bay and Haga Haga beaches last week.
More fish, both common and unknown types, have been stranded on the popular unspoiled wilderness of the ancient Transkei.
Disturbing reports suggest that the incident has created a feeding frenzy in rural communities along the coast of Mqanduli, Willowvale and Xhorha, with locals collecting the dead fish with wheelbarrows.
East London Museum scientist Kelvin Cole investigates a giant oceanic manta ray washed up in Morgan Bay. (Photo: Morgan Bay Hotel)
This was confirmed by the province’s Department of the Environment, Forestry and Fisheries, which warned communities to stop eating fish, as it can be harmful.
The first report came from the Morgan Bay community on Wednesday when a pregnant giant ocean ray carrying a 60kg cub washed up on a rocky shore.
Cole reported that the blanket measured 5.17m from wingtip to wingtip and was found to be carrying a 2m wide baby.
A stingray cub weighing 60 kg was removed from its mother and brought in for a scientific study. (Photo: Morgan Bay Hotel)
He calculated that the animal was 15 years old. This came a day after a slightly smaller lightning strike hit Haga Haga beach. Cole reported on the East London Museum Facebook page that the specimen measured 4.53 m from wingtip to wingtip.
He added that this was the second record of the species for the museum since 1948 when a 5.31m specimen was recovered from the harbor and a cast was made, which is on display in the marine gallery.
According to the South African Association for Marine Biological Research [SAAMBR], the fish that reached the coast was due to the fact that the sea temperature dropped from 26 to 14 degrees Celsius.
Cole said: “The most likely cause of death is a dramatic change in sea temperature in recent days, from very warm to cold (upwelling event). This would have affected the physiology of the warm water species and could not do in the face of rapid change in water temperature. “
A lot of other different interesting fish also suffered a temperature shock and died. (Photo: Morgan Bay Hotel)
Provincial Environment, Forestry and Fisheries Spokesperson Ncedo Lisani said fishermen and coastal communities quickly took advantage of this bonanza, collecting fish and shellfish on the beach and in rock pools.
He added that many of these fish were family catches, but most were those that are rarely seen or caught.
“There is concern around the health aspects of consuming these washed fish. Some may have been dead longer than previously thought, some of the unknowns may be toxic, and we don’t yet know if the abnormality also resulted in ‘red tides.’ or harmful Algal Blooms (HABS).
“Consequently, coastal communities must be aware of the potential risks of collecting and eating these entrained fish and shellfish,” Lisani said.
When asked if the incident was related to climate change, Lisani said: “The general answer is yes, as the Agulhas current and wind regimes have been predicted to become more turbulent under the influence of climate change, which would imply that such meanders and ‘associated marine heat waves’ and ‘cold upwelling episodes could increase in frequency in the future.’
A lot of other different interesting fish also suffered a temperature shock and died. (Photo: Morgan Bay Hotel)
The Department of Environment, Forestry and Fisheries said the “marine heat wave”, “cold wave” sequence resulted in washouts and mortality of fish, invertebrates and seaweed off the east and south coasts.
Oceanographic and meteorological conditions contributed to the incident, the department added.
The event was monitored and tracked by the National Oceanic and Coastal Information Management System (OCIMS).
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So how does the temperature shock happen?
SAAMBR explained in a statement on Facebook: “During the summer along the east coast of South Africa, a strong thermocline is normally established (a strong temperature gradient between two bodies of water with warmer water above and cooler water below) on the continental shelf.
“With a southwesterly wind, Coriolis forces (caused by the spin of the earth) cause surface waters to drift to the left (in the southern hemisphere) and this brings warm, clean water from the Agulhas current into the coast and forces the thermocline into deeper water (a process known as downwelling).
“With the northeast winds, the surface waters are diverted towards the coast and the thermocline moves to a lesser depth (a process known as upwelling). In cases of prolonged strong northeast winds (as experienced last week), the thermocline rises to the surface causing a sudden drop in surface water temperature and, in severe cases, can stun and even kill fish and other marine life that cannot escape the sharp drop in water temperature.
“During winter, the occurrence of strong southwesterly winds and large swells associated with the passage of cold fronts tend to break the thermocline and lead to mixing of the water on the continental shelf. Obviously, this is a fairly simplistic explanation for water movements off the east coast.
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“In fact, they are very complex and, in addition to the great Agulhas Current flowing to the southwest, there are numerous eddies and twists associated with this current. While the current generally follows the fall of the continental shelf that occurs at a depth of about 200 m, it does meander. In addition, the shoreline is often not straight, and the many headlands and bays cause additional changes in coastal water movement patterns. However, this description helps provide a broad explanation of why the water cools after strong northeast winds. “
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