Sardine die-off eases along Western Cape coast
· The South African
The recent sardine mortality event along the Western Cape coast appears to have run its course, with no reports of dead or dying sardines being received by the Department of Forestry, Fisheries and the Environment (DFFE) since Thursday, 6 August.
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West Coast canneries are continuing to accept healthy sardines caught north of St Helena Bay, although some factories in areas affected by the mortality event have opted to wait for the Department’s test results before restarting operations.
The cause of the sardine deaths has not yet been confirmed.
Investigation into sardine deaths continues
A broad investigation involving the DFFE, research institutions, specialist laboratories, the fishing industry and other scientists is continuing.
Samples of dead sardines have been collected from several locations, including Saldanha Bay, Hout Bay, Betty’s Bay, Gansbaai and the Cape Canyon area.
Researchers have also collected apparently healthy sardines from Elands Bay and Lambert’s Bay to provide comparison samples.
The South African Institute for Aquatic Biodiversity (SAIAB) and Rhodes University are conducting disease testing, while SAIAB and a specialist commercial laboratory are screening samples for marine biotoxins.
Departmental scientists are also examining water samples, stomach contents and gills for signs of harmful algae, alongside biological examinations of the fish.
Harmful algae among possible causes
A harmful algal bloom involving Alexandrium catenella was present in Saldanha Bay when the mortality event began.
The species has previously been associated with sardine mortalities in South Africa and remains one of the possible causes being investigated.
However, the algae has not been detected in the water samples or sardine stomach contents examined so far, while preliminary analyses have not identified a harmful-algal cause.
Oceanographic data supplied by the South African Environmental Observation Network (SAEON) and the CSIR has also identified unusual conditions in the region before the event.
These included enhanced upwelling, unusually cold nearshore water and low oxygen levels in St Helena Bay.
Scientists have also noted that a southward-moving coastal current could have transported affected fish from the West Coast towards Cape Point and further east.
The Department stressed that these findings provide important context but do not establish the cause of the mortality event.
No wider marine impact reported yet
There have so far been no reports of wider effects on the marine ecosystem.
However, sardines are an important food source for seabirds, seals and predatory fish, meaning the Department will continue monitoring the situation for any potential impact on sardine populations and marine predators.
As testing continues, the public is being urged not to collect or eat dead fish found on beaches.
The Department said initial disease-testing and biotoxin results are expected most likely early next week.
It noted that the specialised testing takes time because samples must go through several stages of preparation, testing and verification before results can be reliably interpreted.
Further updates will be issued once those results become available.
Media Statement_Sardine deaths ease as wide-ranging investigation continues-compressedDownload