159 dead fish found in Touw River estuary over 10 days
SOUTH African National Parks (SANParks) is monitoring the Touw River estuary closely following the deaths of more than 150 fish in 10 days.
Since August 20, 159 dead fish have been recorded, with SANParks recommending that until more is known about the cause of the deaths, precautions should be taken and the public should refrain from eating fish with abnormal looking lesions on their skin and avoid collecting dead fish for consumption from the Touw estuary.
Wilderness marine ranger Jonathan Britton said the first deaths were noticed mid-August and had been restricted to the lower section of the estuary.
“The mortality event appears to be short-lived, as mortality numbers have dropped off significantly since August 20,” Britton said.
SANParks rangers have intervened with regular patrols in the area to identify species impacted, count total mortalities and remove carcasses.
In addition to water quality being checked, sick fish were caught, euthanised and various blood and tissue samples taken by SANParks Scientific Services in Rondevlei, departmental colleagues from Cape Town and an independent scientist from George to determine the type of infection.
Underwater cameras were also deployed to observe the fish. At this stage superficial examination indicates the presence of both a bacterial and fungal infection, SANParks said.
Fortunately the infections do not appear to be flesh-eating.
“Bacterial and fungal infections in fish are not well documented and this is also an opportunity to increase our understanding of these processes,” Britton said.
Although the cause of the infection was not known at this stage, all water quality monitoring conducted until this point indicated nothing of particular concern, SANParks said.
“The water quality results are well within parameters that would be expected during the closed phase of the Touw River estuary and do not exceed any thresholds that would be detrimental to estuarine fish species. There is also no indication of any sewage or pollution spill,” SANParks said.
The conservation authority said it would continue to monitor the situation and provide updates as they became available.