To conserve Cape pike for future generations, sustainable management must be based on genetic evidence and not just catch numbers. (Photo: US)
Cape pike, one of South Africa’s most important fish species and a staple food for many low-income households, may be more vulnerable than previously thought.
New genetic research suggests that pike populations do not form one large, resilient source, but consist of separate groups that do not mix freely with each other.
The findings stem from a study by Dr. Sihle Mthethwa, from the department of genetics at Stellenbosch University (SU), who recently obtained his doctorate in genetics at the university.
According to Mthethwa, DNA analyzes show that Cape pike in South Africa consist of at least two genetically distinct groups that do not interbreed freely, even if they occur in the same place and time.
“There is also evidence of a recent genetic bottleneck, which means that genetic diversity and numbers have decreased in recent generations,” he says. “This loss of diversity may mean that the species is less able to cope with environmental change and fishing pressure.”
The study was conducted after pike catches, which had historically been relatively stable, began to decline noticeably in recent years. The decline has put pressure on local fishermen and increased reliance on imported New Zealand barracouta pike, often sold as “Cape pike”.
Mthethwa says the verification of species identity can help prevent mislabeling. “The verification of species identity can help prevent imported New Zealand barracouta pike from being incorrectly labeled as South African pike, protecting consumers and improving transparency in the fisheries trade.”
Pike on the beach at Hondeklip Bay. (Photo: Ashraf Hendricks / GroundUp)
The research also shows that pike populations worldwide and along the South African coastline are divided into separate groups.
“This finding challenges the idea that Cape pike are a single, resilient resource,” says Mthethwa. “Instead, the need for prudent, locally adapted management is emphasized to protect this iconic fish and the communities that depend on it for the future.”
He warns that considering different pike populations as one source can hide the overexploitation of individual groups. When gene flow between populations is limited, they struggle to recover their numbers and genetic diversity after overfishing.
Mthethwa believes that sustainable management must therefore be based on genetic evidence. “To preserve Cape pike for future generations, sustainable management must be based on genetic evidence and not just on catch numbers.”