Mysterious Fish Deaths Attributed To Oxygen Deficiency

  • Vets say inflows the Okavango River brought debris that contaminated water and reduced oxygen levels
  • Note that newborns will survive because they are more adaptable to a new environment


FRANCISTOWN: Recent mysterious fish mortalities in the stretch of the Okavango River between Shakawe and Sekondomboro have been attributed to oxygen deficiency caused by water turbidity, the Principal Veterinary Officer in the Department of Wildlife, Dr Comfort Nkgowe, has said.

Hundreds of fish died on that stretch of the Okavango River, raising fears of poisoning. In the aftermath of the mysterious fish mortalities the Department of Wildlife deployed a team of vets to establish what could have been the cause and soon concluded that oxygen deficiency was to blame.

According to Dr Nkgowe, the quality of water in the river was affected by recent downpours and inflows from tributaries of the Okavango that came with debris. The result was that the turbidity of the water has dropped normal oxygen from 5ppp to 1.72ppp, leaving the water uninhabitable for fish.

“Once there is oxygen deficiency in the main stream, the fish – especially large ones – can no longer survive because they cannot breathe,” Dr Nkgowe explained. “Only newly-born fish can survive because they adapt fairly easily to a new environment. The mortality seems to have stopped.

“It is normal for inflowing water to bring debris which ends up affecting water quality. Once the water quality changes, the oxygen content is also affected. As a result, the fish will also be affected.”