INDIGENOUS fish in Lake Kariba are diminishing and researchers are investigating the cause.
The decline in fish volumes in the lake is being met with increased numbers of catfish commonly known as muramba and the exotic Nile tilapia which are reportedly doing well and have been farmed at a large scale by big companies.
In an interview at a recently held Kariba Business Expo, University of Zimbabwe Lake Kariba Research Station chief technician Mr Elmon Dhlomo said indigenous fish species are diminishing in the lake and the reasons have not yet been established.
"Our indigenous fish species like the white bream are diminishing and yet at the same time we find that exotic species like the Nile tilapia and the catfish are doing well. We are yet to establish the cause of the decline," he said.
The tilapia and the Australian red claw crayfish are reported to have escaped cages where they were being bred into the lake and have multiplied. The bream's breeding cycle is slow compared to the exotic species and this is offsetting the indigenous species. Another factor is that the tilapia can evolve from male to female thereby aiding the multiplication of the specie.
Mr Dhlomo said they were now encouraging the farming of fish at a larger scale to balance out demand while also promoting the eating of white meat to stem some cancers known to develop through having red meat. He said fish farming was a way of ensuring food security.
The decline in fish stocks has been attributed to overfishing which does not allow the fish time to breed.