Periphyton fouling as a marginal energy source in tropical tilapia cage farming

In aquaculture, the benefit of autotrophic production within land-based pon ds for fish production has long been recognized. In cage culture, organisms growing on the cage net have so far only been considered as a problem. Thi s study investigated the potential production of periphyton on cage nets us ed in a tropical mixed tilapia culture of Oreochromis mortimeri (Trewavas), Tilapia rendalli (Boulenger) and Oreochromis niloticus (Linnaeus) in Lake Kariba, Zimbabwe. The production of periphyton was assessed experimentally and compared with the energy demand of the caged fish. The tilapias were fo und to graze intensively on the net, and the primary production of periphyt on on the cage net was approximate to 1% relative to the energy demands of the fish.