Inland Fisheries

Tag-recapture study on two selected small water bodies in Malawi. ALCOM Field Document No.38.

Aquatic biodiversity and inland fisheries

A one year study was carried out in two small water bodies in Malawi, southern Africa by ALCOM in collaboration with the Government of Malawi to test length-based, tag-recapture and empirical methods to estimate growth, mortality rates and fish production.

Almost the same estimates of growth performance indicators were obtained using length frequency analysis and multiple tag recapture analysis. Different estimates were found on biomass and production using the methods including empirical models.

While use of length frequency methods (using non selective gears) and tag recapture are recommended for estimating growth parameters, length frequency methods (using non selective gears) have advantage over the latter because of their low input requirement in manhours. Single catch tag-recapture method is recommended for estimating fish standing biomass. It is recommended that studies be carried out to develop empirical models which use easily measurable parameters like morphometrics and limnological characteristics of small water bodies to estimate fish yields/production or biomass. Such models can replace the recommended single catch tag-recapture because they require low inputs of time and manhours.