Predictor variables for moggel (Labeo umbratus) biomass and production in small South African reservoirs

Abstract

The biomass and production of moggel, Labeo umbratus, in five small previously unexploited Eastern Cape reservoirs were estimated and related to environmental conditions. Biomass and production estimates varied widely between the reservoirs. Whilst the production/biomass ratio was not a good indicator of fishery potential, conductivity, mean reservoir depth and surface area proved to be the most suitable predictors of moggel biomass and production, whereas chlorophyll a concentration was somewhat less suitable. Results suggested that reservoirs with high conductivity (>50mS.m⁻¹), small area (<50ha) and shallow depth (<3m) would have the highest moggel biomass and production.