An empirical model for predicting degradation of organic solids in fish culture systems based on short-term observations

The accumulation of organic solids in aquaculture systems is influenced to a large extent by the decay rates of the recalcitrant compounds comprising these solids. Exponential models based on one degradation constant often provide an inadequate prediction of long-term decomposition while exponential models, based on integration of two or more degradation constants of labile and recalcitrant fractions, are often cumbersome and hence not practical. In this study, degradation of organic solids was described in terms of a two-parameter, non-exponential model. Data were obtained by a follow-up of the weight loss of fish feed, incubated in anoxic digestion basins over 56 days within nylon bags (40 μm mesh). The empirical model fitted the experimental data with correlation coefficients of 0.99-1.00 and was found superior to widely used exponential models. Application of this model to data obtained during relatively short incubations enabled an accurate prediction of long-term organic matter degradation.