Mathematical modelling of ammonia nitrogen dynamics in a recirculating aquaculture system

Abstract

The concentration of ammonia nitrogen plays a crucial role in aquaculture, as an excessive level can hinder the growth of aquatic animals or even cause death. Commercially available ammonia nitrogen sensors are expensive, have limited lifespans, require frequent maintenance, and may exhibit drift over time. In this study, we designed a laboratory-scale recirculating aquaculture system using Siberian sturgeon (Acipenser baerii) as the cultured species and conducted a 52-day experiment. Based on this system, a new mathematical model was developed to predict ammonia nitrogen, combining fish bioenergetics with mass balance of ammonia nitrogen. A sensitivity analysis of model parameters was conducted to identify the key ones, and then a Bayesian optimisation method was used to calibrate these key parameters with data collected from the laboratory recirculating aquaculture system. Validation on unseen data demonstrated that the model could provide a reasonable prediction of ammonia nitrogen.