Modelling Gastric Evacuation Rates in Fish With a General Power Function: A Step-by-Step Guide to Parameter Estimation and Analysis Using R Statistical Software

Accurate modelling of gastric evacuation (GE) is a prerequisite for optimising feeding strategies in aquaculture and improving predator–prey interaction models in ecological studies. However, GE analysis is challenging because of the interdependencies of the variables influencing the evacuation process. To overcome this, a general power function was developed in 1992 and refined in 1998 using non-linear regression techniques. The proposed method is robust for identifying the best-fit evacuation function while simultaneously assessing the effects of potential predictor variables. This study demonstrated the application of R statistical software for parameter estimation of the general power function to characterise the influence of fish size, meal size and temperature on GE rate (GER) in brown trout (Salmo trutta Linnaeus, 1758) and rainbow trout (Oncorhynchus mykiss Walbaum, 1792). The statistical methods presented are remarkably adaptable and applicable to a wide range of GE datasets. Furthermore, they can be extended to incorporate additional variables influencing GE, making them integral tools for advancing research in fisheries management, ecological modelling and aquaculture.