Enhancing bioenergetics models to account for dynamic changes in fish body composition and energy density

Authored by James E Breck

Date Published: 2008

DOI: 10.1577/t05-240.1

Sponsors: No sponsors listed

Platforms: No platforms listed

Model Documentation: Other Narrative Mathematical description

Model Code URLs: Model code not found

Abstract

Fish proximate composition and energy density can influence growth, survival, and reproduction, so it is important to develop models to understand the patterns and predict dynamic changes. This paper presents three such models. Model I describes the general pattern of changes in lipid, protein, ash, and energy density that occur with changes in water content. The key assumption this model is that there is a fixed amount of water associated with each gram of protein and a much smaller fixed amount of water associated with each gram of lipid. In combination with a mass balance constraint, this explains the commonly observed linear relationship between the fraction lipid and the fraction water. Because energy density varies in direct proportion to the fractions lipid and protein, the linear relationship between body composition and fraction water makes energy density also a linear function of the fraction water. The model is fitted to data for lake trout Salvelinus namaycush and coho salmon Oncorhynchus kisutch for a limited range in wet weight. Model 2 describes the pattern of proximate composition and energy density that occurs with variation in body size. A strong pattern was found between the mass of water and the mass of protein, suggesting strict control of body water. The model is fitted to data for common carp Cyprinus carpio and bluegill Lepomis macrochirus. This analysis shows that the relationship between body composition, energy density, and fraction water is expected to vary with body size because both the water : protein ratio and the fraction ash change with body size. Model 3 demonstrates how this approach can be used to predict changes in fish body composition and energy density during starvation, as might be done with a bioenergetics model. This model is fitted to data from a starvation experiment involving largemouth bass Micropterus salmoides.

Tags

Simulation-model Individual-based model Largemouth bass Yellow perch Smallmouth bass Bass micropterus-salmoides Gariepinus burchell 1822 Proximate composition Relative weight Electrical-conductivity