The Eco² Model – a Basic Bio-Economic Module Describing the Dynamics of the Cohort Biomass to Exploitation.

31 Pages Posted: 13 Aug 2013 Last revised: 13 Aug 2014

Date Written: July 12, 2013


The aim of this paper is the provision of a set of simple equations, which can serve as a basic module of an ecosystem and can be used to describe the dynamics of cohort-biomass to exploitation sequentially. The approach is based on two growth equations, which are commonly used to describe individual mass of fish as a function of time. In the management of wild fish stocks, the von Bertalanffy-growth function is applied, while research in aquaculture primarily refers to a simple exponential growth model. In this study, both models are merged into a single model and a relationship between growth and feed intake was added. The resulting equation in conjunction with the traditional abundance equation offers advantages for modeling of the dynamics of the biomass of a single cohort of a fish stock as a function of assimilation rate, catabolism rate, natural mortality, fishing mortality and time. The approach provides also a simple link between ecology and economy. Model validation was carried out by computing the annual yield per recruit applying the Beverton and Holt yield model. A simple example shows that overstocking generates an economic loss in the same order of magnitude as overfishing. Obviously it is not sufficient only to protect the fish stocks. Fish needs also feed. This work aims to move this fact more into the focus of fisheries research.

Keywords: Assimilation rate, bio-economic modeling, ecosystem, fisheries management, growth function, stock dynamics, VPA.

JEL Classification: Q0

Suggested Citation

Bethke, Eckhard, The Eco² Model – a Basic Bio-Economic Module Describing the Dynamics of the Cohort Biomass to Exploitation. (July 12, 2013). Available at SSRN: or

Eckhard Bethke (Contact Author)

FiCoBe ( email )

Königsbergstraße 54
Wedel, DE 22880
+49151 50203402 (Phone)


Do you have negative results from your research you’d like to share?

Paper statistics

Abstract Views
PlumX Metrics