Carrying capacity: general principles of model construction

Abstract

Carrying capacity is defined as the maximum biomass of a farmed species that can be supported without violating the maximum acceptable impacts to the farmed stock and its environment. Maximum acceptable impacts on the farmed stock and the environment are expressed by standards for water quality in the farm and the surrounding environment. Environmental quality standards are established in a political process. The scientific part of the problem to estimate the carrying capacity is to develop reliable, objective methods or models for estimating the response of both the environment and the farmed stock to farming. Using such models together with field observations from a specified locality and the quality standards in force, the carrying capacity for the locality can be estimated. Models must properly deal with hydrodynamic and biogeochemical and ecological processes in the environment as well as with oxygen consumption and sources and sinks of organic matter and nutrients due to farm activity. In this paper, the basic principles of model construction are discussed and the Norwegian MOM model is used as an example. Current speed data and farm activity data are identified as two generally large sources of uncertainty in estimates of environmental impact and carrying capacity.