Simulation models of finfish farms

Abstract

A set of simulation models has been developed to aid in the understanding of environmental impacts of finfish mariculture. Because several different kinds of environmental impact are being investigated, it was decided to focus the modelling work on creating separate modules rather than a single monolithic programme. The overall structure of the model package is described and is available for test runs. At the heart of the package is a model (called FISH) which represents a single fish, specifically a salmon. This is a physiological model representing the specific kind of fish and using parameters such as the size and feeding regime, and environmental factors such as water temperature. The output of the FISH model is information on the growth and metabolism of the fish. The next level model is called POINT and represents the combination of fish present at a given site by age and size; it generates point source strengths for oxygen demand, nutrient excretion, and particulates. The output of the POINT model is used for input to three separate models dealing with effects on different space and time scales. One of these models is called FARM and deals with internal oxygen levels within a single farm site. The POINT model is used to calculate the oxygen demand within the farm, and this is combined with benthic and natural oxygen dynamics and a simple hydrodynamic model of flushing to calculate the net oxygen budget. A second model called SETTLE uses average currents and diffusion processes to calculate the benthic deposition of faeces and food particles, again using the point source strength for particulates computed from the POINT model. The third model is a large scale water quality model which uses a set of point sources corresponding to actual farm sites to look at predicted nutrient levels and biological oxygen demand throughout an entire estuary. All models except for the water quality model were developed in Fortran using the BSIM simulation package and run on many different kinds of computers. Currently the models are being used for investigation of the environmental effects of salmon aquaculture in the L'Etang estuary on the South West coast of New Brunswick