Mathematical modelling of flow, pesticide and nutrient transport for fish-farm planning and management
Abstract In recent years, there has been a rapid growth in fish farming, particularly salmon farming, in UK and Eire coastal waters. This increase in production has also led to an awareness by the fish-farming industry that over-production could have a deleterious effect on the hydro-ecology of coastal waters, which would inhibit the maintenance of current production farming levels. In planning a fish-farm configuration for coastal basins, complex deterministic mathematical models can provide invaluable information for farm optimisation, with the models predicting the tidal current structure and solute levels in the basin. Details are given herein of a refined mathematical model for predicting tidal current and Nuvan, biochemical oxygen demand (BOD) and nitrogen levels for a proposed fish-farm configuration in a bay off the Eire coastline. The model accurately predicts field-measured velocities at two sites within the bay, and further predicts Nuvan, BOD and nitrogen levels that are well below those levels which would be known to affect adversely the hydro-ecology of the bay.
Use of a mathematical model to estimate the impact of shrimp pen culture at Patos Lagoon estuary, Brazil.
Ecological modeling has been used as a tool to estimate potential impacts caused by aquaculture to the surrounding environment. In this work, a mathematical model was applied to estimate the maximum amount of pink shrimp (Farfantepenaeus paulensis) culture units (3,100m2 pen enclosures) that could be installed at two shallow estuarine bays of Patos Lagoon (known as Coreia and Porto do Rei) with no significant effects on either water quality or viability of the culture system. To calibrate the model, information about the culture of Litopenaeus vannamei and F. paulensis as well as field data (influence of netting material, water current speed and nitrogen concentrations) were used. Under a bad scenario (water current velocity of 0.01m s-1 and a mesh clogging effect of 40%), it would be possible to install up to 29 pens at the Coreia bay, and 39 pens at the Porto do Rei bay. Results indicate that the model was useful in determining the maximum number of culture units that could be installed at these bays, and thus have the potential to become an important tool in the definition of environmental management strategies in relation to aquaculture development.
Temperature Distributions in Tidal Flow Field
The development and application of a numerical model to predict the two‐dimensional depth mean velocity fields and background temperature distributions in a natural harbor, at Poole, England, is described. The predicted background temperature rises resulted from the proposed siting of either a 700 or 350‐MW capacity power station on the harbor perimeter, with the intake and outfall for the cooling water system being located along the boundary and within the harbor, respectively. The numerical model was based on the solution of the depth‐integrated flow equations, simulating the tidal currents, and on the depth integration of the advective‐diffusion equation for the conservation of heat. The main difficulties encountered in the hydrodynamic model included the representation of the advective acceleration terms, particularly since the harbor had a narrow entrance, and the modeling of the significant changes, which occur in the plan cross‐sectional area as large regions of shallow water, were dried out and fl...