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.
Reducing the environmental impact of seacage fish farming through cultivation of seaweed
Cultivation of Laminaria saccharina (Linnaeus) Lamouroux and Palmaria palmata (Linnaeus) Kuntze was trialled at three fish farm sites in north-west Scotland. Results show that seasonal yields of L. saccharina were enhanced by 50 % and P. palmata by 63 % when cultured adjacent to fish farm cages compared to environmentally similar sites away from the farms. Yields of P. palmata were further enhanced under conditions of optimal water movement. 
Ammonium concentrations in the seawater 0 to 50m away from the fish cages were found to be 2 - 3 μM greater than ambient. Enhanced concentrations of ammonium could be detected 200 to 300 m from the cages although the distribution is heavilyinfluenced by local hydrography. 
Nitrogen content of L. saccharina and P. palmata cultured adjacent to the salmon cages in summer was higher than in seaweeds cultured at reference sites away from fish cages. Stable nitrogen isotope analysis indicates that the nitrogen in seaweeds grown next to salmon cages is derived from the fish farm and farm derived nitrogen is likely to be widely dispersed in the lochs where cages are situated. 
A preliminary economic analysis showed that growing seaweeds commercially, in particular P. palmata, may be at worst cost neutral, with profitability increasing as a result of enhanced production through increased nutrient availability adjacent to fish farms. A one hectare seaweed farm producing 600 tonnes wet weight over two years (300 tonnes per year) of P. palmata could potentially absorb up to 30 % of nutrients generated from a 500 tonnes salmon production unit. 
As farm origin nitrogen is evident in biota at distances of up to one kilometre away from the cages, cultured macroalgae would not have to be sited close to cages to result in net nitrogen removal facilitating the siting of algal farms in areas more suited for individual species requirements while still maintaining bioremediation benefits.
Treatment of salmon lice (Lepeophtheirus salmonis Krøyer, 1838) with Neguvon® — Description of method and equipment
Abstract A bath treatment of 300 p.p.m. Neguvon for 15–60 min effectively eliminates the salmon louse, Lepeophtheirus salmonis , from salmonids cultured in sea water. Serious epizootics caused by this parasite have arisen in recent years in Norwegian salmonid farms. The treatment is applied using a special floating pen enabling the same solution to be used for different fish populations. Neguvon residues in treated fish are negligible within 12 days of treatment. Fish should not be harvested within 3 weeks of treatment and the Neguvon should be used under veterinary prescription in Norway.