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.
Effect of Neguvon® and Nuvan® treatment on crabs (Cancer pagurus, C. maenas), lobster (Homarus gammarus) and blue mussel (Mytilus edulis)
Abstract Survival tests were carried out with crabs, lobsters and blue mussels held in tanks of flowing seawater and subjected to Neguvon at 10, 1, 0.5 and 0.1 ppm and to Nuvan at 1, 0.01 ppm. Homarus gammarus was the most susceptible species; the animals died within 24 h at Neguvon levels of 0.5 ppm and higher and at Nuvan levels of 0.1 ppm and higher. The use of these chemicals in salmon farming appears to have deterious effects on marine invertebrate species.
Improving water use in agriculture : experiences in the Middle East and North Africa
Emerging water shortages are of great concern in many countries of the region. As the agricultural sector is generally by far the most important water consumer and higher priority is given to meeting domestic and industrial water demands, it is to be expected that gradually less water will be available for agriculture. An overview is given of present system and on-farm water use efficiencies and the potential for water savings and yield increases through the use of improved distribution networks and more appropriate irrigation technologies for smallholders. The water conservation efforts of Israel, Cyprus and Jordan are examined in detail with respect to institutions, the irrigation infrastructure, water charges and demand management, operation and maintenance, irrigation scheduling and extension, technology development and transfer, the role of the private sector, quality control on irrigation equipment, land tenure and land consolidation, and water users associations. The World Bank's experience with lending for the irrigation sector in the region is also described. The elements that would need to be considered for inclusion in a national program for water conservation in the agricultural sector are identified.