Waste outputs and dispersion around marine fish cages and the implications for modelling
Aquaculture plays an increasingly important role in food production as the catches of wild fish stocks continue to decline on a global scale through overfishing. However, the rapid development of intensive cage aquaculture in particular, which requires high inputs of energy, food and capital, can re...
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| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
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University of Stirling
2000
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| Online Access: | http://hdl.handle.net/1893/26683 http://dspace.stir.ac.uk/bitstream/1893/26683/1/chen-thesis.pdf |
| Summary: | Aquaculture plays an increasingly important role in food production as the catches of wild fish stocks continue to decline on a global scale through overfishing. However, the rapid development of intensive cage aquaculture in particular, which requires high inputs of energy, food and capital, can result in adverse effects on the environment. While spatial distribution and sediment loading models for particulate wastes from marine fish cages have been under development for more than 10 years, the models still contain numerous assumptions that limit their usefulness. These include the use of very limited data for fish feed and faecal pellets sinking rates that take no account of food manufacturer, type or size or environmental conditions. The present study provides information on a range of pellet types for three of the most important European farmed fish species (i.e. Atlantic salmon Salmo salar L., sea bream Sparus aurata, sea bass Dicentrachus labrax) that may be readily incorporated into models. Such data, combined with validation of predictions through in situ field investigations is designed to help improve the accuracy and usefulness of solid waste dispersal models. The studies comprise four main sections, i.e., quantifying food and faecal pellet characteristics, examining nutrient leaching rates from uneaten food and fish faeces, determining resuspension characteristics of uneaten food, modelling of solid wastes dispersion and thus the development of environmental tools. Existing literature relating to environmental impacts of cage aquaculture is reviewed and the key factors highlighted. Two preliminary studies provided information on the influence of gravity acceleration on settling velocity determination and appropriate techniques for monitoring the rate of nutrient leaching from faecal wastes. Settling velocities of Atlantic salmon diets were significantly greater at 20 psu salinity than at 33 psu and significantly higher for most pellet types at 10°C than, at 20°C. Settling velocities for unsoaked ... |
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