Unit 4: Aquaculture - Environmental Impacts

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  • Environmental Impacts
    • Pollution
      • Organic and Inorganic Waste - from surplus food, excretion and faeces and blood from processing plants
        • Eutrophication and deoxygenation
        • Increased primary production
        • Changes in phytoplankton populations
        • Increases in algal blooms - can be toxic
        • Increased chemical oxygen demand
        • Increased microbial activity
        • Production of H2S and CH4
        • Locate fish farms where currents dilute wastes
        • Wastewater treatment
        • Synchronised feeding times, optimised pellet size, color, texture and shape, even food distribution and exercise reduces food wastages
        • CCTV beneath cages to monitor food wastage
      • Pesticides - control weed and crustacean growth on cages and fish lice
        • Use manual/ mechanical cleaning instead
        • May be poisonous to wildlife
      • Antibiotics - control infections
        • Overuse can encourage antibiotic-resistant pathogens
        • Reduced use using reduced stocking densities
    • Habitat Impacts
      • Overfishing - wild fish caught for farmed fish food
        • May affect wild fish and predator numbers
        • May also cause damage by the fishing methods
      • Predator control - natural predators e.g. herons, otters may be culled if they become pests
        • Use of better cages reduces this need
      • Parasites - fish lice from densely populated cages may be passed to wild fish
        • Wild fish more likely to suffer with infected wounds
        • Less problematic with low stocking densities
      • Gene Pool Contaminators - escaped farmed fish may breed with wild fish, altering gene pools
        • Characteristics of selectively bred fish may be unsuitable for the wild
        • Better designed cages mean fewer fish escape
      • Introduced Species - escaped farm fish may compete with or become predators of indigenous species
      • Habitat Loss - shrimp farms cause mangrove forest loss
        • UK - Environmental Impact Assessments must be made before development occurs


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