Unit 4: Aquaculture - Methods Used

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  • Methods Used In Aquaculture
    • Monosex Culture
      • Higher growth rates and less aggression
      • Prevents gonad production so more energy used in growth
      • Greater uniformity of size
    • Extensive Aquaculture
      • Relatively low inputs
      • Oysters - 'spat' (young larvae) settle on specially cleared estuary beds. Spaced evenly with predators and competitors controlled and are harvested when large enough to eat
      • Carp - predators controlled and nutrients added to stimulate the growth of the water weeds they eat
    • Intensive Aquaculture
      • High yield - all possible factors controlled
      • Selective breeding to increase growth rate and enhance desirable characteristics
      • No competitors and predators
      • Pest and disease controlled by inoculation or pesticides and antibiotics
      • Limiting abiotic factors controlled
    • Artifical Breeding
      • Induced ovulation - hatching times optimised
      • Control of spawning via hormones, pheromones, optimum temperature and appropriate food and nesting sites
      • Example - Salmon
        • Fish with desirable characteristics stripped of eggs (roe) and milk (sperm)
        • Sperm and roe mixed to allow fertilisation
        • Fertilised eggs raised in freshwater aerated tanks with dead or diseased eggs removed daily
        • Hatched fish moved through a series of tanks and fed on fishmeal pellets
        • 12-18 months = 'smolts' - moved to seawater tanks until they are ready for harvest


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