Effects of Human Activities & Sustainability

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  • Over Fishing
    • Problems
      • Drifting nets are so large that they catch large numbers of unwanted species of fish
      • Trawling nets have small gaps in the mesh compared to other nets
        • This is now banned because it prevented fish from escaping
    • Effects on other wildlife
      • Knock on effect along the food chain
        • E.G. Herring is eaten by cod.
          • If the herring are over-fished then cod populations will decrease
      • Fish stocks decrease
    • Solutions
      • Fish Quotas - restricts the number of fish that can be caught
      • Restricted Net Sizes - catches fish of the correct size and age
        • Also allows smaller, less mature fish to escape
      • International Agreements
        • Limits the number of catches and restricts where they can fish
      • Exclusion Zones
        • Cannot fish in these areas
        • Allows the populations time to recover
      • Closed Seasons
    • Fish Farming
      • When fish are bred an grown in lakes and ponds in managed enclosures.
        • Reduces predation and food supply is maintained
        • Fish grow rapidly
      • Impacts
        • Fertilisers are added for phytoplankton to grow rapidly
          • This leads to eutrophication
        • Pesticides
          • Used to control fish parasites
          • Not specific so they affects other marine organisms
        • Overcrowding leads to disease in fish
          • Disease could spread to wild fish
          • The fish live in close proximity so disease can spread faster


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