reducing impacts of aquaculture

• Intensive systems use more energy and require more inputs for a high yield. They are carried out over small areas of land to feed lots of people. 
• Intensive has a high stocking density so a high productivity, but needs inputs to control disease. 
• If a fish farm is extensive it has fewer inputs and a greater efficiency. Coastal water environments are useful for services like waste removal. Fish are more likely to escape and can disrupt local ecosystems. There is a lower stocking density, so fewer inputs and less need for pest control. 
• Intensive:

  • High energy inputs 
  • High stocking density (welfare, disease)
  • Less efficient 

  + feed lots of people 

  +controlled
• Extensive:

  • More waste into environment 
  • More space 
  • Lower productivity 
  • Higher chances of escaping/disrupting ecosystems 

  + lower stocking density (welfare, disease)

  + more efficient 

  + less energy inputs 

   
• Integrated multi-trophic aquaculture contain different feeding levels. Farming many different species together (polyculture), autotrophs - seaweed and heterotrophs - herbivorous fish and detritivore. 
• Herbivorous fish eat algae, the fish waste is eaten by shellfish. Some waste and shellfish waste is decomposed to release nitrates, the seaweed uses the nitrates to produce food for the fish.