aquatic food production

• Pelagic - open oceans 
• Benthic - sea floor 
• Bycatch - removal of non-target species. 
• Methods of fishing:

  • Demersal trawling 
  • Pelagic trawling 
  • Demersal longlining 
  • Pelagic longlining 
  • Purse seine 
  • Drift netting 
  • Shellfish traps 
• 5 impacts:

  • Overfishing 
  • Bycatch 
  • Ghost fishing 
  • Food web impacts
  • Seabed damage 
• Demersal trawling:

  Large nets that are dragged along the sea floor. Very destructive due to heavy nets, destroys slow growing organisms (sea fans). Target catch includes: cod, shrimp and scallops. Catch effectiveness is high because there is not chance of escape. Catch selectivity is low because the whole seabed is trawled. Energy inputs are high because the net is dragged by a boat. Loss of nets can capture fish after being lost. 
• Pelagic trawling:

  Large nets that are dragged through open water. Does not damage seabed but removes large volumes of fish. Very effective due to difficulty of escape from nets. Selectivity of catch is low but higher than demersal. Energy inputs are high due to using boats. Some bycatch is caught. 
• Pelagic longlining:

  Long lines of baited hooks - 100 km in length. Huge bycatch - seabirds. Lower energy inputs from no heavy nets. No seafloor damage but lost lines could trap seafloor organisms. Catch selectivity is higher than trawling. 
• Purse seine:

  Large nets drawn tight around schools of fish, a fish aggregating device is used to concentrate fish. Lots of bycatch due to large scale of nets. 

  Catch effectiveness is high. 
• Drift netting:

  Large flat net dragged through open water. Catch effectiveness id high with a low selectivity. Energy inputs are high. Lots of bycatch and a risk of ghost fishing. 
• Shellfish traps:

  Net boxes that are baited and shellfish make their way inside them. High catch effectiveness and selectivity, energy inputs are low. Lost pots may ghost fish.
• Recruitment - moving of juvenile into the breeding biomass. 
• Maximum sustainable yield is the largest amount of a resource that can be harvested that does not cause a decline in the stock of the resource. 

  • Current biomass 
  • Annual biomass growth
  • Breeding rate 
  • Survival rates