7.3 - Producing food in fish farms
Fish farms (“aquaculture” [水產養殖])
● Farmed fish, e.g.: salmon, tilapia (羅非魚), trout (鱒魚)
○ ALSO - prawns, shrimps
○ Usually kept in ponds/large tanks/mesh cages, anchored (錨定) in
fresh/sea water (depending on type of fish being reared [飼養])
Maintenance of water quality
● Ensure fish obtain materials essential for growth/to remain healthy
○ In order to have high yield in protein (for human diet)......
● Oxygen
○ Oxygen dissolves in water, in which fish use it in respiration
■ If fish very crowded, there may not be enough oxygen for all fish in
pond/tank/cage
○ To keep water oxygenated:
■ For ponds/tanks
● Water agitated mechanically, so air mixes with water, more
oxygen dissolved
● ***Recirculating air with pump
● Oxygenated artificially by bubbling air/oxygen through water
■ For cages (especially in open space - sea/estuary/river/lake)
● Natural movement of water (e.g.: tides/currents in flowing
water) helps to bring fresh oxygen
● Green plants in water (including rooted plants/microscopic
algae) give off oxygen during photosynthesis
● Waste materials
○ E.g.: nitrogenous excretory products (NH3\NH4+ - toxic to fish themselves),
excess/unconsumed leftover food materials
○ ALSO eutrophication - due to high levels of nitrogenous waste →
serious losses of fish through lack of oxygen (“fish kill”)
○ Removal of waste materials:
■ Circulation of water - prevents accumulation of waste materials
● Artificially (with pumps)
● Natural flow of water (result of tides/currents)
1
Fish farms (“aquaculture” [水產養殖])
● Farmed fish, e.g.: salmon, tilapia (羅非魚), trout (鱒魚)
○ ALSO - prawns, shrimps
○ Usually kept in ponds/large tanks/mesh cages, anchored (錨定) in
fresh/sea water (depending on type of fish being reared [飼養])
Maintenance of water quality
● Ensure fish obtain materials essential for growth/to remain healthy
○ In order to have high yield in protein (for human diet)......
● Oxygen
○ Oxygen dissolves in water, in which fish use it in respiration
■ If fish very crowded, there may not be enough oxygen for all fish in
pond/tank/cage
○ To keep water oxygenated:
■ For ponds/tanks
● Water agitated mechanically, so air mixes with water, more
oxygen dissolved
● ***Recirculating air with pump
● Oxygenated artificially by bubbling air/oxygen through water
■ For cages (especially in open space - sea/estuary/river/lake)
● Natural movement of water (e.g.: tides/currents in flowing
water) helps to bring fresh oxygen
● Green plants in water (including rooted plants/microscopic
algae) give off oxygen during photosynthesis
● Waste materials
○ E.g.: nitrogenous excretory products (NH3\NH4+ - toxic to fish themselves),
excess/unconsumed leftover food materials
○ ALSO eutrophication - due to high levels of nitrogenous waste →
serious losses of fish through lack of oxygen (“fish kill”)
○ Removal of waste materials:
■ Circulation of water - prevents accumulation of waste materials
● Artificially (with pumps)
● Natural flow of water (result of tides/currents)
1
