Aquaculture

Aquaculture

Principles
1. Selection of desirable species
2. Control of undesirable species - competitors and predators
3. Provision or encouragement of food
4. Control of abiotic conditions to increase productivity
Major Species Examples
1. Carp
2. Salmon
3. Tilapia
4. Trout
5. Shrimp
6. Oysters
7. Mussels
Methods
1. Extensive
  1. Food production with relatively low inputs
  2. Predatory fish/birds may be controlled to an extent and nutrients could be added to water to stimulate growth if the fish's food (plant species)
  3. Shellfish could be grown in a captivity before being released into the wild for capture at a later date
2. Intensive
  1. A high yield is achieved by controlling all possible limiting factors
  2. Fish selectively bred to increase growth rate and enhance desirable characteristics
  3. Artificial conditions mean there are no competitors or predators, and pests are controlled
  4. Environmental factors that could be limiting factors to productivity are controlled
Control of Limiting Factors
1. Temperature - must not get too high, so farms are usually located in areas with cooler climates (e.g. Scotland)
2. Dissolved oxygen - Levels are kept high with water sprays or weirs that agitate the water
3. Water Flow - Farms are usually in areas with strong currents. Helps fish muscle mass by swimming against the current and allows for higher stocking densities
4. Light Levels - Artificial light can be used if the natural supply is not enough to induce smoltification in young fish
Environmental Impacts
1. Habitat Impacts
  1. Over-fishing of food species causes problems for the food web involved, but also causes damage when taking place - seabed damage from trawling for example
  2. Natural predators may be culled if they are seen as pests
  3. Parasites from the farm stock could transfer on to wild species which have no antibiotics as protection
  4. The construction of the farm itself could destroy existing habitats
  5. Introduced species from the farm may compete/predate on organisms in the local environment
  6. Fish that escape from the farm may breed with wild fish and alter the gene pool, bringing characteristics that might not be suitable for survival in the wild
2. Pollution
  1. Pesticides used can be poisonous to wildlife
  2. Overuse of antibiotics could encourage development of resistant pathogens which could transfer on to local fish
  3. Organic waste may cause deoxygenation of the water
  4. Inorganic waste released in excretion can cause eutrophication

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