aquaculture Flashcards
what is extensive aquaculture
1) a system of aquaculture using small amounts of labour in relation to the area of land being farmed (usually very large)- inputs are spread over a large area of land
2) the yield produced is dependant on availability of natural resources such as nutrients or light
3) It has a high energy ratio as the energy input is low compared to the energy output per unit of land
what is intensive aquaculture
1) a system of aquaculture which involves using large amounts of labor relative to the area being farmed ie pesticide use, supplied nutrients, etc
2) the use of the extra labor produces a greater yield per unit of land therefore less land is needed to produce the same yields as extensive aquaculture
3) has a low energy ratio as a high amount of energy input per output of energy per unit of land
compare intensive and extensive aquaculture
Intensive- low energy ratio as high use of energy subsidies, more productive as the increased labor produces higher yields per unit of land, completed over a smaller area of land, increased labor
extensive- high energy ratio as little energy input for the output produced per unit of land, less productive as lower yields produced, completed over a large area,
list the principles of aquaculture
1) species selection
2) gender control
3) selection of breeding adult
4) control for pests and diseases
5) control of abiotic factors
6) nutrition
7) control of competition
explain the principle of species selection and the factors which need to be considered
1) local constraints- local conditions such as temp and water quality will control if a species survives in that area for example salmon and trout require cooler water temps
2) market demand - in MEDC the main species raised are carnivorous species because they have a better flavor and popularity so profit can be made.
In LEDCs herbivore fish are reared as they are cheaper- feeding on natural vegetation so little input is needed
outline how an adult fish is selected for breeding
1) fish with desirable characteristics
- disease resistance
- a rapid growth rate
- good appearance
how is gender controlled in aquaculture- provide an example
1) the gender of a fish can be controlled hormonally regardless of genetics
2) young fish with an XX chromosome usually become female and XY male
3) if young fish are given female hormones they will develop into female adults and vis versa which gender is desirable depends on the species being cultivated
FOR EXAMPLE
4) Rainbow trout- female fish have a better flavored meat
some of the females are given male hormones so they produce sperm which only carry the X chromosome therefore only females are produced
why can disease and pests be an issue in aquaculture
1) fish are kept in high densities increasing the risk of spread between individuals
2) high densities increase contact and collision between fish increasing risk of pathogen and pest spread
how can pests and disease be controlled
1) when water flows between tanks of fish of different ages it is always from younger to older preventing contamination of new fish stock
2) a lower stock density reduces collision and contact risj
3) pesticide use
4) tanks with circulating water currents encouraging fish to swim in same direction
how is competition and predation controlled in intensive and extensive aquaculture systems
intensive - rarely a problem in closely controlled systems
extensive - harder to control due to large scale but fencing, netting or culling can be used
explain how nutrition is controlled in aquaculture
1) herbivorous fish are likely to find natural food in their lagoons such as phytoplankton or water weeds
2) carnivorous fish are likely to require artificial feeding
what abiotic factors need to be controlled in aquaculture systems
1) temp- requirements depend on the species and their natural adaptations, temps increase metabolic rate and growth but higher temps may reduce dissolved oxygen
2) dissolved oxygen- fish such as trout with high oxygen requirements need a well-aerated tank, food waste, and fecal matter must be removed as it can reduce oxygenation
3) daylength- reproduction is affected by day length, salmon stop growing when they are sexually mature so long daylengths delays maturation increasing the size
4) water flow- fish often swim against the water flow this can be used to cause fish to swim in same direction reducing collision damage and injuries
what is a polyculture
1) an aquaculture system that produces food from more than one species
2) total productively may be increased by rearing species together that arent competitors
what does IMTA stand for
integrated multi-trophic aqauculture
outline an IMTA
1) a type of polyculture system where species of different trophic levels benefit from each other
for example
- the common carp are bottom feeders and feed off of molluscs and insects they resuspend nutrients from sediments increasing growth of plants and phytoplankton which silver carp feed on therefore there is no competition
