Aquaculture System

Culture based on the economic or commercial considerations i.e. cultural operation type fish culture classified into five categories-

1.                  Extensive culture

2.                  Improve extensive culture

3.                  Intensive culture

4.                  Semi-intensive culture

5.                  Super intensive culture  

1. Extensive Culture: Extensive fish culture is the production of fish and water organisms using the natural food supply in ponds. Culture of herbivorous fish shortens the food chain. Fish growth per unit area of herbivorous fish is thus greater than with the production of predominantly carnivorous fish. The highest growth in extensive culture is achieved through polyculture of fish which feed on plants and those which feed on small animals.

Characteristics of extensive culture:

1.                  Extensive culture may be monoculture or polyculture.

2.                  Engineering design may not laid-out.

3.                  Very big ponds may not be fully cleaned.

4.                  No supplemental feeding.

5.                  Pesticides are not used.

6.                  Cropping frequency i.e., crop/yr is 1.

7.                  Cultivable species are variable sizes.

8.                  Stocking density is very low.

Operation: In this culture operation, all groups of cultivable fishes are cultured with the indigenous fishes but herbivorous fishes are more suitable in extensive fish culture. The stocked fingerlings which usually feed on the natural food namely phytoplankton, zooplankton and aquatic weed.

Fish species density: The stocking density is low as is the yield per unit area (e.g. 5000-10000 shrimp post larvae/ha/crop).

Production: Production is generally low at less than 1000 kg\ha\yr. Yield of fish ponds from larva to one summer under extensive management (polyculture) are as follows:

Advantages of extensive culture:

1.                  No care and no managed fish farming.

2.                  Simple production system this form of pond culture can provide food.

3.                  Generating new sources of employment for less qualified personnel.

4.                  Extensive culture presents no danger to the water quality in the pond.

5.                  Small capital expenditure.

6.                  Biodiversity remain stable.

Disadvantages of extensive culture:

1.                  Net income low.

2.                  High losses due to predators/poaching.

3.                  High provability of diseases or pests.

4.                  Lower survival rate (Approximately 20-30%).

2. Improve extensive culture: It is a form of extensive culture system, which is simplified to the extent that individuals or small groups of people can rear aquatic organisms with the less improve to the extensive culture for their own consumption at a rate that provides a relatively continuous supply.

Characters:

1.                  Improve extensive culture may be monoculture or polyculture.

2.                  Engineering design may not be well laid out.

3.                  Ponds may not be fully cleaned.

4.                  No artificial feeding.

5.                  Cultivable species are variable sizes.

6.                  Stocking density is low.

Operation: In this culture operation, all groups of cultivable fishes are cultured with the indigenous fishes herbivorous fishes are more suitable in improve extensive culture.

Different type of food stuffs have been used in improve extensive fish pond ranging from kitchen wastes, fishery and agro-industrial by products, wheat and rice bran, slaughterhouse wastes, damaged fruit terrestrial invertebrates etc.  

Advantages:

1.                  Little care and least managed fish farming.

2.                  Small capital expenditure.

3.                  Conservation of small indigenous fishes.

4.                  It is no danger to the water quality in the pond.

Disadvantages:

1.                  Fish growth per unit area is low.

2.                  High losses due to predators/poaching.

3.                  High provability of diseases.

4.                  Lower survival rate. (Approximately 40-45%)

3. Semi intensive culture: Semi intensive fish farming where fish/shrimp growth is depend upon the consumption of live food organisms and plants naturally present within the water body as well as a direct supplementary source of dietary nutrients.

The use of fertilizers can increase the natural production of the pond and hence its yield.

Characteristics:

1.                  Semi intensive culture should be monoculture.

2.                  Stocking density is higher than improve extensive culture.

3.                  Engineering design and layout with provisions for effective water management.

4.                  Fertilizer used regularly with lime.  

5.                  Pesticides used regularly for prophylaxis.

6.                  Water organisms receive natural food as well as supplemental feed.

7.                  Cultivable species are uniform sizes.

8.                  Water quality analyzed monthly.

Operation: In this culture operation, herbivorous and omnivorous fish species are particularly suitable for increasing fish production if the developing countries. The stocked fish which usually feed on the natural food and processed food.

Fish stocking density: The stocking density is higher than improve extensive culture (e.g., 50000-100000 shrimp PL/ha/crop).

Production: Production ranging from a minimum 1.5-5 ton/ha/crop to higher.

4. Intensive culture

Intensive fish farming is an aquaculture system where fish/shrimp growth completely depends on artificial feed.

Characteristics:

Ø    Intensive culture should be monoculture.

Ø    Higher stocking density.

Ø    Very well engineered system with pumps and aerators to control water quality and quality.

Ø    Fully cleaned pond.

Ø    Fertilizers are not used.

Ø    Pesticides used regularly for prophylaxis.

Ø    Cultivable species are uniform sizes.

Ø    Water quality analyzed weekly.

Ø    Intensive management.

Stocking density: Maximum 100 PLs/m².

Production: 20 tons/ha/year.

Advantages:

Ø    High stocking density.

Ø    Fishes survival rate higher (approximately 90%)

Ø    Low losses due to predators/poaching.

Ø    High yields (20 tons/ha/year in coastal area). 

Ø    High financial profit.

Ø    Low provability of diseases or pests.

Ø    Production fish with high market value (e.g., koral, thai koi)

Disadvantages:

Ø    Higher production cost.

Ø    Greater risks due to mechanical breakdown.

Ø    Reduction of biodiversity due to the cultivation of exotic species.

5. Super intensive culture

It is usually practiced in industrial countries to produce fish in artificial big tank where fish or shrimp growth completely depends on dry artificial feed.

Characteristics:

Ø    It should be monoculture.

Ø    Stocking rate is maximum.

Ø    Engineering design and layout with concrete tank.

Ø    Water quality analysed daily.

Ø    Cultivable species are uniform in sizes.

Stocking density: More than 100 PLs/m²

Production: 30-150 tons/ha/yr.

Advantages:

Ø    High stocking density.

Ø    Fishes survival rate higher (approximately 98%)

Ø    No losses due to predators/poaching.

Ø    Higher financial profit.

Ø    Low provability of diseases or pests.

Ø    Produce high value species.

Disadvantages:

Ø    Higher production cost.

Ø    Greater risks due to mechanical breakdown.

Ø    Reduction of biodiversity due to the cultivation of only desirable species.