🐟 Aquaculture

Important terms, Types, Integrated Fish Farming

Definition

  • Aquaculture or farming in water is the aquatic equivalent of agriculture or farming on land.
  • Defined broadly, agriculture includes farming both animals (animal husbandry) and plants (agronomy, horticulture and forestry in part).
  • Similarly, aquaculture covers the farming of both animals (including crustaceans, finfish and molluscs) and plants (including seaweeds and freshwater macrophytes).
  • While agriculture is predominantly based on use of freshwater, aquaculture occurs in both inland (freshwater) and coastal (brackish water, seawater) areas.
  • It implies some form of intervention in the rearing process to increase production, such as regular stocking, feeding and protection against predators.
  • This farming also implies individual or corporate ownership of the stock being cultivated.

👉🏻 FAO (1988) introduced a definition of aquaculture:

  • Aquaculture is the farming of aquatic organisms, including fish, molluscs, crustaceans and aquatic plants.
  • Farming implies some form of intervention in the rearing process to enhance production, such as regular stocking, feeding, protection from predators, etc.
  • Farming also implies individual or corporate ownership of the stock being cultivated.
  • For statistical purposes, aquatic organisms which are harvested by an individual or corporate body which has owned them throughout their rearing period contribute to aquaculture, while aquatic organisms which are exploitable by the public as a common property resources, with or without appropriate licences, are the harvest of fisheries.
  • The desirable pH for optimum fish production is 7.5 – 8.5. (Alkaline)
  • There should be at least 7 - 10 days interval between liming and manuring in fish pond.
  • While reclaiming acid water in aquatic pond, 250 kg lime IBPS 2018 is required. 🌬as per NABARD Norms
  • Total amount of lime application in fish pond a month should not exceed 600 kg/ha.

Important Terms

Fish Seed

  • Fertilized fish eggs are known as Fish seeds. In simple words, they are the baby fishes used for seeding new Ponds in fisheries.
  • ‘Seed appears to be an industrial/technical term in fish farming used to refer either collectively to the juvenile life stages of fish (hatchling, spawn, fry and fingerling), or specifically to fry (the stage after the yolk sac disappears and before scales form).

👉🏻 The Juvenile stages are:

Hatchling

  • The larvae emerging from the fertilized eggs after hatching is called hatchling.
  • It is characterized by the presence of yolk sac hanging below from where it draws its nutrition for 2-3 days.
  • At this stage the mouth is not formed and hence it does not take food from outside.

Fry

  • When the fishes have developed to the point where they are capable of feeding themselves, the fish are called fry (1 - 2 cm).

Fingerling

  • As soon as the fry grow up to 10 - 15 cm size or roughly equal the size of a finger it is known as fingerling.
  • Fingerling is the proper size for stocking in table fish production ponds.
  • It takes about 30-60 days for the fry to grow up to fingerling size.
  • Note: Sometimes, we come across a juvenile stage called spawn in some places, it is the intermediate stage between hatching and fry.

Feed

  • Most fish farmers feed their broodstock with a supplementary feed comprising of 50 percent rice bran IBPS 2018 or wheat bran, 45 percent mustard oil cake and 5 percent fishmeal (Islam, 1989)

Classification of Aquaculture

👉🏻 Based on the degree of intensity:

  • Intensive production involves the high-density culture of organisms, and regular and nutritionally complete feeding;
  • Semi-intensive systems involve lower densities, with the enhancement of naturally occurring feed, and some direct feeding;
  • Extensive aquaculture involves a low density of organisms, sometimes with the enhancement of naturally occurring feed.

👉🏻 Based on the type of environment within which the cultivation takes place and the species is cultivated (Eg. Based on Salinity)

  • Freshwater: This refers to farming of aquatic animals in zero saline water
  • Brackish water: Brackish water is a mixture of seawater and freshwater with a salinity less than 30 ppt (Parts Per Thousand). Examples are: Estuaries, backwaters, creeks and mangrove waterways.
  • Marine: This refers to farming of aquatic animals and plants in sea water.

👉🏻 The main groups of species are:

  • finfish, such as sea bass, sea bream, trout and carp
  • crustacea, such as marine shrimp and freshwater crayfish
  • molluscs, such as mussels, oysters and clams, and
  • seaweeds

👉🏻 On the basis of species stocked for farming:

  • Monoculture: Only one species is reared in a culture system.
  • Polyculture:
    • Two or more different fish species are farmed.
    • Polyculture practices give higher yield than monoculture.

Principal requirements of different species for polyculture

  • Different feeding habits
  • Should occupy different columns in a pond system
  • Should attain marketable size at the same time
  • Should be non-predatory in behaviour

Various Aquaculture Methods and Practices

  • A number of aquaculture practices are used world-wide in three types of environment (freshwater, brackish water, and marine) for a great variety of culture organisms.
  • Freshwater aquaculture is carried out either in fish ponds, fish pens, fish cages or, on a limited scale, in rice paddies.
  • Brackish water aquaculture is done mainly in fish ponds located in coastal areas.
  • Marine culture employs either fish cages or substrates for molluscs and seaweeds such as stakes, ropes, and rafts.
  • Culture systems range from extensive to intensive depending on the stocking density of the culture organisms, the level of inputs, and the degree of management.
  • In countries where government priority is directed toward increased fish production from aquaculture to help meet domestic demand, either as a result of the lack of access to large waterbodies or the over-exploitation of marine or inland fisheries, aquaculture practices are almost exclusively oriented toward production for domestic consumption.
  • The following are some of the cultural practices: (Basically it is divided on the basis of enclosure used for culture)
    • Fish Pond Culture
    • Pen and Cage Culture
    • Raceway
    • Recirculating Aquaculture System (RAS)

Fish Pond Culture

  • It is the common method of fish culture. Water is maintained in an enclosed area by artificial construction of dike/bund.
  • Depending upon the motive of farming, based on economic and commercial considerations, fish culture practices may be classified as under:

(i) Extensive Fish Culture

  • Large ponds, beels, etc. are brought under this culture where little care is taken with regard to its improvement.
  • So it is the least managed fish farming. Here, the yield is modest and the expenditure is less as it is raised on natural food.
  • In extensive fish farming, economic and labour inputs are usually low.
  • Natural food production plays a very important role, and the system’s productivity is relatively low.
  • Fertiliser may be used to increase fertility and thusfish production
  • The extensive fish farming system is the least managed form of fish farming, in which little care is taken.
  • This system involves large ponds measuring 1 to 5 ha in area with stocking density limited to only less than 5000 fishes/ha.
  • No supplemental feeding or fertilisation is provided.
  • Fish depends only on natural foods.
  • Yield is poor (500kg to 2 ton/ha), and survival is low.
  • The labour and investment costs are low, and this system results in minimum income.

(ii) Intensive Fish Culture

  • In this fish culture an all-out attempt is made to achieve maximum production of fish from an minimum quantity of water.
  • It is the best managed form of fish farming and the fishes are fed on artificial food in addition to the natural feed.
  • Here the yield is very high (over 6 ton/ha/year).
  • Although the cost of investment is high, the earnings from this culture far exceed the cost, so as to ensure high profit.
  • Intensive fish farming involves a high level of inputs and stocking the ponds with as many fish as possible.
  • The fish are fed supplementary feed, while natural food production plays a minor role
  • In this system, difficult management problems can arise caused by high fish stocking densities (increased susceptibility to diseases and dissolved oxygen shortage).
  • The high production costs force one to fetch a high market price in order to make the fish farm economically feasible.
  • An intensive fish farming system is the well-managed form of fish farming, in which all attempts are made to achieve maximum production of fish from a minimum quantity of water.
  • This system involves small ponds/tanks/raceways with very high stocking density (10-50 fish/m3 of water).
  • Fish are fed wholly formulated feed.
  • Proper management is undertaken to control water quality by use of aerators and nutrition by use of highly nutritious feed.
  • The yield obtained ranges from 15 to 100 ton/ha or more.
  • Although the cost of investment is high, the return from the yield of fish exceeds to ensure the profit.

(iii) Semi-Intensive Fish Culture

  • Intensive culture possesses certain hazards, for which a culture between the first two, called semi-intensive culture, is generally practised.
  • Here certain amount of management is required and the net profit is in between the above two.
  • Semi-intensive fish farming requires a moderate level of inputs and fish production is increased by the use of fertiliser and/or supplementary feeding.
  • This means higher labour and feed costs, but higher fish yields usually more than compensate for this.
  • Semi-intensive fish culture system is more prevalent and involves rather small ponds (0.5 to 1 hectare in an area) with higher stocking density (10000 to 15000 fish/ha).
  • In this system, care is taken to develop natural foods by fertilisation with/without supplemental feeding.
  • However, the major food source is natural food.
  • Yield is moderate(3 to 10 ton/ha), and survival is high.

Pen and Cage Culture

  • Pen and cage culture involve the rearing of fish within fixed or floating net enclosures supported by frameworks made of bamboo, wood, or metal, and set in sheltered, shallow portions of lakes, bays, rivers, and estuaries.
  • Both cage and pen culture are types of enclosure culture and involve holding organisms captive within an enclosed space whilst maintaining a free exchange of water.
  • The two methods, however, are distinct from one another.
  • A cage is totally enclosed on all, or all but the top, sides by mesh or netting, whereas in pen culture the bottom of the enclosure is formed by the lake or sea bottom.
  • Cage culture uses existing water resources (ponds, rivers, estuaries, open ocean, etc.) but confines the fish inside some type of mesh enclosure.
  • The mesh retains the fish, making it easier to feed, observe and harvest them.
  • The mesh also allows the water to pass freely between the fish and surrounding water resource, thus maintaining good water quality and removing wastes.

Cage Culture

  • Rearing of fish from juvenile stage to commercial size in a volume of water enclosed on all sides (In some cases, the top maybe open).
  • Advantages of Cage Culture:
    • Effective use of existing waterbodies
    • Technically simple
    • Lower capital cost
    • Easier stock management and monitoring
  • Disadvantages of Cage Culture:
    • Vulnerable to external water quality problems eg. Algal blooms, low oxygen
    • Stock is more vulnerable to predators such as birds
    • Growth rates are significantly influenced by ambient water parameters

Pen Culture

  • Pen culture is defined as raising of fish in a volume of water enclosed on all sides except bottom.
  • This system can be considered a hybrid between pond culture and cage culture.
  • Advantages:
    • Intensive utilization of available space
    • Suitability for culturing many varied species
    • Ease of harvest
    • The flexibility of size and economy
    • Availability of natural food and exchange of materials with the bottom
  • Disadvantages:
    • High demand for oxygen and water flow
    • Pollution
    • Rapid spread of diseases
    • Risk of theft
    • Conflict with multiple use of natural waters

Raceway

  • Raceway culture is defined as raising of fish in running water.
  • Raceways are designed to provide a flow-through system to enable rearing of much denser population of fishes.

Types

Linear Type

  • Ponds arranged in sequence the volume of water entering each pond is larger and as the same water is used repeatedly from pond to pond, occurrence of disease in initial ponds may directly affect the other connected ponds.

Lateral Type

  • Ponds laid out in parallel in this type the volume of water entering each pond is smaller but a fresh supply of water is always ensured, and no transfer of disease from one pond to another.

Recirculating Aquaculture System (RAS)

  • A Recirculating Aquaculture System (RAS) can be defined as an aquaculture system that incorporates the treatment and reuse of water with less than 10% of total water volume replaced per day.

Integrated Fish Farming

  • The principle of integrated fish farming involves farming of fish along with livestock or/and agricultural crops.
  • This type of farming offers great efficiency in resource utilization, as waste or byproduct from one system is effectively recycled.
  • It also enables effective utilization of available farming space for maximizing production.
  • The rising cost of protein-rich fish food and chemical fertilizers as well as the general concern for energy conservation have created awareness in the utilization of rice and other crop fields and livestock wastes for fish culture.
  • Fish culture in combination with agriculture or livestock is a unique and lucrative venture and provides a higher farm income, makes available a cheap source of protein for the rural population, increases productivity on small land-holdings and increases the supply of feeds for the farm livestock.
  • The scope of integrated farming is considerably wide.
  • Ducks and geese are raised in pond, and pond-dykes are used for horticultural and agricultural crop products and animal rearing.
  • The system provides meat, milk, eggs, fruits, vegetables, mushroom, fodder and grains, in addition to fish.
  • Hence this system provides better production, provides more employment, and improves socio-economic status of farmers and betterment of rural economy.

👉🏻 Integrated fish farming can be broadly classified into two, namely:

  • Agriculture-fish and Livestock-fish systems.
  • Agri-based systems include rice-fish integration, horticulture-fish system, mushroom-fish system, seri-fish system.
  • Livestock-fish system includes cattle-fish system, pig-fish system, poultry-fish system, duck-fish system, goat-fish system, rabbit-fish system.

Seaweed cultivation

  • It is the practice of cultivating and harvesting seaweed, also known as kelp farming.

Fish lean/ban period

  • The period during which fishing is banned to enable reproduction of marine species and to increase the marine resources.
  • In India, the annual fishing ban period is 61 days.

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