Aquaculture: Methods and Types

Aquaculture

Aquaculture is the farming of aquatic plants and animals in controlled environments. Finfish and shellfish are grown in artificial containers such as earthen ponds, cages and concrete or fiberglass tanks. The cultured organism is reproduced and offspring raised in captivity. The young organisms are stocked at a known density and fed a nutritionally complete diet to maximize growth rate. Water quality is monitored to maintain a healthy environment. Animals are harvested with nets when they reach market size.

Aquaculture includes culture of fish, crustaceans, molluscs etc.

Types 1. Freshwater includes cold water fisheries

2. Brackish water- cultivation of seabass, mullets, shrimp etc

On the basis of management 1. Extensive

2. Semi-intensive

3. Intensive

Coldwater aquaculture• Cultivable fish species are Trout (Brown & rainbow trout), Indian trout (Schizothorax spp), Mahseer, Common carp including mirror carp among cyprinidae.

• Modern trout farms in India – Himachal Pradesh trout farm, J & K trout farm.

• The potential cultivable species have gained importance due to excellent food value, delicious taste, better meat quality and consumer preferences.

Water resourcesPonds & tanks – 2.25 million haBeels & derelict waters – 1.3 million haLakes & reservoirs – 2.09 million haIrrigation cannals & channels – 0.12 m KmPaddy field – 2.3 million haConsidering the availability of water area of ponds & tanks only 45% utilized shows the potential of horizontal expansion

Fish production

• FW aquaculture account over 70% of total inland fish production.

• Both Indian and exotic carp contribute over 90% of total freshwater aquaculture production.

•FFDAs enhanced the average productivity from 500 to about 2000 Kg/Ha/yr however the potential of technologies is 15 tonnes/Ha/yr.

Sl. No. Culture system Average production rates (T/ha/yr)

1 Composite fish culture 4-6

2 Intensive culture 10-15

3 Clarias culture 3-5

4 Sewage-fed fish 3-5

5 Integrated fish 3-5

6 Pen culture 4-5

7 Cage culture 10-15

8 Running water fish 25-50 kg/m3

9 Shrimp farming 2-5

10 Aquatic weed based 3-4

11 Biogas slurry based 3-5

12 Makhana & air breathing fish 1.52 + 94 kg makhana

Fish production range under different culture systems

Culture of Indian Major CarpsManagement of Nursery Ponds

Pond may be either existing one or newly constructed

Pond Preparation

The shape of pond must be rectangular . Size of pond should be 0.03 to 0.05 ha with water depth of 1 to 1.5 m. It is necessary to expose pond bottom to the sunlight for better mineralization, escape of toxic gases and to keep free from aquatic insects, aquatic weeds, predatory fishes.

Steps (Pre-stocking)

1.Eradiation of aquatic weeds.

2.Removal of unwanted fish.

3.Application of lime.

4.Fertilization.

5.Control of aquatic insects.

1. Aquatic weeds

It is defined as unwanted and undesirable vegetation that grow in waters and if unchecked causes serious problems in fish culture.

Based on the habitat, classified into floating, submerged, emergent, marginal, filamentous and algal blooms.

a. Floating weeds – Don’t have roots, they may be floating in water with leaves over surface of water, drifted by water currents and waves induced by winds. They are more problematic than the other kind of weeds. Eg. Eichhornia (Water Hyacinth), Pistia (Water Lettuce), Salvenia (Water Fern), Duck weed (Lemna, Azolla, Spirodella)

b. Submerged weeds – Present in water column and not seen above water surface, some are rooted at the bottom of the ponds while some are non-rooted. Rooted weeds – Hydrilla, Vallisneria (Tape grass), Potamogeton, Otelia, Najas, Chara (Stone wort), Non-rooted – Ceratophyllum, Utricularia

c. Emergent weed - Rooted at the pond bottom but leaves are floating above surface of water. Eg. Nymphia, Nelumbo, Nymphoides, Myriophyllum.

d. Marginal weeds – They are grown at edge of ponds or at interphase between land and water, grow over moist land. Eg. Typha, Marselia, Cyperus.

e. Filamentous algae and algal blooms – Scum or mat forming type and found floating at pond surface. Eg. Spirogyra.

Algal blooms are formed by unicellular algae. Eg. Microcystis, Euglena.They are formed due to over fertilization or due to input of excess nutrients.

Disadvantages of aquatic weeds

• Interference in culture activities.

• Decrease in DO level

• Restrict space for movement of fish.

• Utilize nutrients.

• Interference in netting operation.

• Restrict light penetration.

• Release toxic gases.

A balance biomass of submerged vegetation and algae is required for ecosystem of composite fish culture but excessive infestation is harmful.

Control of aquatic weeds

Generally the method is selected based on the dimension of the weed infestation, size of the pond and time available.

1. Physical- manual or mechanical, various tools such as sickle, blades, wire mess, hooks, wooden sticks, weed cutter etc. are used.

2. Biological- stocking of weed-eating fishes like grass carp, common carp, gourami and silver barb is an effective method for long term control and maintenance of weed population especially in grow-out.

3. Chemical or weedicides- Marginal & emergent weeds by spraying glyphosate@3 kg/ha, foliar spray of 2-4D @ 7-10 kg/ha, phytoplankton bloom by algicide Somazine or Diuron at 0.3 to 0.5 ppm. Anhydrous ammonia @ 20ppm N is also effective not only in controlling the submerged weeds but also helps to eradicate weed & predatory fish.

Strategies for development

Culture of shell fishes of India

Giant river prawn (Macrobrachium rosenbergii)

It is the largest among freshwater prawn, found in all rivers of east and west coast of India and coastal areas throughout Bay of Bengal. It has long sword shaped rostrum with equal no. of teeth on both upper and lower edges. It is benthophagic omnivorous. It migrates to estuary during breeding season.

Monsoon river prawn (Macrobrachium malcolmsonii)

It is found in all peninsular rivers of India. The second cheilipedes of female are much longer and stouter than the body. It also migrates to estuary during breeding season.

Macrobrachium rosenbergii Macrobrachium malcolmsonii

FRESHWATER AQUACULTURESEED PRODUCTION AND

GROWOUT OF GIANT FRESHWATER PRAWN

Mature male & female

Seed HarvestHatchery Growout pond

Farm raised Scampi(Freshwater Prawn)

PRAWN HATCHERY

Water Quality Management in AquacultureBasic requirement of fish culture, offers favourable environment for

growth, respires with DO and get food suspended in water.

Fish Culture is influenced by various physical, chemical & biological properties of water.

Temperature- fish can perceive a small change less than 0.10C. IMC thrive well in 18-380C. Max. temp. in afternoon and min. in morning. Higher temp. reduces the DO level.

pH- Indirect measurement of hydrogen ion concentration in water, less than 4 only CO2 is absent between 7 to 10 only bicarbonate are present , and at 11 only carbonates are present, fish die at pH 11, diurnal fluctuation is because of CO2 conc. Used in photosynthesis.

DO- Most imp. For survival of fish, gill is the site for exchange of oxygen, reduction in DO reduces metabolism & restricts development & growth, sources are photosynthesis & dissolution from atmosphere, opt. 5-12ppm, loss of DO because of respiration, decomposition, mineralization of organic matter and direct loss to atmosphere. DO can be improved by adding water, recirculation, use of aerators, KMnO4, and beating water surface by sticks.

Different types of

Aquaculture

Extensive aquaculture

Semi-Intensive

Aquaculture

intensive Aquaculture

Flow-through

method/Raceway

Re-circulatory

method

Traditional aquaculture

I) Traditional method Pond culture

Common method of fish culture Water is maintained in an enclosed area by artificial construction of dike/bund.Ponds are very small and shallow bodies of quiet standing waters with slight wind action.

Management Practices

Pond Preparation – There are various aspects in ponds preparation which should be carried out before pond is used for culture for first time & for subsequent crops. The main objective of pond preparation are to provide fish with a clean pond base & appropriate stable water quality.

1. Cleaning – During fish production cycle considerable quantity of organic waste accumulates in pond bottom depending upon the cultural practices followed. Its waste must be removed to ensure sustain fish production from the pond. There are two methods –

a. Dry method – In this method, after the final harvest the pond bottom is dried and crack developed primarily to oxidize the organic components, left over in the pond after the previous culture. The pond bottom should be dried for at least 7-10 days & the soil should crack to a depth of 2.5 – 5.0 cm. After drying the pond bottom is ploughed up to a depth of 15 cm.

b. Wet method – In this method, after the final harvest, the accumulated organic matter at pond bottom is flushed out in form of a thin slurry using a heavy duty pump.

2. Liming – Advantages

a. It corrects acidity of water.

b. It helps to raise bicarbonate content.

c. It supplies Ca, for growth of freshwater flora, molluscs, crustaceans.

d. It helps to establish pH buffer system.

e. It utilizes the action of Sodium (Na+) & Magnesium (Mg2+) ions, due to toxic and caustic property, it helps to kill harmful bacteria.

Pond fertilization

The main objective of adding fertilizers in fish pond is to maintain the sustain production of natural fish food organisms during the entire culture period.

Types –

1. Organic fertilizers

2. Inorganic fertilizers

Fertilization• Purpose is to promote the growth and

development of correct size and species of zooplankton prey for fish fry.

Population Trends

Rotifers Cladocerans

Copepods?

1-2 weeks 2-3 weeks

3-4 weeks

Organic Fertilizers• Plant and animal materials– zooplankton feed on organic or the

bacteria/protozoa feeding on organic

• Long-term application• Selection criteria– low carbon : nitrogen ratio– fine particle size– readily available and economical

Fertilizers Applications• Inorganic Fertilizers– liquid• mixed into wash or mixed 10:1 (sprayed)

– powder• soluble, blown onto pond surface

– granular• fairly insoluble, placed onto shallow wooden

platform 1ft below pond surface

• Organic Fertilizers– apply fertilizers completely around pond edge– frequent application

Inorganic Fertilizers• Limiting factor in freshwater systems is often

phosphorus– in late summer, nitrogen may be limiting

• Fast acting• Selection criteria– adequate phosphorus and nitrogen– economical and ease of application

• Chemical designation N:P:K

Zooplankton Monitoring

• Sample prior to stocking and every week thereafter

• Samplers– zooplankton net– tube sampler– pumps– visual

• Desirable number -> 500+ animals/gallon

2. In organic Fertilizers – These are simple inorganic compounds which primarily contain at least one or more elements of NPK. Commercial inorganic fertilizers used for pond culture are the same as those of agricultural crops. Due to their high solubility in water the nutrients become readily available soon after their application.

According to composition chemical fertilizers are –

a. Nitrogen fertilizers

b. Phosphorus fertilizers

c. Potash fertilizers

a. Nitrogen fertilizers – They contain nitrogen and are available as ammonium sulphate, ammonium nitrate and urea. The form of nitrogenous fertilizers are selected on the basis of acidity and alkalinity of pond soil. Nitrogenous fertilizers are particularly essential for newly constructed pond ( because organic matter is not present in pond bottom). The efficiency of N fertilizers is inhibited by phosphorus deficiency.

It is best to maintain the P:N ratio as 1:4

b. Phosphorus fertilizers – Almost all fish ponds have phosphorus deficiency. Phosphatic fertilizers are most effective & favourable for fish culture.

- Superphosphate are most suitable in water, di-calcium phosphate is partially soluble in water, rock phosphate is almost insoluble in water, single super phosphate (SSP) is extensively used and easily available, generally phosphatic fertilizers are held in soil and its action is extended to subsequent years of its application.

c. Potash fertilizers – Potassium remain available in required quantity in natural water. It is commonly available in form of Muret of Potash (K2CO3) & Sulphate of Potash (K2SO4).

The favourable action of Potassium fertilizers can be seen in ponds with low alkalinity. In general for ponds in which phytoplankton production is rather slow, this fertilizers may be applied. It also improves the hygienic condition of pond.

Advantages of applying inorganic fertilizers

1. Exact composition of inorganic fertilizers is advantageous.

2. Mineralization is very fast, giving quick effect on pond productivity.

3. Lack of pollution.

4. No BOD (Biological Oxygen Demand) is required for chemical fertilizers or in other words there beneficial effect on oxygen content.

5. Used in small quantity and applied as additive manures. Hence convenient for utilization.

Nutrient profile of some common manures & fertilizers

Sl. No. Manures/fertilizers N % P % K %

Manures of animal origin

1. Raw cow dung (RCD) 0.6 0.16 0.45

2. Pig Dung (PD) 0.6 0.45 0.50

3. Duck droppings 1 1.4 0.62

4. Poultry excreta 1.6 1.5 - 2 0.8

Manures of plant origin

1. Mustard oil cake 4.5 2.0 1.0

2. Ground nut) 7.8 1.5 1.3

3. Mahua oil cake 2.5 0.8 1.8

Inorganic

1. Urea 43-46

2. Ammonium nitrate 20.5

Phosphatic

1. Single Super Phosphate(SSP) 16-20

2. Triple Super Phosphate (TSP) 40-45

Potash

1. Muret of Potash 48-62

2. Sulphate of Potash 47-50

• Fertilization in fish pond starts 10-15 days prior to seed stocking depends upon the nutrient status & chemical environment of pond soil.

• Proper analysis of soil & water is essential before deciding fertilization schedule.

Nutrient status of different types of soil pond

Productivity level

pH N(mg/100g of soil)

PotashP2O5 (mg/100g of soil)

Organic carbon (%)

High 6.6 - 7.5 50 6 - 12 1.5

Medium 5.5 - 6.5 25-49 3 - 5 0.5 – 1.4

Low Below 5.5 Less than 25 Less than 3 Less than 0.5

Amount of fertilizers @Kg/ha/yearHigh Medium Low

Raw cow dung 5000-8000 8000-10000 10000-25000

Urea 112-155 156-225 226-260

Ammonium Sulphate 225-330 - -

Calcium Ammonium Nitrate - 350-500 501-650

Single Super Phosphate 150-219 220-315 316-405

Triple Super Phosphate 54-75 76-110 111-145

Fertilization Schedule

Quantity (Kg/ha) Periodicity of application

Raw cow dung (RCD) 2000 Initial

1000 Monthly

Urea (6.5-7.5) 25 Monthly

Ammonium Sulphate (>7.5) 30 Monthly

Cal. Ammonium Nitrate (5.5-6.5) 30 Monthly

Single Super Phosphate (SSP) 20 Monthly

Triple Super Phosphate (TSP) 8 Monthly

Aquatic insects and their controlAquatic insects constituted about 4% of total insect fauna, which exist in the

world. Aquatic insects either in their adult or larval stage prey directly on carp spawn or injured the young ones by sucking body fluid or indirectly competing for food with carp spawn. Therefore, the pond culture technique includes the control & removal of harmful aquatic insects. Such eradication of harmful insects from ponds play a very important role in increasing fry survival rate.

However, common insects found in the culturable ponds being smaller in sizes, can not make any harm to rather bigger sized fish including fingerlings & yearlings. Thus removal or control of insects in stocking pond is not compulsory. Out of 11 orders of Class Insecta - 3 orders 1) Hemiptera 2) Coleoptera 3) Odonata are relatively common in freshwater ponds.

The important families with examples under different orders are - Family Example

1. Notonectidae a. Notonecta (water boatman or backswimmers)b. Anisopes

2. Belostomidae a) Belastoma (Giant water bug)3. Nepidae a) Nepa (Water scorpion)

b) Ranatra (Water stick insect)

Order - ColeopteraThe important families with examples under different orders are -

Family Example1. Dytiscidae a. Cybister (Diving beetle)2. Hydrophilidae a) Hydrophilus (Scavenger beetle)

b) Sternolophus (Water scavenger)3. Gyrinidae a) Gyrinus

b) Dineutes (Whirling beetles)

Order – Odonata Dragon fly nymph

Order – Hemiptera Includes water bugs, are relatively more dangerous as their complete aquatic life both larval as well as adult stage. They have very strong piercing type mandibles.

Intensity of predation• Cybister consumes about 15-20 fry of 20-40 mm in 24 hours.• Anisopes & Ranatra consumes 182 and 122 carp spawn respectively in 24

hours.• Dragon fly nymph consumes about 7 fry in 3 hours & 24 spawn in 24 hours.• These bugs secrete toxic salivary substances which kill the prey.• Sternolophus & Gyrinus suck body fluid and even sometime kill spawn and

fry.

Control measures • Simple way of controlling is by netting but complete removal is not possible

by netting. • Application of Oil Soap emulsion in ratio of (56:18)/ha (56 L oil & 18 Kg Soap

per ha) is an age old practice. It is recommended to apply 12-24 hours before releasing the spawn. The oil film float over the surface of water.

Mode of action of soap-oil emulsionThese insects periodically come to surface regularly for breathing atmospheric oxygen by raising their tracheal tubes over water surface. Oil films enter into tracheal tube and damages respiratory system of insects by blocking.

•Least managed form of farming system•Large ponds ranging 1 to 5 ha in area are used for farming•No supplemental feeding or fertilization is provided•Harvest – 500 to 2000 kgs /ha

II) Extensive fish farming system

Growth is limited by available food (zooplankton feeding on pelagic algae or benthic animals, such as crustaceans and mollusks).Tilapia filter feed directly on phytoplankton, which makes higher production possible.

III) Semi-intensive fish farming system

– Involves rather small ponds (0.5 to 1 hectare in area)– Natural food developed by fertilization and with or

without supplemental feeding for fish but in shrimp supplement feeding is done

– Harvest – 2500 to 10000 kgs (Fish) and 1500 to 2500 kgs (Shrimp)

Intensive fish farming system is the well-managed form of fish farming

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)

IV) Intensive fish farming system

• FLOW THROUGH METHOD (Raceway method)

• 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 .

• Source of water: springs, streams, deep wells, reservoirs.

• These are much smaller and occupy less space than ponds.

• Made up of concrete or cement blocks or may be lined by plastic material.

• Raceway farms can have Series/Linear design or Parallel/Lateral design series.

• Slope: 1-2 %• One segment: 30 m Long, 2.5-3.0 m wide at bottom and

1.0-1.2 m deep.• Contains 10-20 segments.• All segments should be straight to ensure uniform flow.

Linear type/Series design: 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

Linear type

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.

Lateral type

FLOW THROUGH HATCHERY FOR RED TILAPIA

• The main benefit of RAS is the ability to reduce the need for fresh, clean water while still maintaining a healthy environment for fish.

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.

RAS Model

Bio-filtration

Solids removal

Solids are flushed out or vacuumed out manually using a siphon

Oxygenation

. Dissolved oxygen levels can be increased through two methods aeration and oxygenation. In aeration air is pumped through an

air stone or similar device that creates small bubbles

pH control

pH is controlled by :•addition of lime (CaCO3) or sodium hydroxide (NaOH). •degassing CO2 in a packed column or with an aerator

↓ pH leads to ↑ CO2

Advantages• Reduced water requirements as compared to

raceway or pond aquaculture systems.• Reduced land needs due to the high stocking

density.• Site selection flexibility and independence from a

large, clean water source.• Reduction in wastewater effluent volume.• Ability to closely monitor and control

environmental conditions to maximize production efficiency. Similarly, independence from weather and variable environmental conditions

Disadvantages

• High upfront investment in materials and infrastructure.

• High operating costs mostly due to electricity, and system maintenance.

• A need for highly trained staff to monitor and operate the system.