What is Nursery pond ?

It is the pond where rearing of spawn is done having an area of 0.02 ha to 0.05 ha & a depth of about 1.00 to 1.5 m.

It is generally seasonal where 5-8 mm size Spawn is stocked which are harvested within 14-15 days when they attains 25 to 30 mm size.

What is Nursery Pond Management Techniques that evolve

i. Manipulation of pond ecology to ensure optimum production of natural fish food while maintaining the water quality parameters within tolerance limits of the stocked fish species

ii. The husbandry of fish through stock manipulation, supplementary feeding and health care.

Broadly the various steps involved in the management of ponds at all the three stages of culture may be classified as

Pre-stocking

Stocking

Post-stocking Management

Pre –stocking Management It aims at proper preparation of ponds to remove the causes of poor

survival ,unsatisfactory growth etc & also to ensure ready availability of natural food in sufficient quantity for the spawn/Fry/Fingerling to be stocked.

1st Step : Drying & Ploughing of fish pond

Dry the pond till cracks develops in the soil

It also ensures eradication of predatory & weed fishes as well as pond parasites.

It should be followed by ploughing for better mixing up of surface & sub-surface soil.

Plough helps in aeration, facilitates organic mineralisation process of soil for enhancing pond productivity.

2nd Step : Control of Aquatic Weed Applicable for perennial pond.

Aquatic weed infestation in culture ponds pose severe problems like

Nutrition absorption,

affecting primary production

preventing light penetration

causing oxygen deficiency

reduces living space for fish

enhances pond siltation

harbours predatory insects

with netting operations

Effective methods to control Aquatic weeds are Manual method, chemical method, Biological method,mechanical method.

Manual Method :

Pulling,raking,Seining

Mechanical Method :

By using implements like Sickle,Mechanical Cutters,Harvesters

Chemical Methods :

By use of weedicides or Herbicides like Glyphosate,Fluridon,

2,4-d(Systemic Herbicides)

& Diaquat,Endothal(Contact Herbicides)

Biological Methods :

Grass carp : Submersed weed like Chara,Nitella etc

Tilapia : Filamentous algae,Duck Weed etc.

Common Carp : Filamentous algae,Duck Weed etc.

Ducks like Khaki Campbell & Swans :Many type of weed.

Sea cow like Dugon dugon : Pistia

Insects like N.bruchii :Water hyacinth

Samea multiplicalis : Pistia

3rd Step :Eradication of Predatory Fishes Predatory Fishes enters to culture systems through surface run off .

They breed in pond prior to carps & establish their population .

They competes with space, food with that on the desirable species & affects the survival.

They can be effectively controlled by

Manual method

• By use of bio-toxicants

• By use of chemicals like anhydrous ammonia, commercial grade of Bleaching powder, combination of Urea followed by bleaching powder

4th step : Control of aquatic insects Many aquatic insects in their larval & adult stages prey upon fish hatchlings &

fry & compete with them for food.

No.of predatory insects like back swimmer,giant water bug,water scorpion & beetles enter the nurseries,especially during monsoon & prey on spawn & fry.

The basic method of eradication of insects is to apply a thin oily film over the pond surface which chokes the respiratory tubes of aquatic insects.

TREATMENT METHOD :

Soap-oil emulsion : 56 kg vegetable oil + 18 kg Soap

Diesel Oil : 50-60 kg/ ha

Kerosene Oil : 80-100 kg / ha

Turpentine Oil ; 75 kg / ha

5th Step : Liming of fish ponds

Rectifies the ph

Releases nutrients from soil by Leaching

Enhances primary productivity

Acts as pond disinfectant

It should be applied after testing the soil & water ph.

Highly acidic (ph 4-5) : 2000 kg/ha

Moderately acidic (ph 5-6) : 1200 kg/ha

Slightly acidic (ph 6-6.5) : 1000 kg/ha

Near neutral (ph 6.5-7.5) : 200-300 kg/ha

If the soil & water is highly alkaline & ph is above 9.0, then we have to apply raw cow dung @ 20-30 t/ha or Gypsum @ 5-6 t/ha.

LIMINING OF FISH POND :

6th Step : Manuring & fertilisation Manuring & Fertilisation is done to enhance productivity of the

culture system.

Manuring always refers to application of cowdung or poultry manure where as fertilisation refers to use of inorganic fertiliser in terms of Nitrogen, phosphorus & potash.

The conventional dosages of manure & fertilisers used in carp culture are

cow dung :10-20 t/ha/year

Poultry manure :4-8 t/ha/year

Urea :100 kg N/ha/year

Super phosphate :50 kg p/ha/year

MANURING OF FISH POND :

Depending upon the organic carbon content & ph of the soil the manuring & fertilization schedule is

Productivity Organic Carbon

Ph Cow dung Urea SSP

1.Low <0.5 5.5 10-12 t / ha 320 kg / ha 405 kg / ha

2.Medium 0.5-1.0 % 5.5-6.5 8-10 t / ha 225 kg / ha 315 kg / ha

3.High 1.5-2.0 6.5-7.5 5-8 t / ha 156 kg /ha 210 kg / ha

Stocking Management :

After satisfying the physico-chemical nature of the water & plankton growth in the nursery pond ,the spawn can be stocked in the ponds at the rate of 5-6 million spawn/ha. However ,higher densities of 10-20 million/ha can be followed in cement cisterns.

The stocking should be done either in the early morning or late evening after gradual acclimatization of the spawn to the pond water.

Species Combination

Species Combination

Catla Rohu Mrigal Common Carp

Silver Carp Grass Carp

Six Species 20-30 % 15-20 % 15-20 % 20-25 % 10-15 % 5-15 %

Four Species 30-40 % 20-30 % 15-20 % 20-25 % 0 0

Three Species 40 % 30 % 30 % 0 0 0

RELEASING OF SPAWN :

Supplementary Feeding : The natural foods alone produced in the pond through manuring & fertilization is not enough

for sustenance & proper growth of the cultured fish.

Hence,provision of nutritionally balanced supplemental feed is a must to boost fish production from semi-intensive & intensive system of culture.

Therefore,supplementary feeding with diets rich in protein,carbohydrate,lipid,mineral & vitamins are essential.

Research conducted in the past reveals that,the carp diets must contain a minium of 25-30 % protein,30-40 % CHO,5-10 % of lipid ,traces of vitamins & minerals.

Never the less under feed or over feed the cultured fishes which may lead to growth depression in fish & wastage or pollution of the feed or culture media respectively.

Only the feed component constitutes more than 60 % of the total recurring expenditure,hencefeed management is a must.

FEEDINg rate :

1st

day : no feeding

2nd

Day -5th

Day : 400 % of their bw

6th

day -14th

day : 800 % of their bw

Feed required –Estimated fish biomass in the pond × % feeding rate

Biomass – Avg.body weight × No.of fish stocked × % survival

Feeding methods :

1. Broadcasting of powdered feed : For spawn or Fry

2. Basket feeding : For fingerling

3. Bag feeding :Table size fish

4. Automatic demand feeder : Ad libitum feeding

POST-STOCKING MANAGEMENT :

Regular monitoring of water quality.

Applicatioin of split dosage of lime in monthly intervals.

Application of manure & fertiliser at monthly intervals.

Regular application of feed.

Monitoring of feed consumption.

Growth assessment.

Re-scheduling of feeding rate.

Provision for water exchange,if facilities exists.

Health management.

HEALTH MANAGEMENT : For proper growth of fish,a balanced relationship

between host,environment &pathogens is a must.

Any deviation in the recommended package of practices leads to outbreak of disease.

Once disease sets in,it either affects a part of the cultured population or the entire population is affected.

Depending upon the intensity of the diseases ,either partial fish mortality or complete fish mortality can be expected from the culture systems.

Treating a diseased fish is rather difficult in comparison to the terrestrial animals.

Individual treatment for fish can not be recommended or it is not possible,hence mass treatment of the population or the environment is recommended.