Animal Husbandry and Fisheries Assistant · Chapter 7

Fish Seed Production and Pond Management

What to remember

Indian major carps do not breed in still ponds, so seed is produced by induced breeding with pituitary extract or a synthetic hormone such as Ovaprim.
Good pond management has a fixed order: dry and clean the pond, remove weeds and predators, lime, manure, fill, stock, feed, monitor water and harvest.
Seed has stages: spawn (hatchling), fry, fingerling, yearling; each stage is reared in a different pond.

1. Seed sources and stages

Fish seed comes from rivers (wild collection) or from hatcheries. Wild seed is mixed with weed and predator fish, so hatchery seed is now the main source.

Stage	Size (approx.)	Pond used
Egg	Fertilized, floating or sinking	Hatching jar or pool
Spawn (hatchling)	About 5-8 mm, yolk sac absorbed in 2-3 days	Nursery pond
Fry	About 2.5-4 cm	Rearing pond
Fingerling	About 10-15 cm	Stocking (growout) pond
Yearling	One year old, larger	Stocking pond

2. Breeding of carps

Catla, Rohu and Mrigal mature in 2 to 3 years. They breed naturally in running water during the monsoon when rain, flooding and a change in water temperature trigger the pituitary gland. In ponds this trigger is missing, so the brooders mature but do not spawn.

Brood stock management:

Keep males and females in separate ponds, away from the breeding season.
Feed with rice bran and oil cake; supply fresh water.
Choose the ripe female by a soft, rounded belly and a swollen, reddish vent. A ripe male releases milt (white fluid) when the belly is pressed lightly.

Induced breeding (hypophysation):

Pituitary glands are collected from mature fish, preserved in absolute alcohol and homogenized in saline before use. Extract is injected into the muscle at the base of the dorsal fin.
Females get a small preliminary dose followed after about 6 hours by a larger resolving dose. Males get one dose with the second injection of the female.
Synthetic hormones are now common. Ovaprim is a GnRH analogue with a dopamine blocker (domperidone) and is given in one dose. Ovatide and similar kits work the same way. HCG (human chorionic gonadotropin) is also used. Always follow the manufacturer's label for dose.
After injection brooders rest in a breeding hapa or circular pool with flowing water. The time from injection to spawning is the latency period, commonly 6 to 8 hours and shorter in warm water.
Fertilization is external. Fertilized eggs swell by taking in water and are called water-hardened eggs.

3. Hatcheries

Chinese circular hatchery: a circular spawning pool with a central outlet, an egg collection chamber and a hatching pool. Flowing water keeps eggs in motion.
Jar hatchery: conical-bottomed hatching jars (often plastic or fibre glass) with gentle upward water flow. A common modern design.
Hatching takes about 16 to 20 hours in warm water, longer in cooler water.
Healthy eggs are transparent; dead eggs turn white and are removed to stop fungal spread.
Hatchlings are taken to nursery ponds after the yolk sac is absorbed, about 2 to 3 days later.

Fry stages in nursery: Prepare nursery pond 2 to 3 days before stocking. Spawn grow to fry in about 3 weeks and need live plankton at first, then fine feed.

4. Pond preparation

A pond should be dry, clean and free of predators before stocking.

1. Dewatering and drying: dry the pond bottom and till the soil.
2. Eradication of weeds: remove aquatic weeds by hand or by suitable control; grass carp helps control weeds in growout ponds.
3. Removal of predators and weed fishes: use mahua oil cake at 250 ppm. Derris root and bleaching powder are also used. Do not use poison near drinking sources.
4. Liming: agricultural lime (calcium carbonate) or quick lime raises pH, kills germs and acts as a buffer. Dose depends on soil pH; a common range is a few hundred kilograms per hectare.
5. Manuring and fertilizing: organic manure (cow dung) and inorganic fertilizers (urea, single superphosphate) build up plankton. Plankton is natural food of spawn and fry.
6. Filling: fill with clean water through a fine mesh to stop wild fish entering.
7. Stocking after the plankton bloom appears and toxicity of oil cake has gone, usually 2 to 3 weeks.

Worked example: Mahua oil cake at 250 ppm for 1 hectare-metre of water (10,000 m³). 250 ppm = 250 g per m³. Total = 250 × 10,000 g = 2,500 kg.

5. Culture systems

Monoculture: one species in the pond.
Polyculture (composite carp culture): three Indian major carps, or three Indian and three exotic carps (6-species), are stocked together so each uses a different feeding zone. A typical ratio in a 3-species system is 3 Catla : 4 Rohu : 3 Mrigal.
Integrated culture: fish with livestock or crops, such as poultry-cum-fish, duck-cum-fish, paddy-cum-fish. Droppings feed the pond and reduce feed cost.
Air-breathing fish culture: Magur, Singhi and Murrel can be stocked at high density because they take air.
Freshwater prawn: Macrobrachium rosenbergii is farmed in ponds with carps or alone.
Cage and pen culture: used in large reservoirs and lakes.

6. Feeding and growth

Natural food: plankton, which grows with fertilization.
Supplementary feed: rice bran and groundnut oil cake mixed in equal parts is a standard carp feed. Daily feeding is commonly 2 to 5 per cent of body weight, adjusted every fortnight after sampling.
Feed conversion ratio (FCR) = feed given (kg) ÷ weight gain (kg). Lower is better.
Survival % = (number harvested ÷ number stocked) × 100.

Worked examples

1. 3,000 kg of feed gives a gain of 1,500 kg. FCR = 3,000 ÷ 1,500 = 2.
2. 10,000 seed stocked, 7,500 harvested. Survival = 75 %.
3. A 2 ha pond at 5,000 fingerlings per ha needs 10,000 fingerlings.

7. Water quality and plankton

Parameter	Desired range
Dissolved oxygen	5 mg/L or more; below 3 mg/L stresses fish
pH	About 7.5 to 8.5
Temperature	About 25 to 32 °C
Transparency (Secchi disc)	About 30 to 40 cm
Ammonia	As low as possible (toxic)

Secchi disc reading shows plankton density. Very low reading means too dense plankton or turbid water.
Plankton blooms (green water) can crash overnight and cause oxygen depletion. Fish gasping at the surface at dawn is the warning sign.
Remedies: change water, use aerators, stop feeding, apply lime.

8. Fish diseases and health management

Disease	Cause	Sign	Control
Epizootic ulcerative syndrome (EUS)	Fungus Aphanomyces with virus or bacteria	Ulcers on body	Lime, disinfect, avoid cold stress
Argulosis	Argulus (fish louse)	Parasites on skin, restlessness	Dip treatments, pond drying
Saprolegniasis	Fungus	Cotton-like growth	Salt or potassium permanganate dip
Dropsy	Bacteria (Aeromonas)	Swollen belly	Better water, medicated feed
Gill rot	Bacteria or fungi	Rotten gills	Improve water, lime

Prevention: good water, correct stocking density, quarantine of new fish, balanced feed and regular sampling. Potassium permanganate and common salt are standard simple dips.

9. Harvesting and transport

Partial harvest by drag nets; total harvest by dewatering.
Do not feed for one day before harvest.
Seed transport: oxygen-filled polythene bags in cool conditions; high density only for short trips.
Carp seed is sold at spawn, fry or fingerling stage.

10. Andhra Pradesh context

Freshwater carp culture is concentrated in the Godavari and Krishna delta areas, where large ponds are common. Shrimp ponds in coastal belts are managed under separate rules. Hatcheries in AP produce carp seed; seed quality is regulated under state seed law (check the latest official release for current rules). Public hatcheries and fish seed farms run by the Department of Fisheries support farmers.

Exam traps

1. Spawn (hatchling) is not fry; fry is bigger.
2. Latency period is the time from injection to spawning, not the hatching time.
3. Ovaprim is a GnRH analogue plus domperidone; it is not a pituitary extract.
4. Liming raises pH; it does not lower it.
5. Mahua oil cake is a piscicide for predator removal, not a manure.
6. Composite carp culture uses different feeding zones; monoculture does not.
7. Low FCR is better; high FCR means poor feed efficiency.
8. Secchi disc measures transparency, not dissolved oxygen.

One-liners

1. Hypophysation means breeding with pituitary extract.
2. Carp eggs are fertilized externally.
3. Latency period is commonly 6 to 8 hours.
4. Mahua oil cake dose is 250 ppm.
5. Lime raises pH and acts as a buffer.
6. Cow dung and urea build plankton.
7. Rice bran with groundnut cake is a standard carp feed.
8. Desired dissolved oxygen is 5 mg/L or more.
9. Desired pond pH is about 7.5 to 8.5.
10. Secchi disc ideal transparency is about 30 to 40 cm.
11. FCR = feed given ÷ weight gain.
12. EUS causes red ulcers on the body.

Practice questions

A circular hatchery with a central outlet is called
1. Raceway
2. Jar hatchery
3. Chinese hatchery
4. Nursery pond
Answer
C. Chinese hatchery
The Chinese circular hatchery has spawning, collection and hatching pools.
Statements: 1. A very low Secchi reading means very dense plankton or turbidity. 2. Dissolved oxygen of 1 mg/L is ideal. Which is correct?
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
A. 1 only
Ideal oxygen is 5 mg/L or more.
Which instrument measures pond water transparency?
1. Hygrometer
2. Thermometer
3. Anemometer
4. Secchi disc
Answer
D. Secchi disc
Secchi disc reading indicates plankton density.
A farmer stocks 10,000 fingerlings and harvests 7,500 fish. Survival is
1. 85 %
2. 25 %
3. 75 %
4. 7.5 %
Answer
C. 75 %
7,500 ÷ 10,000 × 100 = 75 %.
The first free-swimming stage after hatching is called
1. Fry
2. Spawn
3. Fingerling
4. Yearling
Answer
B. Spawn
Hatchlings are called spawn.
Induced breeding of carps using pituitary extract is called
1. Nursery rearing
2. Polyculture
3. Hybridization
4. Hypophysation
Answer
D. Hypophysation
Hypophysation is breeding with pituitary gland extract.
1 ha-m of pond water is treated with mahua oil cake at 250 ppm. Quantity needed is
1. 2,500 kg
2. 25,000 kg
3. 250 kg
4. 25 kg
Answer
A. 2,500 kg
250 g/m³ × 10,000 m³ = 2,500 kg.
Which stage of seed is larger?
1. Fry
2. Spawn
3. Egg
4. Fingerling
Answer
D. Fingerling
Size grows from spawn to fry to fingerling.
Statements: 1. Lime raises pH. 2. Mahua oil cake kills predatory fish. Which is correct?
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
C. Both 1 and 2
Both statements are correct.
Water-hardening of eggs refers to
1. egg storage
2. swelling after taking in water
3. drying of eggs
4. egg death
Answer
B. swelling after taking in water
Fertilized eggs take in water and swell.
Fish gasping at the surface at dawn mainly indicates
1. low dissolved oxygen
2. cold
3. high pH
4. high transparency
Answer
A. low dissolved oxygen
Plankton respiration drains oxygen at night.
3,000 kg of feed gives 1,500 kg weight gain. FCR is
1. 1.5
2. 0.5
3. 2.0
4. 4.5
Answer
C. 2.0
FCR = 3,000 ÷ 1,500 = 2.
Ovaprim contains
1. Thyroxine and insulin
2. GnRH analogue and domperidone
3. Pituitary extract only
4. HCG only
Answer
B. GnRH analogue and domperidone
Domperidone blocks dopamine inhibition.
Dropsy in fish is mainly due to
1. bacteria
2. virus only
3. cold air
4. plant poison
Answer
A. bacteria
Aeromonas infection causes belly swelling.
Low FCR indicates
1. worse feed efficiency
2. slower growth
3. more feed wasted
4. better feed efficiency
Answer
D. better feed efficiency
FCR is feed per kg gain.
Which fertilizer is commonly used to build plankton in a fish pond?
1. Bleaching powder
2. Mahua oil cake
3. Derris root
4. Urea
Answer
D. Urea
Urea and single superphosphate supply nutrients for plankton.
Statements: 1. Polyculture uses different feeding zones. 2. Monoculture stocks several species. Which is correct?
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
A. 1 only
Monoculture means one species.
Which pond is used to rear fry into fingerlings?
1. Breeding hapa
2. Rearing pond
3. Nursery pond
4. Hatching jar
Answer
B. Rearing pond
Nursery holds spawn, rearing pond holds fry.
Which gives the main food of spawn in a nursery pond?
1. Fish meal blocks only
2. Fruits
3. Large worms
4. Plankton
Answer
D. Plankton
Spawn need small live plankton.
A pond of 5,000 m³ is treated with a chemical at 50 ppm. The amount needed is
1. 50 kg
2. 2.5 kg
3. 250 kg
4. 25 kg
Answer
C. 250 kg
50 g/m³ × 5,000 = 250,000 g = 250 kg.
Statements: 1. Fish are fed on the day of total harvest. 2. Seed is transported in oxygen-filled polythene bags. Which is correct?
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
B. 2 only
Feeding is stopped about one day before harvest.
Which fungus-like disease shows cotton-like growth on skin?
1. Gill rot
2. Dropsy
3. Saprolegniasis
4. Argulosis
Answer
C. Saprolegniasis
Saprolegnia forms cotton-like growth.
Liming of a pond mainly
1. reduces transparency
2. raises pH
3. lowers pH
4. adds oxygen
Answer
B. raises pH
Lime raises pH and buffers the water.
Statements: 1. Indian major carps breed naturally in still ponds. 2. Induced breeding is used in hatcheries. Which is correct?
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
B. 2 only
Major carps usually do not spawn in still ponds.
Argulosis is caused by
1. a fish louse
2. a virus
3. a bacterium
4. an alga
Answer
A. a fish louse
Argulus is a crustacean parasite.
Desired minimum dissolved oxygen for fish ponds is about
1. 20 mg/L
2. 1 mg/L
3. 5 mg/L
4. 0.5 mg/L
Answer
C. 5 mg/L
5 mg/L or more is good.
Which treatment is a simple dip for fungal infections?
1. Urea
2. Cow dung
3. Mahua oil cake
4. Common salt or potassium permanganate
Answer
D. Common salt or potassium permanganate
Salt and KMnO4 dips are standard.
Poultry-cum-fish farming is an example of
1. Monoculture
2. Pen culture
3. Integrated culture
4. Cage culture
Answer
C. Integrated culture
Poultry droppings feed the pond.
Statements: 1. High FCR shows efficient feeding. 2. Secchi disc measures transparency. Which is correct?
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
B. 2 only
High FCR means poor efficiency.
Statements: 1. Cow dung builds plankton. 2. Ovaprim is a pituitary extract. Which is correct?
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
A. 1 only
Ovaprim is a synthetic GnRH analogue.
Which agent is used to remove predatory fish from a pond?
1. Urea
2. Cow dung
3. Rice bran
4. Mahua oil cake
Answer
D. Mahua oil cake
Mahua oil cake is a piscicide.
Statements: 1. Males and females are kept together in all seasons. 2. Brood stock are fed rice bran and oil cake. Which is correct?
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
B. 2 only
They are usually kept separate, away from the breeding season.
A pond of 2 ha is stocked at 5,000 fingerlings per ha. Total seed needed is
1. 10,000
2. 5,000
3. 2,500
4. 20,000
Answer
A. 10,000
2 × 5,000 = 10,000.
Which is a physical sign of a dead egg in a hatching jar?
1. It stays transparent
2. It floats upward
3. It turns green
4. It turns white and opaque
Answer
D. It turns white and opaque
Dead eggs turn white and spread fungus.
A pond of 0.5 ha receives feed at 3 per cent of 2,000 kg fish biomass daily. The feed per day is
1. 600 kg
2. 6 kg
3. 60 kg
4. 30 kg
Answer
C. 60 kg
3 % of 2,000 = 60 kg.
In composite culture of carps, the three species used are
1. Catla, Rohu, Mrigal
2. Rohu, Singhi, Magur
3. Mrigal, Tilapia, Murrel
4. Catla, Grass carp, Tilapia
Answer
A. Catla, Rohu, Mrigal
Indian major carps are the base species.
Which is a standard supplementary feed mixture for carps?
1. Wheat flour and sugar
2. Sand and clay
3. Rice bran and groundnut oil cake
4. Maize and salt
Answer
C. Rice bran and groundnut oil cake
Equal parts rice bran and oil cake is common.
Fertilization in carps takes place
1. in the male mouth
2. in the brood pouch
3. inside the female
4. externally in water
Answer
D. externally in water
Eggs and milt are released into water.
A ripe female carp shows
1. a soft rounded belly and swollen reddish vent
2. a thin belly
3. dark colour only
4. large dorsal fin
Answer
A. a soft rounded belly and swollen reddish vent
These are signs of ripeness.
Which synthetic hormone preparation is widely used in carp induced breeding?
1. Adrenaline
2. Thyroxine
3. Ovaprim
4. Insulin
Answer
C. Ovaprim
Ovaprim contains a GnRH analogue and domperidone.
Statements: 1. Spawn are larger than fingerlings. 2. Spawn are reared in nursery ponds. Which is correct?
1. 1 only
2. 2 only
3. Both 1 and 2
4. Neither 1 nor 2
Answer
B. 2 only
Spawn are tiny hatchlings.
Which carp helps control weeds in a growout pond?
1. Silver carp
2. Catla
3. Mrigal
4. Grass carp
Answer
D. Grass carp
Grass carp eats aquatic vegetation.
Which is a notifiable ulcer disease of freshwater fishes?
1. Epizootic ulcerative syndrome
2. Dropsy only
3. White spot of shrimp
4. Argulosis
Answer
A. Epizootic ulcerative syndrome
EUS shows red ulcers on the body.
In the 3-species composite culture, a ratio of Catla : Rohu : Mrigal is commonly
1. 5 : 5 : 0
2. 9 : 1 : 0
3. 3 : 4 : 3
4. 1 : 1 : 8
Answer
C. 3 : 4 : 3
Typical stocking ratio is 3:4:3.
The time from the injection to spawning in induced breeding is called
1. Incubation period
2. Latency period
3. Gestation period
4. Lag phase
Answer
B. Latency period
Latency period is commonly 6 to 8 hours.

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