Fish Production and Fish Farming

The Biology Topics of ecology involve studying the relationships between living organisms and their environment.

What is Pisciculture? – Its Types and Methods

Fish is an important aquatic food which is rich in proteins. A large section of the Indian population uses fish as food, particularly those living in coastal areas. It is highly nutritious and easily digestible. Fish can be useful in eradicating the problem of malnutrition. Fish liver oil is rich in vitamins A and D. Out of the total fish obtained from the Indian oceans, 45% is procured by India.

Fishery or Pisciculture

Pisciculture is the process by which the species of fish that can be kept successfully in captivity throughout their lives from egg to adult is exceedingly limited in number. The various breeds of goldfish are familiar examples, but the carp is almost the only food fish capable of similar domestication. Various other food fishes, both marine and freshwater, can be kept in ponds for longer or shorter periods, but refuse to breed, while in other cases the fry obtained from captive breeders will not develop. Consequently, there are two main types of pisciculture to be distinguished the rearing in confinement of young fishes to an edible stage, and the stocking of natural waters with eggs or fry from captured breeders.

Cultures, the scientific method of capture or harvesting and preservation of economically important as well as edible aquatic animals like different fishes, crustaceans like prawns, crabs, and mollusks like snails, bivalves, and cuttlefishes are considered as fishery. However, the culture and cultivation of all economically important aquatic organisms and their exploitation for the economy is known as aquaculture. Aquaculture includes pisciculture, pearl culture, prawn culture, etc. According to FAO aquaculture is “the farming of aquatic organisms, including fish, molluscs, crustaceans and aquatic plants.’’ Farming refers to some kind of intervention in the rearing procedure such as stocking, feeding, and protection from diseases and natural predators, etc. Fishery in its strictest term may represent the culture of fin fish and shellfish. Before we go into the details of fishery or pisciculture, we must understand the role of fish as food.

Fish as Food

Fish is one of the cheapest sources of animal protein available on Earth. In fact, fish can be a very good source of almost all nutrients except carbohydrates and vitamin C.

Biochemical Composition of Fish Muscle:

Moisture	65 – 80%
Protein	15 – 20%
Fat	5 – 20%
Ash	0.5 – 2%

Nutrient Profile of Fish

1. Macronutrients
Protein: The protein available in fish contains all the essential amino acids including cysteine and methionine. It has three major roles in nutrition.

• Provides both essential as well as non-essential amino acids that are building units for protein biosynthesis.
• Amino acids are precursors of hormones (e.g. non-adrenaline, adrenaline), porphyrins, and other biomolecules and secondary metabolites.
• Supports the total daily energy requirement of the body.

Lipids:
Fish lipid enjoys an edge over mammalian lipids in the fact that they may include upto 40% long-chain fatty acids (C14-C22). These chains are highly unsaturated and may contain 5 to 6 double bonds.

Fatty Acids (Fish Oil):
Mainly three main types of fatty acids – saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), and polyunsaturated fatty acids (PUFAs). Humans avail PUFAs like α-linolenic acid (ALA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), etc. through diet and cannot synthesize them.

Beneficial Aspects of ω-3 PUFAs of Fish:

Age Category	Prevention
Children	Prevents childhood asthma and attention deficit hyperactivity disorder (ADHD)
Adult	Cardiovascular disease (CVD), hypertension, etc.
Old Age	Dementia, Alzheimer’s disease, age-related macular degeneration, etc.

2. Micronutrients
Micronutrients from fish chiefly comprise vitamins and minerals. Small indigenous fish like Amblyphanygodon mola and Puntius sophore are rich in micronutrients.

Micronutrients in Fish	Examples
Vitamins	Fat Soluble: A, D, E, and K Thiamine (B1), Riboflavin (B2), Niacin (B3) and Vit C.
Minerals	Copper, iron, zinc, selenium, iodine (from marine fish) magnesium, cobalt, manganese, calcium, phosphorus, and fluorine.

Oysters provide a significant amount of zinc. 100 gm of fish (sea fish) can provide the dietary requirement of iodine per day (40 mcg/day) as per UK recommended dosages. Fish like cod provide a good amount of selenium. Besides, inland fish species like Singhi [Heteropneustes], Magur (Clarias sp.), Murrel (Channa sp.), and Koi (Anabas testudineus) are known to have therapeutic properties. Pisciculture means the culture of fish in aquatic bodies. Pearl culture means a culture of pearl oysters for harvesting pearls from them. Prawn culture comprises of culture of prawns for food and economy.

Fisheries: Indian Scenario

In a report published, it has been shown that about 800 million people all over the world depend upon fisheries or aquaculture for their livelihood: In India as per the report published by the National Fisheries Development Board (NFDB), 2017-2018, about 14 million people get their livelihood from this segment.

Indian Fisheries
Global Position	3rd in fisheries 2nd in Aquaculture
Contribution to Fisheries to GDP (%)	0.91
Contribution to Agriculture GDP (%)	5.23
Per capita fish availability (kg)	9
Annual export earnings (Rs. in crore)	45,106.89
Employment in sector (million)	14

Under the centrally sponsored scheme on “Blue Revolution: Integrated Development and Management of Fisheries”, an amount of Rs. 3,000 crores has been approved towards budget outlay for a period of 5 years from 2015-2016 to 2019-2020.

Different Divisions of Fishery

Primarily fishery may be divisible into two types namely inland fishery and marine fishery. Each of these fisheries is again divided into several branches as indicated.

A. Inland Fishery

For the purpose of fishery when water bodies confined in the landmasses of the countries are used, it is known as inland fishery. Inland fishery may be divisible into freshwater fishery and brackish water fishery.

1. Freshwater fishery:
When fishery water bodies contain fresh water, it is known as freshwater fishery. Freshwater fishery may be classified as riverine fishery, lacustrine or lake fishery, and pond fishery.

• Riverine Fishery: This refers to the harvesting of fish and other aquatic animals from the rivers. The fishes that may be collected from rivers are Rohu, Catla, Mrigel, Calbasu, Chital, (Notopterus) Boal, Punti, etc.
• Lacustrine Fishery: When lakes or large water reservoirs are used in fishery it is known as Lacustrine or lake fishery. Besides the fish as indicated before from a lake fishery, prawns may also be harvested.
• Pond Fishery: The culture of fish and their harvesting in small confined water bodies known as ponds are called pond fishery. Pond fishery is principally used for carp culture. Besides Channa, mystus, Boal, punti, Tilapia, and Jeol fishes like koi, catfishes, etc., minor carp may also be obtained from pond fishery.

2. Brackish water fishery:
Cultivation and harvesting of fish in slightly salty brackish water is known as brackish water fishery. This type of fishery is practiced in the water bodies in the regions near the estuary. From brackish water fishery, we usually obtain fishes like bhetki, topse, khoyra, arr, parse, hilsa, tangra, prawn, etc.

B. Marine Fishery

Harvesting of fish or other aquatic animals from seawater is called marine fishery. It is to be pointed out that in maritime water culture of fish and their management is practically impossible. Therefore, only harvesting is the leading practice in this fishery. A marine fishery may also be divisible into the coastal fishery and offshore or deep sea fishery.

• Coastal fishery: This refers to the harvesting of fish & from the waters of the coastal region. From such fishery, we obtain usually Sardins, Lates, Bombay duck, Macarel, Hilsa, Pomfret, etc.
• Offshore fishery or deep sea fishery: Harvesting of fishes or other aquatic animals from deep sea water for food and economy is termed as deep sea or offshore fishery.

With the aid of boats, trawlers, steamers, and ships people used large nets and other devices to harvest fish from deep sea waters. The fishes that may be obtained from deep sea regions are sharks, cod, salmon, Halibut, Sphyrna, etc.

Technology in Fishery

Apart from employing various tools in culture fishery to increase quality and quantity in fishery, technology has been used in capture fishery too. Using remote sensing techniques it has been possible to increase the catch in case of wider areas. India has a huge coastline of about 8114 km with about 2.02 million square kilometers of EEZ (Exclusive Economic Zone), and 0.52 million square kilometers of continental shelf, India has a huge potential to increase or encash upon the ocean exploits. Previously remote sensing was employed through observation. Through observation from various watch towers, watching for the concentration of fish-eating sea birds, etc., and through devices lodged in buoys of vessels. However with advancements in technology, satellite images have been employed to trace PFZ or potential feeding zones. Data on parameters like SST or sea surface temperature, the direction of the wind, the presence of chlorophyll (colour of oceans), etc. enables one to locate the potential feeding zones in order to capture a commercially viable cache of fish. Bhaskara I and Bhaskara II were the initial satellites used for the purpose. Recently data from satellites like IRS-P4, have been employed for this purpose.

Feeding Fish

Feeding of fish during culture aims at producing the maximum weight of marketable fish within the shortest time at the least cost. The feed should supply the energy for movement and all other activities the fish engages in. It should also provide nutrients for body maintenance, growth, and reproduction. Feeding increases fish growth and makes fish farming profitable. Feeds must be nutritious and economical in any farming system and must be properly managed to be effective. The nutrients needed by fish include carbohydrates, fats, protein, vitamins, and minerals. Other components of feed are fiber and moisture. Fish diets must contain all the nutrients in the right proportions to bring about growth.

Types of Feed
Fish in culture can be maintained solely on natural food in a pond, on artificial (formulated) feedstuffs, or a combination of the two. The natural food in a fish pond includes mainly phytoplankton, and also zooplankton, detritus, insect larvae, etc.

Carp

The body of freshwater bony fishes having swim bladders is covered with cycloid scales, but the fishes having no accessory respiratory organs, without teeth on the jaws, and no scales on the head are called carps.

A. Endemic Carp
The carp which have originated in India and are adapted to the Indian climate with reproductive potentiality is known as endemic carp.

• Major carp: The endemic carp that are larger in size and have significant commercial value are known as major carp.
• Minor carp: The endemic carp which are smaller in size and economically less important are known as minor carp.

Common Name	Scientific Name
Major Carp
1. Rohu	Labeo rohita
2. Catla	Catla catla
3. Mrigel	Cirrhinus mrigala
4. Kalbasu	Labeo calbasu
5. Mahseer	Tor tor
Minor Carp
1. Bata	Labeo bata
2. Saral Punti	Puntius sarana
3. Common Punti	Puntius ticto

Comparison between Major Carp and Minor Carp:

Characteristic Features	Major carp	Minor carp
1. Size	Size bigger.	Size smaller.
2. Significance	Economically important.	Economically less important.
3. Nutritional Value	More	Less
4. Egg	Lays egg once a year but does not lay egg in enclosed water reservoirs.	Lays eggs more than once and can lay eggs in enclosed reservoirs.
5. Growth Rate	More. May grow upto 1 m in length.	Less. Grows upto 6-15 cm in length.
6. Dorsal fin	Fin rays of dorsal fin more than 11.	Dorsal fin rays less than 11.
7. Lateral Line Scales	More than 35 scales along lateral line sense organ.	Scales along the lateral line sense organ within 30-35.
8. Examples	Labeo rohita (Rohu), Catla catla (Catla).	Puntius ticto (Punti), Labeo bata (Bata).

B. Exotic Carp
The carp that have been brought to India from some other country are adapted to the Indian climate and may reproduce comfortably in this climate, are known as exotic carp.
Examples:

• Silver carp (Hypophthalmichthys molitrix).
• Common carp or American Rohu (Cyprinus carpio).
• Grass carp (Ctenopharyngodon idella).
• Tilapia (Oreochromis [= Tilapia] mossambicus).

Habitats and Characteristic Features of Five Types of Major Carps:

Indian Minor Carps:

Characteristic Features and Habitats of Three Exotic Carps:

Induced Breeding or Hypophysation

The mechanism by which mature male and female fishes of a particular species are induced to liberate male and female gametes in captive water, with an injection of pituitary gland extracts, is known as induced breeding. The process is also known as hypophysation or artificial breeding.

Principle of Induced Breeding
Gonadal maturity depends upon pituitary hormones such as FSH and LH and under the influence of the pituitary hormones the matured male and female fishes liberate their gametes in water. The male and female gametes fertilize to produce progeny. Hence, by injecting pituitary extracts to the matured fishes during breeding seasons, they may be induced to liberate gametes in water for fertilization. Therefore, induced breeding is based on the principle of inducing the matured fishes with pituitary extracts to liberate gametes in water.

Method of Induced Breeding
Requirements: For induced breeding the following components are essential.

1. Mature Male and Female Fishes:
The fishes that normally do not breed in captive water, require induced breeding for breeding in closed waterbodies.

The major carp belong to this category. Rohu and Catla are commonly used for induced breeding and when the fishes become 2-4 kgs by weight they are considered as ideal for induced breeding. However, a fish selected for the purpose of induced breeding should be healthy and actively energetic. Such types of male and female carp are stored in the storage tank before they are taken for the purpose and they are provided with sufficient food and sporting facilities. For the purpose of induced breeding one healthy female and two male fishes are taken at a time. Male and female carps are recognized by the following features:

Distinguishing Features of Male & Female Carps (In Breeding Season):

Male Carp	Female Carp
1. Abdomen appears slender as in normal cases without swelling in the breeding season.	1. The abdomen becomes broad and swollen in the breeding season.
2. Pectoral fins appear rough dorsally during the breeding period.	2. Pectoral fins remain smooth dorsally all the time.
3. Vent whitish and remains inward.	3. Vent pinkish and protruding.
4. On application of pressure on the abdomen, milt that is semen & sperm come out through the anus.	4. On application of pressure on the abdomen, eggs & blood come out through the anus.

2. Pituitary Extracts:
Extracts of pituitary glands are essential for the induction of breeding in carp. To obtain pituitary extracts, glands are collected from matured carp with the help of needles and spatula from the skulls of the matured fishes. The gland is homogenized with a little distilled water in a centrifuge tube. Then the homogenized material in solution is centrifuged to get the clean supernatant.

The supernatant solution contains the protein hormones of the pituitary including FSH and LH. This supernatant solution may be injected into male and female fishes for induction in breeding. Presently samples containing pituitary extracts are available in the market and those may be used for induced breeding.

3. Injection Syringe and Needles:
These are needed for the injection of pituitary extract in the fish. There are two common places to inject hormones into a fish. An intraperitoneal (within the body cavity) injection is given through the ventral (bottom) part of the fish behind either the pelvic or pectoral fin. Intramuscular (within the muscle) injections are commonly done on the dorsal (upper) part of the fish above the lateral line and below the anterior part of the dorsal fin. In either case, it is important to place the needle so that it slides under the scale rather than through it.

Two dosage levels are commonly used: A preparatory dose and a decisive, or final, dose with a time gap generally of 12 to 24 hours between the two injections. The preparatory dose brings the fish to the brink of spawning and the decisive dose induces ovulation. In general, the preparatory dose is about 10 percent of the total dose. For some fish, several preparatory doses may be necessary.

4. Hapa:
Hapa is a type of enclosure in the form of mosquito net for fishes made up of nylon net or markin cloth. The hapa is set in the pond with the help of four bamboo poles, when the open side of the inverted mosquito net-like hapa is tied with poles at four corners and the closed basal part is also tied with the base of the poles with strings. Such enclosure (Hapa) in the water body like a pond is used for the breeding of carp. For breeding purposes usually two types of hapa are used namely breeding hapa and hatching hapa.

(a) Breeding Hapa:
The hapa that is used for the breeding of male and female fishes is known as breeding hapa. The breeding hapa measures 1 1/2 m × 1 m × 3 m (height) and during its placement, its lower part remains submerged by about 1/2 meter. After injecting the pituitary extracts in fishes, they are kept in the breeding hapa and after a period of sporting for 3-4 hours, the male and female fishes liberate their gametes in the breeding hapa.

(b) Hatching Hapa:
Hatching hapa is used for obtaining spawns from fertilized eggs. The fertilized eggs are collected from the breeding hapa and are kept in the hatching hapa for the emergence of spawns. It takes about 14-18 hours after fertilization for the emergence of the spawns from the eggs. Hatching hapa is made up of two mosquito net-like enclosures placed in an inverted fashion in water. The inner enclosure is made up of nylon net, but the outer enclosure is made up of Markin cloth. The outer enclosure of the hapa measures 2 m x 1 m x 1 m (height) and the inner one measures 1.5 m × 0.75 m × 0.5 m (height).

Procedure of Induced Breeding

The method of induced breeding follows the steps:

1. For one experimental set at a time one matured female and two matured males are collected from the stocking pond. The fishes are set free separately in a breeding hapa.

2. Now pituitary extracts are taken in the syringe for injection. The syringe is fitted with a suitable needle.

3. Then the female fish is taken out from the breeding hapa and she is placed by one side of the body on a wooden plank. The needle of the syringe is pushed into the body at a site above the lateral line sense organ towards the post-pelvic region. The female fish is given two doses of injection at 6-7 hours intervals. The initial injection requires a dose of 2-3 mg per kg of body weight but the second injection requires a dose of 5-8 mg per kg of body weight. The injection is applied obliquely at an angle of about 60°.

After applying the second dose of injection to the female, the males are taken out of the breeding hapa and each of them is injected with pituitary extracts in the same manner but at a dose of 2-3mg per kg of body weight. The males are given this injection for one time only. Immediately after giving injections to the fishes they are set free in the breeding hapa. For breeding purposes by injecting pituitary extracts, time selection is an important thing. Normally a cloudy day with slight drizzling rain is favourable for induced breeding.

4. Following the injection for the second time to the female fish, she liberates her eggs in the breeding hapa after about 5-6 hours. In the contemporary period, male fishes liberate seminal fluid in water. After 4-5 hours following this, the eggs become fertilized by the sperm.

5. The fertilized eggs are then transferred to the hatching hapa with the help of a suitable container. After about 16-18 hours, the eggs hatch into spawns and the spawns may come out through the pores of the inner enclosure of the hatching hapa. The left-away remnant of the eggs are left outside.

6. The spawns in the hapa are taken care of for their growth.

Advantages of Induced Breeding

• Induced breeding helps in collecting all the fertilized eggs from fishes of the set at a time.
• It promotes the collection of spawns of one species and therefore saves us from mixing of spawns as occurs in nature.
• It helps to collect about 1-2 lakh eggs from a fish.
• It promotes the breeding and collection of spawns according to the desired schedule.
• Induced breeding promotes the collection of spawns with minimum effort and transportation cost is also less.
• Spawns collected by this method are also of superior quality and thus help to earn more.
• In a year induced breeding may generate income twice and therefore, it is quite profitable.
• During induced breeding less amount of eggs get damaged.
• Induced breeding may be carried out on both exotic and Indian carp and therefore, this process may help in the promotion of mixed culture.

Bundh Breeding

Bundhs are special types of perennial and seasonal tanks or impoundments where riverine conditions are simulated during monsoon months.

Prerequisites for Bundh Breeding to be Successful

• Heavy monsoon showers.
• Water current created due to flow of water from upper land areas to bundhs and then through the outlet.
• Inlet pipes and outlets of the bundh should be kept closed after the water level reaches the brim.
• Sudden fall in temperature.
• no definite depth for breeding as breeding can take place in a depth of about 30 cm.
• Smaller and bigger fishes get induced to breed. The bundhs are ordinarily of two categories, viz., a perennial bundh commonly known as “wet bundh” and a seasonal one called “dry bundh”.

Wet Bundh:
Wet bundh is generally located in a gradual slope of catchment areas with an inlet towards the high land and an outlet at the opposite side towards the lower end to regulate the inflow and outflow of water respectively during heavy showers.

The wet bundh contains a deeper area that retains water throughout the year and maintains adequate brood fish stocks. During heavy rains, a major portion of the bundh is submerged and excess water, if any, is drained through the outlet which is guarded by bamboo fencing (locally termed “Chhera”). The shallow areas of the bundh (moans) serve as breeding grounds for fishes present in the bundh. The wet bundh varies in shape and size from place to place. Generally, the ponds covering a waterbody of 1-2 ha with a catchment area ranging from 20-100 times are considered wet bundhs, but a bunch could be as large as 300 ha.

Dry Bundh:
Dry bundhs consist of only one shallow depression (or one shallow pond) and a catchment area located on a gradual slope. The upper highland area is considered as a catchment area. The shallow depression or pond is enclosed by embankments on three sides which impounds freshwater from the catchment area during the monsoon season. There should be provision for an outflow for drawing excess water from the pond during heavy rains. The outlet is guarded by fine bamboo fencing. Such bundhs remain more or less dry during the greater part of the year.

Comparison of Dry and Wet Bundh:

Dry Bundh	Wet Bundh
1. Seasonal.	1. Perennial.
2. May consist of storage ponds, hatcheries, and an observation post.	2. No storage ponds or hatcheries and observation posts.
3. Shallower.	3. Deeper.
4. Breeders kept in storage ponds.	4. Breeders are kept in deeper parts that retain water even during summer.
5. Easily manageable.	5. Difficult to manage.
6. Production and collection of desired quality eggs easier.	6. Production of quality eggs as well as collecting them is difficult.
7. As many as 5 crops can be obtained.	7. As many as two crops can be obtained.
8. More economical venture.	8. Less economical venture.

Breeding Operation

Wet Bundh:
With the onset of monsoon, the fresh rainwater from the catchment area enters into the bundh and the latter is inundated. The excess water flows out from the bundh creating a water current. The breeders present in the deeper area of the bundh migrate to shallow areas where they start breeding.

Dry Bundh:
Rain water which accumulates in the catchment area during premonsoon showers flows in to fill up the pond seasonally. Thereafter, the brood fishes from a perennial pond are introduced into the seasonal ponds to breed, preferably on cool rainy days. Spawning usually commences during and after heavy showers when the bundh as well as the catchment area are flooded with fresh rainwater.

Drawbacks of Bundh Breeding

• Indiscriminate destruction of brood fishes particularly the males result in improper sex ratio.
• Hygenic maintenance of mud-hatching pits is difficult.
• Spawn mortality may affect production.
• Monitoring the collection and hatching of large quantities of eggs becomes practically challenging, especially in wet bundh breeding.
• During egg collection, unwanted fish spawns and insects, especially the predatory species may get collected posing a future threat to the desirable ones.
• In the case of dry bundhs, the breeding in most cases becomes a secondary activity and gains less attention, case, or importance.
• Gillnets or castanets used for catching brood fish may cause injury. The brood fish carry injury or infection.
• Late harvest of fish seed with reduced water may invite illegal poaching activities.
• Loss of sizeable stock may result due to drainage of water for irrigation purposes.

The above drawbacks can be taken care of through scientific management and skilled and knowledgeable labour.

Culture of Major Carp

Rohu, Catla, Mrigel, and Calbasu are the major carp of India. These freshwater fishes may be cultured together in the pond. However culture of only one type of fish is called a monoculture. indigenous method of carp culture includes two steps namely collection of spawns and the rearing of spawns in the pond.

A. Collection of Spawn

Spawns may be collected by two different methods natural procedure and artificial method.

1. Natural Procedure
During the breeding season, i.e., in the rainy season (June-July) the major carps swim in the river against the current. The female fish lay eggs in shallow water. However, Catla fish do not lay eggs in the flowing water, rather these fish lay eggs in the areas adjacent to the river which become inundated by river water. Prior to the discharge of gametes the female and male fishes come into sport, when the female and male fishes move in water at close proximity. The sport ends with the liberation of eggs by the female and sperm by the male. This event is known as spawning. Spawning is followed by fertilization of eggs by sperms and the fertilized eggs hatch into small fries or spawns within 18-24 hours. The fishermen with the help of fine mesh collect the small fries or spawns from river water. Initially, they collect the eggs in big vessels and transport to the hatcheries as soon as possible. During transportation, the water of the vessel is constantly agitated to supply oxygen to the vessel water.

Disadvantages in Collecting Spawns by Natural Method:

• Spawns collected from rivers or barrages are usually contaminated with unwanted living components like eggs of carnivorous fishes.
• Thus natural procedure of collection of spawn is antagonistic to the healthy culture of carp.
• A hardly sufficient amount of spawns may be collected by natural methods.
• Transportation of spawns collected by natural method is inconvenient and costly.

2. Artificial Method of Spawn Collection
The collection of spawns by following induced breeding is known as artificial spawn collection. With the introduction of induced breeding technology, the Bengal farmers adopted the technology early with a view to producing quality seeds in captivity. In this method collected spawns are of the same kind. They may also be collected as per the designed schedule. Transportation of spawns also does not require much effort and it is economic. The amount of the spawns also becomes more in comparison to that by natural method. Chances of contamination by unwanted living detrimental species are also nil. Hence, the artificial method of spawn collection is far superior to the natural method of spawn collection. A comparison between the artificial method of spawn collection and the natural method of spawn collection may be given in the following.

Comparison between artificial and natural methods of spawn collection:

Artificial Method	Natural Method
1. It follows the induced breeding of carp.	1. It follows the natural breeding of carp.
2. It is practiced in captive water within the hatching hapa.	2. It occurs in natural waters in rivers & barrages.
3. Through artificial method pure variety of seeds may be collected without contamination.	3. The natural method of collection of seeds is prone to contamination.
4. Collected amount of seeds is more in quality.	4. Collected amount of seeds is less in quality.
5. Transportation of spawns to the hatchery requires less effort with less cost involvement.	5. Transportation of spawns to the hatchery requires much effort with much cost involvement.
6. Management is easier and schedule-specific.	6. Management is troublesome and hardly follows a schedule.

At present, it has been realized that due to certain profit-making approaches, the seeds are losing out on their quality and this in turn is having a negative impact on the culture. It is here that the Bundh breeding practices are gaining importance.

Method for Identification of Eggs from Different Carps:

Name of the Fish	Colour	Shape of Eggs	Diameter of Eggs	Physical Nature
1. Catla	Faintly Red	Oval	5.3 – 5.5 mm	Fertilized egg submerges in water and does not float
2. Rohu	Reddish	Oval	5 mm	–
3. Mrigel	Brownish	Oval	5.5 mm	–

B. Rearing of Spawn

For the rearing of spawns, four types of ponds are required and those are hatchery, nursery tank, rearing tank, and stocking pond.

1. Hatchery
The hatchery is a place in which the artificial life cycle of fish takes place. It is absolutely influential in the modern aspect of aquaculture. It refers to the small pond which is used for hatching of the fertilized eggs. One hatchery usually measures 20-40′ × 15-30′ × 2-3′. Before the breeding season and prior to inducing the fishes with pituitary extracts hatchery is prepared. The hatchery should be devoid of any weeds or other unwanted fishes. During summer, the hatchery remains dry, and only during the breeding period, it is fed with water. Hatchery is used only for storage and hatching of the eggs before emergence of small fries or spawns. In the hatchery, the spawns remain for 2-3 days and after that, they are transferred to the nursery pond. Besides the hatchery, hatching hapa may be used for hatching the eggs.

2. Nursery Tank
Those spawns that emerged from the fertilized eggs are cultured in the nursery tank. A nursery tank measures about 60-70′ × 40-50′ with 5-6′ depth. Before storing the spawns in this tank it is processed and prepared for growing plankton in it. During summer when the tank remains dry, the bottom soil of the tank is ploughed and mixed with cow dung, oil cake, superphosphate, and ammonium phosphate. The tank is then cultivated with dhaincha plants which are uprooted afterwards to be mixed with bottom soil. At this time the water level of the tank is low. With this exercise, the tank may develop enough phytoplankton. Before storing spawns in this pond 2-4 kg of soap water mixed with 7.2kg of oil per acre of water body is applied to the nursery tank. This exercise helps in destroying unwanted insects and other arthropods in the tank.

Such a pond is ready for storing the spawns within it. In the nursery tank usually 9-12 lakhs of spawns are stored per acre of water. Usually, spawns are added to the nursery tank before dawn or after dusk. The spawns are added to the pond water carefully by slanting the open edge of the spawn-carrying vessel. The spawns are reared in the nursery until they are 1 inch long. Such spawns are known as fry.

3. Rearing Tank
The pond used for cultivating the fries is known as a rearing tank. A rearing tank measures 60-70 × 50′ with a 9-10′ depth. Preparation for the rearing tank is identical to that of the nursery tank. But this pond is supplied with cow- dung and chemical manure every month. In the rearing tank the fry grows to finger length and such fry is known as fingerlings. Fingerlings are transferred to the stocking pond.

4. Stocking Pond
Stocking Pond promotes a culture of fingerlings for their growth upto marketable size. Such ponds are far bigger than the rearing pond and measure about 390′ × 80′ with 6-9′ depth. The stocking pond is also processed like a rearing pond. Mahua oil cake is applied to this pond to destroy the unwanted and carnivorous fishes before storing the fingerlings of the carp.

The stocking pond is also supplied with oil cakes, rice grains, and fish meal as foods for the fingerlings. These promote rapid growth of the fingerlings. Besides the pond is netted to promote the exercise of the fingerlings and by this exercise the growth of the fish becomes satisfactory. The water of the pond should maintain alkalinity at a range from pH 7.8 to pH 8.2. For this, the acidic water is treated with the required amount of lime.

Composite Culture

The culture of all the major carp in the same pond on the basis of differential food habits and habitats for the purpose of obtaining maximum yield, is known as polyculture or composite fish culture. On the contrary, when only one type of fish is cultured in a pond it is known as monoculture. Three Indian major carp, Catla, Rohu, and Mrigel, are found to inhabit the surface, middle, and bottom water of a pond.

This type of zonal differentiation in habitat selection is based on their food habits. For example, the plankton on the surface water is devoured by Catla, while the vegetation along the middle water is taken as food by Rohu. The Mrigel fish is a bottom dweller and it utilizes dead and decomposed organic matter from the bottom. Therefore these three types of fish are known as surface feeder, column feeder, and bottom feeder respectively. For this reason, three types of carp may be cultivated together in the same pond. Conventionally by culturing one type of carp in the pond annual yield comes to about 300-600 kg per hectare. But by culturing all three major carps together in the same pond the yield can be increased to 3000 kg per hectare. Hence, the composite fish culture is more profitable than a monoculture of fish.

Objectives of Composite Fish Culture

• Maximize yield or production.
• Maximum utilization of niches.
• Fish cultured should not in any way disturb the ecological balance.

In fact, they may help in maintaining ecological harmony. For instance, the faecal matter of one may be consumed by the other. Balanced optimum exploitation of food and niches is & the chief essence of composite fish culture.

Again the exotic species of carp, like grass carp, silver carp, and cyprinus carp also differ by their habits and habitats. All these fishes are herbivorous and they are distinguishable as surface feeders (Silver carp), column feeders (Grass carp), and bottom feeders (Cyprinus carp). Therefore, three Indian carp may also be cultivated together with three exotic carp. When all these six species of carps (3 Indian carps and 3 exotic carps) may be cultured together in the same pond the method is called mixed composite fish culture. By mixed composite culture, the yield per year has further been increased from two to three times in comparison to that from composite culture of only Indian carp.

Combination of Fish Practiced under the Indian Polyculture System

Surface Feeder	Catla feeds on plankton
Column Feeder	Labeo rohita feeds on decaying aquatic plants, and algae; larvae feed on zooplankton algae.
Bottom Feeder	Cirrhinus mrigala feeds on decaying plant and animal matter etc. Labeo calabash feeds selectively on benthic and epiphytic organisms and organic debris.

Fish breeders have introduced exotic carp such as grass carp, silver carp, and common carp in the compos¬ite culture. Apart from this benthic-feeding grey mullets (Mugil cephalus) and carnivorous fish like Notopterus are also introduced.

Ratio of Fishes in Composite Culture
In composite culture, different types of fish are cultured in defined ratios in order to obtain maximum yield. Therefore, for establishing a composite culture the estimated ratio of the carps for a pond is required to be known.

From the above table, it appears that composite culture may be of three types, namely

• The composite culture of Indian carps takes three Indian carps, Catla, Rohu, and Mrigel with a ratio 4 : 3 : 3.
• Composite culture of exotic fishes taking three exotic fishes namely, Silver carp (Hypophthalmichthys molitrix), Grass carp (Ctenopharyngodon idella), and Common carp (Cyprinus carpio) in a ratio 3 : 1 : 2.
• Mixed composite culture taking both the Indian carp and exotic carp with the ratio 1 Catla : 2.5 Silver carp : 3 Rohu : 1 Grass carp : 1.25 Mrigel : 1.25 Common carp in the same pond.

Different Parameter of Composite Mixed Fish Culture:

Species	Feeding Habit	Feeding Zone
A. Indian Major Carp
Catla	Zooplankton feeder	Surface feeder
Rohu	Omnivorous	Column feeder
Mrigel	Detrivorous	Bottom feeder
B. Exotic Carp
Silver Carp	Phytoplankton feeder	Surface feeder
Grass Carp	Herbivorous	Surface, column, and marginal areas
Common Carp	Detrivorous/Omnivorous	Bottom feeder

Methods of Composite Culture

Composite fish culture is achieved through various steps such as preparation of pond, stocking of fingerlings of different carp, food addition, netting of pond, and health examination of fishes.

1. Preparation of Pond:
Composite culture requires comparatively large ponds and the area of a pond should be 1-5 bigha with 6-7 feet depth. The pond should have high boundaries to prevent inundation during the rainy season. Besides, there should remain several shade trees at the sides to prevent excessive warming of water during day time. The pond should also be well-lighted with enough scope for air circulation.

Such a pond having requisite dimensions is to be prepared before stocking the fingerlings. Initially, unwanted weeds and carnivorous fishes are removed from the pond. Application of mahua oil cake in the pond may remove unwanted animals from the pond. After 15-20 days of the application of mahua oil cake, the fingerlings may be released into the pond. If the pond has much clay at the bottom that should also be taken out prior to stocking the fish.

Further accumulation of sufficient plankton and other vegetation in the pond is also required. For this purpose application of cow dung at a rate of 270kg/bigha of water, 10 kg urea/bigha, and 6-7 kg superphosphate/bigha of water is necessary. This treatment promotes the growth of plankton and other vegetation. Besides these, the pond should also be treated with lime at a rate of 30-40 kg lime per bigha of water. This treatment is required about 7-10 days prior to release of the fingerlings.

2. Stocking of Fingerlings of Different Carps:
A prepared pond may be stocked with fingerlings of carp for the purpose of composite fish culture. The ratio for release of different fishes should be at par with the ratio stated above per hectare of water. 3600 fingerlings of different carp may be stocked proportionately. In one year each fish may grow upto a size of 700g. Therefore, per year yield per hectare comes to about 25-30 quintal.

3. Food Addition:
For the promotion of the growth of fingerlings in the pond addition of food is required. Rice bran and mustard oil cake or groundnut oil cake are applied in the pond uniformly with the help of a vessel or boat. The daily additional food requirements for six types of crops 100 in number is

• For the first three months – 800 g.
• For the second three months – 1.6 kg.
• For the third three months – 2.4 kg.
• For the fourth three months – 3.2 kg.

4. Netting of the Pond and Health Examination of Fishes:
Proper growth of the fish in the pond, requires exercise and to provide exercise to the fish netting in the pond is required. Besides this, at regular intervals health of the fish is required to be examined. Maintenance of water quality with adequate oxygen supply and pH optimum is favorable for the health of the fish.

Advantages of Composite Culture:

• Composite culture is less expensive and more profitable.
• All the layers of one water body may be exploited in a composite culture.
• Different varieties of fish may live together without any competition in the same water body.
• Composite culture promotes the production of 3-6 types of fish in the same pond without hampering yield amount.

Drawbacks in the Polyculture System:

• Additive food in the pond usually increases the amount of nutrients in the pond and for this reason, unwanted growth of algae may occur in the pond. This leads to the depletion of oxygen concentration in water.
• For grass carp in the pond sometimes aquatic plants are applied in the pond and these may settle down in the bottom with decomposition. Such condition produces obnoxious gases in pond water and results in the detrimental condition of water.
• The collection of fingerlings of different fishes in the required proportion appears difficult sometimes.
• greater number of species combinations not flexible.
• Providing supplementary feed is economically viable.
• Procuring or deciding upon the number of seed stocks for different species and their management requires the utmost skill and efficiency.
• Harvesting requires an additional workforce.

Breeding in Bengal

The fish seed producers in Bengal had been practicing captive seed production via bundh breeding. They preferred induced breeding to combat transportation hazards. In this context, fish breeders of the Bankura district of West Bengal deserve a special mention. Here, the seed producers have come up with a new and unique approach, the results of which can be compared to the wild collection and can be compared to induced breeding in terms of economy. With this new look, fish breeders of Bankura and Midnapore district of West Bengal have started raising carp seeds using scientific approaches. The fish breeders are now using WOVA-FH, a synthetic agent, and not all the fish among the total group are infected to induce sporting. The sympathetic breeding in which a small fraction of the whole breeding group is induced and released into the bundh, for the noninduced ones to get induced by the opening behaviour of the induced fishes. This approach not only reduces the hazards of inducing individual fish but it also reduces costs.

Fish Culture in Sewage

Sewage is a rich nutrient resource, cheaply available around big cities and towns. It can be well utilized for cultivating paddies, aquaculture, etc. Waste recycling also helps in maintaining a clean environment.

• Sewage: Waste water from domestic or industrial sources that may include excrement.
• Sludge: Solid precipitate obtained during treatment of effluents before discharging them into water bodies.
• Raw sewage may cause health hazards and sewage farming is not a very good option for sewage disposal as it may cause serious pollution and hygiene problems.

The Central Public Health Engineering Research Institute, Nagpur (CPHERI) has been a pioneer in the field of sewage and industrial waste treatment by oxidation pond treatment method. The wastes first need to be stabilized through aerobic and anaerobic or facultative modes of stabilization in waste stabilization ponds. Aerobic decomposition consists of the degradation of higher organic matter into volatile organic acids and the fermentation of the latter into methane and other gases.

The Method of Fish Culture in Sewage

• First maximum water is drained out from a 0.4-hectare pond and 200 kg lime is mixed with water. It remains dry for 10-15 days.
• On the first of June, the pond is filled with sewage water to a level of 30 cm. In July, the level rises to 1.2-1.3 ln., due to monsoon showers.
• Then 3 types of 2000 fingerlings of carp (Catla-40, Rohu-30, Mrigel-30) or 6 types of 3000 spawns (Catla-45, Silver carp-25, Rohu-25, Grass carp-5, Mrigel-20, Common carp-10) are transferred to pond.
• Sewage is mixed with water to raise the water level.
• An interval of 15 days netting is required.

Advantages of Fish Culture in Sewage

• Huge waste recycling helps in maintaining a clean environment.
• Mass production of fish at cheap rates by using sewage.

Disadvantages of Fish Culture in Sewage
A sharp fall in O2 level in highly toxic sewage may cause the death of fish. Invasive species (sucker mouth catfish) may kill other fish. Urbanization and enclosement spoil wet land.

Common diseases of carp
A problem in pisciculture is the diseases of the fishes and due to these disease, sometimes great loss comes to the cultivators. Several common diseases of carp are Gill rot, fin and Tail rot, and Dropsy. The description of the diseases with their causative agents and the measures to control them may be given in the following way:

Species Combination Ratio:

Importance of Fisheries

• As food: Fish is an easily digestible source of protein. Cod liver oil and shark liver oil are good sources of vitamins A and D.
• Nowadays, food like fish macaroni, fish biscuits, fish sausages, fish fin soup, etc. are gaining popularity.
• As disease control: Mosquitoes spread diseases like malaria and filaria.
• Some larvivorous fish like Gambusia and Panchax eat the larva from stagnant water where mosquitoes lay eggs.
• Fish manure and guano: Wastes of fish are used as fertilizer and also to feed the fish.
• Artificial pearl: Artificial pearl is produced from the scales of some fish like the European cyprinids.
• Fish glue: Fish glue produced from the skin of cod fish, and bones of tilapia is used as gum.
• Fish meal: Dry unused fish is used as a fish meal. Fish meal contains 60% protein. This is used as food for ducks, poultry birds, cattle, etc.
• Ishin glass: Prepared from the swimbladder of certain fishes, ishin glass has been used in breweries, the cement industry, confectionery, etc.
• Ornamental fish has a huge market.

Fisheries are establishments connected with the capture, preservation, exploitation, and utilization of various types of fish, prawns, lobsters, crabs, oysters, other mollusks, etc.

On the basis of product, fisheries are of two types:

• Fin fishery: It is the capture, management, and exploitation of cartilaginous and bony fishes.
• Shell fishery: It is the capture management and exploitation of crustaceans (crabs, prawns, lobsters) and mollusks (oysters, mussels, octopods, etc.).

Depending upon the mode of obtaining fish, fisheries are of two types, capture, and culture.
1. Capture fishery:
The fish is caught in natural waters, both marine and inland. Modern technology is used for capture and storage before marketing. Electronic equipment is used to locate fish in the sea. Mechanized fishing boats and deep sea trawlers are often employed in capture fishery.

2. Culture fishery:
It is cultivating, rearing, and harvesting of fish. Culture fishery is also called fish farming or pisciculture. The growing of various types of aquatic organisms in water bodies is called aquaculture.

Differences between capture fishery and culture fishery

Capture fishery	Culture fishery
1. It is a method of obtaining fish from natural resources.	1. It is a method of obtaining fish from fish farming (water agriculture).
2. There is no seeding and raising of fish.	2. The fish is seeded and reared.
3. Capture fishery is undertaken in both inland and marine waters.	3. Culture fishery is undertaken mostly inland and near the sea shore.

In common usage, the term fish has often been used to describe a mixed assortment of water-dwelling animals, we speak of jellyfish, cuttlefish, starfish, and shellfish, knowing fully well that when we use the word “fish” in such combinations, we are not referring to a true fish.

A true fish is a gill-breathing, ectothermic, aquatic vertebrate that possesses fins and skin that is usually covered with scales. The word fish is commonly used both as singular and plural, but a zoologist uses fish to mean more than one kind of fish.

Seventy percent of the Earth is covered with water. Based on the water sources of fish production, the following three types of fisheries can be recognized.

• Marine fisheries: They include capture fisheries of oceans and seas.
• Freshwater fisheries: They include capture and culture fisheries in freshwater systems such as rivers, canals, lakes, reservoirs, tanks, ponds, and paddy fields.
• Brackish water fisheries: They include fishing activities in brackish water (slightly salty) such as estuaries (the last part of the river that gets tidal water from the sea), lagoons (shallow saltwater lakes separated from sea banks, coral reefs, etc.) and mangrove swamps (tropical trees growing in the mud of sea-shore).

Freshwater fisheries and brackish water fisheries are collectively called inland fisheries. With the increase in our population, fish production has increased both for food and as a business activity. Modern technologies are being used both for capturing and culture of fish in marine and freshwater ecosystems. In this section, we will study various methods for increasing the production of fish in all sorts of aquatic ecosystems.

Few Facts about Indian Fisheries (including both capture and culture)

• Total fish production in India – 7th position in the world
• Marine fish production in India – 10th position in the world
• Aquaculture production in India – 2nd in South East Asian countries
• Fish industry contribution – Rs. 400 crores annually as foreign exchange

Kinds of Freshwater Fish Culture Systems:

• Carp culture (composite fish culture)
• Sewage-fed fish culture
• Air-breathing fish culture
• Fish culture in cages
• Paddy-cum-fish culture
• Integrated fish culture
• Fish culture in cold water
• Fish culture in bundhs
• Fish culture in seasonal ponds
• Freshwater pearl culture

Marine Fishery – An Overview

India has a vast scope of marine fishery. Our marine fishery resources include a 7500 kms coastline and extensive deep sea. Marine waters providing profitable fishing are the Arabian Sea, Bay of Bengal, many small bays, gulfs, lagoons, coral reefs, etc. Central Marine Fisheries Research Institute (CMFRI) at Ernakulam, Cochin, Kerala has been set up to explore and utilize the marine resources of the country.

The following 12 marine fishes of India are the most preferred sea fishes or table fishes, i.e., popularly consumed fishes:

• Pomphrets
• Mackerels
• Tuna
• Sardines
• Bombay duck
• Eel
• Hilsa
• Salmon
• Ribbon fish
• Flat fish or sole
• Seer
• Flying fish

These marine table fishes are caught by fishing nets and gears operated by fishing vessels. A vessel that drags a net behind it is called a fishing trawler; such fishing trawlers fitted with electronic fish locating devices have been put into service for boosting deep-sea fishing. The modern technologies for catching more fish include echo sounders and the use of satellites to fish shoals or schools (assemblages of fish).

What is Aquaculture, and Why Do We Need It?

Aquaculture pertains to the production of useful (i.e., of high economic value) aquatic plants and animals such as fishes, prawns, crayfish, lobsters, crabs, shrimps, mussels, oysters, and seaweeds by proper utilization of available waters in the country. It is an important means of increasing the country’s food output. India has great potential for aquaculture because of its long coastline and numerous inland water spreads.

Aquaculture includes mariculture and freshwater culture fisheries.
Mariculture: The marine fishes cultured in coastal waters of India on a commercial basis include mullets, bhetki, pearl spots, sardines, eel, and milkfish.

Freshwater culture fishery of exotic carp has good prospects in lakes. These carp include the common carp, English carp, tench, and trouts. Trout hatcheries have been established in Kashmir and other places.

Inland Fisheries in India

It includes (i) riverine fishery; (ii) reservoir fishery; (iii) lake or lacustrine fishery; (iv) pond fishery and (v) estuarine fishery. Inland capture fisheries are rapidly expanding in our country. The introduction of exotic species from abroad and inter-regional transplantation of fish from northern to southern waters have proved to be a great boon. Increasing pollution of water is adversely affecting inland fisheries. The construction of dams has harmed many regional fisheries. Indiscriminate fishing is also causing immense damage to fisheries.

The major share of fish production from inland resources is, however, through aquaculture practices. For table fish production, the common and most advantageous culture system is composite fish culture. Fish culture in an integrated fish culture system is also taken up with agriculture farming including paddy-cum-fish culture.

Some interesting fish culture systems are the following:

• Cage culture: Fish is cultured in large cages, made of bamboo or steel, which are lowered into the river. Generally, carnivorous species are cultured in cages.
• Integrated fish culture: Fish culture is practiced along with some agricultural crops such as paddy, banana, and coconut to give higher yields.
• Fish is also cultured in ponds near the poultry or piggery, and the excreta of these animals is used as food in ponds.

Paddy-cum-fish culture
The fish species that can be stocked in paddy fields include Catla catla, Labeo rohita, Cirrhinus mrigala, and Clarias spp. (catfish), Channa spp. (Murrells), Mugil spp., fates calcarifer, etc. These species are able to live in the shallow water of paddy fields and able to tolerate high temperatures or turbidity.

Composite Fish Culture (Polyculture of Fish)

Fish production by culturing a single species in a pond (called monoculture) using old traditional methods gives a low yield; but if several species of fish are stocked together in a pond, the production increases with the same cost. Hence it is necessary to select species having different feeding habits so that all the available food in the pond is effectively utilized. Fast-growing compatible species are selected, so that, there is little competition between them, and all ecological zones are exploited for achieving maximum yield. This method is called composite fish farming or polyculture of fish.

Experiments have shown that Indian major carps (i.e., Catla, rohu, and mrigal) when stocked along with three species of exotic carps (i.e., silver carp, grass carp, and common carp; all three species are transplanted from China), the yield goes up 8-9 times, as compared to monoculture. The food habits of these six species are as follows:

• The silver carp (Hypophthalmichthys molitrix) is a surface feeder and feeds on phytoplankton.
• The catla (Catla catla) is also a surface feeder and it feeds on zooplankton.
• The rohu (Labeo rohita) feeds in the middle zone of the pond, i.e., column feeder, and feeds on decaying plants and detritus.
• The grass carp (Ctenopharyngodon idella) feeds on all macro-vegetation and consumes the aquatic plants/weeds not used by other species in this group.
• The mrigal (Cirrhinus mrigala) is a bottom feeder using decaying plants and detritus.
• The common carp (Cyprinus carpio) is an omnivorous bottom feeder.

These six species have complementary feeding habits and do not harm each other, and constitute a good combination of polyculture.

Important factors to be taken into consideration for fish culture include:

• Topography or location of the pond
• Water resources and quality
• Soil quality, i.e., the composition of particle size as well as nutrients.

The time of stocking also depends on the water temperature. Low water temperature (18-20°C) is most favourable for growth.

Qualitative and Quantitative Improvement of Fish and Fish Seed. The different fish used in the composite culture do not breed in the pond environment. The carp breed in rivers during monsoon months (July, and August). The eggs and seeds collected from riverine water were seldom pure.

Fish seed is a commercial term for

• Spawn (fertilized developing eggs)
• Hatchlings (upto 4-5 mm in size)
• Fry
• Fingerlings (adult-like fish)

The problem of quality seed and breeding the carp in ponds was solved by Alikunhi (1957) through the technique of induced breeding by injecting fish pituitary hormones (called hypophysation). This technique of induced spawning (release of fertilized developing eggs) in fishes led to the blue revolution through fish culture. Currently, synthetic hormones such as ovaprim, ovatide, and nova are used for induced breeding. This technique ensures the supply of pure seeds of fish in the desired quantity.