Brood Fish Transport

In India two successful models of closed system live fish carrier tanks have been designed to carry brood fishes. One is due to Mammen (1962b), which is known as “splash less tank”. The latest model of the “splash less tank” is of petrol tanker design of 150l capacity with an auto clave type lid. It has a built in aeration system for supplying compressed air, which works on a belt driven by the engine of the transporting vehicle. An oxygen cylinder is carried only as a stand by emergency. The inside of the tank is lined by U-foam which prevents the physical injury to live fish during transport. A total weight of 250kg brood fish can be transported at a time in “splash less tank” Adult Catla weighing about 60kg has been transported in this tank successfully. Generally one kg fish is transported with 4.5l of water.

The other live fish carrier is designed in India by Patro (1968). Patro’s carrier is of a laboratory gas supply design type and comprising an outer chamber of 120cm dia open from top and slightly smaller inner one closed from top, the later during transport, fits inside the former. The inner chamber is provided with an air vent and an oxygen valve. The outer chamber serves as a storage tank and initially filled with water along with fishes to be transported. The U-foam prevents the fishes from injury during transport. The double barrel sized carrier described by Patro, can transport 100kg of brood fish at a time. The oxygen is supplied in the tank with an interval of 5hrs to keep the fish healthy.

Some chemicals are also used to transportation of live brood fish. The sedatives are used in transportation can decrease the rate of oxygen consumption and reduce the rate of excretion of carbon dioxide, ammonia, and other toxic wastes. It can control the excitability of the fish, thus reducing the chances of injury.

Natural Resources of Seeds:

In early days generally seeds of Indian Major Carps are collected from natural resources for culture in fish farms. The techniques of collection of seeds from natural resources are described bellow.

Site Selection for Collecting Fish Seeds:

Before selecting a suitable site for collection of spawn in a given stretch of river, a pre monsoon survey is generally conducted. The river meandering with oxbow lakes, flooded areas of river banks, shallow areas flooded with rain water are suitable for collection of fish seeds. The bends and curves of various shapes in the river course often show a precipitous, fast eroding bank on one side, called here, ‘erosion zone’ and a flat, gently slopping bank exactly opposite, called ‘shadow zone’. Both these banks are unsuitable for collection of spawns. Better collection sites lie on the side of the slopping bank, but at spot where the current just diverges casting off spawns to the sides, as if by centrifugal force. At such sites, a large number of spawn collection nets are usually be operated.

Gears Used for Collection of Spawns:

The spawns are collected by special type of nets, called shooting nets. This is a funnel shaped, net of finely woven netting and is operated in shallow margins of flooded rivers with mouth of the net facing the current. At the end of the net a bag like structure is attached, called ‘gamcha’ to store the spawn inside of it. After a certain periods of time, the cod the spawns are collected at this cod end. The net is fixed by four bamboo poles, against the current of rivers. Various types and modification of these nets are used in different parts of India. In North-east Bengal, the spawn collection nets are called benchi jal. In South-western part, the nets are called Midnapur type nets.

Methods of Collection:

The shooting nets are fixed in such a way that its axis is in line with current directions. To start with bamboo pole is planted firmly in the selected spot, the loops of one end of the nets mouth slipped over it, the other end is stretched firmly across the path of the current and fixed in place with the help of another bamboo pole. The net is then allowed to drift in the current, mouth facing to the current of water. The net is then stretched firmly along the axis, by pulling the cod end ring which is then fixed in place with the help of more bamboo poles. The anterior end of ‘gamcha’ is then tied round the ring, while the posterior end is fixed in position with the help of two more bamboo poles. In order to prolong the life of the net and ‘gamcha’, they should be invariably pulled out of the water after 12hrs operation and dried for at least 24hrs.

After storing suitable quantity of fish seeds, the tail pieces of nets are removed and the spawns or seeds of fishes are scooped out. The collection of seeds from tail pieces are carried on after an interval of 15min, 30min, 1hrs, or 2 hrs depending on the intensity of the collections. Before scooping, the debris accumulated inside the ‘gamcha’ are removed carefully with expertise hands.

Methods of Measuring the Quantity of Spawns:

The spawn collected is to be measured in 200ml, 100ml, 50ml, 30ml, 20ml, 10ml or 5ml measuring cups, depending upon their bulk. For temporary storage the spawns are stored in hapas, made up with muslin cloth, fixed in the shallow water of river margins or creeks.

Site Selection for Aquaculture

Introduction

The success of an aquaculture enterprise is dependent on many factors including the selection of a suitable site and the design and construction of facilities that enable efficient and economic operation. This information briefly discusses the major factors that must be considered when selecting a site and designing grow out facility for the aquaculture of finfish; most factors also apply to crustaceans. Success or failure of any aquaculture venture largely depends on the right selection of the site for it. In choosing a site several factors other than the physical aspect of the site are to be considered.

Sites suited for aquaculture and culture types

Several types of water bodies can be used for fish culture - the choice of a specific body would depend on the objective of the investors and also the type of aquaculture.

Among the sites suitable for aquaculture could be listed: land-swamps, rivers, stream beds; coastal areas - bays, estuaries backwaters, lagoons, salt marshes and mangrove swamps; lakes, reservoirs and other water bodies, including irrigation tanks and canals.

The specific site to be chosen would be based on the requirement of the culture systems. Static water ponds are the most common, hence pond culture the most important system. Most of these are confined to freshwater areas, but brackish water ponds are also becoming more common. There is a variety of culture systems which can be developed in open waters - the stocking and management of open waters themselves being major occupation, e.g. extensive stocking of man-made reservoirs and lakes. In the larger freshwater bodies and coastal areas cage and pen culture can be developed. Site selection for these culture systems has to be carefully done, based on the requirements of the species to be cultured and the structures to be erected for the culture. Here and in the culture systems where closed systems are used, the inputs required can be costly and management intensive. Thus there can be gradation of culture, systems based on the input costs and management strategy employed, from extensive, through semi-intensive to intensive.

Culture types (Systems)

The different culture systems in vogue are listed below:

Static water ponds, running water culture, culture in recirculation systems (closed or reconditioned water); culture in rice fields and integrated culture systems, as the duck-cum-fish and pig-cum-fish culture - or any fish-livestock-crop combination; culture in raceways, cages, pens and enclosures; also mollusk/oyster culture - hanging, on-bottom and stick methods. As mentioned already the choice of site for a specific culture system, would depend on the characteristics of the site and the requirement of the culture system - the latter again has two components, the species requirements and the structural requirements of the culture system.

Various Factor Affecting the Site Selection of Aquaculture:

1. Socioeconomic and Political factor:
They are socio-economic aspects such as
Social and religious customs’
Consumer preference;
Nature of manpower (labor) - quality and quantity - available;
Transportation and communication facilities; i.e. infrastructure facilities;
Accessibility and nearness to market;
Availability of construction materials

2. Political and Legal Consideration:

The aquaculture project execution should be a part of the overall planning for the specific area under the national plan for development, so that the project can fit into the country's or provincial plan for development of industry and agriculture. This is specially needed when aquaculture is a part of rural development programme, as indeed most such projects are. This should specially help in sharing infrastructural facilities of transportation (road), power supply and communications and also in judicious sharing of imports and recycling outputs. The advantages of their consideration in sitting a project are obvious. We shall look into these aspects of macro-economic planning subsequently when “socio-economic aspects” and “aquaculture planning” are discussed in detail. Legal aspects, such as security of tenure, maritime laws controlling coastal waters (in cases where sites are coastal), legal size limits with reference to the ponds/culture area, as well as the species under culture, and closed reasons, should also to be considered. Several countries already have certain regulations concerning these legal aspects, some of which are in force, much before aquaculture was thought of as an industry.
In many cases these legal clauses cannot be easily modified, even though some attempt in this direction would be necessary, especially with reference to size-limits of fish and closed seasons. The latter regulations have been included to protect the species' survival under intensive capture systems of wild stock. While this protection may be necessary for such a case, here in aquaculture, and capture from the wild fish of certain size, when the season for capture is closed legally, is only for protection of the fish by way of transferring the fish to culture ponds - either as brood fish or as fry or fingerlings in grow-out ponds. In some cases maritime areas through which navigational routes and certain other country priorities exist. These aspects should be considered in choosing the site for the aquaculture ventures planned.
3. Major Climatic and Environmental factor:

Climatic factor: Fishes and crustaceans are poikilotherms (cold-blooded animals) and temperature directly affects all aspects of their biology. Each species has a range of temperatures in which it can live. Temperatures reaching the upper or lower lethal limits will kill the animals. If animals are subjected to extreme but not lethal temperatures for extended periods, growth and other biological activities will be adversely affected and mortalities will occur; either directly through malfunction of one or more physiological processes or indirectly (for example, through stress-induced disease and starvation). Within the tolerance range, each species has a range of temperatures, which enable maximum growth (the optimum temperature range). At temperatures outside this range, feeding rates and the efficiency of food conversion are generally poorer, resulting in slower growth and lower production. Locate aquaculture facilities in an area that has the optimum temperature regime for the selected species. Regions where lethal temperatures are reached, or approached, are unsuitable for pond culture.

Other Environmental Factors:

a) Topography and Ground Elevation: Large commercial fish farms are typically built on flat land. Pond bottoms drop approximately 0.2 foot for every 100 feet of length, a slope of 0.2%. Topography with slopes of 0-2% is better for pond construction. Extensive earth moving may be required on land with slopes greater than these; increasing construction costs. Some innovative farmers use terracing -- stair-stepping -- for pond layouts in hollows or on land with slopes greater than 2%. However, the economics of that method should be carefully examined. It is important that ponds have an adequate drainage area for harvest. The site should be above the 25-year flood plain.
b) Soil: the site must have soils that hold water and can be compacted. If pond levees are constructed with soil that has high water permeability (leakage), the cost of pumping water could become prohibitive. Soils should contain no less than 20% clay. Soils with high sand and silt compositions may erode easily and present a piping hazard -- soil-water flow along pipes -- which could wash out a levee. Anti-seep collars can help minimize that problem. Clay oil with greater than 40% clay is suitable for pond and pond dyke construction. Silt clay (40-60% clay), sandy clay (35-55% clay), Clay loam (27-40% clay) are also suitable for aquaculture site.
c) Water Supply, Water Quality: Aquaculture requires large volumes of good quality water. While you may be able to fill a pond with your garden hose, it may take six months to do so. Normally, a well or surface water source (river, stream or spring) is required. Surface sources may be polluted, intermittently available (affected by weather, e.g. drought) or contain wild fish populations which might be introduced into your pond. Wild fish can be a source of disease and will often compete with cultured fish for feed. Many of the most successful aquaculture operations in the U.S. depend on large aquifers (underground water supplies) for water needs. Typically, commercial aquaculture requires a water flow rate of 25-40 gallons/minute, on demand, for every surface acre (4 acre-feet) of pond water. Water must be of high quality and free of pollutants, sewage and toxic contaminants. Generally, water that is safe for livestock and domestic use or that supports wild fish populations is safe for aquaculture. However, livestock and aquaculture do not mix. Manure from just a few farm animals can pollute a pond. There are several chemical characteristics of water that are desirable for good fish growth. Water should have a pH of 6.5-9.0, total alkalinity of 75-250 mg/l and total hardness of 75-250 mg/l. Total hardness and alkalinity should not be less than 20 mg/l. Low alkalinity and acid water are usually related to acid soils. Agricultural limestone can be used to raise pH, alkalinity and hardness to the minimum required levels in soft, acid water. If striped bass or red drums are being considered, calcium hardness and total alkalinity between 100-250 mg/l are preferable; a calcium hardness value of 250 mg/l is ideal. Often, well water contains no oxygen and high levels of carbon dioxide and nitrogen, necessitating aeration before use or pH testing.
d) Productivity: The soil must be productive and fertile enough to produce require micro and macro vegetation of the pond and planktonic growth.
e) Other Factors:
· Susceptibility of the site to flooding
· Non availability of migratory birds, predators
· Previous land use and surrounding land use
· Environmental Consideration: Aquaculture is an Environmentally Relevant Activity and will require an Environmental Authority or approval from the Environmental Protection Agency (EPA) to authorize activities
· Wind drift and Arial application

Methods of Liquid Waste Treatment

Sewage Treatment

A high BOD indicates the presence of excess amounts of organic carbon. Oxygen depletion is a consequence of adding wastes with high BOD values to aquatic ecosystems. The higher the BOD of a source of wastes the higher the polluting power of that waste. BOD's of certain wastes are listed in the table below.

Type of Waste BOD(mg/L)
Domestic Sewage 200-600
Slaughterhouse Wastes 1000-4000
Cattle Shed Effluents 20000
Vegetable Processing 200-5000

There are numerous ways to reduce the BOD of waste before discharging it into the water. Treatment of the wastes is aimed at removing organic material, human pathogens, and toxic chemicals.

Primary sewage treatment involves physical separation to lower the BOD of the waste. Suspended solids are removed in this step through the use of settling tanks. Primary treatment usually removes from 30% to 40% of the BOD from typical domestic sewage. Secondary treatment uses microbial degradation to reduce the concentration of organic compounds further; it involves microbial processes which can be aerobic or anaerobic. The combined use of primary and secondary treatment reduces approximately 80% to 90% of the BOD. However, because secondary treatment involves micro organisms it is extremely sensitive to toxic chemicals. Finally, tertiary treatment uses chemicals to remove inorganic compounds and pathogens.

Oxidation Ponds

Oxidation Ponds are also known as stabilization ponds or lagoons. They are used for simple secondary treatment of sewage effluents. Within an oxidation pond heterotrophic bacteria degrade organic matter in the sewage which results in production of cellular material and minerals. The production of these supports the growth of algae in the oxidation pond. Growth of algal populations allows furthur decomposition of the organic matter by producing oxygen. The production of this oxygen replenishes the oxygen used by the heterotrophic bacteria. Typically oxidation ponds need to be less than 10 feet deep in order to support the algal growth. In addition, the use of oxidation ponds is largely restricted to warmer climate regions because they are strongly influenced by seasonal temperature changes. Oxidation ponds also tend to fill, due to the settling of the bacterial and algal cells formed during the decomposition of the sewage. Overall, oxidation ponds tend to be inefficient and require large holding capacities and long retention times. The degradation is relatively slow and the effluents containing the oxidized products need to be periodically removed from the ponds. An oxidation pond can be seen in the figure below.

Trickling Filter

The trickling filter system is relatively simple and inexpensive. It is an aerobic sewage treatment method in which the sewage is distributed by a revolving sprinkler suspended over a bed of porous material as seen in the Figure below.

The sewage slowly moves through the porous bed and the effluent is collected at the bottom. This porous material becomes coated with a dense slimy bacterial growth which provides a home for a heterogeneous microbial community which includes bacteria, fungi, and protozoa as well as other organisms. As the sewage drains through the porous bed, this microbial community absorbs and breaks down dissolved organic nutrients in the sewage; this reduces the BOD. Aeration of the sewage occurs by the movement of air through the porous bed. The sewage may need to be recirculated several times through the filter in order to reduce the BOD sufficiently. One dissadvantage to this system is that an excess amount of nutrients produces an excessive amount of slime on the bed which in turn reduces aeration, leading to the need to renew the porous bed. Cold winter temperatures also reduce the effectiveness of this method in outdoor treatment facilities.

Activated Sludge

Activated Sludge is a widely used aerobic method of sewage treatment. After primary settling, the waste stream is brought to an aeration tank. Air is put in and/or there is mechanical stirring which provides aeration of the waste. Sludge from a previous run is usually reintroduced to the tanks to provide microorganisms. This is why it is called activated sludge. During the period in the aeration tank, large developments of heterotrophic organisms occur. In the activated sludge tank the bacteria occur in free suspension and as aggregates or flocs. Extensive microbial metabolism of organic compunds in the sewage results in the production of new microbial biomass. Most of this biomass becomes associated with flocs that can be removed from suspension by settling. A portion of the settled sewage sludge is recycled and the remainder must be treated by composting or anaerobic digestion. Combined with primary settling, activated sludge reduces the BOD by 85% to 90%. It also drastically reduces the number of intestinal pathogens. An illustration of an aeration basin is shown below.

Anaerobic Digestors

Anaerobic digestors are large fermentation tanks which are continuously operated under anaerobic conditions, as seen below.

Anaerobic decomposition could be used for direct treatment of sewage, but it is economically favorable to treat the waste aerobically. Large-scale anaerobic digestors are usually used for processing of the sludge produced by primary and secondary treatments. It is also used for the treatment of industrial effluents which have very high BOD levels. The mechanisms for mechanical mixing, heating, gas collection, sludge addition and removal of stabilized sludge are incorporated into the design of large-scale anaerobic digestors. Anaerobic digestion uses a large variety of nonmethanogenic, obligately, or facultatively anaerobic bacteria. In the first part of the process, complex organic materials are broken down and in the next step, methane is generated. The final products of anaerobic digestion are approximately 70% methane and 30% carbon dioxide, microbial biomass and a nonbiodegradable residue.

Tertiary Treatment

The treatment processes used to reduce the BOD of sewage waste are secondary treatment processes. Tertiary treatment is any practice beyond secondary treatment and is designed to remove nonbiodegradable organic pollutants and mineral nutrients such as nitrogen and phosphorus salts. For tertiary treatment, activated carbon filters are commonly used.

Disinfection

Disinfection is the final step in the sewage treatment process and is designed to kill enteropathogenic bacteria and viruses that were not eliminated during the previous stages of treatment. Disinfection is commonly done by chlorination with chlorine gas or hypochlorite. Chlorine gas reacts with water to yield hypochlorous and hydrochloric acids which are the actual disinfectants. A disadvantage of using chlorination for disinfection is the formation of disinfection by-products, such as chlorinated hydrocarbons. Chlorinated hydrocarbons are toxic and difficult to mineralize. Trihalomethanes may also be formed such as chloroform and bromoform, which are suspected carcinogens. Ozonation is an alternative to chlorination, which uses ozone as the oxidant. This however, is more expensive. Currently, alternative disinfection processes are being sought.

Inbreeding

In fish farming, if proper care is not taken the fishes can breed with their close relatives or same parental generation which may cause early mortality of fish, poor growth rates and other genetical abnormalities. This phenomenon is called inbreeding or homozygosis and the offspring is called homozygote. Homozygosis is the condition when two genes at particular locus are with same allele. Inbreeding causes the reduction of desirable traits and some times may cause fertility. If a farm based on limited number of population of brood stocks the progeny over long periods can face inbreeding problems.

The advantage of inbreeding:

Sometime the inbreeding is not encouraged and has some advantageous point also. Production of inbreed lines are very use full in improvement of stock. Production of inbreed lines have following advantages.

· To produce pure lines of fish
· Pure lines of strains are used for perfect hybridization of fish to obtain favourable heterosis, monosex.
· Pure lines help in gene mapping
· To determine

1. Phenotypical variations
2. Extent of inbreeding depression
3. chromosomal makeup to the fish

Integrated Fish Farming

Integrated fish farming is the methods by which fish is cultured along with paddy, piggery, poultry or any livestock, or flower culture.

Fish farming along with paddy culture:

In certain areas, paddy fields are flooded with water for at least 3-8months in a year. During which the fishes or prawns can be cultured along with the paddy fields to increase the annual income of a farmer. Fish culture in paddy fields can be categorised by following ways –

1. The water is allowed to enter into the paddy fields during cultivation with some wild verities. The paddy fields are surrounded to prevent the escape. No special attention is taken for that. This is a type extensive culture.
2. The paddy fields can be used as temporary ponds after harvesting of paddy. In this method fish and paddy is not cultured together. Fish seeds of suitable species are stocked with minimum care.
3. A continuous fish culture is done in specially prepared ditches or canals when fields are drained.

Advantages:

· The excretory matter of fish is used as manure for paddy cultivation
· Insects which can harm paddy crops are eaten by the fishes
· Fish destroy the unwanted weeds and increased the production of paddy.

Generally in WB, Rohu, Catla, Mrigal and all air breathing fishes are cultured along with paddy. Fresh water prawns, Tilapia and other cyprinids are also cultured.

Fish farming along with Duckery or Poultry:

Fish can be cultured along with livestock. The system is advantageous because duck feeds miscellaneous items from water like insects, crustaceans, molluscs which are not economical. The duck droplling is used as foods as well as fertilisers of ponds. The dabbling of duck in pond water in search of feeds release the nutrients from soil as well as it mixes the oxygen to the water which enhances the biological productivity and consequent increase of fish growth. The duck does not need any elaborate house and most of the time they prefer to live in water. Improve stocks of ducks like – India Runners, are used in poly culture system. 200 – 300 ducks are culture along with fish which can make sufficient amount of fertiliser to the pond water. The culture can yield from one ha area – 3,500-4000kg of fish, 18,000 eggs and 500kg of duck meat in one year.

Fish cum Pig Farming:

Fish farming with pig rearing is also cost effective and extra source of income to the fish farmers. Four types of pigs are used in that case in India of which Hampshire and Land Race are mostly cultured. They are prolific breeders and attain slaughter house maturity (60-70kg) with in 6 months and give 6-8 piglets. Fish attains marketable size in a year during which two crops of pigs can be reared. Pig manure is also rich with all nutrients found in cow dung. Fully grown pigs can void 500-600kg manure in a year. 30 – 40 pigs are sufficient to one ha farm for adequate fertilisation.

The yield is about from poly culture system –

6000 – 7000kg fish/ha/yr with 3,600 – 5000kg of pig meat

Cross Breeding

Crossbreeding is the solution of inbreeding depression, because the fishes are allowed to breed with different breed verities, strains or genotypes of farmed species. To improve the stocks artificial selection techniques are applied. This is called selective breeding. From heterozygosis the stocks can be improved and the aims of cross breeding to achieve –
· Better growth rate
· Better desired qualities
· Better FCR value
· Increase the survival rate and lowered the early stage of mortality

Gynogenesis

It is the process to produce individuals from maternal chromosomes only eventually to obtain homozygosity. Gynogenesis in fish farming is used to form inbred lines to achieve proper hybridization and selective breeding.

Methods:

Sperm nucleus is inactivated prior to fertilization by use of X-Rays, chemicals – dimethyl sulphate.
Upon fertilisation the resulting diploid individuals retain the second polar body nucleus (maternal) besides the egg nucleus, because the eggs are exposed to sub lethal temperature shocks before or after fertilization which suppress the meiotic divisions of eggs i.e. ensuring the non reduction of nuclear components.

In India Gynogenesis are tried on Indigenous as well as Exotic carps. Eggs of rohu are fertilised with irradiated sperms of Catla and then exposed to cold 12°C and heat 39°C shocks to obtain gynogenetic rohu.

Need for Genetically Selected Fish

The fishes from mass selection are not found to be successful for faster growth rate, or with better FCR value. In other hand in captive condition there is the chance of inbreeding. So we need genetically improved stock for following purposes –
Selective breeding and formation of improved species with better growth rate, low mortality and resistance to the diseases
To obtain better fertilisation rate
To achieve better fertilisation rate
To achieve better FCR value
To achieve better flesh content and shape of the fish

Selection Methods:

· The fishes are to be selected from different rivers to avoid close relatives of the fishes. Reservoirs should be avoided, because there is a chance of inbreeding.
· Genetically superior and pure lines are used for this purpose
· Mutant fish with superior character are used
· The brooders from different parental families much have deeper bodies with desirable qualities, like small heads, greater fatty make up.
· The population can be separated from original sources from at least two generations
· The brooders should have fastest growth rate, grater disease tolerance capacity and adaptable to extreme environment
· By chromosomal manipulation – Gynogenesis or Androgenesis
· Hormonal manipulation – Feminisation or Masculisation
· By genetic engineering – trangenesis or mutation

The fishes are selected by following criteria –

1. Body and development of fins
2. Better growth rate and better FCR value
3. Better disease tolerance capacity
4. Fatty make up (larger size and heavier growth rate)
5. Greater longevity
6. Higher fecundity
7. Greater adaptability in different stages and temperature variations
8. Hardier etc

Sex Control of Fish

Sex control is the technique to produce desired sex by various ways. The species achieved faster growth rate with better FCR. These are economically important and prolific breeding or over crowding due to prolific breeding can be avoided. The methods are as follows –

Feminisation ----------------- Hormonal treatment
----------------- Back cross with sex reversed male and normal female

Masculization ---------------- Hormonal Treatment

Contracept ---------------------- Drugs/Chemicals/Hormones

Sterilisation -------------------- Drugs/Chemicals/Hormones
-------------------- Hormonal Treatment
--------------------- Heat & Cold Shock/Pressure Shock
--------------------- X-ray

The role of Hormones in sex reversal –

Sex reversal has been achieved by hormonal control methods. The hormone which is used in feminisation is estradiol – 17-ß, ethyl estradiol. The hormones are used in early maturation stages administered by food and the undifferentiated gonads are transferred to the female ovary. Dose and treatment period is specific to the single species as for example 20g estradiol is used per kg of food, with 120 days treatment period for salmon fry for 100% feminisation. The female hormone which is use in early developmental stages in male fishes can change the male to female phenotypically, but genetically it would be XY.

For synthetic hormone oestrogen, one has to take care and should avoid high level of dose because it may cause liver damage and mortality of fry.

In case of masculisation the 17-α Methyl testosterone is used in early maturation period of fish. It can convert the female fish into male fish phenotypically, but genetically it would be XX. Generally much higher dose of androgen can be used in two ways – I. by food, II. Bathing of larvae in hormone treated water. In case of salmon fry the dose of hormone in food is about 3mg/kg and for Tilapia it is 20-30mg/kg of food. The androgen is also growth stimulating hormone.

Transgenic Fish

A transgenic fish is one which carries one or more than one foreign genes. The foreign genes are selectively incorporated by micro injection into the egg with a view to produce transgenic fish.

The progress was made in genetic engineering to isolate eukaryotic genes in 1970s and by 1980s. However, the technique was applied to the fish much later; nevertheless some significant progress was made which has potential of application in fisheries. More than a dozen of fish is produced by 1989.

Fish transgenies are difficult because of tough egg-chorion which impedes microinjection. A prior puncture or use of micro pile (an opening in the egg surface for sperm entry during fertilisation) has to be made for microinjection. The micropile is made by or by using trypsin digestion. The gene can be transferred by electroporation (exposing the egg chorion in an electric shock for a fraction of second) or by retroviral injection. The foreign gene then transferred into the nucleoplasm or the cytoplasm. In case of retroviral injection, the genes are first incorporated into the viral genome, and then through the virus the gene are transferred into the host by injection. However in case of fish the method is also not tough as because the fertilisation and embryonic development is external.

Application:

· The fish of superior quality or desired traits are produced by this process. Giant sized fish or super fish can be produced. This can be achieved by incorporating the growth promoting genes – bovine growth hormone gene or human growth hormone gene. Example in China, the giant loaches are made by growth hormone gene of human.
· The transgenic Atlantic salmon are given with anti-freeze protein gene of polar flounders. This was done to promote to make resistance power of salmon in polar region and habit of salmon can be extended to Polar Regions also.

Future goal:

The technique has great promises in future to make desirable traits of various farm fishes. Such dream fish of fast growth rate withy fatty make up, greater longevity in all environmental condition, omnivorous feeding habit with higher fecundity, greater adaptability, more resistance to disease, biocides and pollutants, lack of bones and other undesirable features can be made in future. Aquarium fish trade can also be rise by using this technique. Various beautiful coloured fish can be made by this technique.

Composite Fish Culture

In order to achieve highest production per unit area of water bodies, fast growing compatible species of different feeding habits, different growth rate and different weight class are stocked or cultured together in the same water bodies so that all ecological niches are used or exploited by that species. This technique of culture of different aquatic organisms is known as composite culture or poly culture, or mixed farming. This technique is based on principle that all compatible species should be stocked to make no harm to each species. There is no competition between the cultured species and they may have the beneficial effect on the growth of others.

To achieve the maximum yield from any water bodies the very common combination of culture is done by three species of IMC. i.e. Catla catla, Labeo rohita, and Cirrhinus mrigala in 3:4:4 ratios. This method is very common in West Bengal since long past. Catla is the surface feeder, Rohu column and Mrigala is the bottom feeder. In some cases Calbose (L. calbasu) was also introduced with Mrigala. Then the ratios are 3:3:3:1.

The culture of three species of IMC with correct ratios is an example of appropriate selection of species with maximum utilization of pond with different zones. However the mixed farming is done by other ways by using exotic carps – Common carp (Cyprinus carpio), grass carp (Ctenopharyngodon idella) and Silver carp (Hypophthalmichthys molitrix).

Feeding habit of different species:

Catla catla – a surface feeder consuming zooplankton and detritus.
Silver Carp – a surface feeder consuming phytoplankton and other vegetative parts from surface

Labeo rohita – column feeder consuming decaying plants
Grass Carp - column feeder feeds on both coarse and macro vegetation.

Cirrhinus mrigala – bottom feeder consume decaying plants and detritus.
Common Carp – an omnivore and scavenger of both animals and plants.

From above feeding habit we can see that the ecological niches are well distributed among all species and there is no competition. Silver carp though a surface feeder, they consume phytoplankton where as other surface feeder Catla used zooplankton as their food. The common carp is omnivorous utilizing mainly the food which does not take Cirrhinus mrigala. The grass carp is known as efficient eater of macro-vegetation and all noxious and excessive vegetation growth can be controlled by using this species. Rather their faecal matters further serve as the food of common carps and also accelerate the plankton production of pond water.

The ratios used in six species culture are –

Catla catla 3 2 8
Labeo rohita 2 2 1
Cirrhinus mrigala 5 5 25
Common carp (Cyprinus carpio) 2 1 1
Grass carp (Ctenopharyngodon idella) 5 5 25
Silver carp (Hypophthalmichthys molitrix) 2 3 1

However the species combination entirely depends on the choice of culturists, area of pond, market value of individual species and climatic and ecological conditions of pond water.

In certain cases freshwater prawns (Macrobrachium rosenbergii) are also released. They are mostly carnivore and mostly feeds with supplied food and do not compete with carps. The faecal matter of fish also serves as additional sources of food to prawns, which are also detritus feeder or scavenger.

Stocking density: Stocking density is generally kept 5000-6000 fingerlings per ha. Stocking rate and proportion of fingerlings depends upon the availability of natural foods, the rate of fertilization and physiochemical condition of water.

Annual Yield: It was found that the average yield of indigenous major carps in intensive mixed farming is about 4000kg/ha/yr. Yield of exotic carp is about 3000kg/ha/yr. In mixed poly culture of IMC and Exotic carp the yield is about 8000kg/ha/yr. If prawns are released, average output of prawn is about 450-500kg/kg/ha. Further rising of output can be done if two crops in a year can culture. In that case the annual out put will be 11,000Kg of fish/ha. and 800-1000kg of prawn/ha of water bodies.

The low cost coupled with high yield in composite fish culture of six species will help spread the practice over the entire country. Extension services and programmes envisaging field demonstration, dissemination of relevant information will go a long way in popularization and earlier adoption of the technique. It has been found that the hypophysation in case of exotic carps as well as in case of indigenous. Thus the problem of seed will not encounter in the way of composite culture.

Experiment has also been conducted on integration of aquaculture with livestock rearing which can reduce the cost of fish production. In composite culture introduction of various types of foods into the pond (most common: rice bran and oil cake) can maximize the production of fish as well as prawns.

Sterile Fish

Sterility is the loss of reproductive power due to any reason leads better growth and food conversion efficiency. A huge energy is utilised for gonadal maturation and production of gametes in fish. If the sexual maturation is stopped the fish can grow more rapidly. The all foods supplied in that case are transferred to the flesh and no wastage of food or energy for gonadal maturation can be seen in sterile fish. Not only this, sterility avoids prolific reproduction and over crowding of fish. Sterile fish can be produced in various ways –

Induction of autoimmunity of gonads
Extirpation of gonads
Chromosomal manipulation for production of polyploidy
Hybridization
Hormonal sex reversal to super males and super females of giant sized fish
Non hormonal chemicals which can sterile fish
Exposure to UV rays or radioactive substances

Among the above mentioned process hormonal sterility is applied in case of sterile fish production where insufficient application of male hormone or female leads partial change of male to female or female to male and can produce sterile fish. The method is very easy but not acceptable in all countries because hormone treated fish is bad for human consumption.

Non hormonal chemicals like methallibure or cyproterone acetate. Both these are chemosterilants can reduce Gonadotropin production and lower androgen secretion, but do not prevent the gonad maturation. These drugs will have to be administered to the young fry in their diet; hence the utility in commercial purpose is doubtful.

Hybridization of some species can produce sterile fish which is very easy, economical and no doubt to human consumption.

Exposure of fish or fry in UV rays or any other radio active radiation cause gonadal destruction leads to the sterility of fish. The method needs well equipped laboratory with very much experienced workers. The production of such type of sterile fish is not encouraged in commercial purpose.

Polyploidy (Broiler Fish): It is one of the methods to produce sterile fish most easily. The triploid can be achieved experimentally by chromosomal manipulation brought about the suitable exposure to thermal or hydrostatic pressure shock at early stages of development. The mechanism involved to prevention of second polar body from the eggs.

Triploid can produce by a cross between the female common carp and rohu are sterile by following way:

By intergeneric mating between a diploid female of one species (any IMC, for example) and triploid male of another species (common carp)

By subjecting the fertilised eggs involving the egg of one species and sperm of another, to the action of antibiotic cytochalasin or colchicines which are mitotic inhibitor & so disrupt the first cleavage mitosis. By subjecting the normally fertilised eggs, involving artificial insemination of egg of one species (common carp) by the sperm of another species (rohu), to heat cold or hydrostatic pressure shocks. The shocks suppress the release of 2nd polar body (i.e. early metaphase of meiosis II).

Mono Sex Culture

Mono-sex culture is based on the culture of fish by producing all males or all females depending upon the sex which have better food conversion ratio and growth rate. Sex of fish genetically is determined by the sex chromosomes (X, Y, Z, or W). The male determining gene M is present on any of the three X, Y and W. in XY mechanism, the females are XX and males are XO. Some species have ZZ female and ZW male. In platy fish there are 3 sex chromosomes – X, Y and W; XX, WX and WY are some combinations.

However for all male or female productions the flowing procedures are maintained –

The sex of fish is identified before maturity and male and females are separated. The process is laborious. Desired quantity of male or females are not produced by that process.

Experimental hybridization in Tilapia can produce monosex stock. Inter specific and intra specific mating yields monosex male stocks as follows

♂ T, macrohir × ♀ T. nilotica
♂ T. hornorum × ♀ T. mossambica
♂ T. mossambica × ♀ T. nilotica
♂ T. mossambica (African) × ♀ T. mossambica (Malaysian)

Treatment with sex hormones: It is another easiest way, when male sex hormone methyl testosterone is administered through feeding in early developmental stages of female fish. The genotype female (XX) then transferred to phenotype male (XX). If such sex reversed male are crossed with normal female, the progeny will be 100% female. The gonads of fish (teleost) are undifferentiated at early stages of maturity and it can be triggered to produce male or female gonads by that process.

Sex reversed male (XX) × Normal female (XX)
↓
Female (XX) ……. F1

The hormone treated sex reversed male are generally not fit for human consumption. But F1 progeny is normal female and suitable for human consumption. But sometimes the culturist does not produce F1 progeny to produce only male population. In case of Tilapia the little amount of methyl testosterone (15-60mg/kg of food) is administered. The drug is given for 30-50 days of life, during which gonadal differentiation takes place. The uses of estrogenic steroids are not successful. However the production of all females has been attempted in salmon and trout. Oral administration of 17-ß estradiol at 20mg/kg of food is given to the juvenile trout & salmon up to 60 days resulted sex reversal of males to females. In pacific salmon (Onchorhynchus spp.), the immersion of young fish in drug as well as feeding appears to be necessary for sex reversal.

Necessity of Monosex Culture:

Some time one sex of certain species has better growth rate and food conversion efficiency. To culture that sex (male/female) monosex culture is essential. For example we can say that the male Tilapia grows faster than female, then the culture of male is beneficial in case Tilapia.

When the fecundity of certain species is very much high and if they can breed in captivity without any inducing agent, there is the possibility of overcrowding of fish, which leads to stunted growth (due to the prolific reproduction e.g. Tilapia).

The production of monosex fish is easier than the production of sterile fish, so in commercial purpose generally monosex cultured is mostly prefer.

Example of Monosex Production in Nature:

According to recent report, the flat fish population in the estuary of British River Tyne, a heavily polluted river, was found more than 50% of males possessing abnormal testes. The tendency of their sex change from male to female was probably due to the female hormones. But the actual reason and mechanism of the action is not known.

Hybridization of Fish

It is the technique of breeding of fishes between two species or genera which ordinarily do not breed.

Hybridisation in nature:

Most fishes release their eggs and sperms in water and fertilisation are external. Fish hybridizes more frequently than tetrapodes so fertilization of closely related species which leaves in same water bodies, are common. Reservoir is the most important area where natural hybridization occurs frequently than rivers, because the area is not too large as rivers and scarcity of certain species with preponderance of others. Naturally hybridized fishes are found in following families – Esocidae, Catastomidae, Cyprinidae, Salmonidae, Poecillidae etc of about 56 families.

Technique of Hybridization:

The hybridization is done actually by inducing the virgin fishes or small aged group fishes. The hybridized fish possess intermediate character of two species. This type of hybridization is also known as diploid hybridization. This hybridized fishes are capable to produce new fish up to F2 progeny. Inter specific and Inter generic both type of hybridization is done in India.

Inter specific hybridization – Inter specific hybrids are generally producing by mating between two different species in same genus. In India mating female kalbasu and Labeo rohita is highly successful. Over 94% fertilisation was obtained. The growth rates of hybrids are superior to the parent Kalbasu. It attains maturity in two years. The hybrids also can be bred by hypophysation and can be obtained F2 generation. However the fishes are selected by following process –

The brooders are selected in first maturity generally virgin.
One pair of males (rohu) and one pair of females are injected to induce them prior to breeding by hypophysation technique.
The breeders are kept separated for some times and then they are released in breeding hapa with suitable breeding conditions.

The inter generic hybridization – In this method male and female are generally selected from different genera and produced by above mentioned methods. In India, successful hybrids are as follows –

Parent ♂ Parent ♀ Hybrids
Catla catla Labeo rohita Rohu-Catla
Catla catla Labeo calbasu Catla-Kalbasu
Catla catla Cirrhinus mrigala Catla-Mrigal
Labeo rohita Cirrhinus mrigala Rohu-Mrigal

Inter generic hybrids between Catla and Rohu attains full maturity in 3yrs and they also be induced to breed. Crossing between Rohu and Mrigal is more successful and 90% fertilisation is done and hybrids attain full maturity in 2yrs and showed intermediate character. Mrigal-Kalbasu hybrids attain full maturity within 2-3yrs. These hybrids are also capable to produce new ones. These are –

Parent ♂ Parent ♀ Hybrids
Catla catla Mrigal-Kalbasu Catla-Mrigal-Kalbasu
Labeo calbasu Mrigal-Kalbasu Rohu-Mrigal-Kalbasu

These hybrids are matured within one year.

Jano Fishery

Jano is a type of pen culture, practiced in Chilka Lagoons. It is a traditional intensive culture technique especially in brackish water regions. In Chilka Lagoon, the Janos are constructed in shallow water areas to form a suitable enclosure or impoundments. These are constructed with split bamboo, with single layer, single layer with net webbings, doubled layer Janos. Fishes which are herbivorous, detrivorous, fast growing and tolerant to fluctuating salinities are cultured in Janos. Chanos chanos, Mugil cephalus, Mugil tade, Etroplus suratensis, are highly suitable for pens. Prawns like Penaeus indicus, Penaeus monodon, Penaeus semisulcatus can also be undertaken. However carnivorous fish like Lates calcarifer, Elops machnata, Megalops cyprinoides have to be stocked in separate pens along with tilapia or supplementary foods are also done in the Janos. Stocking densities of such Janos are high. About 112 Janos are exclusively leased out in Chilka for fisheries. About 13% to 22% of the production come from the lake comes from Janos.

Cage Culture

Cage is constructed by various materials of various sizes and shape with closed bottom or the bottoms of the cages are not fixed in the ground of cultured water bodies. Cage can be fitted in any water bodies with any depth. Cage is installed by means of floats and sinkers. The main advantages of the cage are that it can be shifted from one place to another place in any time and it can be installed in deep sees also or any deeper waters. Depth of the water body is not a factor of cage culture. It can be installed in lentic or lotic water.

Certain invertebrates and vertebrates are reared in cages, but mainly warm water fishes are culture in the system. Fishes in the cages are confined in natural environment with known quantity. After stoking, generally no attentions on feeding and diseases treatment are paid. Sometimes in case of some super intensive marine farms, attentions are given to the organisms confined in the cages.

Cage culture is practiced in Cambodia rather traditionally. In Japan, some cage based marine farms are developed in recent years. Now Japan is the leading country for cage based fish production. Now many maritime countries are adopted this culture technique. The cage culture opens a new way of easy exploitation of natural water body or marine water as well as fresh waters.

Shape, Size and density of Cages: Cages are of varying shape and sizes according to the need. It may be circular, rectangular or square etc. Cages for research purpose is not more than 1m3 in volume and may contain several hundred organisms with 500gm at the time of harvest.

Large cages of marine or fresh water farms are of 3.6×3.6×2.4m3 to 7.2×7.2×2.4m3 deep. For growing market sizes the cages are measured from 35 to 100m2 in area with 3.6m of depth.

The cages should be placed in that place where water freely flows through the cages.

Materials Used for Cage Culture - The traditional cages are made up with bamboo screen. Modern cages are made with metals, rubber, fibre glass, plastic coated metal wire with a mesh size of 1.3 – 2.5cm2. Plastic coated wire can be attached to a steel frame to produce cages that can lasts for several years. Cages must have good buoyancy and installed in water by floats and sinkers. The netting materials should be hard enough to with stand the attack of marine predators.

Fish Culture – The following fishes are cultured in cages

Yellow tail (Japan)
Carps (Indonesia)
Trout (USA)
Eels (USA)
Puffer (Japan)
Red Porgy (Japan)

Production: Cages of 1.2m deep×2.4m wide×2.4m long can support 1800 – 2000kg of fish when stoked with 350 – 505fish/m­3. Although the density of fish in per unit volume is high (248-276kh/m3).

Advantages of cage Culture:

The management cost in cage culture is low
High densities of stocking can be possible
Relatively simple and cheap technique
Plenty of natural food is available in natural water so need of supplementary food is less
Fishes can be reared in natural environment, but the cultured organisms can not escape
Cages provide well protection of fry and fingerling stages with plenty of water flow
Harvesting is simple and easy
Free from the attack of predators
The growth of the fish is much higher

Problems in Culture:

The construction of cages and initial investment to make a such type of farms are quite high
The netting materials of the cages have to be periodically changed due to the damage by predator attacks or fouling organisms
Some organisms tend to attach with the cages which are not economical but they obstruct the easy flow of water inside the cages and cause further damage due to the pathogens carried by them
Theft or loss of cages due to the extreme environmental conditions in the sea
Pollute the water bodies used by human beings

Pen Culture

Pen is someway can be considered as transitional structures between pond and cages as so far as environmental and stock control are concerned. Some times large cages of 200m3 are called pen. For some farmers the word pen means only those cages with no top netting. Generally the bottoms of the pens are fixed into the ground of water bodies. Pens were first used in culture of milk fish Philippines.

Site Selection for Pen Culture: For pen culture, site selection is necessary for sustainable production of fish. The design of pens may depend upon the characteristics of water bodies. The water bodies for pens may be categorized by two ways –

Category – I: Narrow rivers irrigation canals – ox-bow lakes: A part of this type of pen can be divided by a number of connective sections by erecting portion of fencing across the narrow water bodies. Thus one or several pens are arranged in a series.

Category – II: The Shallow Reservoirs Margins or Tanks: In this type pens are four walled. This may be constructed according to the depth of the water bodies.

Shape, size and design of the pens:-

On the basis of the pen culture it may be circular, square, and rectangular in shape for depending upon the harvesting.

The size of pens depends upon the number of physical factors such as location, water depth and biotic parameters. Large cages of 200m3 or above may construct for pen culture. The height of the pens depends upon the water level during entire culture periods. The height also depends upon the jumping behaviour of cultured species. The height of pen may be at least 50cm. But about 30cm of the cages are fixed into the bottom to keep the pen wall secured.

Materials Used for Pens:

Screen – The screen materials used for pen should be
Small meshed to prevent the escape of fry and fingerlings
Resistant to long exposure in sun and water
Steady enough to resist current, wind action and wave action
Resists the attack of crabs and other animals
Cheap and easily available, easy to handle

The screens are usually made of split bamboo mats in eastern countries. Metal or metal coated with resin, nylon or HDPE, even rubber are used in western countries and Japan.

Supporting Structures – Matured and well seasoned bamboo are generally used as supporting materials, relatively in shallow waters. Other supporting materials like floats and heavy sinkers like stones are used as supporting materials.

Types of Pens:

Bamboo Screen Pens – This is the simplest type of pen made with fixed bamboo poles in the bottom soil of water bodies, surrounded with fine meshed netting materials. Bamboo screen fencing is suitable in narrow and shallow rivers, flooded fields and other very shallow water bodies.

Monofilament Cloth Fencing Pens – This type of pens are surrounded by monofilament netting material with required size. The screen wall is arranged just like a fry net.

Production: The pen culture is experimentally conducted in kalli backwaters. The net production is about 250kg/ha/year of Penaeus monodon. Similar experiment is also done in Chilka Lake with average production in three months – 100kg/ha with 50% survivality. In kakinada calm waters pen culture is conducted in submerged condition @ 100 individuals/m2 with monthly yield of 385kg/ha (survival rate – 88%). Pens are also used in nursery pond production of carp seeds. In Howrah and South 24 Parganas the culture of ornamental fish is done in pen constructed in pond or in irrigational canal. Fry stages to grow out are sometimes cultured in that manner. Some report says that experimental culture of catla, mrigal and rohu with 3:1:4 ratios may yield upto 4t/ha/6 months. How ever main advantages of that type of culture is that the fish can be cultured in natural environment of river streams or irrigation canal without any supplementary food or little supplementary food.

Brood Fish Maintenance

Culture of brood fish or care of brood fish which is called brood fish management is the essential factor or key factor for successful artificial induced breeding. The benefits of brood stock management are the availability of brooders in proper condition during the breeding season. For this the healthy stock of brood fish is specially taken care in well managed ponds for proper sexual development.

Selection of Brood fish Pond:

The size of brood fish ponds may vary from 0.5-1.0ha and with depth of 1.5m-2.0m preferably rectangular shaped ponds with uniform slope. The bottom of the pond should be compact and flat with clay-loam soil with bottom silt not exceeding 10-15cm. The pond should be with controlled pipe system for complete drainage system with proper inlet and outlet facilities. Flashing system of pond is required to provide riverine condition. The pond should be well protected with flood and draught and its should be in such condition to get sufficient wind and exposure of bright day lights for at least 6-8 hrs a day for at least 2-3 months (January-February onwards) (Nataranjan, 1984). The temperature should be moderate with 27°C - 32°C, to optimise the gonad development.

Selection of Brood Fish:

Healthy disease free breeders of Catla catla, Labeo rohita, Cirrhinus mrigala with some exotic carps of 2-4yrs of age with 1-5kg of weight are normally selected.

Sources of Brood Fish:

The brood fish are selected from different river systems, to avoid inbred species. Brooders can also be selected from selective breeding process. The better brood fish can also be selected from different farms or different lakes or reservoirs. To prevent inbreeding in a hatchery, it is necessary that fresh fish germplasm from natural sources are introduced regularly with timed periodicities. If it is not done, inbreeding depression may set in, which is apprehended to have occurred in some existing aquaculture system in India.

Stocking of Brood fish

Stocking of fish is done @ 1000-3000kg/ha with species composition of 4:3:3. That is surface feeders catla – 30 to 20 and silver carp 10 to 20, depending upon the concentration of phytoplankton. The column feeder i.e. rohu 20 and grass carp 10 with bottom feeder i.e. mrigal 20 & common carp 10. The species ratio appears to be quite proportionate in Indian tropical environment since the different niches of water bodies are fully exploited. Brood fish can be stocked in following ways also,

· Sex-wise segregation of all six species individually or sex wise stocking in individual brood fish ponds; this system will require 12 brood fish ponds.
· Segregation in following way i.e. common carps in 2 ponds, catla in 2 ponds, and others in 2 ponds needs 6 ponds.
· Segregation of catla in 2 ponds and others in 2 ponds can be done also, if the numbers of ponds are not sufficient.
The reason why catla is especially sought to be separated from rest of the species, if sufficient numbers of brood fish ponds are available, is that relatively the species shows considerable frigidity to hormonal injection due to ill understood reasons and it is believed that catla spawners need special diet such that deposition of mesenteries fat in the maturation phase dose not hinder gonad development of the species.

Fertilisation of Pond:

Initial manuring of brood fish pond is done by 3 weeks prior to stocking with cattle dung @ 20,000kg/ha or compost manure prepared from land/aquatic weeds and farm animal droppings at the ratio of 1:1 with 5% quick lime @10,000kg/ha. A prophylactic quicklime treatment @ 200kg/ha given in the pond 7 days before of manuring. Monthly dose with raw cow dung @ 2000kg/ha are given also.

Constant manuring and using heavy supplementary feed may cause repressive factor (Swingle, 1956) and this might inhibit the maturation to the point of ovulation and spawning of fishes in the captivity. Frequent changes of water (monthly, fortnightly or weekly) can reduce the chances of accumulation of metabolic wastes. Fresh ground water/canal water/rain water at the volume of 1/4th or 1/8th of the total volume of water in each operation. Sudden lowering of temperature are beneficial for maintain good health of breeders and development of this gonads.

Others Management:

Regular netting should be done to increase the D.O level in the pond water. Regular netting is helpful to exercising the fish in the pond water also. It removes the harmful gases from the pond bottom also.

Supplementary Feeding:

Supplementary food is given to the breeders with well balanced food at a fixed schedule until the water blooms appeared, when the feeding is stopped. The feeding is resumed after disappearance of the bloom.

Composition of Feeds:

· The semi-composite mixture – prepared from half-cooked rice and pulses (1:1, 50%)
· Oil cakes – 20%
· Cattle dung – 20%
· Fish Meal or Silk worm pupae
· Cooked slaughter house refuses – 10%

The food should be given in sunny days, and stopped in cloudy days. Supplementary foods with vegetative matter such as Hydrilla, Vallisneria, Najas, Utricularia, and soft young leaves of other plants are given some times as food for better results. The grass carps are always fed with vegetative matter. Thick planktons – Spirulina, Oscillatoria and Chlorella are cultured and given to the pond for silver carp. The feeding rates should be lowered with the maturity of gonads. Feeding should be stopped before a week of breeding.

Inducement:

To accelerate the gonado-somatic development, HCG (activity 30 IU/mg powder; dilution of the prepared solution 10mg/ml distilled water is administered to catla and grass carp spawners at 5mg/kg body weight at one month intervals during last week of December, January & February. Rohu & Mrigal are dealt with two doses of HCG at 4mg/kg of body weight in the last week of December and first week of February. Silver carps do not any maturation dose. The HCG administered fishes are found to attain maturity relatively faster than the non injected fishes. A fairly good percentage of brood stock achieved full maturity between last week of February & middle of March, when their first breeding can start.

Some Important Steps:

1. If the fishes appear to surface, due to depletion of oxygen, application of manure and supplementary feed should be stopped.
2. To add fresh water to the pond
3. To agitate the pond water
4. Small pieces of banana plants to scattered in the pond
5. To carry out repeated netting in the pond
6. To apply common salt @ 30-40kg/ha
7. If the snails are coming out of the pond during day time signifies that their would be severe oxygen depletion at night.

Induced Breeding

Induced breeding is a technique whereby ripe fish breeders are stimulated by pituitary hormone or any other synthetic hormone introduction to breed in captive condition. The stimulation promotes timely release of sperms and eggs.

History of Induced breeding: The technique of induced breeding was first evolved in Argentina after producing pituitary extract by Houssay 1930 where viviparous fish was injected with the hormone to make premature birth. In the year of 1934, Brazilians were succeeded in induced breeding by pituitary extract. This technique was also followed in America (Merlin & Hubs) and in Russia (Gerebilisky). In India first attempt of induced breeding was made by Khan in 1937 on Cirrhinus mrigala. Later in 1955 Dr. Hiralal Choudhuri applied this technique in minor carps (Esomus danricus, Pseudeotropius atherinoides). Ramaswamy and Sunderaraj first induced to breed Clarias batrachus & Heteropneustes fossilis. The first successful induced breeding on major carps was done by Dr. Hiralal Choudhuri 1957– Cirrhinus mrigala, C. reba, & Labeo rohita. Parameswaran & Alikuni successfully bred the exotic Chinese carps – Hypophthalmichthys molitrix & Ctenopharyngodon idella in 1963.

Why Fish does not breed in Captivity??

Many cultural farm fishes like IMC do not breed in captivity. The reason may be environmental and consequently hormonal. Certain environmental parameters like photoperiods, rain, temperature, current of water influence the hormonal activity from pituitary and gonads. Disturbances arise in environment may cause the insufficient release of hormones in captive conditions and thus, the fish does not breed in captivity.

Other factors like poor foods or insufficient natural foods, exposure to biocides and other pollutants badly affect the maturation of ovary.

Why induced breeding is necessary??

The technique of induced breeding gives very promising result in fishery point of view due to –
· It gives pure spawn of certain species of fishes under cultivation. Spawn collected from natural water is not pure as because some undesirable wild species may come with them in culture pond. Sorting of pure seed is quite impossible in those stages. In later stages it is possible, but time consuming.
· It assures timely available of pure seed, where as in nature the availability of seed is quite uncertain.
· It can fulfill any quantity of demand in any time.
· It also cuts short the holding potential spawners over long periods in uncertain hope of their breeding in time. Many carps take their full maturity in confined water but do not breed.
· The technique is very simple and does not need too much technical assistance or knowledge. It can be easily learnt by a layman without much training.
· The cost of expenditure is very low than the natural collections of spawns.

Technique of Induced breeding:

Preparation of Pituitary Extract – For preparation of gland extract the glands are removed carefully from freshly killed fish called donor fish. For best result the donor fish should be fully ripe and mature. Common carp is the best donor fish, because it breeds through out the year and the individuals are available in all parts of the world. The pituitary glands of such species are relatively large. The gland should be collected prior to spawning. However the gland doesn’t show species specificity and any carp species can be used as donor. However the glands of relative or closely related species show best result.

Removal of Glands –

The removal of glands can be done by following two processes:

Removal through foramen magnum – the foramen magnum was first exposed by removing vertebral parts adhering to skull. Fat is removed first by means of forceps and then cotton piece. A pair of forceps then inserted into foramen magnum dorsally to the brain and anterior part of the brain now detached and remaining is carefully lifted out through the foramen magnum. The gland is then located and removed.
Removal of gland by dissecting head – This technique is not used commercially as because the heads are damaged by this process. The first method of removal is less time consuming and economical as the heads are used for human consumptions later. At first the head is dissected using sharp butcher’s knife, a portion of scalp is chopped off in a clean cut with one stroke. Fat surrounding the brain is removed with the help of cotton. Olfactory and optic nerves are now severed, and then brain is lifted up and removed. Locate the gland. The gland may come up along with the brain or may remain behind on the floor of brain cavity often covered with a membrane. In any case the gland is carefully removed after separating it from membrane or the brain proper. The gland must not be damaged or torn.

Preservation of Glands:

The gland after removal needs to be preserved for certain periods or for future use. The glands are taken in absolute alcohol and can be stored in room temperature. In certain countries like Russia the glands are preserved in acetone at 10°C. The glad may be preserved in refrigerator immediately for certain periods. But alcohol preservation of glands is very common and easy methods. It is widely used in India. Glycerin preservation is another technique but less popular in our country.

Preparation of Pituitary Extract:

The preserved glands of known quantity are taken out and macerated in a homogenizer after evaporation of alcohol with little amount of distilled water. Then the extract is freed of suspended particles by means of centrifugation. It is the diluted with required amount of distilled water or 0.3% saline water or a suitable physiological solution. The extract is now ready for use.

Preservation of Extract:

The extract can also be preserved for future use. In this process in place of saline water glycerine is used and extract can be preserved in room temperature or in refrigerator. Other methods of preservation are done by propane and trichloro-acetic acid in place of glycerine.

Selection of Brooders:

Proper selection of are the key of success in case of induced breeding. The breeders should be healthy, fully ripe and of medium sized. They should preferably come into the age group ranging from 2 – 4yrs and have the weight of 1 – 5kgs. Large sized breeders are avoided for difficulty in handling. For ripe male and female carps, it can be easily identified. The male shows roughness on pectoral fins when belly pressed milt freely oozes out. The ripe female shows relatively smooth pectoral fins and operculum. The eggs are released when the belly is pressed smoothly in female. The belly of ripe female is generally soft and round or budged. The vent is swollen, protruding and pinkish in colour. It is wiser to practice to keep ready adequate stock of potential brooders. For this a few months before breeding season potential breeders are kept away under care, and fed on supplementary feed (rice bran and oil cake mixture).

Injection to the breeders:

The pituitary extract is administered into the body of breeders by means of hypodermic syringe either intra muscular or intra peritoneal. To ensure a higher percentage of fertilisation during induced spawning it is necessary that there is synchronisation between ovulation and milt shading. This difficult to achieve with a set of breeders having one male and one female. Therefore the common practice is to use a set consisting of one female and two males.

Determination of correct dosage of pituitary extract to be given to the breeders is very important though a difficult matter. Dosage depends upon the size and state of maturity of the recipient (breeders) as well as upon the state of maturity of the donor for the glands. It has been found that the potency of the gland is influenced by the size, the age, the sex, the state of sexual maturity of the donor fish as also the size of the gland itself. Great difficulty is encountered because it is not easy matter to ascertain the state of maturity of fish from external examination. Usually the female is given a preliminary dose of 2-3mg/kg of body wt. The preliminary dose is not given to the male. After an interval of time about 6hrs a second dose of 5 – 8mg are given per kg of body wt of female. The male was given then the first dose of injection with female @ 2-3mg/kg of body wt. The dose may be depending upon the maturity of fish, age, sex and also the environmental conditions.

For intra muscular injection the fish is laid on its side while held in hand net and the needle is inserted either in the caudal peduncle or in the shoulder. For intra peritoneal the injections are given in the bases of paired pectoral fins. But it is avoided because less expert hand can puncture heard of the fish.

Spawning:

After injection to the brooders a set of brooders are released into breeding hapa. In hapa breeding the hapa is the fine netting, rectangular in shape and is held by four bamboo poles one at each corner. Closed meshed mosquito netting is preferred for that purpose, as its meshes will allow a good circulation of water and will also not let the laid eggs and milt escape through the meshes. The hapa measures the range of 3m × 1.5m × 1m for breeders weighing to 3 to 5kgs. The height of the hapa should remain about 20cm above to the level of water. The roof can be open or closed. The roof can be opened or closed.

The spawning takes place with in 3-6hrs following the second dose. It turns out the midnight if the second injection was given in the evening. Successful induced breeding results in the spawn of fertilised eggs. The fertilised eggs are transparent, pearl like where as unfertilised eggs are opaque or whitish.

Factors influencing the breeding:

Climate - 24°C to 31°C with cloudy days and rainy periods. Light drizzling following heavy rains is ideal. In absence of rain artificial showers are used.
Water – Flowing water is preferred.
Turbidity – 100ppm 1000ppm.
Light – It is known to bring that light may help in early maturation and spawning of fish.

Linpe Method of Induced Breeding

Working together, Canadian and Chinese researchers have now developed a fish breeding method that increases the efficiency of aquaculture production. Injecting a GnRHa followed by (or in combination with) a dopamine antagonist has been called the Linpe method, after Lin, Hao-Ren; Peter, R.E. 1988, the researchers who started it. Most of the work resulting in the Linpe method was done on cyprinids, and there is convincing evidence for these fish that the method is effective where injection of GnRH alone is not. Linpe method — induces ovulation in female fish by injecting them with a combination of a synthetic gonadotropin-releasing hormone analogue (LHRN-A) and the drug domperidone. The hormone stimulates the sex organs of the fish, while the drug inhibits the action of dopamine, a substance produced by the fish that inhibits ovulation.

With traditional fish spawning methods, carp, for example, are raised and killed to produce a pituitary extract used to induce spawning. Many fish are sacrificed in the process and the extract has a poor shelf life. The technique also requires that fish are injected at two separate intervals to induce ovulation.

The new method reduces the cost of production, increases the supply of seed fish, and is more convenient. Rates of spawning, fertilization, hatching, and survival were significantly higher in research trials than could be achieved with pituitary injections. The hormone and drug can be introduced together, which means that brood fish stocks are handled only once, reducing the risk of disease or damage to the fish. This method does not alter the reproductive cycle of the fish, and the fertility and viability of offspring are normal. The solution does not require refrigeration and has a long shelf life. It has been tested on a wide range of fresh, salt, and brackish water species, including carp, bream, salmon, catfish, loach, and others.

It is tempting to generalize about the superiority of the Linpe method for all cultured fish, but because comparative experiments under field conditions - GnRHa-domperidone versus GnRHa alone - have only been done for carps; it is still too early to do this. Some researchers have tried to put fish in categories that reflect the strength of dopamine inhibition, ranging from cyprinids (strong dopamine effect) to salmonids (weak dopamine effect). The danger of making this kind of list relates to what we have already said about differences in the effect of GnRH itself: factors such as the general readiness of the fish can outweigh any advantage or disadvantage of a particular treatment.

The commonly voiced view that marine fish do not require domperidone along with GnRHa requires more proof; in milkfish and mullet, for example, two of the most important warm-water marine species, there are no published reports of its having even been tried. Until use of the Linpe method is more widespread, we will avoid such lists. In species that become fully sexually mature in captivity and respond to GnRHa readily - many salmonids fall into this category - a dopamine antagonist is not needed. In other species - the best evidence is still from cyprinids - even though they will spawn with GnRHa alone, delay to ovulation is shorter and more predictable when domperidone is added. Administering the two drugs is easy, with a single injection of a mixture being as effective as two separate injections. This has led to the manufacture of a commercial GnRHa-domperidone spawning~kit" that combines the two in a single solution (Ovaprim-C@). Enterprising fish farmers can of course always opt, as in Thailand, to buy GnRHa and domperidone as over-thecounter pharmaceuticals, and reconstitute them for injection into fish.

According to Dr. Lin Hao-Ran of China's Zhongshan University, the Linpe method has become "...more and more popular in Chinese fish farms and has replaced the traditional fish spawning methods in recent years". Dr. Lin has established a commercial operation to sell the active compound in China through the Ningbo Hormonal Products Factory in Ningbo City.

Commercialization was identified as a specific objective in Phase II of the research project. In addition, Syndel International Inc. has submitted an application (pending) to register Ovaprim at the regulatory agency in China, after running clinical trials in Wuxi, Beijing, and Harbin in 1994.

Linpe method (domperidone/sGnRH-A) of induced spawning of cultured freshwater fish are used in many countries, for leading to commercialization of the method; to determine the effectiveness of sGnRH-A and domperidone in induced ovulation and spawning of marine teleosts; to determine the effects of aging on reproductive function of key species in the Chinese freshwater polyculture system; to determine means of increasing growth rates of cultured fish and; to continue the training of young Chinese scientists in relevant disciplines.

Doses of GnRH and domperidone

Although there will never be a standard method for spawning all species, culturists working with a single species can standardize methods by systematically eliminating sources of variability and using the lowest effective dose. Effective doses of GnRHa and domperidone vary widely and are not comparable because of differences in species, temperature, state of maturity, and GnRHa. The trend is toward single injections and, although GnRHa doses between 1 and 100 ~g/kg have been effective, culturists should aim for the 5-20 ,~g/kg range. Domperidone is usually effective at doses of 1-5 mg/kg.

To facilitate economical use of GnRHa, without the need for tedious weighing of tiny amounts, it is best to buy preweighed small amounts of the hormone (e.g., 0.5 or 1 mg aliquots) and prepare a concentrated stock solution (e.g., 1 mg/mL) in sterile water in the original container. Appropriate amounts of a more dilute solution in 0.7% NaC1 can then be prepared at the time of injection. GnRHa is most stable as a dry powder, but the sterile stock solution can also be kept for several months if frozen.

Domperidone and pimozide are not readily soluble in water and are sensitive to oxidation. They are best used as a suspension in 0.7% NaC1 containing 0.1% metabisulphate as antioxidant, or can be dissolved (and injected) in propylene glycol. Commercially available domperidone tablets for humans (Motilium0) have been powdered, dissolved in propylene glycol, and used uccessfully in induced reproduction of fish (Fermin 1991).

Multiple Breeding

Carp seed production is no more confined to monsoon months. Now a days carps have been domesticated to breed much ahead of monsoon and months beyond the monsoon, ensuring the seed during pre and post monsoon periods. Such availability of carp seeds promises success in intensive carp culture practices. It also can compensate the loss of seed due to the natural calamities like flood and draught etc. surprisingly the brood involved in pre-monsoon are not different individuals but one and the same as professional brood.

Pre-monsoon Breeding: Success in Pre-monsoon breeding depends on a precocious gonad maturity. This can be achieved by simple brood stock management practices. Pre monsoon breeding commences as early as March. The yield is 0.5 – 0.6 lakh spawn/kg body weight of fish. Second spawning of same fish is achieved with in a time interval of 40 – 45 days. The production rate increases to 1.0 – 1.5 lakh spawn/kg body weight. Both the spawning are completed between March & May.

Monsoon Spawning: A time lapse of another 40-45 days following the second spawning brings the 3rd crop (June-July). During this period climatic conditions are more favorable than any other breeding period and they yield further increases to 1.5 – 2.0 lakh spawn/kg of body weight.

Late Monsoon Spawning: Quality of mature eggs can not be maintained in situ for indefinite period. Therefore, monsoon dependant traditional broods are not useful for late monsoon breeding. This is possible only to spawn when the same fish repeatedly with an optimum time interval between two successive spawning. The fish has already spawned two or three times in a seasons expected to come for late monsoon breeding i.e. between August & September. However, the yield of spawn declines when compared to monsoon breeding.

Principle of Multiple Spawning: Multiple spawning is the timely harvesting of mature gametes repeatedly by more than two spawning. The fishes are bred by adopting routine hypophysation technique. Major carps have been bred as many as four times between March and September. Brood recovery I to II and II to III within the stipulated period (March – August) is observed almost 100%. Further re-maturation rate declines 30 – 50% which may need some more management manipulation for the purpose.

Brood Stock Management and Multiple Breeding:

Gupta et al (1990) reported advancing maturity spawning of Asiatic Carps during April & May through brood stock management. Futher maturity could be preponed by following improved management practices for which spent brooders of proceeding breeding season are preferred as the initial stock for the programme. However the age of the fish should be 2 to 3+ years stocked at 1000kg/ha. They are fed on formulated protein rich feed fortified with vitamins and minerals at 1-2% of their body weight. As water replenishment has a considerable impact on gonadal maturity of fish, it should be done twice a month preferably with fresh canal/reservoir water from February to May. Other management practices are of routine nature. Such managed brooders show precocious gonadal maturity at least three months earlier than monsoon dependant in the locality.

Breeding Status of Multiple Spawners:

Type of brood raised for such multiple spawning is termed as professional brood. These broods certainly spawn early and show better breeding response as compared to brood maintained for monsoon dependant traditional breeding. The brood 4 – 5+­­ years of age show consistent yield of spawn. Therefore, it is essential that the overage fish should be excluded from the multiple broods, rearing programme. Further, to build up a stock of professional brood is a continuous process for successive multiple spawning programme.

Care of Multiple Breeding:

Spent brood monitoring programme is an important aspect better survival and recovery of the spent brood, most care is suggested at every stage for handling as follows.

· The brood should be transported in the canvas bags along with water
· Hormone administration should preferably be intraperitoneal which reduces the stress of injection.
· Stress should be minimized in spawning pool by providing required flow and duration of water supply in the pool for spawning.
· Spent brooders should be removed from spawning pool as soon as breeding operation is over.
· Spent brooders should be treated at regular intervals with potassium permanganate solution (5 ppm). This keeps a check on secondary infection and also quickens recovery from spawning stress.
· Feeding and other management practices should be followed meticulously for subsequent maturity.

Larval care:

The performance & Survival of spawn produced through multiple breeding are comparable to that of traditional seed. However, spawn produced through multiple breeding need special care as the yolk gets absorbed within 60 hrs of fertilization. So food is essential after 60 hrs of fertilization. The food may be micro-plankton or particulate materials suspension.

Conclusion:

It is possible to produce seed during pre-monsoon, monsoon and late monsoon in a calendar year. A cumulative yield of spawn per kg body weight of fish is enhanced to 3 – 4 folds than single breeding. Further cost of seed production is reduced. It also provides opportunity for multiple cropping in aquaculture practices.

Bundh Breeding

Alikunhi et al (1960) stated that “Bundhs are specialized ponds where the condition of reverine flow are created by constructing embankments against the large catchment area, subjected to rapid flooding during monsoon” Bundh are special type of perennial and seasonal pond or impoundments where reverine conditions are simulated during monsoon months. The bundh after heavy rain, receive large quantities of rain water, washing from their extensive catchment and provide large shallow marginal areas which become the spawning ground for carps. Bundh-breeding, this is prevalent only in the States of Madhya Pradesh and West Bengal, accounted for 5.38% of the total fish seed production in the country. It is however, reported that wet bundhs are existent in certain parts of Andhra Pradesh, Uttar Pradesh and Bihar, wherein breeding of major carps reportedly takes place; but no definite information as to their occurrence and magnitude is available with the concerned State Governments.

Bundhs are Two Types:

1) Perennial Bundh – Wet Bundh
2) Seasonal Bundh – Dry Bundh

1. Perennial Bundh – Wet Bundh: A wet type of bundh is a kind of small or large perennial pond or tank, from a few acres to over a square mile, in the midst of a low-lying and bounded on three sides by high embankments. In summer, generally a quarter parts of most of these bundhs dries up and is cultivated, with the central part, deeper than the surrounding area, always contains some water and harbors mature fish

Many large irrigation tanks having rich coverage of forests wood/fields in the catchment can also serve as good wet bundh. After heavy monsoon shower, freshwater with washing form the upland areas rushes in the bundh and the major portion of the tank or reservoir may even overflow, the excess water being drained out through the outlet known as “bundhs”. The outlet is protected by bamboo fencing known as “Chhera”. The shallow gradual slopping is know as “Moans” in W.B. are the main spawning ground. As soon as the monsoon starts, with first and second heavy shower the wet bundh gets inundated, particularly the gradual slopping area with run off water. It stimulates the fishes in the bundh and they migrate to the shallow marginal area, start breeding in suitable ground.

2. Dry Bundh: A dry bundh has been described as a shallow depression enclosed by an earthen wall (locally known as bundh) on three sides, which impounds fresh rain water from the catchment area during the monsoon season. Such impoundments, which remain more or less dry during a greater part of the year, are known as dry bundhs.

The topography of the land has a great role to play in the location and distribution of dry-bundhs. The undulated land, which provides a large catchment area and facilities for quick filling of the bundhs even with a short rain and at the same time quick and easy drainage due to gravitation, in the Midnapore and Bankura districts of West Bengal has specially favoured the construction of large number of such bundhs in the private sectors. In Madhya Pradesh, dry bundhs are mainly distributed around Nowgang in Chhatrapur district, where topography of the land and the soil type are almost similar to that in the two districts of West Bengal referred to above.

Spawning in both wet and dry bundh usually occurs after continuous heavy showers for days, which large quantity of rain water rush into the bundh. The technique adopted for dry bundh breeding from time to time in different areas may be broadly classified in two stages which are presented bellow.

First Stage: - In this stage after accumulation of sufficient rain water brooders were transferred from some other perennial ponds, generally during rainy days, in Bundh. No importance is to be given to the brooders related to maturity and sex ratio. By inlet & outlet flow of water created & this breeding is observed within 3-4 days. After total dewatering the eggs are collected. In single season three operations can be done.

Second Stage: - The technique adopted in this stage is much improved as it was done by better understanding of sex ratio, size and no. of brooders. Fully ripe male and female (1:2 in number & 1:1 in weight) are introduced with accumulated rain water in rainy days, with injecting 2-3 sets (sympathetic breeding). Successive spawning could also be achieved as five times in one times in one seasons (Dubey 1969).

Synthetic Hormones Used in Induced Breeding

Human Chorionic Gonadotropin (HCG):

Human Chorionic Gonadotropin (HCG) is a glycoprotein hormone produced by the placenta in pregnant women. During early pregnancy the hormone appears in the urine in large quantities. When it is injected to the mature fish, the hormone is known to cause the release of gametes. It is thought that the action of releasing gametes is due to the joint action of pituitary glands hormone and HCG. Generally when HCG is injected singly it does not give good result. So it is injected with pituitary gland extract.

In India the use of HCG was started late in 1980s. Both Indian and Chinese carps show good result.

HCG is cheap compare to pituitary extract and has long shelf life. The product is grinded in distilled water (2mg in 0.2ml) and centrifuged. The supernatant is used as injection. The first injection is given to female followed by second dose of injection in both male and female. In second dose the mixture of HCG and pituitary is used. The dose is weight dependent.

Other New Generation Drugs:

A number of new generation drugs are also be used in place of pituitary gland extract. These are very efficient even in lower doses also and cheaply available. Some important drugs are –

Ovaprim (Salmon Gonadotropin): “Ovaprim” is a very efficient drug in place of pituitary extract produced by salmon Gonadotropin RH and Domperidon. It is available in India after 1988 and extensively used. In India good result is shown in West Bengal, Madhya Pradesh, Andhra Pradesh, Karnataka, Kerala, Orissa, and Maharashtra. This hormone is given in very low quantity to the IMC which gives best result. The results suggest that intervention of “Ovaprim” holds considerable promise in future. It is the product of Syndal Lab. Ltd. Canada, distributed in India by Glaxo India Ltd. Mumbai.

Pimozide: It is a dopamine antagonist having ovulatory role of LH-RH- A. It is quite effective in IMC. The LH-RH (Luteinising Hormone – Releasing Hormone) and its analogue LH-RH- A are very effective on brackish water fish – Mugil and Lates. They are cheap but the hormones are short lived.

DOC A: (II-Desoxycorticosterone-acetate) is another very effective drug which has been tried in cat fishes – Clarias & Heteropneustes. They not only help in ovulation but also in maturation of eggs. However, the commercial importance is low due to the high cost.

Anti oestrogen tamoxifen (anti androgen): This hormone gives promising result in Coho-salmon especially when it is administered with pituitary extract. This anti androgen can bring early ovulation. Still the hormone is in experimental result.