Tilapia Seed Production

8/14/2019 Tilapia Seed Production

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Training Course on Tilapia Seed Production

Held at the

Mon Repos Freshwater Aquaculture Demonstration Farm and Training Centre,

Agriculture Road,

Mon Repos, East Coast Demerara

May 30th

to June 3rd

2005

Prepared by:

Tejnarine S. Geer,Senior Fisheries Officer,Aquaculture and Inland FisheriesDepartment of Fisheries

Kamila Singh,Limnologist/Hydrochemist,Department of Fisheries


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Contents

I. Preliminaries 3II. Introduction 6III. The Importance of Tilapia in World Aquaculture 7IV.

Site Selection 9V. The Aquatic Environment 10

VI. Fertilizing and Development of Natural Food Organisms 20VII. Biology of Tilapia 23VIII. Selection and Handling of Broodstock 26IX. Seed Production: Semi Intensive 28X. Seed Production: Intensive 34XI. Transferring and Stocking of Fry and Fingerlings 39XII. Feeds and Feeding 46XIII. Fish Health and Disease 52XIV. Record Keeping 57XV.

Tilapia Grow-Out 58XVI. Outline of Practicals 61

XVII. References 62


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I. Preliminariesa. Aims of the Course

This training course on tilapia seed production is being conducted as part of the FAOProject TCP/RLA/3003: The introduction of aquaculture and other integrated production

management practices to rice farmers. This project involves the introduction ofaquaculture (initially tilapia) into rice fields, as an integral component if integrated pestmanagement.

This course therefore aims to offer technical training on tilapia seed production to riceextension personnel, so as to enable them to better support the project activities, and tosupport the introduction of aquaculture into rice farming systems, beyond the duration ofthe project.

b.

Objectives to be AchievedThis training course is designed to achieve the following objectives:- To expose participants to the general concepts relating to aquaculture, such as

water quality, feeding and fertilizing

- To expose participants to tilapia seed production techniques, both semi-intensiveand intensive, and to aquaculture of tilapia in general

- To give participants the opportunity to develop hands-on, practical skills relatingto tilapia seed production and tilapia aquaculture in general

c. Strategy for DeliveryThis course is designed to be implemented over five days, in 30 hours. The training willbe conducted utilizing a comprehensive approach, including:

- theoretical lectures 30% of the allocated time- laboratory sessions, videos and

photographic displays, demonstration activities andfield practice 70% of the allocated time


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d. Capacity of the Mon Repos StationThe Mon Repos Freshwater Aquaculture Demonstration Farm and Training Centre wasconstructed by means of a collaboration among the Government of Guyana, the Food andAgriculture Organisation of the United Nations (FAO) and the Canadian InternationalDevelopment Agency (CIDA).

Phase 1 of the facility was commissioned on July 13th 2001. Since then, the facility hasgrown steadily, and now contains the following:

- One Laboratory/Office Building- Ten (10) Concrete Ponds- Eight (8) Earthen Ponds- Spawning Tank

The objectives of the Mon Repos facility are as follows:- To provide training to farmers so as to enable them to practice

scientific, sustainable aquaculture

-

To provide high quality seedstock and broodstock to farmers,to enable them to attain high yields- To perform adaptive research, and to provide the information

to farmers, so as to improve the productivity of the sector

The station regularly offers training courses on aquaculture. These courses are designedto impart to participants the basic, essential elements so as to enable them to practicescientific, sustainable aquaculture. Participants are exposed to theoretical knowledge, aswell as practical exercises, such as pond preparation, fertiliser application, identificationof male and female fish, calculation of cost of production and profit and preparation ofproject proposals.

An important part of the training courses involves the presentation to participants, on anongoing basis, data obtained from research conducted at the facility. In this way, personsare able to benefit from recent local research in aquaculture.

The Mon Repos facility produces fingerlings and broodstock of Red Tilapia, Nile Tilapiaand Hassar, for sale to farmers, to enable them to commence aquaculture activities.

Research is required to generate basic information, which can then be used to evaluatethe economics of aquaculture, using particular species and different inputs. When theinformation is provided to farmers in the correct form, decisions can then be made onimportant issues, such as what species to rear, how much to stock, what type of feed touse, and what growing period is required.

Consequently, the Mon Repos facility is engaged in a continuous research programme.The species presently focused on are Jamaican Red Tilapia, Freshwater Prawn( Macrobrachium rosenbergii), Hassar ( Hoplosternum littorale) and Freshwater Pacu(Colossoma macropomum).


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These species been carefully selected, to suit various water parameters, managementneeds and marketing possibilities.

Fingerlings and broodstock of Red Tilapia, Nile Tilapia and Hassar are produced by thestation, and are available for sale to farmers, to enable them to commence aquaculture

activities.


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II. Introduction 15 Minutesa. Definition

Aquaculture is defined by the FAO as The farming of aquatic organisms including fish,mollusks, crustaceans and aquatic plants. Farming implies some sort of intervention in

the rearing process to enhance production, such as regular stocking, feeding, protection

from predators, etc. Farming also implies individual or corporate ownership of the stockbeing cultivated.

Aquaculture is therefore different from capture fisheries, since:For statistical purposes, aquatic organisms which are harvested by an individual or

corporate body which has owned them throughout their rearing period contribute to

aquaculture, while aquatic organisms which are exploited by the public as a common

property resource, with or without appropriate licenses, are the harvest of fisheries.

While the earliest records of aquaculture can be found in the ancient Chinese, Japaneseand Egyptian cultures, dating back several thousand years, until quite recently,

aquaculture was not adopted as a means of commercial food production. However, withworld population increasing at a rapid rate, there has been an increased demand foranimal protein. This has in turn created a strain on marine and inland capture fisheries,and has resulted in the collapse of valuable fisheries around the world.

Because of this situation, aquaculture production has been increasing, and is nowregarded as one of the more reliable means to increase the availability of fisheriesproducts to an ever increasing human population.

b. Overview of Global AquacultureAccording to FAO statistics, the contribution of aquaculture to global supplies of fish,crustaceans and molluscs continues to grow, increasing from 3.9 percent of totalproduction by weight in 1970 to 29.9 percent in 2002.

In 2003, aquaculture supplied 41.9 million tons out of a total of 132.2 million tons ofworld fisheries production. This amounted to 31.6% of the total world fisheriesproduction.

Aquaculture continues to grow more rapidly than all other animal food-producing sectors.Worldwide, aquaculture has grown at an average rate of 8.9% per year since 1970.During this period, capture fisheries has only grown by 1.2%, while land-based meatproduction farming systems have grown by 2.8%.

The majority of aquaculture is practiced in freshwater (57.7%), followed by mariculture(36.5%), and brackish water culture (5.8%). Production is dominated by Asian countries,particularly China.

It is important to note that aquaculture has grown at a more rapid pace in developingcountries (10.4% per year) than in developed countries (4% per year).


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With the exception of marine shrimp, most of the aquaculture production in developingcountries in 2002 comprised omnivorous/herbivorous fish or filter-feeding species.However, 74% of finfish aquaculture in developed countries comprised carnivorousspecies.

The most widely cultured fish are the carps, which are grown in China, India and parts ofEurope. Tilapia are widely grown in many tropical countries, and in North America, fishlike salmon, trout and channel catfish are cultured. Non-fish species, such as oysters,clams, seaweed, shrimp and eels are also cultured. Aquaculture is also carried out forpurposes other than the production of food fish, such as pearl culture and the productionof aquarium fish.

III. The Importance of Tilapia in World Aquaculture 15 MinutesTilapia is the generic name of a group of commercially important food fish, belongingto the family Cichlidae, and are endemic to Africa. The name tilapia probably originatedfrom the native African Bechuana word "thiape," meaning fish.

The group consists of three aquaculturally important genera: Oreochromis, Sarotherodonand Tilapia.Several characteristics distinguish these three genera, but possibly the mostcritical relates to reproductive behavior.

In all Tilapia species, the fertilized eggs are guarded in the nest by a brood parent.

The Sarotherodon and Oreochromis species are mouth brooders. The eggs are fertilizedin the nest but the parents immediately pick up the eggs in their mouths and hold themthrough incubation and for several days after hatching.

In the Oreochromis species, only females practice mouth brooding, while in theSarotherodon species either the male or both male and female brood the eggs.

Tilapia have been raised as food for human consumption for a long time. The Nile tilapia(O. niloticus) was one of the first fish species cultured. Illustrations from Egyptian tombssuggest that Nile tilapia were cultured more than 3,000 years ago. Tilapia have beencalled Saint Peters fish in reference to biblical passages about the fish fed to themultitudes.

During the last half century fish farmers throughout the tropical and semi-tropical worldhave begun farming tilapia. Today, all commercially important tilapia outside of Africabelong to the genus Oreochromis, and more than 90 percent of all commercially farmedtilapia outside of Africa are Nile tilapia (Oreochromis nilotica), which is favored becauseof its high growth rate. The red or pink hybrids are favored because of their attractivecolour, of which the Jamaican Red is popular.


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Less commonly farmed species are Blue tilapia (O. aureus), Mozambique tilapia (O.mossambicus) and the Zanzibar tilapia (O. urolepis hornorum).

In 2002, the production ofOreochromis nilotica alone amounted to 1.2 million metrictons, with an approximate value of US$1.3 billion, and tilapia are second only to carps as

the most widely farmed freshwater fish in the world.

Tilapia are a good fish for warm-water aquaculture. They are more tolerant than mostcommonly farmed freshwater fish to a range of salinities, high water temperature, lowdissolved oxygen, and high ammonia concentrations.

They are easily spawned, use a wide variety of natural foods as well as artificial feeds,tolerate poor water quality, and grow rapidly at warm temperatures. These attributes,along with relatively low input costs, have made tilapia the most widely culturedfreshwater fish in tropical and subtropical countries. Consumers like tilapias firm fleshand mild flavor, so markets have expanded rapidly, most notably in the United States.


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IV. Site Selection 30 MinutesSite selection is very important for successful aquaculture. Many areas are deemedunsuitable for specific types of aquaculture, or require too much modification foraquaculture to be economically successful.

The following general criteria are to be considered for proper site selection:

a. Land: For successful land based aquaculture, the land must have somebasic attributes. Steeply sloping land is generally deemed unsuitable foraquaculture. On the other hand, a gentle slope is required to facilitateeither irrigation or drainage by gravity. Generally, the slope of the landshould be between 1-1.5.

b. Water: Water is essential for aquaculture. Whereas the land available canbe amended to some extent, water is much more difficult to alter. The site

should have easy access to adequate supplies of either fresh or salt water,or both, if required.At the same time, the site should also have access to another water bodyfor drainage and disposal of used water.

c. Access to Infrastructure: The site should be serviced by proper roadsand communication links, and should have access to electricity. Otherimportant aspects include proximity to processing facilities and technicalexpertise.

d. Market Analysis and Survey: The site should have easy access to themarket for the product. This also includes access to roads, waterways fortransport, or an airport, if required. A financial analysis of the proposedmarket should be done.

e. Seed Supply: The site should be near the seed supply ideally, to minimizeboth cost and mortality of seed. However, if seed is to be produced on thefarm, then this consideration is minimal.

f. Room for Expansion: The site selected should have room for expansion.As the enterprise grows, several other needs may become evident. Theremay be the need for a hatchery, feed production facility, freezing area, etc.

g. Financial Aspects: Ideally, the site selected should have some financialincentives associated with it, e.g., duty free provisions, tax holidays,subsidies, etc.

h. Climate: The site should have the required temperature, light availability,rainfall, etc., as required by the species.


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V. The Aquatic Environment 60 MinutesThere are two major types of factors associated with water, biotic factors and abioticfactors. Biotic factors include all the living things associated with water, such asphytoplankton, zooplankton, worms, insect larvae, snails etc. Abiotic factors are the non-

living factors such as light, temperature, salinity, dissolved gasses such as oxygen andcarbon dioxide, and nutrients such as nitrates and phosphates.

The water in which the aquaculture species is farmed has a profound effect on the healthand growth of the species. The water quality may deteriorate considerably over theculture period due to the addition of nutrients via feeding. The major water qualityfactors that affect aquaculture animals are; dissolved oxygen, pH, dissolved nutrients andgasses, temperature and plankton.

a. Dissolved OxygenOxygen is essential to the survival of all animals, and aquacultured animals are no

exception. Air contains approximately 21% oxygen, but the amount present in water isquite low, due to the low solubility of oxygen in water.

Oxygen becomes less soluble in water as the temperature increases.

Solubility of oxygen in pure water in relation to temperature from saturated air

Salinity has a similar effect on oxygen solubility. As salinity increases, oxygen solubilitydecreases.

Oxygen passes from air to water by diffusion, and the amount present in water can beincreased by water circulation due to wind, since this exposes more surface water to theatmosphere, thereby increasing the rate of diffusion.

In ponds used for aquaculture, the major source of oxygen is photosynthesis byphytoplankton. Phytoplankton are tiny plants that produce the green colour in many fish


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ponds. Plants containing the green pigment chlorophyll in the presence of light usecarbon dioxide to produce carbohydrate and oxygen:

6CO2 + 6H2O C6H12O6 + 6O2

Since sunlight is essential for photosynthesis, this activity is carried out only in daylighthours. In the night, the phytoplankton carry out only respiration, a process in which theyuse up oxygen and produce carbon dioxide. This means that the dissolved oxygen levelsare lower in the night, and higher during the day. The lowest levels of oxygen areencountered very early in the morning, just before the sun rises. At this time, the fishfarmer should check his ponds, and be prepared to aerate, if necessary.


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b. Signs of Oxygen Depletion In PondsOxygen depletion (loss) is the single biggest problem that occurs in fish ponds, especiallywhen the stocking rate is high, and the fish are being fed heavily.

The following signs indicate that there is not enough oxygen in the pond water:

- Fish coming to the water surface in an effort to breathe from the thin, betteroxygenated surface film - this behavior is called piping

- Tadpoles gathering at the pond edges- Water snails leaving the pond water- An odour of rotten egg rising from the water- Fish not feeding well or not eating al all

c. Factors leading to oxygen depletion in pondsThe following factors may contribute to oxygen loss in ponds:

i. Cloudy or Rainy Weather: Several days of cloudy or rainy weather maylead to a phytoplankton die-off, since photosynthesis stops due to lack ofsunlight. In addition to oxygen not being produced, the deadphytoplankton will use up oxygen, as they decay.

ii. Lack of Nutrients: Nutrients, such as phosphates and nitrates, areessential for the growth of a phytoplankton bloom. If these nutrients arenot available, phytoplankton may not be present to produce oxygen byphotosynthesis. If the fish are being fed, however, this is rarely a problem,since the feed acts as a source of nutrients. Nutrients may also be added byfertilizing fish ponds.

iii.Overstocking: The greater the number of fish in a pond, the greater is theconsumption of oxygen as well as the amount of waste products produced.The waste products in turn use up oxygen when they decay. For thesereasons, farmers are urged to follow the recommended stocking rates forthe particular species of fish or shrimp.

iv. Blue-green Phytoplankton Scum: A certain type of phytoplankton,called blue-green algae or Cyanophyceae, may form a dense scum on thesurface of the water. This limits photosynthesis to only the top fewcentimeters, since the scum blocks sunlight from penetrating the watercolumn. This means that oxygen levels will be very high in the surfacewaters but lacking in deeper waters. These scum are dangerous since they


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prevent fish such as tilapia from accessing surface water as they normallydo when oxygen levels are too low, which can result in total fish kill.

v. Hot Weather: Very hot days with no breeze provide a condition foroxygen depletion. Very warm water, above 32C (90F), holds very little

oxygen. With no breeze, little or no oxygen is added through circulation.In addition, the culture species is more active, requiring more oxygen.Decay processes are also speeded up, thus using more oxygen.

d. Avoiding and Combating Oxygen DepletionIn tropical countries, problems with oxygen depletion occur all year round due to the hightemperatures, and the problem is even greater in brackish water, since oxygen is lesssoluble as salinity increases. By knowing what to look for and what to do, losses can beavoided.

i.

Check Pond Water Daily: Dissolved oxygen should be checked inponds at daybreak. In large operations, farmers are advised to purchase adissolved oxygen meter, which quickly and easily gives an accuratedissolved oxygen reading. For smaller operations, the cost of a meter isprohibitive and farmers are advised to use a Secchi disc to monitorphytoplankton levels, which gives a rough guide as to the oxygenproductivity of a pond.

A Secchi disc is a round flat surface on which twoalternate quarters are painted black and the otherswhite:

A rope or a pole is attached to this instrument, andmarked at 10 cm intervals. To take a reading, thedisc is lowered into the water until it just disappears.The following table gives a guide to various Secchidisc readings, and their implications:


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Secchi Disc Visibility Comments

Less than 20 cm Pond has too much plankton. There will be problems with lowDO.Water should be exchanged to reduce the amount of plankton.

20 to 30 cm Plankton becoming excessive, but the pond is still in goodcondition.

30 to 45 cm Pond is in good condition.

45 to 60 cm Phytoplankton becoming scarce. Pond should be fertilised.

More than 60 cm Water is too clear. Pond should be fertilised, using an increasedamount.

From this table, it is seen that a desired Secchi disc reading is between 30 to 45 cm.

NOTE: Turbidity occurs when the water is muddy. For the Secchi Disc readings to be ofuse, the transparency should be due to plankton.

ii. Check Phytoplankton Blooms: A healthy bloom in ponds is indicatedby a green colour, similar to the colour of vegetation. A change in colourfrom green to brown indicates that the bloom is dying, and is oftenassociated with a sour smell.As mentioned before, blue-green algae often form scums on the surface ofponds, sometimes with bubbles of gas. These can cause fish to suffocatewhen they surface due to the inevitable low oxygen levels that occur in thelower waters.

iii.Adjust Feeding Rates: In ponds with no artificial aeration, feeding ratesshould be lowered during very hot, still weather; in the event that there isan undesirable plankton bloom; or if the culture species is not eating theration that they are being fed. If a floating feed is used, it is easy to see ifall the feed is being eaten. With a sinking feed, it is advisable to checkfeed boxes before every feeding.

iv. Water Exchange: Whenever the water quality seems to be deteriorating,it is advisable to exchange water in a pond. It is best to always removewater from the bottom of a pond since that is where the water quality isthe worst. Clean water is then added to replace the dead water that hasbeen removed. Always remove water first, before adding new water to a

pond.

v. Mechanical Aeration: The quickest method for combating low dissolvedoxygen is by using a system to expose a large surface area of water to theair. Commercial aerators are available, some of which use electricity, butmay be too expensive for small farmers. A water pump, fitted with adevice for spraying water in the air at the discharge end has been found tobe effective.


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e. pHThe pH of a liquid refers to its acidity or alkalinity, and is measured on a scale from 0 to14. Substances that have a pH below 7 are said to be acidic, while those above 7 are saidto be alkaline. A pH of 7 is neutral, that is, neither acidic nor alkaline. Pure water has apH of 7.

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14Increasing Neutral IncreasingAcidity Alkalinity

The pH values of natural waters vary considerably depending on the soil type and theamount of organic matter present. Dark coloured water is often acidic, due to humic acidthat is dissolved in it. Water found in regions where a lot of pagasse is present is alsoacidic. On the other hand, water found in limestone regions may be slightly alkaline.

The desirable pH range for freshwater fish culture is between 6.5 and 9.0. Low

production occurs below 6.5 and above 9.0. In a fishpond with phytoplankton, the pHfluctuates, increasing during the day and decreasing at night, similar to the change indissolved oxygen. However these changes are not large enough to cause problems. Theacid death point is 4 and the alkaline death point is 11, meaning that fish can die below 4pH units and above 11 pH units. If a farmer wants to carry out aquaculture in an areawhere the pH is below 6.5, liming may be done, but this will incur an extra cost, whichwill have to be considered.

D = Decreasing fish production - correction neededX = Reproduction questionable

Y = Eggs/fry questionable

The pH of water has an effect on the availability of some nutrients and the toxicity ofsome compounds. For example, ammonia becomes more toxic with increasing pH levels.


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f. Dissolved Nutrients and GassesMany substances are found dissolved in natural waters, and some of these are of particular importance in fishponds. Some, such as phosphate and nitrate, are fertilizersthat enable phytoplankton to bloom. Others, such as nitrite, and the gasses ammonia andhydrogen sulphide, are poisonous when present in certain lethal amounts. The levels of

these substances increase with increased stocking and feeding rates, but whenrecommended stocking and feeding rates are followed, and good water qualitymanagement is carried out, they are rarely a problem.

g. TemperatureWater temperature is an important consideration in aquaculture, since it affects thegrowth and reproduction of culture species. Fish grow faster when temperatures arewarmer. In temperate countries, where there are warm and cold seasons, the growth period for fish is generally limited to the warm months, and reproduction for somespecies only occurs when the water temperature reaches a certain minimum value. In

Guyana, however, water temperatures are warm all year round, and the species grown arenot affected by varying temperatures. Growth and reproduction for these tropical speciesare year-round activities.

h. PlanktonPlankton refers to living material that is found floating in water. There are two majortypes; phytoplankton and zooplankton. Phytoplankton are tiny plants and zooplanktonare tiny animals.

1. PhytoplanktonAs described before, the major function of phytoplankton (also known as algae) is theproduction of oxygen during photosynthesis, which is used by the farmed fish or shrimp.It is also a natural food source for some fish, e.g. tilapia and some Chinese carps.Phytoplankton can be divided into several groups, including green, blue-green, brownand red algae.


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- Clorophyceae: These are the green algae, and cause waters to appearolive green in colour. They are the most important group both in termsof oxygen production and as a food source.

- Cyanophyceae: These are the blue-green algae and may cause watersto appear blue-green or bright green in colour. They are the mostdangerous type of algae to fish and are found when the water ispolluted with a lot of organic matter. They form scums as described

before and also produce harmful substances.


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2. ZooplanktonThese tiny animals usually feed on phytoplankton and are very important as a food sourcefor the larval stages of most fish and shrimp. There are three major types that areimportant in aquaculture.

- Cladocera: These are a type of crustacean and are commonly calledwater fleas due to their resemblance to fleas.

- Copepoda: These are another type of crustacean and are almostcylindrical in shape. Although some are useful as food, others are parasites on fishes, e.g., Argulus, or Fish Louse, which occurs ontilapia reared in brackish water.


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- Rotifera: These zooplankton are closely related to a group of animals

called flatworms and are very important as a food source for the firstlarval stage of fish.


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VI. Fertilizing and Development of Natural Food Organisms 30 Minutesa. Fertilizing

1. What are FertilizersFertilizers are natural (organic) or man-made (inorganic) substances that are used inaquaculture to increase the production of the natural food organisms to be eaten by thefish. Fertilizers supply various nutrients in different amounts. Therefore, differentfertilizers have different uses, and are to be used in different amounts.

2. What is a Liming AgentA liming agent is a substance, either natural or man-made, that is used to reduce acidity,and therefore increase pH, in a culture system.

3. Reasons for FertilizingFertilizers are added to ponds to improve the level of nutrients present in the water. These

nutrients assist the growth of plankton, which may be used by the fish.Also, by improving the amount of plankton, fertilizers enable the correct stocking rate tobe maintained, since adequate plankton produce oxygen for the fish.

4. Inorganic FertilizerInorganic fertilizers are man-made, and usually supply high amounts of one particularnutrient. Examples are Urea and ammonium nitrate, which supply nitrogen, and triple orsimple super-phosphate, which supply phosphorus.

5. Organic FertilizerOrganic fertilizers are usually occur naturally, and supply a variety of nutrients in varyingamounts. Examples are animal manure, crop residues and compost.

6. RatesFertilizer rates vary widely, and depend on the species to be grown, the soil and watertype. The rates are important to achieve the desired water condition. If the watercondition is suitable, then fertilization is not necessary. Fertilizer is added at thebeginning of a culture cycle, to get the pond ready for the introduction of the fish.At the Mon Repos Aquaculture Station, cow manure is applied at the rate of 500 poundsper acre of pond surface, per month, and Triple Super Phosphate is applied at the rate of50 pounds per acre of pond surface, per month. Once the fish are introduced, fertilizer isadded to maintain the appropriate water condition, if necessary.

7. Methods of ApplicationFertilizers should be uniformly applied over the whole pond surface, or distributed inspecific places carefully selected to get a uniform distribution by the water current or thewaves.In the case of inorganic fertilizers, they may be dissolved in water, which is then broadcastover the pond surface.In the case of organic fertilizer, they may be placed in bags and submerged into the ponds, at


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the windward side. Holes should be made in the bag, to allow the nutrients to seep out intothe water.

b. Development of Natural Food Organisms Natural fish foods present in ponds occur as a mixture of several types of

organisms, both plant and animal. As has been stated in The AquaticEnvironment some of the organisms present in ponds can be microscopic, orthey can be larger, such as snails, worms and larger insect larvae. The deadmaterial at the bottom of the ponds (detritus) can also form food for severalspecies of fish.

Natural food organisms can be found in various parts of the pond:- near the shore, e.g., rooted plants- suspended in the water (plankton)- associated with the pond bottom (benthos), e.g., worms, snails, etc.- covering the surface of objects in the pond water (aufwuchs)-

swimming in the pond water (nekton) e.g., aquatic insects, frogs andfish

Natural food organisms are very important for the early development of fry, sincethey form an important part of their diet. As the nutrients in the yolk sac becomedepleted, very small fry start to eat natural foods comprising the smallestplankton, such as phytoplankton and rotifers.

As their mouth size increases, the fry start to eat larger plankton, such ascladocera and copepods, as well as insect larvae and insect pupae. As the fry growlarger, they begin to eat the same foods as the adults. However, in the case oftilapia, natural food, especially plankton, continue to play an important part intheir diet, throughout their life cycle.

In order for these organisms to be present in the quantities required by the fry andadult fish, proper fertilization is required. Fertilizers will supply the natural foodorganisms with the nutrients required for their growth and development.

Since living organisms require a variety of nutrients for proper growth anddevelopment, both organic and inorganic fertilizers should be applied in ponds.Inorganic fertilizers will supply large quantities of the major nutrients, such asnitrogen and phosphorus. The organic manure will supply small quantities of avariety of nutrients, such as copper, zinc, iron, calcium, etc.

New ponds, or ponds recently filled with water, take some time to develop naturalfood. The first natural foods to develop are the smallest plankton, such as phytoplankton. As the ponds age, the zooplankton develop, which feed on thephytoplankton, and smaller zooplankton.


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There are several techniques that are available for the culture of individual speciesof phytoplankton and zooplankton. This is important in those cases where the fryof some fish species require a specific type of natural food for their growth anddevelopment.

Tilapia fry, however, can survive and grow utilizing a mixture of plankton, whichare available in properly fertilized ponds, with the correct transparency.


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VII. Biology of Tilapia 60 Minutesa. Physical Characteristics: Tilapia have a very deep, laterally compressed body,

with long dorsal fins and an interrupted lateral line. The body color is generallydark, with darker vertical bands down the sides of fry, fingerlings and sometimes

adults. Scales are large and often tipped with white; the throat and belly arewhite.The forward portion of the dorsal fin is heavily spined, and spines are alsofound in the pelvis and anal fins. There are usually wide vertical bars down thesides of fry, fingerlings, and sometimes adults.

The main cultured species of tilapia usually can be distinguished by differentbanding patterns on the caudal fin. Nile tilapia have strong vertical bands, Bluetilapia have interrupted bands, and Mozambique tilapia have weak or no bands onthe caudal fin.

Color patterns on the body and fins also may distinguish species. Mature male

Nile tilapia have gray or pink pigmentation in the throat region, whileMozambique tilapia have a more yellow coloration. However, coloration is oftenan unreliable method of distinguishing tilapia species because environment, stateof sexual maturity, and food source greatly influence color intensity.

The Red tilapia hybrids have become increasingly popular because of their similarappearance to the marine red snapper, which leads to higher market value.

b. Reproduction: Tilapia attain sexual maturity at approximately two to threemonths. However, sexual maturity is a function of age, size and environmentalconditions. The Mozambique tilapia reaches sexual maturity at a smaller size andyounger age than the Nile and Blue tilapias. When growth is slow, sexualmaturity in Nile tilapia is delayed a month or two but Tilapia in ponds may spawnat a weight of about 1 ounce (20 grams).

Adult tilapia will breed naturally, once both males and females are present. Inmales the genital papilla has only one opening (the urinary pore of the urethra)through which both milt (sperm) and urine pass. In females the eggs exit througha separate oviduct and only urine passes through the urinary pore. Examination ofthe genital opening can therefore be used to determine the sex of tilapia, once asize of approximately 30 gram is reached.

The number of eggs per spawning is related to the size of the female. A female ofabout 100 grams may produce approximately 100 eggs per spawning while largerfemales can produce as much as 1,500 eggs per spawning. A female weighingabout 300 grams can produce about 450 eggs per breeding cycle. Each female canachieve about 6 cycles per year, giving a total of 2,700 eggs per year.

In all Oreochromis species the male excavates a nest in the pond bottom


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(generally in water shallower than 3 feet) and attracts several females to spawn(release eggs). After a short mating ritual the female spawns in the nest and themale fertilizes the eggs. The female then collects the eggs and incubates them inher mouth until they hatch.

The eggs of hybrid tilapia are yellow-brown in colour, egg shaped, and will sinkto the bottom when spawned. The eggs vary in size from an average of 2 to 4 mmin diameter, depending on the species and number of spawns.

After fertilization, eggs hatch in 2 to 4 days, depending on water temperature. Theresulting fry contain a yolk sac, and remain congregated together, at or near thewater surface. The fry absorb the yolk sac in 3 to 4 days, before beginning to feedon external foods, such as plankton and detritus.

The fry are protected by the female for several days to two weeks. During thistime, the female will keep the fry in her mouth in times of danger.

Adult fish are known to live six to eight years, but some fish eleven to twelveyears of age have been reported.

c. Management of Reproduction: As has been noted, tilapia breed readily. Theyalso reach sexual maturity at an early age, in many cases well before market sizeis attained. These two factors combine to cause overcrowding in production pondswhich are stocked with both male and female fish. The resulting overcrowding


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and competition for food results in stunted tilapia, which fetch less low marketprices.In order to solve this problem, all-male culture, or male monosex culture, isperformed. Males are preferable because they grow approximately twice as fast asfemales, since they do not have to devote resources to egg production.

There are several methods which can be used to achieve all male culture. Theseare:i. Manually separating the sexes based on visual examination of the genital

papilla of juvenile fish (hand-sexing), and discarding the femalesii. Hybridizing between two selected species that produce all-male offspring

(for example, Nile or Mozambique females crossed with Blue or Zanzibarmales)

iii.Feeding a male hormone-treated feed to newly hatched fry for 3 to 4weeks to produce reproductively functional males (hormonal sex reversal)

iv. Use of Super-male (YY) male technology


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VIII. Selection and Handling of Broodstock 30 Minutesa. Selection of Broodstock: The broodstock are adult tilapia which will be used to

produce the fry and subsequently, fingerlings and adult fish, for market. The broodstock will also contribute to the production of the next generation ofbreeding stock, to sustain the aquaculture enterprise. Therefore, care and attention

must be applied in the selection of the broodstock, both male and female.Broodstock should be selected that have the general characteristics required of theoffspring. Larger, faster growing adults with good body conformity (thickness)and the required colouration should be selected for breeding. They should also behealthy, free from physical deformities, well fed and in good condition.Broodstock (both males and females) should be approximately 300 grams, sincethis size will permit easy handling, and at the same time, produce adequate fry.In order to obtain healthier offspring, it is important that inbreeding be avoided.Males and females that are closely related should not be used together forbreeding, since this will result in inbred offspring that may be weaker, and have alow growth rate. Therefore, it is advisable to source one half of the broodstock,

either the males or the females, from outside the farm, when it is time to replacethem.Broodstock should be well cared for and kept in water of optimum quality. Theyshould be held separately (males and females in different ponds), and onlybrought together when seed production is required. They should also be held at alow stocking rate (1 fish for every 4 square feet), to reduce stress, since this willlead to higher seed production.Broodstock should be replaced at least once every two years, to ensure that theoptimum seed production is achieved.

b. Handling of Broodstock: Broodstock should be handled carefully andtransported rapidly, so as to reduce stress, and therefore maintained in optimumcondition for seed production.In capturing broodstock, ensure that the fish are never gilled, but rather, onlyphysically restrained by the net. This means that the mesh size of the fishing gearused must be small enough not to allow the head of the fish to pass through.Below are some guidelines for mesh sizes as relates to fish weights, which if usedcorrectly, allow capture, but prevent gilling.


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Broodstock may be captured and transported individually, using the following method:

Tilapia broodstock are not very large when compared with other species. Therefore, it ispossible to always transport them in containers containing water.

Water for fish transport should be clean, and well water or rainwater should be used.Pond or canal water should not be used, if possible, since it will deteriorate faster,stressing the fish. Room temperature water can be used. However, adding a small amountof ice, to reduce water temperature, will aid in the survival of the fish.


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IX. Seed Production: Semi-Intensive 90 Minutesa. Introduction

The semi-intensive method of tilapia seed production is characterized mainly bythe following:

- Utilization of a medium level of technology-

Utilization of earthen ponds for breeding, fry production and fingerlingproduction- Dependence on natural food for early fry rearing- Production of mixed sex fingerlings

In this system, male and female broodstock are placed into a suitably prepared breeding pond, where reproduction takes place. The resulting fry are thentransferred to fingerling rearing ponds, for growing to fingerling size. Thebroodstock are then removed from the breeding pond, and returned to broodstockholding ponds.

Since this system uses earthen ponds, a section of this topic is devoted toconstruction of earthen ponds.

b. Earthen Pond Constructioni. Basic Principles

All ponds should be individual units. This means that each pond shouldhave an individual inlet and outlet, so as to provide for individualirrigation or drainage of each pond.All ponds should be constructed with a slope towards the outlet, so as tofacilitate drainage. Usually, there should be a difference of 30 cm in depthfrom the inlet to the outlet.The sides of a pond should be sloped, usually about 30 degrees, so as toprevent the sides caving in. The more clay the soil contains, the steeper thepossible slope that may be used.Ponds should be constructed to take advantage of gravity for eitherirrigation, drainage, or if possible, both.All ponds should contain an inlet, for irrigation, an outlet, for drainage,and an overflow, to remove excess water in a controlled manner.All water entering ponds should be filtered, so as to prevent otherunwanted species from entering the pond.All water leaving the ponds should be filtered, so as to prevent thecultured species from escaping.For breeding and fingerling production, ponds of 1,000 square feet areusually adequate.


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ii. Pond InletsInlets can be made of 3-inch or 4-inch PVC pipe. When placing the inlet,ensure that:

- It is at the shallow end of the pond- Its bottom level is low enough so that water flows in from the

irrigation canal, and ideally, that it is at least 10 cm above themaximum level of the water in the pond

- It is horizontal, with no slope- It has a filter, to prevent unwanted fish from entering the pond

iii.Pond OutletsOutlets can also be made of 3-inch or 4-inch PVC pipe. Outlets arerequired to keep water at a suitable level in the pond, and to allow for thecomplete draining of the pond and harvesting of the fish whenevernecessary.An outlet should ensure that- The amount of time necessary to drain the pond completely is

reasonable- There is no loss of fish during the draining period- Any reasonable excess of water is carried away- The outlet can be reasonably cleaned and serviced


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c. Water RequirementIt is recommended that breeding and fry rearing take place in freshwater, sincesalinity reduces the survival of fry. Therefore, the breeding pond and fingerlingponds should contain clean, unpolluted freshwater, ideally with 0 ppt salinity. ThepH should be between 6.5 and 9.0.

d.

Pond PreparationPreparations for both the breeding and fingerling ponds are the same. The pondshould be completely drained, and the bottom allowed to dry until it cracks, toensure that all unwanted fish are killed. Drying the pond also allows for thedecomposition of substances which can be harmful to the fish.After the pond has been properly dried, water should then be allowed to enter thepond through the filtered inlet, to a depth of 6 inches (15 cm). Organic fertilizer(cow or sheep manure) should then be broadcast into the pond, at the rate of 500lbs/acre. Triple Super Phosphate should then be dissolved in water, and applied tothe pond, at the rate of 50 pounds/acre.When the pond water starts to become green, the water level should then be raised

to 3.5 to 4 feet.When the transparency reaches 20-30 cm, the fish can then be stocked, since thislevel of transparency will ensure that enough natural food is available for theyoung fry.If the transparency is below 20 cm, some water should be let out of the pondthrough the outlet, and fresh water should then be added to replace the waterremoved. This should be repeated as necessary, until the transparency range of20-30 cm is attained.


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e. Stocking and Management of BroodersBrood fish should be captured and transported to the breeding pond, using thepreviously stated guidelines. Brood fish should be stocked at a ratio of one maleto every three females, and should be stocked at a rate of one fish for every 6square feet.

When in the breeding pond, brood fish should be fed at a rate of 5% of their bodyweight per day, or if this is found to be excessive, then they should be fed ad lib.Once stocked, the broodfish should not be recaptured or otherwise disturbed, untilit is time to remove them from the pond. Any disturbance will interrupt thebreeding, and result in a reduction in the number of fry produced.If 300 gram females are stocked, then approximately 450 fry per female should beproduced.Broodfish should remain in the pond for a maximum of four weeks, but can beremoved and returned to holding ponds before this time, if enough fry have beenproduced.If at the end of four weeks adequate fry have not been produced, the broodfish

should be removed, and all fry and fingerlings remaining in the breeding pondshould be transferred to fingerling ponds.A new set of brooders should then be placed in the breeding pond, to complete thefry production.

f. Fry and Fingerling ProductionThe first fry should appear around ten to fourteen days after the brooders havebeen stocked. The fry will be more easily visible during the early morning andearly evening, swimming in a cluster. Each cluster of fry is usually the offspringof a single female.The fry should be caught using a hand net with a very fine mesh size, andcounted, before being transferred to a suitably prepared fingerling pond. Countingof fry may be done by using a milk scoop, or a similar container whose capacityhas been previously determined, as shown below:


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The stocking rate for fry in the fingerling pond is 1 fish for every square foot ofpond surface. This will allow enough natural food to be available for the growthof the fry, while maximizing the use of available space.

A high protein supplemental feed (28 to 30% protein) should be made available tothe fry about seven days after stocking. Rice Bran can be used as well, but caremust be taken to ensure that the pond contains adequate plankton. Fry willgradually move from consuming natural food only, to consuming thesupplementary feed as well as some natural food. Feeding should be done twiceper day (9 am and 4 pm). The feed should be placed in a feed box or feeding tray(diagram), submerged about 6 inches below the water surface. One feed box ortray for every 500 square feet of pond surface is adequate.Before feeding, the feed box or tray must be examined, to determine if any feed isremaining.If feed is remaining, then the feed box or tray should be removed from the pond,

washed out thoroughly, and then replaced in the pond. Feed should still beprovided, but in a lesser quantity. Fry and fingerlings should be fed ad lib at thisstage, until they attain 20 grams, to ensure proper growth. When the fry becomefingerlings, at about 20 grams, they can then be fed at 5% of their biomass perday.At approximately 30-35 grams, it is possible to hand sex the fingerlings. At thissize, they can be safely stocked into grow-out ponds.Using this method, an 85% survival rate in the fingerling pond can be achieved.


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g. Pond ManagementThe water level in the pond must be kept constant. Therefore, water should beadded to replace loss by seepage or evaporation.The transparency of the pond is very important, and should not be allowed to fallbelow or rise above the 20-30 cm range. If the transparency falls below the range,

water exchange must be done. If the transparency rises above the range, thenmore organic and inorganic fertilizer must be added, until the transparency returnsto within the normal range.Fish should not be overfed, since this can cause the water in the pond to becomepolluted, and result in an unhealthy environment for the fish.Feed boxes must be taken out of the pond once per week, cleaned and left to dryin the sun, to disinfect them.Ponds should only be fertilized if there is a need to do so, and should only be doneon sunny days. All water entering and leaving the pond must be filtered.All weeds growing in the pond, and along the banks trailing into the water mustbe removed, so as to keep the pond environment healthy.

h. Advantages and DisadvantagesThis method has the advantages of low technology, less inputs, and relative easeof management, resulting in cheaper fingerlings.However, this method produces mixed sex fingerlings, which must be hand-sexedif all male culture is required.Also, some fry are left in the breeding pond, since it is not possible to remove allof them using hand nets. They can be removed as soon as the brooders have beenremoved, counted and placed in a fingerling pond. Or, they can be left in thebreeding pond, where they can be raised to fingerling size, and then utilized.


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X. Seed Production: Intensive 60 Minutesa. Introduction

The intensive method of tilapia seed production is characterized mainly by thefollowing:

-

Utilization of a high level of technology- Utilization of a specially constructed hatchery for breeding, fryproduction and fingerling production

- Preference for concrete tanks, due to space requirements andmanagement considerations

- Very little or no dependence on natural food for early fry rearing- Production of both mixed sex and all male fingerlings

In this intensive system, artificial aeration is provided to ponds and tanks,enabling the fish to be stocked at much higher densities when compared with thesemi-intensive system. Frequent water exchange is required, in order for the tank

environment to be able to support the stocked biomass.

Natural food is either absent entirely, or present in such small amounts as to beinsignificant. Consequently, nutritionally complete feeds, usually in the form offloating pellets, are used, to achieve the required production. Fertilization ofponds and tanks is usually absent as well.

Due to the intensity of the culture, and the control over most of the aspects of therearing process, it is possible to produce either mixed sex fry, or all male fry.However, given the level of investment required, this system is usually utilizedfor the production of all male fry for use in commercial grow-out operations.

Using this system, male and female broodstock are placed into a spawning tank,where reproduction takes place. The resulting fry are then transferred to fry tanksfor special management purposes, where they are held for some time, beforebeing transferred to fingerling rearing ponds or tanks, for growing to fingerlingsize.

b. Hatchery Design and Constructioni. General Factors: The hatchery should be located below the water source,

to facilitate irrigation by gravity, and sufficient pressure without pumping.Consideration should be given to automatic feeding, and mechanizedtransport of fish within the facility, to reduce labour costs.

ii. Specific Factors: The main buildings in a hatchery facility are an officefor record keeping, the hatchery building itself, a repair and servicing area,a storage area, and a laboratory for conducing water analyses.The hatchery building should contain the spawning tanks and fry tanks.The fingerling tanks and broodstock holding tanks can be located outsidethe building.


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c. Water RequirementDue to the intensity of the culture system, water quality is very important, and plays a significant part in the success or failure of a hatchery. Physical andchemical characteristics of the water such as suspended solids, temperature,dissolved gases, pH and mineral content need to be carefully considered.

The water supply should consist of clean, unpolluted freshwater, ideally with 0 ppt salinity. The pH should be between 6.5 and 9.0. The concentration of thefollowing gasses should be considered:

- Oxygen 5 parts per million or more- Carbon Dioxide 10 parts per million or less- Hydrogen sulfide 0.1 part per billion or less- Hydrogen cyanide 10 parts per billion or less

Turbidity should be less than 2,000 parts per million, and hardness within therange of 120 to 400 parts per million.

d. Stocking and Management of BroodersBrood fish should be captured and transported to the spawning tank, using thepreviously stated guidelines. Brood fish should be stocked at a ratio of one maleto every three females, and should be stocked at a rate of one fish for every 2square feet, if aeration is being provided.

When in the spawning tank, brood fish should be fed at a rate of 5% of their bodyweight per day, or if this is found to be excessive, then they should be fed ad lib.Once stocked, the broodfish should not be recaptured or otherwise disturbed, untilit is time to remove them from the spawning tank. Any disturbance will interruptthe breeding, and result in a reduction in the number of fry produced.

If 300 gram females are stocked, then approximately 450 fry per female should beproduced.

Broodfish should remain in the spawning tank for a maximum of four weeks, butcan be removed and returned to holding ponds before this time, if enough fry havebeen produced.

In the intensive system, fry production is an ongoing process. Therefore, at theend of the four-week period, the broodfish are removed from the spawning tank,and replaced by another batch of brooders.

Broodstock are usually rested for 4-6 weeks, before being returned to thespawning tanks to continue fingerling production.


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e. Fry ProductionThe first fry should appear in the spawning tank around ten to fourteen days afterthe brooders are stocked. Due to aeration activities, fry may be more difficult toobserve, but are usually found clustered at the edges and corners of the tank.

The fry can be caught using a hand net with a very fine mesh size, or they can beremoved using a siphon. They are then counted, before being transferred to frytanks. Fry are usually captured and transferred to the fry tank within the first threedays, while their yolk sacs are still visible, to permit hormonal sex reversal.

There are several methods for counting fry, such as the volumetric method.However, counting can be done easily using the method displayed previously.

The stocking rate for fry in the fry tank varies, since aeration makes very highstocking densities possible. Fry may also be stocked volumetrically, rather thanby surface area. In very intensive systems, it is possible to stock as many as 100

fry per liter of water.

As the fry get older, the stocking density should be reduced. For example, fryweighing 0.02 grams (yolk sac fry) to 1.0 grams should be stocked at 8,000 persquare meter; fry weighing 1-5 grams should be stocked at 3,200/square meter.

Complete feeds are used in these systems, containing all the nutrients required forfry growth and development, with as much as 45% protein. Due to their smallstomach size, fry are unable to consume a large amount of feed at any one feed,and must therefore be fed frequently. They may be fed as many as 6 times per dayin the first 28 days, and less frequently as they become older.

After approximately 28 days in the fry tanks, fry are usually transferred out of thehatchery. At this stage, fry weigh approximately 5 grams, and may be sold, if thatis the business of the hatchery. Or, if the hatchery is producing fry for use on thefarm, the fry are transferred to fingerling tanks.

A: Rounded hand net for working with fingerlings; B: Squared hand net forcatching fry. C: Sleeve hand net for handling breeders.


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f. Fingerling Rearing: The stocking rate in the fingerling tanks is lower than in thefry tanks. Fry weighing 5-20 grams may be stocked at 1,600 per square meter; fryweighing 20-50 grams may be stocked at 1,000 per square meter. The feed used atthis stage should contain approximately 35% protein. Fingerlings may be kept inthe fingerling tanks until they reach about 50 grams, or 60 days old, at which time

most of the mortality would have occurred. The fingerlings may then sold if thatis the business of the hatchery, or stocked into grow-out ponds on the farm.

g. Hormonal Sex ReversalWhen tilapia are hatched, they are genetically determined as male or female.However, at the time of hatching, they are physically indeterminate, i.e. they donot possess sex organs.

It is therefore possible, in the early stages of fry development, to influence thedevelopment of the sex organs by hormonal intervention.

If fry are exposed to an excess of male hormone in this early stage, male sexorgans will develop, irregardless of the genetic composition of the fry. Similarly,if fry are exposed to an excess of female hormone in the early stages of frydevelopment, female sex organs will develop, irregardless of the geneticcomposition of the fry.As has been stated previously, males are preferred for rearing. Therefore, the process of hormonal sex reversal, for the production of all male tilapia, is asfollows.

i. Preparation of Hormone: The most commonly used hormone forhormonal sex reversal of tilapia is 17 alpha-methyl testosterone, applied tofry in their feed, at a rate of 60 milligrams of hormone per kilogram offeed. The feed containing the recommended amount of hormone can beprepared according to the following procedure:

- Dilute 3g of hormone in 1000ml of 95% ethanol and store this stocksolution at 4C.

- Add 20 ml of stock solution to 210ml of 90% ethanol and then sprayover one kilogram of feed.

- Spray the feed in a covered mixer and mix thoroughly for 20 minutes.- Spread the feed in a 5cm deep layer on a table inside a shaded

enclosed area, at 26C for 12 hours, to evaporate the solvent.

- Seal the feed in plastic zip-loc bags and place in a freezer at -2 C.


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ii. Treatment of Fry: For the hormone to be effective, fry need to beexposed to the feed containing the hormone as soon as they start to feed onexternal food sources.Therefore, fry need to be captured while their yolk sac is still visible, sincethis indicates that they have not commenced feeding on external food

sources.Fry should then be placed in a fry tank, at a suitable stocking rate, and befed the hormone laced feed four times per day, for 28 days.

iii.Results: At the end of this period, approximately 95% of the fry will bemale. It is possible to obtain a higher percentage of males by increasingthe frequency of feedings, and the length of time the fry are exposed to thehormone laced feed.

h. Supermale TechnologyAnother method of obtaining all-male tilapia is by the use of the Supermaletechnology.

It is possible to obtain male tilapia which will produce all male offspring when bred to anormal female. These Supermales can be obtained from specialized suppliers, but arequite expensive.

The Supermale has two Y chromosomes, instead of having one X and one Ychromosome, as in a normal male tilapia. This means that all the offspring of aSupermale tilapia and a normal female tilapia will contain a Y chromosome and an Xchromosome, and therefore will be male.

Once obtained, this technology is simpler to implement on the farm, and uses nohormones.


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XI. Transferring and Stocking of Fry and Fingerlings 30 Minutesa. Capturing Fish

It is important to be able to obtain fry and fingerlings from their natural environment, inan efficient manner, so as to minimize stress and injury.

Fishing gear commonly used in hatcheries and on aquaculture facilities in general, tend tohave very small mesh sizes. This is to ensure that fish are not gilled, or physicallyharmed, during capture and handling. Rather, the fish should be physically restrained, tomake handling easier.

This is necessary since the fry and fingerlings will usually be handled several times before they are ready for market. If they are not handled with care during the variousstages of the culture cycle, mortality will result, which will reduce the profit margin.

The most commonly used fishing gear for fry and fingerlings are hand nets of varioussizes. They have long and very small mesh sizes, and can even be made of some types of

cloth.


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b. Transporting FishThe development and expansion of aquaculture has made it necessary to transport livefish from one place to another, for various reasons. This movement of fish may be withinthe farm, between farms in the neighbourhood, or even between countries or continents.

Live fish transported may be broodstock, for use in breeding operations; fry andfingerlings, for use in grow-out culture; or market sized fish, which are required to bealive for specific markets, for example in Asia.

Fish should be able to be transported at any growth stage in their life, in such conditionsso that they do not suffer lethal stress, while at the same time being economical. It is possible to transport fishes and have total survival, using large amounts of space andwater. However, this may not be economical. There must be a balance betweentransporting as many fish as possible, using as little water and space as possible.

As fish are placed for long periods in the same small amount of water for transport, the

water quality starts to deteriorate. Dissolved oxygen content is reduced, carbon dioxidecontent increases, and other toxic compounds such as ammonia and nitrite increase.

An easy way of overcoming this problem is to change the water frequently duringtransport. However, this may not be possible at all times. Therefore, there are somesimple rules and devices, which enable fish survival during transport.

i. Preparation of Fish Before TransportFish for transport should be captured and held in a separate area 24 hours before beingtransported. This will reduce the stress during transport, since the fish will be easilyrecaptured. The fish will also become accustomed to a new environment outside of thepond.

Fish should not be fed for 24 hours before transport. This will enable them to empty theirintestines before being transported, so that they do not foul the water during transport. Itis also possible to use certain chemicals (sedatives) to reduce fish metabolic rate duringtransport. These chemicals are applied to the water before transport. However, thesechemicals are expensive, and some of them are not safe to use with food fish.

ii. Water Quality for TransportWater being used to transport fish should have the following qualities:

- Water should be cool, so fish and bacteria will be less active, thusreducing DO consumption and production of ammonia/carbon dioxide.Ice should be used, to reduce the water temperature to 15-20 degreesCelsius.

- The pH should be about 7 to 7.5.


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- It should befree from mud or suspended solids, to reduce stress to thefish gills, to reduce bacteria in organic solids, and to reduce risk of lowoxygen levels caused by decomposition of organic material.

- It should be free of harmful chemicals, such as hydrogen sulphide,dissolved iron, pesticides and various pollutants.

Therefore, well water or rainwater should be used. Pond or canal water should beavoided, will deteriorate faster, stressing the fish.

iii.Stocking Rate for TransportThe amount of fish that can be safely transported in a fixed volume of water depends onthe species, the size of the fish, and whether or not aeration is supplied.

Some species are very susceptible to poor water quality, and these should be transported

using a low stocking rate. Others, such as tilapia, are more tolerant to poor waterconditions, and can therefore be transported using a higher stocking rate.

Larger fish require will occupy more space and utilize more oxygen. Therefore, they haveto be transported using a lower stocking rate than smaller fish.

If aeration is supplied, this greatly increases the amount of fish that can be transported.This is discussed in more detail in the following section.

iv. Methods of TransportA simple and efficient way of transporting small amounts of fish, without continuousaeration, is by the use of a plastic bag containing approximately 20 litres of water and 20litres of pure oxygen, as illustrated below:


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This system may be used to transport tilapia fry and fingerlings. The plastic bags should be protected during transport, by placing them in a cardboard or wooden box, or in acanvas bag. This has the added advantage of keeping the bags cool, and reducing the fishactivity due to the darkness, thereby reducing oxygen consumption.

Broodstock can also be transported using this system, but only a maximum of three 300gfish should be placed in each bag.

The plastic bag may be doubled, to minimize leakage through the seams. Using thissystem, the following amounts of fish can be transported:


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Guidelines for the transport of Warm-water fish Juveniles in sealed plastic bags filledwith 20 l water and at least 20 l oxygen1

(loading capacities as number of fish per bag)


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Another way of transporting fish is by the use of rigid containers. Containers are usuallymetal or plastic, and are fitted with a portable aeration device. These containers haveproven to be very efficient and reliable for transporting fish locally.

This system is more efficient for transporting large fish, when compared with the plastic

bag, but less efficient for transporting smaller fish.

c. Stocking FishesWhen the transported fish reach their destination, the fish inside the container should begradually acclimatized to the quality of the water where they are to be stocked.Temperature and chemical characteristics may be very different from those of thetransport water, especially if the transportation time was relatively long.

Therefore, the fish must be acclimatized to the water conditions into which they are to bestocked.

If plastic bags were used for transport, the sealed bags should be floated in the receivingwater, for at least 15 to 30 minutes to allow the water in the bag to attain the sametemperature as the water outside the bag. Failure to this may cause thermal shock to thefish, and may cause death.

The bags should then be opened, and some of the receiving water added, so as toaccustom the fish to the new water. Finally, the opening of the bag should be loweredinto the receiving water, and the fish should be allowed to swim out, or should be slowlyemptied out into the receiving water.


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Stocking of Transported Fish

If containers were used, then some of the receiving water should be slowly added to thecontainer, to equalise the temperature. At the end of 15 minutes, the water in thecontainer should have approximately the same temperature as the water into which thefish will be placed. Only then should the fish be removed from the container and placedinto the new water.


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XII. Feeds and Feeding 60 Minutesa. Tilapia Feeding Characteristics

Tilapia are capable of ingesting feed material from the surface, middle and bottom of thepond. However, fry and fingerlings feed mostly on the surface and in the middle layer ofthe pond.

Tilapia ingest a wide variety of natural food organisms, including plankton, some aquaticmacrophytes, planktonic and benthic aquatic invertebrates, larval fish, detritus, anddecomposing organic matter. With heavy supplemental feeding, natural food organismstypically account for 30 to 50 percent of tilapia growth. This is relatively high, comparedwith other species.

Tilapia are sometimes classified as filter feeders because they can efficiently harvest plankton from the water. The gills of tilapia secrete mucus that traps plankton. Theplankton-rich mucus, or bolus, is then swallowed.

Digestion and assimilation of plant material occurs along the length of the intestine(usually at least six times the total length of the fish). Two mechanisms help tilapia digestfilamentous and planktonic algae and succulent higher plants:

- physical grinding of plant tissues between two pharyngeal plates offine teeth

- a stomach pH below 2, which ruptures the cell walls of algae andbacteria.

Generally speaking, tilapia use natural food so efficiently that the nutritional value of thenatural food supply in ponds is important, even for commercial operations that feed fishintensively.

Very careful attention should be paid to fish feeds and feeding. In semi-intensivesystems, feed usually accounts for 60-75% of the total running costs of a fish crop.

If tilapia are fed properly, then they will be less susceptible to disease. Appropriate use ofa good feed will improve growth rates, reduce crop time, and result in larger fish.

b. Types of FeedThere are three types of food used in fishponds:

- Natural food- Supplementary feeds- Complete feeds.

i. Natural food: This is found naturally in the pond. It may include detritus, bacteria, plankton, worms, insects, snails, aquatic plants and fish. Theirabundance greatly depends on water quality. Liming and fertilization, in particular organic fertilization, can help to provide a good supply ofnatural food for the fish. Natural food is very important in the extensivesystem of aquaculture.


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ii. Supplementary feeds: These are feeds that are regularly distributed to thefish in the pond, and which contain many, but not all, the nutrientsrequired for growth. . They usually consist of cheap materials locallyavailable such as terrestrial plants, kitchen wastes or agricultural by-products. Supplementary feeds are important in the semi-intensive system

of aquaculture.

iii.Complete feeds: These are feeds that are regularly distributed to the fishin the pond. They are made from a mixture of carefully selectedingredients to provide all the nutrients necessary for the fish to grow well.They must be made in a form which the fish find easy to eat and digest.These feeds are quite difficult to make on the farm and are usually quiteexpensive to buy. Complete feeds are important in the intensive system ofaquaculture.

c. On-Farm Feed Formulation and ManufacturingFeed is the largest cost in semi-intensive aquaculture, usually comprising more than 50%.

Therefore, any savings on feed will amount to significant savings, which will increase the

farmers profit.

One way of reducing feed costs is to manufacture feed on the farm, using locally

available ingredients.

i. Feed FormulationThe formulation of feed on a farm depend on several factors, such as the market value,

nutrient requirements and natural feeding habits of the species being reared, and thefinancial resources of the farmer.

Tilapia fry and fingerlings, and to a lesser extent, adults, are able to utilize natural food

found in well-fertilized ponds, to contribute to their nutritional requirements.

For tilapia, the feed ingredients used should be low cost, since Tilapia have a medium

market price. The ingredients can also be mainly of plant origin, since Tilapia are able to

digest plant proteins relatively efficiently, and convert these plant proteins to fish flesh.

Ingredients such as rice ban, wheat middling, copra meal, soy meal and wheat flour can

be used to make a good supplementary feed.

In feed formulation, it is important to ensure that the ingredients used will result in a feed

with the required amount of the main nutrients (protein, carbohydrates and lipids), so as

to provide proper nutrition for the fish.

ii. Feed ManufactureIngredients used should be dried, for better handling and ease of storage. All ingredients

should also be ground to a fine particle size, for ease of mixing.

Ingredients should be weighed out, according to the recommended amounts, and placed

in separate containers.


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Mixing should be done using clean implements (e.g. a spade), on a flat, clean surface, in

the shade.

The two ingredients in the smallest amounts should be evenly mixed together first. The

ingredient in the next smallest quantity should then be added to this mixture. Finally, the

previously mixed ingredients should be mixed evenly with the ingredients in the largest

amounts. This will enable thorough mixing of all the ingredients.

A small amount of water should then be added to the mixture, to help in bind the feed

together. This damp dough-like mixture can then be pelleted by extruding it using a

simple hand mill.

The extruded pellets should then be dried in the shade, before feeding to fish.

For fry, the size of the feed particles is important, as indicated below. The dried pellets

may have to be ground to a suitable size before being presented to the fry.

Recommended Sizes of Feed Particles (mm)

iii.Locally Formulated Farm-Made FeedsThe following feeds have been formulated and used locally:

Feed No.1

Ingredients Percentage Protein Inclusion Rate Percentage Protein

IncludedSoya Meal 43 40 17.2

Shrimp Dust 30 20 6

Rice Bran 9 10 0.9

Copra Meal 20 20 4

Flour 12 10 1.2

29.3


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Feed No.2


Included

Soya Meal 43 50 21.5

Copra Meal 20 30 6

Rice Bran 9 10 0.9Flour 12 10 1.2

29.6

Feed No.3


Included

Soya Meal 43 50 21.5

Copra Meal 20 20 4

Wheat Middling 11 10 1.1

Rice Bran 9 10 0.9

Flour 12 10 1.228.7

d. Reasons for Feeding FishFish should be fed for the following reasons:

- Natural foods may not be enough to give the required growth rate- More fish may need to be stocked in the pond than the natural food

will support- Larger fish may be required, in a short amount of time- It may be uneconomical to rely on natural food

There are several occasions on which it is advantageous or even compulsory to stopfeeding the fish:

- When the water temperature is too low or too high- When dissolved oxygen content is low- On the day you manure is applied to the pond- If a disease epidemic appears in the pond

e. Types of Artificial FeedsThere are several types of artificial feeds:

- Mash (powder)- Cakes- Pellets (sinking and floating)- Green Feeds


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f. Methods of Applying Artificial FeedsThere are several methods of artificial feeding:

- Broadcasting: feed is evenly distributed over the surface of the water- Hand-feeding: feed is distributed by hand, in specific parts of the rearing area- Automated (Demand) Feeder: feed is released by way of a trigger mechanism

which is activated by the fish- Select Feeding: feed is distributed using a boat, etc., at specific parts of therearing area

- Feeding Trays: feed is placed in trays, which may be submerged or floating- Feeding Frames: feed is placed in floating frames, which prevent floating

feeds from dispersing

g. Advantages and Disadvantages of Artificial FeedsThere are several advantages of artificial feeds:

- When properly made, they can provide the correct balance of nutrients needed-

They are usually easily available to the farmer- The cultured species usually grows very quickly- They are easily stored for relatively long periods

There are several disadvantages of artificial feeds:- They are usually expensive- Unsuitable for some species- May pollute the water- May lead to allergic reactions if not properly made- May lead to pathogen virulence- May be lacking in completeness

h. Feeding RatesThe feeding rate describes the amount of feed that is applied to a particular area, over aperiod of time.

Different fish species are grown using different feeding rates. Feeding rates are usuallygiven to farmers in the form of a chart, showing the amount of feed to be applied eachday.

Sometimes, feeding is done according to the weight of the fish

At other times, fish are fed as much as they can eat. This is called ad lib feeding.


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Feeding Rates Based Upon Biomass

i. Basic Feeding PrinciplesThe following are some basic feeding principles:- Underfeeding leads to a loss in fish productivity, while overfeeding is

uneconomical, and also leads to poor water quality and production losses- The feed conversion ratio (FCR) is very important. It can range from 1.45:1 to

50:1- More feed is required in warm water than in cooler water


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XIII. Fish Health and Disease 30 Minutesa. Significance of Disease: It is important to ensure that fish grown on aquaculture

farms are healthy and free from disease. Around the world, disease has caused thecollapse of several important aquaculture enterprises, such as the shrimp industriesin China and Ecuador.

Fish diseases may cause severe losses on fish farms through:- Reduced fish growth and production- Increased feeding cost caused by lack of appetite and waste of uneaten feed- Increased vulnerability to predation- Increased susceptibility to low water quality- Death of fish.

b. Behaviour and Characteristics of Healthy Fishi. Reflexes

The following four reflex actions indicate healthy fish:

- Escape reflex: Fishes are usually not easy to catch. They escape at anyminor shadow or movement in or near the water. If the fish is slow toescape, then it is probably sick.

- Fight reflex: When a fish is caught, it tries to defend itself by vigorousmovements of the tail and fins. If the fish rests quietly and makes littleattempt to escape, it is probably sick.

- Tail Reflex: The tail of a healthy, captured fish remains strongly archedor exhibits a rapid back and forth movement. A fish which does notmove its tail in this manner, or allows the tail to hang flaccidly, isprobably sick.

- Eye Reflex: A healthy fish, when captured and lying on its side, turns itseye so as to keep it in the position it would normally be if the fish wasupright. If the fish keeps it eye pointing upward while lying on its side,then it is probably sick.

ii. External Characteristics of Healthy Fish- Bright, wet and normally pigmented skin- Flat and firm scales- Red, wet gills which are covered with a slight layer of mucous- Firm and elastic muscles- Anus closed and normally coloured- Clear, transparent and slightly protruded eyes- Characteristic fish-like smell- No nodules, parasites or ulcerated on the skin- No excessive mucus


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iii. Internal Characteristics of Healthy FishGenerally speaking, no fluid, gas or parasites should be evident inside the fish.

c. Types of Fish DiseasesThe three main causes of fish diseases are:- Attack by disease organisms

- Improper feeding;- Stress through extreme or toxic condition;

Consequently, fish diseases are grouped as follows:

- Infectious and invasive diseases- Nutritional diseases- Environmental diseases

i.

Infectious Diseases: Infectious diseases are caused by external orinternal invasion of the fish body by disease causing organisms. Bacteria,fungi, viruses and parasites like protozoa are the most common agents ofinfectious diseases. Rapid death of many fish is usually a sign of aninfectious disease.

ii. Nutritional Diseases:Nutritional diseases are caused by too much or toolittle of a particular nutrient, and are usually indicative of improperfeeding practices.Excessive feeding, or feed that contains too much fat cause the followingproblems:- Obesity with fatty deposits on internal organs, especially on the liver- Water retention in tissues due to kidney failure- Problems with the gills extracting oxygen from waterThe other group of important nutritional diseases is related to the lack ofvitamins and minerals in the diet. The lack of vitamins and minerals cancause a variety of problems, such as reduced growth rate, gill corrosion,eye opacity, skin problems, fluid retention, etc.

These nutritional problems are due mostly to improperly balanced feed,as well as feed degradation caused by feed being stored for too long aperiod before use.

iii. Environmental Diseases: Strictly speaking, environmental diseasesare not really diseases. Rather, they are related to unsuitable conditionsin the environment in which fish live. They are usually grouped intofour classes:


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- Asphyxia: This is due to low dissolved oxygen level in the water, andusually occurs in the early morning.

- Traumatisms: The traumatisms are skin lesions caused by poorhandling in capturing, stocking or general handling. This may lead to

other disease conditions, such as infections.

- Bubble Illness: This usually occurs in fry and small fishes. It resultsfrom too rapid transfer of fish from one water condition to another.

- Poisoning: Poisoning is due to the presence of harmful substances in thewater. These may be pesticides, oil, household waste, etc. It is importantto keep the pond and its surroundings clean to avoid this problem.

d. Fish Defence Against Infectioni. Mucus: Mucus (slime layer) is the first physical barrier that inhibits entry

of disease organisms from the environment into the fish. It is also achemical barrier, containing enzymes and antibodies that can kill invadingdisease organisms.

ii. Scales and Skin: Scales and skin function as a physical barrier that protects the fish. These are injured most commonly by handling, roughsurfaces of tanks or cages and by fighting caused by overcrowding orreproductive behavior. Parasite infestations can also result in damage togills, skin, fins, and loss of scales.

iii. Inflammation: Inflammation is a natural immune response by the cells toa foreign protein, such as bacterium, virus, parasite, fungus, or toxin.Inflammation is characterized by swelling, redness, and loss of function. Itis a protective response, an attempt by the body to wall off and destroy theinvader.

iv. Antibodies: Unlike inflammation and other nonspecific forms ofprotection, antibodies are compounds formed by the body to fight specificforeign proteins or organisms. The first exposure results in the formationof antibodies by the fish that will help protect it from future infection bythe same organism.


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e. Preventing diseases through good managementThe following points are important, and should be carefully followed:

- Ensure good water quality: sufficient supply, with adequate dissolved oxygenconcentration and free of pollution

- Keep the pond environment healthy, e.g., control pond silt, control unwantedplants

- Keep a healthy balance of phytoplankton and zooplankton and exchange water ifneeded.

- If necessary, use mechanical aeration.- Disinfect the pond regularly, using simple methods such as allowing the pond to

dry after each crop.

- Keep the fish in good condition, e.g., control stocking density, by placing onlythe recommended amount of fish in each pond.

- Keep different sizes or sexes separate if necessary to control fighting. Woundscan become inflamed, leading to disease problems.

- Ensure good food supply. Make certain that the feed is not spoilt or deteriorated.- Handle the fish properly, especially during harvesting and sorting/grading. Use

fishing gear with mesh size appropriate to the size of fish.

- Care for your fish during storage and transport.- Prevent the entry of disease organisms from outside the farm, by controlling

wild fish by using filters and screens. Regularly remove them from canals andponds.

- Disinfect all fish stocks imported from outside as eggs, juveniles or adults.- If a disease breaks out on the farm, remove dead or dying fish from the ponds as

quickly as possible, at least daily.

- Disinfect fishing gear regularly, by soaking in bleach.- A simple disinfecting bath for fish can be made using common salt in a 3%

solution for 5 minutes


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f. Tilapia DiseasesTilapia are more resistant to viral, bacterial and parasitic diseases than other commonlycultured fish, especially at optimum temperatures for growth.

Lymphocystis, columnaris, whirling disease, and hemorrhagic septicemia may cause high

mortality, but these problems occur most frequently at water temperatures below 68 o F.

Ich caused by the protozoan Ichthyopthirius multifiliis, can cause serious losses of fryand juveniles in

Tilapia Seed Production

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