ANSC 365: AQUACULTURE /FISHCULTURE /FISH FARMING.

Introduction
Aquaculture is breeding, raising, and harvesting fish, shellfish, and aquatic plants. Basically, its
farming in water. Aquaculture may also be defined as the “farming and husbandry of
economically important aquatic animals and plants under controlled conditions”. Fish farming/
fish culture is the growing of fish in ponds to allow feeding, breeding, growing and harvesting in
a well-planned way without fish escaping.
There are 30,000- 40000 different types of fish in the world that differs in size, shape, habitat and
habits. Aquaculture- farming of aquatic organisms in fresh or salt water.
Other methods of fish farming include; in cages, dams and reservoirs, offshore fish pens and in
rice paddies.
History of fish farming.
Fish were cultured as long as 2698 B.C in China. The first written account of fish farming was
by Fan Lai, a Chinese fish farmer, in 475 B.C. Tilapia was introduced in Kenya in 1924 in dams
(culture) in Sagana (Mt. Kenya)

Why grow fish in ponds?

-It is easier to get fish out of pond than to catch from river or lake.
-Fish growth can be controlled by giving extra feed and protection from natural enemies.
-The farmer is able to grow only what he/she wants.
-It allows the farmer to produce cheaply and have a supply of fish available when required.

Importance of fish farming.

1. Fish as food
 Fish is rich source of protein
 Its easy to grow
 Are cheap than some kind of meat.
 It’s available as food all the year round.
 Low cholesterol level.

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2. Better land use.

 The aim of growing fish, crops or animals is to increase the production of food
from land.
 When crops have used up all the nutrients in the soil, fish ponds can be built.
 Land may not favour crops because it is sandy. But there are ways of building a
pond.
 Fish ponds can be built as part of the water supply and irrigation.
3. Source of income
 A farmer can generate additional income through selling surplus fish.
4. Co-operatives
 Fish ponds can be built through co-operatives-an organization of people who
come together to do something they could not or would not do alone. Pupils living
close together can co-operate and develop joint fish ponds.
5. Employment in fishing industries- both direct and indirect
6. Foreign exchange earner
7. Recreation
8. Research
9. Raw materials to industries
10. Waste land utilization
11. Integration:- crop, animal and fish farming- residues fish feeding, manure-fertilizer
for fish pond

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General challenges facing fish farming in Kenya.
i) Uncoordinated promotion of fish farming through many
institutions including government, research institutions,
universities, NGO’s and regional authorities.
ii) Lack of comprehensive policy on fish farming including legislation
which indicates low priority the policy-makers have accorded fish
farming as an economic activity.
iii) Lack of certified seeds (fingerlings0 and commercially produced
fish feeds.
iv) Weak research programmes that are not demand-driven.
v) Inadequate training programmes for farmers and extension
workers.
vi) Inadequate outreach programmes and inefficiency in dissemination
of technology transfer to farmers.
vii) Poor record-keeping by farmers and inefficient data collection.
viii) Low funding of sub-sector by government and low investment by
private sector.
ix) Inadequate entrepreneurship skills by farmers and lack of credit.

Terminologies used in fish farming.

Capture fisheries -refers to catching fish from their natural habitat e.g.
river, lakes, oceans, sea streams.
Culture fisheries- refer to fish produced through human intervention in
the organisms’ productivity. (Artificial habitat) e.g.dams, ponds-man
made.
Monoculture- growing of only one kind of fish in a pond.
Polyculture- growing of two or more kinds of fish in the same pond.
Monosex culture- growing of one sex of one species of fish in a pond.
Spawning- the release and fertilization of eggs.
Stocking – the act of placing fish into the pond.
Stocking density- the total number of fish which can be stocked.
(Reproduction rate $ food available).
Stocking rate- the number of one species put in a pond.
Smoking-Method of fish preservation involving use of smoke coating to
prevent microbial growth.
Aquarium-Tank or container that is filled with water and stocked with
fish and vegetation for observation and study.

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Fresh water fisheries.
 Comprises of lakes, rivers, springs. (capture and culture fisheries)
 There’s permeability of water into fish through: -gills, buccal membrane and
alimentary canal; mineral salts are higher inside fish than outside, hence osmotic
pressure is higher inside than outside, thus water goes inside through the above
areas.
 Water influx counteracted through: - dilute urine, a lot of glomeruli, short
nephrons.
 Examples: Amphilusjacksonii(Cat fish/ Mumi); Anguilla bicolor(Eel/ Mkunga);
Oreochromis niloticus(Tilapia/ Ngege); Protopterusaethiopicus(Lung fish/
Kamongo)
Brackish water fisheries/ back water fisheries.
 A mixture of fresh and salt water with fluctuating salinity.
 Examples: Shrimp species (Penaeid monodon $ Penaeid monoceros); Tilapia;
Cyprinus carpio (Common carp) and Clarias (Mumi)
Marine fisheries
 Coastal and off-shoe deep sea fisheries (open water). Coastal marine fisheries
offer a better environment for fish to live because of salinity, light, temperature
and plenty of food. Fish species found are prawns, shrimps, lobsters, and crabs-
edible part is tail area.
 Marie environment is highly concentrated than inside the fish.
 Dehydration counteracted through: - drinking plenty water, gills impermeable to
urea; possess trimethylamine; few glomeruli, long, nephrons, gills impermeable to
salts and ammonia.
 Examples; Sail fish (Sulisuli); Marlin fish, Broad bill fish (Gladiator); Trevally
(Karambasi); Tuna; Shark, Kingfish, Dorado (Falusi), Hag fish.
Limitations of capture fisheries.
 It is easier to get fish out of a pond than to catch fish from a river or stream.
 Fish growth cannot be controlled by giving extra growth and protection from
natural enemies.
 The farmer cannot grow only those that he wants.
 Does not allow fish farmer to produce cheaply and to have a supply of fish
available on his own land.
Advantages of culture fisheries.
 It is easier to get fish out of a pond than to catch fish from a river or stream.
 Fish growth can be controlled by giving extra growth and protection from natural
enemies.
 The farmer will only grow those that he wants.
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  Allows fish farmer to produce cheaply and to have a supply of fish available on
his own land.

Criteria Used for Pond Site Selection

1. Reliable clean water source
Fish depend on water for breathing, eating, growing and reproducing.
Sites with water all year round are the best (water supply must be constant)
Pond water comes from rainfall, run-off, natural waters, and springs.
Smell, taste and observe water to use.
Very clear water lack nutrients, put fertilizer
Muddy water must settle before reaching the pond.
Dark, smelly and brown water may have acid in it, add lime.
Bright green water has a lot of fish food in it.
2. Soil type
Should not be porous e.g. sandy soil
Must be able to hold water.
Should contain nutrients e.g. iron, calcium and magnesium.
Wet a handful of soil with some water to make it damp, squeeze the soil, if it holds its shape then
it’s good for a pond
Well-constructed pond can also fit the sandy soil.
3. Topography
Refers to land elevation (sloppiness or flatness), built on gently sloping land for ease of filling
and draining off the pond.
Should be near dwelling place e.g. houses for security reason.
Should be near market places to ease transportation and sell fresh fish.
4. Proximity to a market

• Does market demand justify production?

• Will the existing physical infrastructure meet the farmer ’s needs for marketing the fish?

• Will there be sufficient demand nearby or will transporting to a distant market often be a
necessity? It is easier to sell at your doorstep or to have a permanent buyer who takes everything
you can produce and either picks the fish up or is close enough that you can deliver the fish to
them.

5. Infrastructure

• Are the roads good enough to bring supplies to the farm and take the product to the market?

• Are telephone service and electrical power available at the site?

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w If an intensive production system is necessary due to constraints of space or water, access to
power is a must. Electrical power is about two times cheaper than diesel power in Kenya (2006
prices).

w Telephone service may be needed for ordering supplies, arranging marketing, or requesting
technical assistance.

6. Availability of needed inputs

• Are fertilizers and lime available at reasonable cost?

• Are fingerlings available at a reasonable cost?

• Are fish feeds available for purchase, or are suitable ingredients available so the farmer can
produce his own?

7. Personnel

• Hire qualified people as farm staff. Raising fish requires specific knowledge acquired only
through training. Look for workers who understand farming and are dedicated to a successful
operation.

8. Access to Technical Advice

• Be sure good technical advice is readily available. Local extension agents or trained consultants
are good possibilities. Double-check advice received with a qualified individual (meaning they
have produced a few tons of fish before) who is sincerely interested in your success. Good
consultants admit when they don’t know the needed information.

• Consider both criticism and compliments very carefully: The best advice may come in the form
of criticism, and compliments can be misleading.

9. Competition

• Know who your competitors are and how much they sell their fish for. Consider whether you
will be able to match their price and quality or even outsell them by producing a better product or
selling at a lower price.

• If fish demand is high, cooperating with nearby fish producers to market the fish might be a
possibility. The presence of several fish farmers in an area may make it possible for inputs to be
obtained less expensively by forming a purchasing block (cooperative or group).

10. Legal issues

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Consider whether or not there are any legal issues that will affect your ability to culture fish at
this site. Would any of the following prevent you from going into fish farming: Land Use Act?
Water Act? Environmental Management and Coordination Act? Etc

Pond construction

Planning and design

Some specific design considerations to address include:

1. The source of water used to fill the pond

2. How water will be brought to the pond

3. The type of soil available for building the pond

4. The size, shape, and depth of the pond

5. The slope of the pond bottom

6. The height, width, and slope of the dykes

7. The type of drainage system that will be used

8. The layout (arrangement) of ponds used for different sizes of fish

Steps for Pond Construction

The logical sequence of steps that you should follow to build it. These are:

1. Survey the land

2. Clear all vegetation from the site

3. Remove the topsoil from the site

4. Determine pond, drain pipe, and supply canal elevations

5. Peg out the pond, including core trenches, dyke tops, and dyke toes

6. Dig core trenches and pack them with good soil

7. Excavate the pond area

8. Build the dykes

9. Install the drainage system

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10. Install the water supply system

Preparing the fishpond for stocking

1. For an old pond, drain all water from the pond and allow it to dry for a period of
fourteen days.

2. Apply lime to the pond bottom and dyke slopes.

• You should always choose agricultural limestone (CaCO3) for application in your
fishpond. But other liming materials, e.g., quick lime or slaked lime can be used.

• Distribute the powder evenly around the pond bottom and on the slopes of the dykes. This can
be done using a shovel. Always wear gloves when working with any kind of lime.

• If necessary, you can also apply lime by spreading it over the water surface

after filling the pond.

3. Apply organic fertilizer to the pond before filling it with water.

The most common examples of organic fertilizers are animal manures (e.g., from cattle, poultry,
donkeys, rabbits, sheep, goats) and decaying plant matter, such as cut grasses.

• Apply the manure to your pond in one of the following ways:

NB Spread dry manure on the pond floor before filling with water.

NB Spread (broadcast) dry manure on water surface periodically.

NB Place dry manure in a crib or compost bin in a corner or along the side of the pond

NB Set sacks filled with manure to float within the pond and shake them daily to allow nutrients
to leach out and enhance water fertility.

NB Construct poultry houses or pig pens above or adjacent to ponds to facilitate easy movement
of the manure to the fishpond

• Apply plant matter in one of the following ways:

o Combine dead plant material with animal manure to form compost, which can then be
applied into pond waters.

o These materials can also be mixed as compost heaps in cribs in a corner or along the side
of the pond.

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o Hay and other grasses can also be spread over the pond water as fertilizers.

4. Fill the pond with water.

5. Apply inorganic fertilizer to the pond after it has been filled.

• Inorganic fertilizers, sometimes called “chemical” fertilizers, are manufactured from mineral
deposits for use in land agriculture.

They are usually available from farm input shops in 50- or 100-kg bags. Inorganic fertilizers
commonly used in fishponds in Kenya are Di-Ammonium Phosphate (DAP) and UREA.

• Apply DAP and UREA to your fishpond at the following rates:

o DAP: 2 g/m2/week (or weekly applications of 15 tablespoons DAP for every 100 m2)

o UREA: 3 g/m2/week (or weekly applications of 30 tablespoons urea for every 100 m2)

• Apply inorganic fertilizers to your pond using one of the following methods:

• Dissolve the fertilizer in a bucket of water by stirring with a stick and then sprinkle the
solution around pond.

• Place small mesh bags of fertilizer on platforms just under the water surface in the pond,
where the material can slowly dissolve and become available to phytoplankton.

• Suspend small bags of fertilizer from stakes just under the water surface.

• Do not apply inorganic fertilizers directly to the pond bottom, because important nutrients may
be absorbed by the mud and not be available to benefit your pond.

• Plan to continue applying fertilizers to your pond at the given rates on a weekly basis
throughout the culture period.

• Avoid applying too much fertilizer to your pond, however, as this can lead to water quality
problems as well as higher costs for you.

Fish Pond(s) - is a place where fish are kept and raised for personal consumption or
commercial purpose. It is a controlled pond, artificial lake, or reservoir that is stocked with fish
and is used in aquaculture for fish farming or is used for recreational fishing or ornamental
purposes.
Types of ponds-classification based on source of water

a. Barrage pond.

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These ponds are usually filled by rainfall or by spring water. A spring sends the water flowing
through a small valley or down a slope into a low place or a spring bubbles form the ground into
a natural depression. The pond is formed by collecting water at the base of the valley and in the
low places. The number of pond walls to be constructed depends upon the slope of the land and
drainage system to be provided. Barrage ponds should not be built where the flow of water is too
great; it is difficult to keep the water from breaking down the wall, if the pressure of water is too
great. Even when the flow of water is not great, however, barrage ponds require over flow
channels. Because barrage ponds are usually built in low areas they are likely to fill up with
heavy rains. The over flow channels discharge the extra water away from the ponds. If this extra
water is not taken out, the pond wall may break.
Advantage(s)
 The cost of construction is less.
Disadvantages
 Difficulty to manage.
 Difficulty to control disease.
 Difficulty to prevent the entry of unwanted things

b. Diversion pond.
These ponds are made by bringing water (diverting) from another source like stream or river.
Channels are dug to carry the water from the source to the pond. The diversion pond is fed
indirectly by gravity or by pumping through a diversion canal (which becomes the main feeder
canal), from a spring, stream, lake or reservoir. The water flow is controlled through a water
intake. There is an inlet and an outlet for each pond.

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 Water from another source like a river or stream is diverted into the pond through the dug
channels.

Other types of fish ponds for fish farming

 1.Earthen Pond- An earthen pond is a near-natural habitation for fishes (catfish, tilapia, etc)
like a river or stream. Although it is constructed to suit the design of the fish farmer, it is mostly
constructed in sloppy or waterlogged areas to accommodate the fish and make them a natural
feel when they are being raised.
2. Concrete Pond- This is very common for fish farmers to raise their fish, especially catfish. A
Concrete pond is using blocks, sands, and cement to build a habitation for you to raise your fish.
Constructing concrete ponds requires the help of experts compared to other types of ponds. This
is so because any mistake in the construction of the pond can lead to leakages and it might cost
more to repair than to construct another one. One advantage of the concrete pond over the
earthen pond is that it can be constructed anywhere even in your house.
3. Plastic or Rubber Pond- is a common for beginners in fish farming. One of the benefits of
the plastic pond is that it is easy to set up. One amazing thing about the plastic pond is that you
can turn the old overhead tank into ponds that can be used to raise catfish.
4. Cage or Pen Ponds -This type of pond is always constructed inside freshwater. Cage tanks
are always constructed in the middle of oceans and large quantities of water. They are held and
surrounded by pegs.
Advantages of Cage or Pen Tanks
1. Fish tend to eat natural feed as they are raised in oceans (their natural habitation).
2. You can stock as many as the number of fish that you want.

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 3. Fishes raised in this type of pond tend to grow faster

Disadvantages of Cage or Pen Tanks

1. Water pollution can happen which can make you lose all your fish
2. Poaching can occur in this type of pond
3. Requires tight security for you to succeed in raising fish with this type of pond
Fish farming systems
1. Monoculture- growing of only one kind of fish in a pond.
Can be Nile tilapia, Oreochromisniloticusor cat fishClariasgariepinus
2. Polyculture- growing of two or more kinds of fish in the same pond.
3. Monosex culture- growing of one sex of one species of fish in a pond.
Tilapia is a prolific fish and should reach maturity to breed at just 3 months
This aspect leads to stunted growth which is not required since most people opt for hand size
table fish
Therefore, effort have been made to breed a monosex culture
In monosex culture males are preferred as they grow to bigger size faster
Monosex is important since energy for resting and fighting over females is reduced for growth
This is achieved through the following
Sexing of Fish
 Manual Monosex separation, not 100% efficient
 Use of steroids; male steroids are put into the feeds during initial growth stages. This
reverses the sex of the females. Through this 99% of males have been realized. Generally
hormonal feeds are used
4. Integrating Fish Culture farming
Introduction
In addition to producing fish to eat or sell, there are other advantages to growing fish. Adding
fish farming to other farm enterprises can make your overall operation more efficient and more
profitable. This comes about by sharing space, inputs, byproducts, and labor associated with
other crops, and especially by using or re-using materials available on the farm.
Factors to consider

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Some considerations of integrating fish culture into overall farm activities include:
• How much are you willing to invest in the project?
• How much time will be spent on fish production compared to other farm activities?
• Will growing fish enhance your food supply (when stocking fish for domestic use) or increase
your income? Or are you engaging in the activity just because your neighbours have a similar
project?
Fish pond construction.
Planning and designing – area of site in the farm depends on: -
 Type of fish pond and number of ponds required.
 Land survey; gradient slope, topography-
 Use a ball to detect direction of the slope.
 Put sticks/ pegs on land, 100cm apart, on upper side string is tied $ distance from
ground measured. The string is tied a gain on the next peg. The string has a
carpenter level, watch until air bubbles in the centre. Dig one end deeper than the
other.
 Land gradient recommended is 2-5% for easy drainage.
 Rectangular ponds are more productive than square ponds due to more water
circulation/ oscillation.

Principles of pond construction

1. Survey the land.

This involves identifying the direction of the slope in order to establish where and
how to site and establish walls and drainage.
2. Mark out the pond.
This involves use of pegs to show where what will be established and how.
3. Measure the walls-using strings.

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 Plan the depth of the pond and the height of the walls. A 2m deep pond should be
2.5m on the deep end and0 .5m on shallow end.
4. Dig the pond bottom/ pond excavation.

 The pond bottom must slope downward from shallow end to the deep end. Pond
bottom have a slope of 2-5% meaning that for every 100cm I length there’s a
change of 2cm in height.
 The soil excavated taken to place between the set of sticks in an even manner.
 Excavation goes hand in hand with wall construction.
 For earthen ponds the topsoil is usually kept aside $ not used for wall
construction.

5. Build drainage system.

Establish the drainage system before the walls. This helps to maintain desired
water level as well as protect the walls from damage.

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 Incorporate inlet as well as outlet pipe. Inlet normally placed at top of water for
the sake of oxygen, should not allow unwanted fish and materials into the pond.
Outlet helps to escape excess water. Elbow joint mixed in outlet; outlet is fitted to
prevent any fish from escaping with water.
Siphons and pumps.
Siphon is merely a flexible plastic or rubber tube which operates by vaccum
created in the pipe by sucking the end outside the pond until water begins to flow
out. Pumps can also be used to drain water.

6. Building the water inlet.

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 Ensure that the inlet supplies adequate quality and quantity of water into the pond.
It should not allow unwanted fish and other materials into the pond.

Siltation tanks.
They are built to prevent siltation of the pond which would otherwise reduce
capacity of the pond as well as clog the gills of the fish.

7. Build the walls.

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 Walls have to be watertight as well as the pressure of water in the pond.
 Strength of wall depends on soil used e.g. mixture of sand and clay is the best.
Clay alone cracks
 Soil also determines slope of the wall.
 Tamp the soil to pack them very tightly hence giving strong walls.
 Plant grass and not trees on the walls, trees crack walls after growing.
8. Pond sealing .

 Seal the pond bottom so that it does not leak.

 Soils with a lot of sealing do not need sealing.
 Built a clay core into the walls and clay over bottom as lining.
 Russian method: use pig dung, apply it at bottom of pond followed by banana
leaves or any other vegetation(easily disintegrate).cover it completely with soil.
 Leave it for two weeks forming biological plastic or “grey” and the pond is
sealed.
 Polythene plastics can also be used in the pond bottom and aroud the sides in one
place then covered with soil.

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 Fencing- off the pond.

Stocking the Pond

Stocking is the act of placing fish in the pond
Rules of stocking.
-Do not handle the fish too much.
-Make sure the fish gets enough oxygen.
-Avoid too warm or too cold temperatures.
-Stock the fish in the morning when temperatures are low and the fish less active.
Stages of fish development
1. Fertilized egg
 Eggs grow and hatch into small fish ( fry)
2. Fry
 Eat tiny plants and animals (planktons), swimming in water.
 They range from 2mm to 30mm in length.
 Takes 2 to 6 or 8 days depending on type of fish.
 Not easily identified.

3. Fingerlings
 Size of person’s finger 4 to 10 cm long.
 Have preference to certain food
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 Easily identified.
4. Adult fish /brood fish
 Sexually mature fish which are chosen as good to spawn (breed) produce eggs
and begin the whole cycle again.

Criteria for fish species’ selection.

 Marketability – type and population of fish to keep depends on available
market for the product both locally and international; known and liked as food,
requires adequate transport incase market is far, if near advertise date of harvest,
or use tradesmento buy the fish.
 Adaptation - able to reproduce (breed) naturally in your area, able to leave in
confinement (pond), able to find the right food in the pond, relatively free of
parasites and diseases, resistant to diseases and withstand wide temperature
ranges.
 Productivity- able to grow fast, breed easily in ponds.
Characteristics of a good breeding stock.
 Average size
 Injury, disease and parasite free
 Mature in terms of gonads
 Lively and active.
Sources of breeding stock.
 Natural waters
 Fish dealers /fishermen
 Other pond owners.
 Government fish farms
Transportation of the breeding stock.
 Do not handle the fish too much
 Make sure the fish get enough oxygen
 Keep the fish from getting too warm or too cold

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  Stock fish in the morning when temperatures are low and fish are
less active.
 Carry fry in small plastic or metal tubs.

Procedure of Stocking the Pond

Conditioning the soil
A layer of lime should be placed on the bottom of the pond evenly, two weeks before water is
put.
Why apply Lime?
 Lime corrects pH to desirable level thus neutralize acidity;
 its also anti-parasitic thus clears micro-organisms (sterilization).
 It improves soil texture
Types of lime
Ground limestone-1140kg/ha (common)
Agricultural lime – 2270kg/ha
Hydrated lime- 114kg/ha
Quick lime (Cao) -220kg/ha.
Hydrated and quick lime are the easiest to handle
Liming should be done after pond sealing
Pond filling
Introduction of water into the pond
-water should enter through the inlet so that it mixes with oxygen from air as it falls into the
pond.
-fill the pond slowly; fast introduction leads to a lot of siltation, leading to turbidity to water
characterized by mud.
Turbidity is the amount of suspended soil particles e.g. silk particles
- Let water stand for another 2 weeks to encourage primary productivity e.g. production of
planktons in the pond
Nb. Unless turbidity disappears primary production will not take place in water. Water should be
very clear to allow sunrays into the pond. In absence of primary productivity, fertilizer is applied.
Water parameters include;

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Check the temperature of that water.
-Check both minimum (night) and maximum temperature (day), since every fish spp has specific
temperature e.g. common carp=20-25, grass carp= 25-30, tilapia=25-35.
Parameters of a good pond
1. Check oxygen range using an oxygen meter.
Incase oxygen range goes to or below 4mg/litre then fish is in danger. Normally oxygen range is
6-8 mg/litre.
Incase of 5 mg/litre most fishes exhibit oxygen stress except tilapia.
Oxygen supply should not be less than oxygen consumed.
Any disturbance by man or nature helps put oxygen in water e.g. beating, stirring with stick,
small motors.
2. Check for the PH
Normally best PH is 6.5-9, beyond this, add water to counteract the alkalinity. Incase it’s below,
use lime to neutralize acid.
3. Determine the turbidity of water
Foreign particles suspended, phenomenon of water being not transparent due to presence of
particles, hence prevent penetration of sunlight for phytoplankton’s growth.
Secchi disc is used 2 opposing sides have different colours, allow it to sink in water (it has
weight), if the disc is dipped upto 30cm without colour disappearance turbidity is nil. If
colour disappears before depth of 30cm them water is said to be turbid.
Stick your arm under water, if hand disappears when water is at elbow deep, the water is too
turbid. If it disappears before water reaches elbow, it’s very productive. If the entire arm is seen
under water, it’s neither turbid nor productive.
4. Determine water hardness/ saltiness
Hardness is a measure of total salts dissolved in water (calcium and magnesium) help fish to
grow. Phytoplankton also needs these salts for growth.
If water is too soft, increase the hardness by adding lime to water.
5. Check the fertility of the pond

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If green colouration (due to phytoplanktons-bloom of algae) has not taken place, then the pond is
not fertile. Then add some fertilizers. Stick your arm in the pond, if hand disappears from
sight at elbow, the pond need no fertilizer.
Too fertile pond with thick layer of green blocks sunlight from the pond hence no oxygen can be
made by phytoplankton. Fish require carbon, nitrogen, oxygen, phosphorus, potassium, sulphur,
calcium, iron and magnesium and trace elements. Fish gets these elements from pond soil, the
pond water and food they eat.
Application of fertilizers (organic and inorganic)
a) soup form; place the manure in a container, pour water stir to form soup-like substance then
pour in pond.
b) a crib- a section of the pond is isolated using sticks then manure is poured inside there so
that only fertilizing effect of the manure leaves the isolation and water remains clear.
c) a sack – put manure in a sack and tie, put a stick at the deepest end of the pond and tie the bag
to the stick inside water, the fertilizing effect will be diffusing into water. For large pond apply
manure at the bottom before introducing water.
Application rates:
cow dung 1000kg/ ha;
chicken droppings 114-228kg/ha for new ponds, old ponds require less fertilization
Inorganic are NPK in ratio-8-8-2, 20-20-5; phosphorus is applied in singular form: SSP-
114kk/ha, DSP-57kg/ha, TSP-38kg/ha
Routine pond management
 Check leakage on the walls of the pond, repair immediately
 Filters should be attended to regularly
 Check how fish are responding to feeding to check health status
 Feed the fish depending on stocking density of the pond
 Add fertilization if necessary
 Check the predators eg hammer carps, African fish eagle king fish pelican’s alligators
etc.
 Check oxygen levels, ph on daily basis to see whether there is any turbididty.
Importance of routine observation of the fish / fish pond.

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  Check the pond walls, cut the grass around it.
 Check and remove the weeds which might be a problem during harvest time.
 Make sure the water is flowing freely.
 Check the fertility and turbidity of water.
 Check signs of diseases.
 Add lime if needed
 Check the pond for leaks.
 Clean the filters.
 Watch fish behavior near feeding area.
 Feed the fish
 Add fertilizer if necessary.
 Watch for predators.

 Feeding of fish
The growth of fish is directly related to the amount of food in the pond.
Fish do not need the same kind of food.
Different species eat different types of food, and fish eat different foods depending on the stage
of their life.
Newly hatched fry eat from their yolk sac.
The fry then eat the smallest phytoplankton.
Fingerlings eat bigger foods as it grows.
Adult fish eat plankton, higher plants, worms, insect larvae
Natural foods-include phytoplankton, zooplankton, snails, worms, insects, weeds and grass. If
fish is carnivorous, it will eat flesh of other animals and small fish.
Supplementary foods- include bread crumbs, rice bran, fish meal, ground- up maize, broken
rice, soya bean cakes, sweet potatoes, left over animal feeds and some animal manure.
The farmer must know what his fish will accept before he puts the fish into the pond.
Supplementary foods are better at encouraging growth.
Always feed the fish at same time in the same pond at regular intervals during the day.

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Feed the fish from the shallow end of the pond where one can see them eat and determine how
much more to feed
Do not overfeed. Excess food will decay in the pond.
Feed only 6 days each week.
Ensure that pond is well fertilized, so that it produces its own food.
Provide compound feeds in form of pellets for easy collection by fish in water, also to reduce
disappearance of feed. Pellets- proteins prepared in proper levels in factories.
Summary on fish feeding: “Four Fixes:”
• Fixed feed quality: Feed should be fresh and palatable with a high nutritive value. Spoiled
food should be thrown out to prevent disease.
• Fixed feed quantity: Fish should be provided with a fixed amount of feed every day. Uneven
feeding causes poor digestion, poor absorption, and slow growth.
• Fixed feeding time: Feeding should be around 10:00 am and 4:00 pm.
• Fixed feeding location: Feed should be given at the same place at each feeding, e.g., on a
feeding platform.
Harvesting and post- harvesting handling
Harvesting is the collection of fish from a pond for sale at the market or for cooking and
preservation for family use. To have efficient harvesting, you have to learn their feeding habits.
Always active when feeding during sun-rise and sun set or at night since they are attracted to
light hence use light. Take care not to injure the organisms.
Equipment’s used in harvesting.
• Gill nets.
• Seine nets.
• Hooks and line-time consuming.
• Poisoning-dangerous.
Techniques of fish harvesting
Gear –is anything that can be used to seize fish out of water, mostly use hands.
1. Passive gears – examples, traps, gill nets (those apparatus, you do not need to operate
during catch of fish, they are stationary gill nets and drifting gill nets. They have floaters on top
and sinkers at bottom.

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2. Active gears –examples, seine nets, perse nets, trolley lines, angle lines trawl nets. They
are activated to catch fish.
Electric fishing- fish are immobilized using electric currents move from Anode (+) to Cathode
(-), hence fish will get attracted to the anode pole.
Graft – are vessels from which gears are operated from. E.g.sesse boats, dugout canoes, ships.
Harvesting/Capturing methods
 Repeated drag netting-seine nets are regularly dragged in ponds; Clarias (mud fish) are
difficult to draw out of water.
 Angling using the hook and line
 Pond draining to get the fish. Clarias will still remain$ survive in the mud.
 Poisoning not preferred- the poison should be specific and has no effect to others. The
drug should not accumulate or make the fish unsuitable to human consumption; should be
cheap. Should be easy to apply. Some chemicals used are plant derived e.g. Derris plant’s
powder.
Fish handling and Preservation methods of fish
Use healthy people to handle your fish and clean containers.
Grading of fish during harvesting
In culture system, fish are put in sorting trays. The fish are separated in this manner:
Diseased and injured fish.
Small and big healthy fish.
Fingerlings to be put in a separate pond.
This is because different categories of fish attract different prices.
Preservation methods.
1.Sun- drying – open the fish and dry it to have the environment not favoring micro-organisms’
growth. It’s efficient on small size fish.
2.Smoking- cut open and smoke them on a wire mesh over a drum on flame of fire. This put a
smoke coating that prevent micro-organism’s growth.
3.Salting- cut into smaller portion and apply salt that has dehydrating effect and prevent bacteria
entering into the fish.
4.Brine- a saturated salt solution, the fish are dipped into.

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5.Chilling –cold rooms and ice are used.
6.Canning – fish is first mixed with spices, cooked and then preserved in cans.
Fish products
Fresh fish -Fish sold immediately or temporarily in cold storage
Salted and smoked fish-fish preserved through salting or smoking.
Cooked fish-can be boiled or fried.
Canned fish-fish is canned in its own or in olive or vegetable oil.
Fish meal-mainly dried waste of cannery and used as animal feed as well as fertilizer.
Fish Liver oils-best known is the cod liver oil. They have physical and chemical values
including medicinal and also contain sterols and vitamin D.

Marketing Your fish

Currently most fish produced in subsistence operations (usually less than 50 kg per harvest) are
sold at the pond site. This way farm families satisfy their needs and sell excess to neighbours.
For harvests larger than 50 kg, for example in semi-intensive settings, arrangements can be made
with a buyer.
Harvesting should be done regularly to satisfy the customer’s needs, even if the amount they buy
monthly or weekly is very little. This is called a “niche market,” i.e., a market where the seller
is assured of a small but regular outlet for their produce.
You may also sell fish to restaurants or institutions such as schools or hospitals. It is advisable
that small-scale producers form marketing groups, which will assure them a regular market.
Marketing studies
Before beginning a fish farming enterprise, a farmer should conduct a market study to help
determine:
• The type and size of fish preferred by consumers (fingerlings, whole-fish, fillets, etc.)
• The quantity of fish required by the market.
• The best time to market fish.
• Which other farmers are supplying fish.
• The prices at which fish are being sold.
Farmers must bear in mind that the focus of all marketing activities is to satisfy the consumer.

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• Every time a consumer buys fresh fish, whether in large or small quantities, what they are
telling you is that you should continue to grow and sell fresh fish. In the case of fish traders,
consumers are passing a signal back to the farmer telling them “produce more because I am
ready to buy your product.”
• If the consumer stops buying, the trader will also slow down on purchase of your fish. If this
happens, they could be passing on information about the price of your product, the form of your
product (fresh, frozen, or otherwise), or the quality of your product.
• A marketing system enticing consumers or traders to buy more fish from you is best.
What do consumers want?
• A marketing system that provides high-quality fish on demand at the lowest cost.
• Efficiency in the delivery of services.
• Reliability or assurance that the product will be there when needed.
Some basic marketing principles
• The efficient transfer of fish and fish products from the fish farmer to the consumer is vital in
any fish marketing system.
• Fish is a perishable commodity and must be transported to the market quickly to avoid
spoilage. If the market is not readily accessible, the product should be processed promptly before
it loses quality.
NB. Transportation and storage costs, which are directly related to physical handling of fish
products, must be considered.
NB. Storage of perishable commodities such as fish is more expensive than storage of
nonperishables because of the cost of refrigeration.
Some tips for marketing your fish
• When fish are ready for sale, harvest and send them to the market immediately.
• You can increase the value of your product by doing some basic processing, either of the whole
fish or of parts of the fish. Some possibilities include:
• Deep fry the whole fish, starting with the smaller fish. This will prolong the shelf life of
the product.
•Cut the fish into several pieces, such as head, chest, tails, or fillets, then deep fry and sell
them by the piece.

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• When taking fish to the market, check prices and sell as quickly as possible. There are risks in
holding fish for a long time waiting for the best price:
NB Time lag in the sale of products is a cost to the fish farmer. It will be less expensive to sell
your fish at relatively lower prices than to store them for sale the next day.
NB. Fish held for too long may spoil, becoming smelly or even unsafe, discouraging potential
customers, and giving you a bad reputation. It will be difficult to overcome any negative
perceptions that consumers develop about farmed fish, and all farmers in a given market area
may suffer.
• You should keep track of current consumer preferences and market prices for your product.
• It is often useful for farmers to organize themselves into cooperatives or use marketing agents;
cooperatives have better bargaining power than solo operators.
• A useful rule of thumb is that fresh farmed fish whose source is known and whose quality is
assured will fetch better prices and will out compete wild caught fish in Kenya
Fish Health management
Fish health management is a term used in aquaculture to describe management
practices which are designed to prevent fish disease. Once fish get sick it can be
difficult to salvage them. Successful fish health management begins with prevention of
disease rather than treatment.
General characteristics of fish which is sick.
 Discoloration of the body
 Their excrete is shiny and grey
 They are sparse at the bottom of the pond (gasping at surface for air)
 Have black and white spots on the body
 Change behavour e.g. sluggish, do not reproduce.
 Have sores in the body.
 Rubbing the body or head at the sides of the pond.
 Stop feeding
Control

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Organic fertilizers encourage growth of microorganisms. Control is cleanliness, adequate
feeding and oxygen supply; using baths of potassium permanganate, salt, copper
sulphate, formalin and malachite green.
Parasitic diseases
1. Bacterial diseases.
 Fin and tail rot. Symptoms: fins deformed at margin, secondary
infections due to injury. Treatment; D.P: CuSo4 (1:200).
 Ulcers. Symptoms; open sores in the body. Treatment: CuSo4 and
KMno4 0.5 ppm.
 Dropsy disease. Symptom; most internal organ and internal
cavity, water accumulation in the peritoneum. Treatment:
disinfection using KMno4 1ppm; 5ppm treatment using KMno4;
Chloromycetin(drug) 60mg in 45 litres for 3-7 days continuous.
(Study fish behavior; allow it in the mixture until it shows some
stress).
 Epidemic eye disease. Symptoms: eye ball affected-vascularised
eye turns opaque at the end and will eventually putrify; fish tilt
towards the side of the eye that is affected.
 Treatment: chloromycetin 8-10 mg per litre for 2-3 days; disinfect
the pond using 1ppm of KMno4.
2. Fungal diseases
 Ulceration and haemorrhage. Symptoms: ulceration (open sores
in the body), weakness, white hair-like structures on body –caused
by saprolegnia species. Treatment: dip in 3% of NaCl; CuSo4
solution of 1:200 for 5 days; KMno4 1:1000parts of water;
malchite green (antifungal) 1:20,000 parts of water for 30 seconds.
 Gill rot. Symptoms; initially the gills have red flecking and at the
end will putrefy. Treatment: 150-200kg of Ca (OH) 2 per hectare
on pond surface to prevent the fungi that causes disease.
3. Protozoan diseases

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 Itchryophythrisis (white spot). Symptoms: white spots all over
the body. Treatment: formalin 1;5000 dip in body of fish for one
hour for 7-10 days; sodium chloride solution 3% for more than 7
days.; remove fish with stress.
 Castiasis. Symptoms: a lot of blue mucus seen coating on the
body. (Long flagella seen under microscope). Treatment: NaCl
solution 3% for 10 minutes; formalin 1:4000 parts for one hour.
4. Worm diseases
 Gyrodactilus. Symptoms: fading of colour of fish and mucous
discharge in the body of fish; gills and fins affected. Treatment:
acetic acid solution 1: 550 for 1-2 minutes; NaCl 3% 2-4 days;
formalin 1:4000 for 2-3 days(monogenetic).
 Diplostomiasis. Symptoms: black spots on the body surface.
Treatment: pyloric acid 3: 100,000 parts for one hour; isolate the
fish and remove it mechanically.
 Hurudinea (leech) –fresh water parasites, killed by alteration of
salinity. They are blood suckers, also affects gills and fins.
5. Non –parasitic diseases
 Asphyxiation. Symptoms: air bubbles below the skin, fish
swimming at an angle 45*C with the head downward. Treatment:
isolate the fish, change water in the pond.
 Chocking. Symptom: fish get chocked. Treatment: change water
in the pond.
 Dysentery. Symptoms: excessive yellowish mucus in the gut.
Treatment: stop feeding fish / make fish fast, change water in the
pond.

Practical
 Visit a fish farm/ fishery.

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