CULTURE AND MANAGEMENT
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VOLUNTEERS IN TECHNICAL ASSISTANCE
1600 WILSON BOULEVARD, SUITE 500
ARLINGTON, VIRGINIA 22209, USA
APPROPRIATE TECHNOLOGIES FOR DEVELOPMENT
FRESHWATER FISH POND
CULTURE AND MANAGEMENT
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FRESHWATER FISH POND
CULTURE AND MANAGEMENT
[C] VITA, 1976
May be reproduced without
payment of royalty for official
U.S. Government purposes.
About this manual....
Freshwater Fish Pond Culture and Management is the second in a series
of publications being prepared by the United States Peace Corps and
VITA, Volunteers in Technical Assistance. These publications combine
Peace Corps' practical field experiences with VITA's technical expertise
in areas in which development workers have special difficulties finding
useful resource materials.
PEACE CORPS
Since 1961 Peace Corps Volunteers have worked at the grass roots level
in countries around the world in program areas such as agriculture,
public health, and education. Before beginning their two-year assignments,
Volunteers are given training in cross-cultural, technical,
and language skills. This training helps them to live and work closely
with the people of their host countries. It helps them, too, to
approach development problems with new ideas that make use of locally
available resources and are appropriate to the local cultures.
Recently Peace Corps established an Information Collection & Exchange
so that these ideas developed during service in the field could be made
available to the wide range of development workers who might find them
useful. Materials from the field are now being collected, reviewed,
and classified in the Information Collection & Exchange system. The
most useful materials will be shared. The Information Collection &
Exchange provides an important source of field-based research materials
for the production of how-to manuals such as Freshwater Fish Pond Culture
and Management.
VITA
VITA people are also Volunteers Who respond to requests for technical
assistance. In providing solutions, their aim is the most appropriate
answers for specific situations. Therefore, VITA specialists often must
produce new designs or adapt technologies so that they are of value
in developing areas.
Many VITA Volunteers have lived and worked abroad. Most VITA people now
work in the United States and other developed countries where they are
engineers, doctors, scientists, farmers, architects, writers, artists,
and so on. But they continue to work with people in other countries
through VITA. Thanks to their contributions of time and expertise, VITA
has been providing technical assistance to the Third World for more than
15 years.
Requests for technical assistance come to VITA from many nations. Each
request is sent to a Volunteer with the right skills. For example, a
question about fish pond operation might be sent to a VITA Volunteer who
has had years of experience working to develop fish ponds in Asia, and
who is now a university professor.
THE PURPOSE
Freshwater Fish Pond Culture and Management is a how-to manual. It is
designed as a working and teaching tool for extension agents. It is for
their use as they establish and/or maintain local fish pond operations.
The information is presented here to 1) facilitate technology transfer
and 2) provide a clear guide for warm water fish pond construction and
management. A valuable listing of resources at the end of this manual
will give further direction to those wishing more information on various
aspects of fish pond operation.
THE PEOPLE WHO PREPARED IT
The strength of both Peace Corps and VITA lies in Volunteers. These
manuals represent an excellent means of communicating important know-how
gained through Volunteer experiences and inputs.
The author of Freshwater Fish Pond Culture and Management, Marilyn
Chakroff, served with Peace Corps in the Philippines for three years
in a number of fisheries programs. Ms. Chakroff, who holds a B.S. in
Biology, now is an advanced degree candidate in the field of Environmental
Communications at the State University of New York, in Syracuse.
This manual is written out of her first-hand experience as a Peace
Corps Volunteer.
Joan Koster, the illustrator, has been a VITA Volunteer for more than 3
years. She is a teacher, professional artist, and writer. Ms. Koster,
who has travelled and studied in Greece for a number of years, currently
is preparing a manuscript on looms and weaving.
OTHER CONTRIBUTORS
Many thanks are due here to a number of people who aided the preparation
of this manual:
Dr. David Hanselman, Dr. Peter Black, and Dr. Robert Werner -- Faculty
of the College of Environmental Science and Forestry, State University of
New York, Syracuse, New York.
Dr. Shirley Crawford, Agricultural and Technical College, State University
of New York, Morrisville, New York.
William McLarney, New Alchemy Institute, Woods Hole, Massachusetts.
A.F. D'Mello, Hawkesbury Agricultural College, New South Wales,
Australia.
Richard T. Carruthers, Bioproducts, Inc., Warrenton, Oregon.
Dr. William Ribelin, Department of Veterinary Science, University
of Wisconsin, Madison.
A special note of thanks is due John Goodell, VITA, for his layout work
and staff assistance with this manual.
REPLY FORM
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more helpful. If the reply form is missing from your copy of the
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Arlington, Virginia 22209 USA
Tel: 703/276-1800 * Fax: 703/243-1865
Internet: pr-info@vita.org
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NOTE TO THE USER: This manual was published because Peace Corps and
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interest. In order to provide the most effective help, the preparers
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VITA
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1. How did you find out about the PC/VITA Freshwater Fish Pond Culture
and Management manual? How did you get your copy?
2. Which parts of the manual have you found most useful? Least useful?
Why?
3. Did you find the manual easy to read, too simple or too complex,
complete or incomplete?
4. How has this manual helped your work? What have you done to apply
the information?
5. Which plans have you used? Did you make changes in any of the plans?
(For example, when you were building a drainage system, did you
substitute any materials for the ones mentioned or change the design?)
If you made changes, please describe what you did that was different.
Include photos, sketches, etc., if possible or important.
6. Can you recommend additional methods or equipment which you feel
should be included in a new edition of the manual? If you do know
of such methods, etc., please include the information here.
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Privacy Act Notice: Furnishing tile information requested herein is
completely voluntary. It is requested under authorities contained in
the Peace Corps Act (22USC 2501 et seq.). The only uses which will be
made of this information are as follows: 1) For management purposes
involving the format of future issues of this publication; 2) For incorporation
in a mailing list for this other similar publications.
Table of Contents
Section
"About This Manual"
Reply Form
1 INTRODUCTION
2 PLANNING: THE SITE AND THE TYPE OF FISH FARM
3 PLANNING: SELECTION OF FISH
4 FISH POND CONSTRUCTION
5 PREPARING THE POND
6 MANAGING THE POND
7 HARVESTING THE POND
8 PRESERVING FISH
9 PROBLEMS OF FISH IN PONDS
10 OTHER METHODS OF FISH CULTURE
Glossary
Resources
Measurements Used in This Manual
Index
1 Introduction
What is Fish Culture?
Fish culture is the growing of fish in ponds. Growing fish in ponds,
from which they cannot escape, allows feeding, breeding, growing, and
harvesting the fish in a well-planned way.
Fish culture is one form of aquaculture. Aquaculture is the science
which deals with methods of growing (cultivating) animal and vegetable
life in water. Some other kinds of aquaculture are concerned with growing
frogs, oysters, seaweed, and even rice.
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History of Fish Culture in Ponds
Growing fish in ponds is a very old practice. Carp were cultured as long
ago as 2698 B.C. in China, where they were grown in ponds on silkworm
farms. Fish culture seemed to occur whenever civilization was settled
for a long period of time. For example, fish culture was done in ancient
Egypt and in China, which has had a continuous civilization for over
4,000 years. The first written account of fish culture in ponds was by
Fan Lai, a Chinese fish farmer, in 475 B.C.
The ancient Romans introduced carp from Asia into Greece and Italy. By
the seventeenth century (1600's), carp culture was being done all over
Europe. A book written in England in 1600 by John Taverner gives the
details of good pond management and talks about growing the common carp.
Taverner also wrote about pond construction, fertilization and feeding.
Another book, written in 1865, gave the details of the stripping methods
of spawning fish. The methods of culturing common carp have not changed
very much since that time.
The common carp is still a very important pond fish. In addition,
today, other fish also are being cultured in ponds. Some of the most
well-known are fish of the tilapia genus, like Tilapia nilotica and
Tilapia mossambica. Some of the other Chinese carps -- the silver, grass,
and bighead carps -- also are often used in pond culture. Most importantly,
countries all over the world are using time and money to discover which
of the fish commonly found in their own waters will grow well in fish
ponds.
Why Fish are Grown in Ponds
The practice of culturing fish in ponds developed because growing fish in
ponds is a more useful practice, for some purposes, than trying to catch
fish from lakes, rivers, or streams. For example:
* Many interested people discover that building a fish pond
close to home is possible and far more convenient than going
to the nearest market or river. Ponds can be built wherever
the soil, shape of the land, and water supply are right. This
may sound as if a lot of factors are involved. But since a
wide variety of soils, land shapes, and water supplies can be
used for pond culture, a fish pond can even be made from a
rice paddy or an unused grain field.
* It is easier to get fish out of a pond than it is to catch a
fish from a river or stream. Also, the number of fish taken
out of a pond can be controlled. But it is very difficult to
know how many fish can be caught in a river or stream or lake
at any one time. When the farmer goes to his fish pond to get
dinner, he knows he can take out the number of fish he needs
-- quickly and easily.
* Fish growth can be controlled. The fish can be fed extra
food to make them better for market; natural enemies can
be kept from killing the fish. For a person who relies on
fish for his food or his income, these are important factors.
* The only fish grown in a pond are the ones the farmer
wants to grow. When he takes a fish out of his pond, the
farmer knows what kind or kinds he will be getting. When
he catches fish in a lake,
stream, or river, many of the
fish will not be the ones that
are good to eat or to sell.
* Growing fish in ponds allows
the farmer, or other fish
grower, to produce fish
cheaply, and to have a supply
of fish available on his own
land. Fish in ponds belong
to the pond owners; fish in
the rivers and lakes do not.
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Why Growing Fish is Important
There are some very good reasons why a farmer or small land owner might
be interested in fish farming:
* Fish are an important food source.
* Fish farming can help a farmer make the best use of his land.
* Fish farming can provide extra income.
There may be additional reasons; you and the pond owners can determine
these from the local situation. The three points listed above are very
broad, however, and apply, at least in part, to most situations.
Therefore, each point is discussed more fully below.
FISH AS FOOD Farmers know that all living things need food, and that
without food, living things die. However, they are not as likely to know
the characteristics of food which make it valuable (or not) to the body.
Food is important because it provides proteins, vitamins, minerals, fats,
and carbohydrates. These things are called nutrients: they are materials
that the body must have to live and grow. Every kind of food has different
amounts of each of these nutrients. For example, some foods
contain more protein; others have more fat than protein.
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Because foods contain different amounts
of proteins, fats, and carbohydrates,
for example, it is necessary to eat a
number of different kinds of food to
get the right amounts of each nutrient.
All the foods together then give the
body what it needs to grow.
The food that people eat is called
their diet. Eating the right kinds of
food -- foods that give the body the
right amounts of proteins, fats, etc.
-- is called eating a balanced diet.
People who eat a balanced diet usually
are healthy and strong; people who do
not eat the right kinds of food are
more likely to be weak and get sick.
Proteins are the most important part of food. Protein is made of carbon,
hydrogen, and nitrogen. These are called elements. The combinations of
elements in protein make it the most useful nutrient. Foods that contain
a lot of protein are especially good for people to eat. And fish contains
a lot of protein.
The table on the opposite page shows a list of foods that humans eat.
The first number beside the food shows the number of grams of protein in
the food when it is fresh. The second number tells how many grams of
protein there are in food which has been dried. The table shows that
fish -- whether fresh or dried -- is a very good source of protein.
(100gm of dried fish contains more protein than 100gm of fresh fish only
because dried foods have water taken out. Therefore, 100gm of fresh fish
weighs less when it is dried.)
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If the farmers in your area already eat a lot of fish, or like fish, fish
farming for food may not be hard to introduce and have accepted.
If they do not eat fish often, you will have to keep this in mind when
you talk about fish as a healthy food. Food just may not be the most
important reason, from their point of view, for wanting to grow fish.
PROTEIN CONTENT OF FOODS (*)
Fresh, gms protein Dried, gms protein
Food per 100gm per 100gm
FISH
Fatty (herring) 17 46
Non-fatty (haddock) 16 84
MEAT
Beef 20 67
Pork, loin 20 67
Liver 20 67
DAIRY PRODUCTS
Milk 3.4 26
Eggs 12 46
CEREALS
Wheat 12 14
Maize 10 11
Oats 10 11
Rice 8 9
OIL SEEDS
Soya 33 37
Cottonseed 20 21
Sesame 21 22
GREEN LEAFY VEGETABLES
Cabbage 1.4 - 3.3 24
Spinach 2.3 - 5.5 26
ROOTS
Cassava (manioc ) 0.7 2
Potatoes 2.1 9
Yams 2.1 7
Plantains 1.0 3
(*) These values are estimates only; the amount
of protein varies according to the age, size,
and quality of the food, and how it was
cooked and stored.
Source: Aylward and Jul (1975)
But there are other reasons you can offer a farmer. For example, a
farmer may consider cultivating fish if he realizes that fish are easy
to grow, cheaper than some kinds of meat, available as food all year
round, etc. You will have to see which combination of arguments works
best for getting farmers interested.
BETTER LAND USE Some farmers may be more interested in fish farming
when they realize they can accomplish two purposes: provide a reliable
food supply and make the best possible use of their land.
"Fish farming" is a good thing to call "fish culture" because it can
start the farmer thinking about raising fish with the same kind of planning
and land-use management ideas that he puts into raising crops.
Whether the farmer raises fish, crops, or animals, he is using his land
in certain ways. His aim in all cases is to increase the production of
food and the yield from the land. What farmers, and other people, often
do not realize is that fish culture can help get more out of the land.
Here are a few ways in which fish culture can help support and extend a
farmer's land use:
* Land gets tired when it is used for growing the same crop
year after year. These crops use up nutrients in soil, and
they begin to grow poorly. Fish ponds can be built on this
land and fertilized to provide food for the fish. After a
few years of fertilizing and growing fish, the soil inside
the pond regains some of the nutrients used up by the growing
of crops year after year. The land can then be used for
crops again.
* Some farmers own land that may not be very good for growing
crops: it is too sandy, for example. But there are ways of
building fish ponds in sandy soil. So the farmer would be
able to use land that was once not of much value to him.
* There are many ways that fish farming can fit into the
farmer's plan for his land. The important thing is that all
of these ways help the farmer make the best use and get more
out of what he has -- readily, and often without much expense.
For example, a farmer who grows paddy rice can grow fish in
that paddy; fish ponds can be built as part of water supply
and irrigation systems; vegetable scraps and animal manures
can be collected and used for fertilizing ponds. The farmer
should know that a farm with a fish pond or ponds can give
a total food yield that is higher than a farm with no fish
ponds.
The following diagram illustrates some of the ways in which the fish
pond fits into the farm: The same water source is used by both the
garden and the fish pond; the mud from the bottom of the pond makes
good fertilizer for the garden; vegetable matter from the garden can be
used to fertilize fish ponds; manure from the animals can be used for the
pond and parts of fish can be used to feed animals; etc.
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ADDED INCOME Fish ponds can be quite small, or they can be large.
They can be made using expensive equipment and drainage systems, or they
can be dug using hand tools and drained by a bamboo pipe. Fish can grow
successfully in both of these types of pond, as long as the ponds are
managed correctly.
If the major reason for building the fish pond is to get increased and
better food for his family, a farmer certainly does not need fancy ponds
or expensive equipment. Fish ponds can be very inexpensive to keep.
Fish do not require fancy foods. Many ponds provide all the food the
fish need. But besides the foods they find in water itself, some fish
eat leafy garbage, mill sweepings, beer residues, spoiled grains, broken
rice, and many other waste products that might not otherwise be used.
A farmer makes his income go further by growing more of the family's
food and by selling leftover fish the family cannot eat.
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Growing fish to sell can also be
very profitable. But the costs
involved in getting started and in
maintaining the effort are greater:
if the farming is to be a solid
commercial enterprise, then more
ponds, more time, more money, and
nearby marketplaces are needed.
The business may or may not show
a profit right away; in fact, the
chances are that it will not. A
farmer might be better advised to
start small and work into a bigger
enterprise slowly as he learns to
manage the art of growing fish in
ponds.
A Word about Cooperation
Often fish ponds are built by cooperatives. A cooperative is an organization
of people in an area who come together to do something they could
not or would not do alone. In this way, four or five people or families
can pool their resources and build a fish pond operation together.
Sometimes an entire village will form a cooperative and will build and
operate a pond as a group. This kind of cooperation makes possible
better pond construction and management. A fish pond cooperative may be
a good way for a village to improve the diet of the community and to sell
enough fish to maintain the enterprise. If the farmers in your area are
not interested in, or are concerned about, building ponds individually,
a cooperative may be a very acceptable idea.
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Getting Ready to Plan a Fish Farm
A farmer or other person interested in growing fish should read the
following list carefully before going further. The following factors
must be considered before the farmer builds his fish pond. Many pond
owners have small fish ponds that are only used for their own families,
but a farmer who sells fish must look for a market and a way to get his
fish to that market. It does no good to harvest fish which cannot be
sold or used by the farmer and his family.
* Is the soil able to hold water for a fish pond?
* Is there an adequate supply of water for a pond?
* Is the land a good shape for a fish pond?
* Is the pond area close to your home?
* Who owns the land where the pond will be built?
* Are there enough people to help build and harvest the pond?
* Can the equipment for building a pond be built, borrowed, or bought.
* Is there a marketplace nearby?
* Are there roads from the pond area to a market place?
* Are the roads passable even in the rainy season?
* Is there a good way to get the fish to market?
* Is there a vehicle available for transportation, if necessary?
* If there is no market nearby, or if it is hard to get to the
market, can the fish be kept by drying, smoking, or salting?
* Is there enough food for the pond fish?
* Are there fertilizers available?
* Do the people in the area like fish? Do they eat freshwater fish?
* Can the people in the area afford to buy the fish produced in the
pond?
If the farmer can answer yes to the questions which most fit his
situation, he has a good chance of having a successful fish pond.
But he must consider these factors. Each is discussed in detail in
the "Planning" sections.
2 Planning: The Site and the
Type of Fish Farm
Before construction can begin, the farmer must look over his land to
choose the place or places where ponds can be built, and decide what
kind and how many to build. He must also decide on the kind of fish
culture he wants to do, and on the type of fish that he wants to raise.
He must look at his resources and his needs very carefully before he
actually begins building and operating a fish pond. This section will
give information to guide the farmer in the planning of ponds and kind
of fish culture.
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The Site
One of the most important parts of planning is finding the right place
(selecting the site) for the pond. Fish ponds use the land in a different
way from agricultural crops such as rice or wheat, but fish also are a
crop. And when a farmer builds a fish pond, he is choosing one use of
his land instead of some other use. If the site for the pond is well-chosen,
the pond can be more productive than the land by itself. But if
it is not chosen well, the farmer may lose, or, at best, gain nothing
from his fish pond. When considering a site for the fish pond, the
farmer should remember and consider several points that were made in the
introduction:
* Often poor agricultural land can be turned into very good fish
ponds. In general, the better the soil of an area, the better
the fish pond. But this does not mean that a pond cannot be
built on poor land. It does mean that the farmer will have to
work harder to maintain the pond and the fish.
* If the pond is built on agricultural land which is not producing
good crops, but the pond is cared for well, eventually the pond
bottom soil will become more fertile than it was before. If
this pond is a large one, after harvesting the fish, the pond
can be planted again with a land crop, like corn, and allowed
to grow. Then when the corn is harvested, the land can be
turned back into a fish pond. This means that a farmer can get
two good uses out of his land instead of one poor crop.
* Other farmers may want to grow fish in rice paddies by digging
trenches around the edges of the paddy for fish to swim in.
This is another way of culturing fish which will be discussed
in somewhat more detail later in the manual.
The point of the discussion above, is that a fish pond is just one use
that a farmer's fields can have, and the choice of how the land can be
used is important.
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There are three factors that work together to make a good site for a
fish pond:
* Water supply
* Soil
* Topography
WATER SUPPLY Water supply, soil, and topography all are important,
but water supply is the most important factor in selecting a site. Fish
depend upon water for all their needs: fish need water in which to
breathe, to eat, and to grow and reproduce. If a site has water available
year-round, that site meets its first test easily. If water is not
available all the time but there is some way to store water -- in large
tanks, barrels or drums, in depressions, ponds, or wells -- for use when
the natural water supply is low, then that site may still be all right.
The key, of course, is that water must be available at all times and in
good supply.
Where Can Water for Fish Ponds Come From? Water used in ponds comes
from many sources:
* Rainfall. Some ponds, called "sky" ponds, rely only on rainfall
to fill their need for water.
* Run-off. Some ponds are gravel and sand pits which fill when
water from the surrounding land area runs into them.
* Natural waters. Most ponds are filled with water that comes
from natural springs or wells, or with water that has been
channelled (diverted) and brought in from streams, rivers,
or lakes.
* Springs. Some ponds are built where there is a spring to supply
water. Spring water is water under the ground that has found a
way to get out. It leaves the ground and becomes a stream as it
flows away. Spring water is good for fish ponds because it is
usually clean (uncontaminated) and has no unwanted fish or fish
eggs in it. If the water from a spring has travelled very far,
it may need to be filtered before it is used for a fish pond.
But filtering is easy to do (see the "Construction" section)
and the important fact is that the water supply is available.
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* Wells. The best source of water for a fish pond is well water.
Well water has few contaminants and, if the well is a good one,
the water is continuously available. Well water and spring
water, however, are both often low in oxygen content. Fish
need to have oxygen in their water to live. Since this problem
is overcome easily (see water quality information in the section
on "Preparing the Pond") the major factor to be considered
here is an adequate water supply.
Most fish ponds use water that comes from a stream, river, or lake.
A diversion ditch or channel is dug between the water source and the
pond to take water from source to pond. This is a good way to fill a
pond because the water can be controlled easily. When the pond is full,
the channel can be blocked with a gate or a plug (see "Construction"
section), and the water will stop moving into the pond.
There can be problems with this kind of water supply; for example, often
in tropical areas streams flood in the rainy season. This extra water
can be dangerous to the pond and must be diverted away from the pond by
a channel built for that purpose. IT IS BEST NOT TO CHOOSE A PLACE THAT
IS KNOWN TO FLOOD WHEN CHOOSING A WATER SUPPLY AND SITE FOR A POND. When
a pond floods, all the fish escape, and the pond is empty at harvest time.
If the water for the pond is being taken from a stream, lake, or river,
then the farmer should plan to filter the water carefully when filling
the pond. Water from these sources sometimes contains unwanted fish or
fish eggs. Filtering prevents these fish or eggs, and other harmful
animals, from entering the pond.
Quality of the Water Supply. Finding an adequate water supply is the
first step. Then the farmer has to check that supply to make sure it
can be used for a pond. This check of the water should include:
* looking at the water, smelling it and tasting it.
* looking to see if there is a family upstream who take baths in
the water before it gets to the pond.
* making sure that there is no family or village downstream that
depends upon the source for their drinking water.
If the water supply seems all right, the farmer must also find the
answers to some other questions. Where the water comes from, how far it
travels to get to the site for the pond, and what kind of soil it travels
over will all affect the quality of the water. These questions and their
answers tell what must be done to make the water right for a pond:
* Is the water very clear? Then the farmer may have to fertilize
the pond because there are not enough nutrients in the water.
* Is the water very muddy? Then it will have to settle before it
is used in the pond: a special place will have to be made
where the mud can settle out of the water before the water
goes into the pond.
* Is the water a bright green? It probably has a lot of fish
food in it.
* Is the water a dark, smelly brown? It may have acid in it,
and the farmer will have to add lime to the water.
There are many things which can be done to make water good for a pond.
If the farmer knows his supply and the kind of water he has, he can
take the steps necessary to use his supply well.
SOIL The second important part of site selection is the soil of the
area. The soil of the pond must be able to hold water. It also contributes
to the fertility of the water because of the nutrients it
contains.
Ability of Soil to Hold Water. The best soil for a pond contains a lot
of clay. Clay soil holds water well. When a place with a good water
supply is found, the farmer must test the soil. He can tell a lot about
the soil simply by feeling it. If the soil feels gritty or rough to the
touch, it probably contains a lot of sand. If it feels smooth and
slippery, it probably means there is a lot of clay in it. This smooth
soil is good for a fish pond.
A very good way to tell if the soil is right for a fish
pond is to wet a handful of soil with just enough water
to make it damp.
<FIGURE>
12p15.gif (256x256)
Then squeeze the soil.
<FIGURE>
12p16a.gif (230x230)
If it holds its shape when the farmer opens his hand, it will
be good for a pond. Remember, the more clay in the soil, the
better it is for building a pond.
<FIGURE>
12p16b.gif (230x230)
If the soil is sandy, or does not contain much clay, the farmer can still
build a pond. There are ways of building ponds in these soils. But he
should be aware that building a fish pond in such soils requires more
effort and may not be as successful. Digging test holes will tell the
farmer what his soil is.
Larger ponds can be built in soils with clay. If the soil is rocky or has
shifting sand, etc., only small ponds are possible. If there are other
locations available, the farmer would be wise to see if there is another
place with soil better suited to the fish pond. More information on soil
is included in the "Construction" section.
Ability of Soil to Provide Nutrients. Soil also contributes to the pond's
fertility. Fertility is a measure of the nutrients in the pond, and it
simply refers to how much food there is available in the pond for the
fish to eat. A very fertile pond is one which contains a lot of fish food.
The soil of the pond contains some of these necessary nutrients -- like
iron, calcium, and magnesium. In addition, however, soil also can contain
acids; these substances often are harmful to fish. Whatever a soil has
in it is drawn into the pond by the water and thus comes in contact with
the fish. Sometimes after a heavy rainstorm, there are big fish kills
in new ponds. This happens because the heavy rain carries larger
amounts of acids from the soil into the pond. So the farmer who is aware
of the kind of soil he has for his fish pond can prevent this problem
before it happens.
REMEMBER: One good indicator of the quality of soil is whether it has
been used for growing crops. If crops grow well in that location, the
soil will probably be good for the fish pond. If crops did grow well
there before the nutrients were used up, then it will probably still be
free of harmful substances.
TOPOGRAPHY The third factor in site selection is topography.
Topography is a word used to describe the shape of the land -- whether
it is flat or hilly, upland or lowland, etc. The topography of the land
determines the kinds of ponds which can be built. Ponds can be built in
valleys or on flat ground. They can be square or rectangular, or uneven
in shape. They can be large or small. All of this is determined by
topography of the land, as well as by the farmer's requirements.
The most useful topography for fish ponds is that which allows the farmer
to fill and drain ponds using gravity. Ponds built on a slope, for
example, can be drained easily. If ponds are located on flat land, the
pond must be built with a slope inside it so it can be drained by gravity,
or it will have to be drained using a pump.
Slope. If the farmer looks at a hillside, he can see that it rises. It
is higher at one point than at another. This difference in height, from
high to low point, is the slope of the land. In more scientific terms,
slope is the relationship between the horizontal distance (length) and
the vertical distance (elevation) over a piece of land.
Slope is usually written as a ratio (1:2) or as a percentage (5%). A
slope of 1:2 means that for every change in length of 2 meters, there is
a change of 1 meter in height. A slope of 5% means that for every change
in length of, say, 100cm, there is a change in height of 5cm. Pond
bottoms usually have a slope of 2-5%, whether they are on level ground
or in a hilly area. As long as the pond bottom has a slope, it can be
drained completely.
A farmer does not require a scientific understanding of slope to build
a pond. He does need to know how the shape of his land determines the
best place for building ponds. Ponds built in hilly places often are
made part of the hill. The picture on top of the next page, of a pond
with a spring as a water source, shows how the slope of the land has
been used to set up the pond's drainage system.
<FIGURE>
12p18.gif (437x437)
In flatter areas, ponds are usually square or rectangular because it is
easier to use a harvesting net in ponds of these shapes.
The farmer will learn quickly to recognize by sight the slope that is
best for a pond. Because a slope is so important, the first thing a
farmer should look for is a site with a slope and a water supply. If
he can use a natural slope for his pond, the pond will be cheaper and
easier to construct.
The best places to look for such combinations of slope and water supply
are where water collects from streams and flows through the valley at
the bottom of a slope. If the pond is built on the slope above the
water flow, water drained from the pond can flow directly into the stream.
Water might be brought to the pond in a number of ways depending upon the
situation -- by streams running down the slope upon which the pond is
situated, for example. Another good place to look for a good combination
of slope and water supply is on plains or flattish ground between hills.
These plains often receive water from brooks or streams.
There are many possibilities. The important thing is that the farmer
look for a topography that makes fish farming as easy and as successful
as possible.
The Type of Fish Farm
After the farmer has found a site or sites for his fish pond, he must
consider what kinds of fish culture are possible in the space he has
available. He also must decide what his resources will allow him to
get started. This planning is necessary because the answers will
determine the number of fish ponds the farmer builds and the kind of
fish he will want to culture. The following pages present a range of
ideas concerning the kinds of fish farm operations (raising fish or
breeding fish); the types of pond used in fish culture; fish culture in
one or several ponds; advantages of small and large ponds; and mixing
or separating fish types and sexes. A discussion of these subjects will
provide the farmer with the background he needs to decide what kind of
fish farm is possible for him, given his resources and the kind of fish he
wants to raise.
A NOTE OF CAUTION Before a farmer even begins, however, it is important
for him to include in his planning the fact that some fish will die.
This is an extremely important fact for the first-time fish grower to
understand. It is very natural for some fish, the weaker fish, to die in
ponds. As long as fish are protected in ponds and are well taken care of,
fewer fish will die in ponds than would die in natural waters. But a
farmer who does not expect some death may get discouraged and give up
before he has given his pond a chance to work. It is never too early to
introduce this idea.
KINDS OF FISH FARM OPERATION In nature, many fish never reach
adult size because they are eaten by other animals (predators), or they
die from disease or lack of oxygen. In fish culture, the farmer tries
to control the pond situation in order to produce more fish. In ponds,
predators and so on can be controlled so that the pond yields more fish
per hectare than do natural waters.
There are two major kinds of fish farms -- those which breed fish and
raise the fry, and those which rear fry and fingerlings (the young fish)
to market size. So the farmer, after finding possible sites, etc., must
decide if he is going to breed his fish and raise the fry. Or if he is
going to buy fry and fingerlings and rear them to market size, not
getting involved in breeding.
Breeding fish requires more time and more ponds than simply rearing
fingerlings. And building more ponds can be more expensive and require
more ongoing management. So the farmer must finally determine his reason
for raising fish: to eat; to sell; to use his land better; or all of
these. He will have to have all these things firmly in mind so that he
can:
* build the right kinds of pond.
* build the right number of ponds.
* stock the right kinds of fish.
TYPES OF PONDS The types of pond a farmer can build depend on water
supply, soil, and topography, the factors which were just discussed. The
two types of pond most often built are barrage ponds and diversion ponds.
Many aspects of the construction of these ponds are the same. The main
difference between these two types of pond is the water source.
Barrage Ponds. These ponds are usually filled by rainfall or by spring
water. A spring, for example, sends water flowing through a small valley
or down a slope into a low place. Or a spring bubbles from 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 farmer does this by building
a wall (dam) which holds the water inside what now is the pond area.
The wall keeps the water from entering and leaving except as needed.
<FIGURE>
12p20.gif (486x486)
The number of pond walls the farmer must construct depends upon the land
and on how he fixes his drainage system. A barrage pond usually needs
only one wall -- the main wall between the water source and the pond area.
One kind of drainage system called a sluice (see "Construction" section)
can be used to let water both in and out of the pond. There are also a
number of simple drainage systems which can be used that do not require
any complicated construction.
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 the water is too great. Brooks and streams which flow well,
but not too strongly, make good sources for barrage ponds.
Even when the flow of water is not great, however, barrage ponds require
overflow channels. Because, barrage ponds are usually built in low areas,
they are likely to fill up in heavy rains. Overflow channels are any
kind of system which can be set up to stop the pond from collecting too
much water. The overflow takes extra water away from the pond. If this
extra water is not taken out, the pond wall may break. Therefore, the
overflow system is needed to help the drainage system handle the flow of
water when there is too much water in the pond.
The overflow system can be wide grooves cut into the top of the wall
toward the ends away from the middle; it can be large hollow tree trunks
which are set into the tops of the wall and work as pipes to drain the
water into ditches, or even to carry the water into storage areas for use
later when the water supply is low. Another kind of overflow can be
ditches, dug into the ground above pond level, which take the extra water
away when the water rises to that level.
An overflow often is not screened, because if something large catches
on it, the pressure of the water behind it might cause the entire wall to
break. This fact results in a loss of fish at time of flooding.
<FIGURE>
12p21a.gif (486x486)
Diversion Ponds. These ponds are made by bringing (diverting) water from
another source like a stream or river. Channels are dug to carry the
water from the water source to the pond.
<FIGURE>
12p21b.gif (486x486)
Diversion ponds can be made in a number of ways. Sometimes a pond is
dug in flat ground or can be made by slightly enlarging a natural depression
in the land.
These ponds, like the barrage ponds, require walls depending upon the
topography of the land, the drainage system used, etc. A pond dug in
flat ground often requires four walls; a pond built in a natural depression
may not.
With a diversion pond, the water is always brought to the pond instead
of running directly into the pond. Water can be diverted in a number
of ways. For example, a small stream which gets its water from a larger
stream nearby can be dammed and used as a diversion channel to feed a
pond. Or water can be diverted to a pond from an irrigation ditch which
carries water to agricultural crops from a nearby well or lake.
A farmer may have one diversion pond, or if his space allows and the
water supply is sufficient, he may have several. When a series of diversion
ponds is built, they are built in one of two ways:
* Rosary system. These ponds are built one after another in a
string. In this system, all the ponds drain into each other
and must be managed as if they were one pond. Therefore, if
the first pond in the series (the pond with the water inlet)
is full of predators which must be poisoned, all the other
ponds in the system have to be harvested (have the fish taken
out) and drained before the first pond can be poisoned and
drained.
<FIGURE>
12p22.gif (486x486)
* Parallel system. In this series, each pond has its own inlet
and outlet. Therefore, each pond can be managed as a separate
pond.
Each kind of pond is going to have advantages or disadvantages depending
upon the farmer's situation. A parallel system of diversion ponds, in
most cases, is a better system. But rosary systems are cheaper and
easier to build, and therefore, more possible for some farmers to undertake.
Also, if the water source is good, and can be kept free of predators
and unwanted fish, and if the management of the pond is done well,
a rosary system can be very successful.
Diversion ponds are often better than barrage ponds because they are less
likely to overflow, and the water source is often more dependable throughout
the year. But barrage ponds require less construction and are likely
to be cheaper. In addition, for some farmers, barrage ponds are the best,
and perhaps the only, way for them to use their land for fish ponds.
The art of constructing and planning a fish pond or fish operation is
very much an individual thing. There are basic ways of using resources,
for example, land and water resources. But the exact shape and type of
fish pond must be decided by the farmer for his situation. There are
many ways of making fish ponds which will work, and the "right" way for
any given farmer is the way which works best for him. Many aspects of
fish farming are determined by experimenting with pond operation, but
much can be done by good planning before fish pond construction.
Therefore, the farmer must look at his sites and consider the types of
ponds he can build from the viewpoint of the number, size, and depth of
the ponds he is going to need. If, for example, the farmer thinks he
has a good area for a diversion pond, but hits solid rock at 1m and needs
a pond 2m deep, he can find this out before he invests a great deal of
time and money. If he has room for two small diversion ponds and a
barrage pond, or for a large diversion pond and a barrage pond, he can
base his decision on what kind of pond to build upon the number, size,
and depth of pond he needs for what he will be doing.
The Number of Ponds. The number of ponds depends on the possible sites
and on what the farmer plans to do with his fish ponds. If he is going
to raise fingerlings to market size, he will need one or a few "rearing"
ponds. If a farmer plans a larger operation in which he will breed fish
for the eggs and fry, he will need space for nursery pond, rearing pond,
and a pond for brood stock. Nursery ponds can hold eggs and fry until
they are fingerling size; rearing ponds hold the fingerlings until they
are market size; brood ponds hold the fish to be used for breeding.
It is possible to breed fish in a corner of a large, single pond, and a
farmer interested in raising fish for his own use may want to do this.
But a farmer interested in marketing fish probably will want at least
two large ponds. If he has two medium-large ponds, he can use one for
rearing fingerlings and one for broodstock. Eggs and fry can be taken
care of in very small ponds or even containers.
The Size of Ponds. The size of ponds depends upon the same factors --
topography, water supply, and need. Nursery ponds usually are smaller
than rearing ponds because the fry are very small. The size of nursery
ponds depends on the fish species being cultured. In fact, eggs and fry
can even be kept in washtubs, oil drums or any other such container which
holds enough water for the number of fry and is supplied with enough
oxygen.
<FIGURE>
12p24.gif (486x486)
As the fish grow, they need more space. So rearing ponds are usually
bigger than nursery ponds, and brood ponds are bigger than rearing ponds.
Sometimes a farmer will have to choose between one large pond or several
smaller ponds. His site would allow him to decide either way.
Here are some advantages of small and large ponds:
Small Ponds: * harvest easily and quickly
* drain and refill quickly
* treat for disease easily
* are not eroded by wind easily
Large Ponds: * cost less to build per hectare of water
* take up less space per hectare of water
* have more oxygen in the water
* can be rotated with rice or other crops
For most farmers, a few small ponds are better than one or two large
ponds. Farmers must also manage their agricultural crops, and it is
difficult for them to manage large ponds. Also, most farmers just do
not have a lot of land. A good size for a single fish pond is probably
between 1 and 5 ares (100 and [500m.sup.2]).
Farmers are going to be most interested in working the fish pond into an
already going farm as simply and easily as possible. This is why
culturing fish in rice paddies is popular in some areas. In fact, fish
ponds can be set up in almost any area where a rice paddy can be located
-- even on steep hillsides.
Small ponds are easier to care for and construct. As a farmer gains
experience, he can go on and build larger ponds. Starting small is a
good idea until the farmer feels he knows what he is doing and is successful.
Depth of Ponds. The depth of ponds depends upon the fish being grown.
Fish species like different kinds of food, and the depth of the ponds
affects the kinds of food produced by the pond. A common carp, for
instance, eats worms and other bottom organisms and must have a pond
that is not deeper than 2m. But when the carp are fry, they eat only
plankton, the tiny free-floating plants and animals suspended throughout
the water. So nursery ponds for carp fry are often only 0.5m deep.
(As mentioned before, eggs and fry can be taken care of in almost any
container which holds enough water and has enough oxygen.)
Other fish feed at other levels in the ponds depending on their life
stage and on their own food preferences. A very deep pond will not
produce as much food because the sunlight cannot light the water below
a certain depth, and the plankton will not be able to make oxygen for the
fish (see water quality). On the other hand, a very shallow pond might
be turbid, covered by water plants easily, and become very hot. Most
pond owners make sure that the water depth at the edges of the pond is
at least 75cm to discourage water plants. It is best if the pond is
about 75cm deep at the shallow end and up to 2m deep at the deepest end.
This will give the best results with most pond fish.
THE ONE-POND OPERATION If the farmer's site can only have one
pond, his decision is easy. It is hard to breed fish when only one pond
is available. Usually a single pond is used only for rearing fish from
fry or fingerlings to market size. This is the case in small, backyard
fish ponds that are used to supply fish for only one family. A good
minimum size for such a pond is [15m.sup.2] in area and 1m deep. A smaller
pond would probably not be worth the effort to build and maintain.
A single pond is stocked with the fry or fingerlings. For example, a
pond of the size mentioned above could be stocked with 60 fingerlings.
These young fish are cared for until they reach adult size. Then the
pond is harvested (the fish are taken out). The pond area can then be
prepared for a new batch of fish and stocked again.
One pond can provide a good food source for the family. However, rearing
fish means that somewhere there must be a source of fry or fingerlings
for use in the pond. The farmer must check his area carefully, so that
he is sure the young fish are available before he builds one pond.
The source can be a river where he collects the young fish, or a local
fish farm which breeds fish to supply farmers who have small ponds, or a
government hatchery where the farmer can buy the young fish. If the
farmer decides that he wants to breed fish in his pond, it is possible
to breed some fish inside small nets placed in the pond. A single pond,
though, is usually used just for rearing fry or fingerlings to a good
size for food and market.
While one pond usually means that the farmer is wise to concentrate on
raising one batch of fish from fry or fingerlings to market size, he
still must decide what kind or kinds of fish he will raise in his pond.
He can raise one kind of fish alone (monoculture), or he can raise
several kinds together (polyculture).
<FIGURE>
12p26.gif (393x393)
MONOCULTURE Monoculture is the culture of only one species (kind) of
fish in a pond. It can be tilapia of one species, common carp, or any
other single fish species.
Monoculture has some advantages. One advantage is in intensive fish
culture practices, where fish are fed a lot of supplementary foods for
fast growth. It is easier to give there foods if there is only one type
of fish in the pond. Another possible advantage is that monoculture
gives greater control over the age and sex of the fish. In monocultures,
fish can be of all different ages and life stages, or they can be
separated into fry, fingerlings or brood stock.
<FIGURE>
12p27a.gif (437x437)
A monoculture allows a farmer who is unfamiliar with fish farming to get
to know his one type of fish very well. And there is some advantage to
this.
<FIGURE>
12p27b.gif (393x393)
One disadvantage of a monoculture
pond is that it is more likely
for a single disease or parasite
to kill all fish in the pond.
Different fish are susceptible
to different diseases. If only
one fish type is present in the
pond, a bad fish disease could
easily infect and kill all the
fish if it were not stopped in
time.
<FIGURE>
12p27c.gif (437x437)
In monoculture ponds, fish are harvested
selectively by using nets which
have meshes of different sizes. For
example, if the farmer wishes to
harvest larger fish for market or
breeding, the net will not catch or
hurt the fry or fingerlings, because
they are too small to be caught by
a large-mesh gill net. This allows
the farmer to keep his pond in
operation and producing fish for
food all year.
Monoculture is the most common kind of pond culture. For a small fish
farmer who is most interested in having a nearby, year-round supply of
protein (and who does not have a lot of time or interest to give to the
pond), a monoculture may be a very good idea.
POLYCULTURE
<FIGURE>
12p28a.gif (393x393)
Polyculture is the culture of two or more fish species together in a
pond. A good polyculture uses the natural food sources in a pond better:
if the polyculture is mixed correctly, each of the species eats a
different food from the pond.
<FIGURE>
12p28b.gif (317x317)
Polycultures are more
resistant to disease.
Disease, if present,
usually attacks the
smaller, weaker fish,
and the healthier fish
continue to live and
grow.
Fish stocked in a polyculture must be able to live together. And living
together successfully means that the fish put into the pond together do
not all need to eat the same food. A polyculture can have fish of any
size or age -- as long as a balanced relationship is maintained.
Some examples of polycultures are:
* fingerlings of two or more species stocked together in a
fertilized pond and left to grow. A good mixture in this
kind of polyculture is a mixture of Chinese carp -- silver,
grass, and bighead carp stocked together. The silver carp
eats phytoplankton; the grass carp eats pond vegetation;
the bighead carp eats zooplankton.
<FIGURE>
12p29a.gif (534x534)
* A few large fish (brood size) are stocked with fingerlings
of another species in a pond and left alone. A good example
of this is stocking tilapia fingerlings together with a few
adult-sized Clarias catfish. The catfish feed on bottom
organisms and serve as a population control on the fry that
are produced in the tilapia ponds. Since one of the problems
which can be associated with culturing tilapia is overpopulation,
this is a very complementary relationship.
<FIGURE>
12p29b.gif (393x393)
* Another example of this type of polyculture is a stocking
of any kind of fingerlings mixed with a few large grass
carp for weed control.
<FIGURE>
12p30.gif (348x480)
Polyculture is a good way to use a pond, especially if there is only one
pond to use. A careful examination of local fish and their habits should
tell a farmer what kinds of polycultures are possible in his pond. The
important thing to remember is that the fish must not compete with each
other. If stocked and managed correctly, polyculture ponds can give
maximum production to a fish farmer. In very practical terms, the farmer
could raise as much as three times more fish in a polyculture of three
species than he can raise in a monoculture pond of the same size.
MONOSEX CULTURE A word should be said about monosex culture, even
though few farmers will choose or be able to choose this way of operation.
Monosex culture means growing only one sex of one species of fish in a
pond. When only males or only females are stocked in a pond, all the
energy of a fish goes into growth and not into reproduction.
An all-male stocking has faster growth rates than a mixed stock of males
and females. So some farmers try to stock only males or females in a
pond. One fish species that often is used in monosex culture is tilapia.
Tilapia reproduce at a very small size, but when separated by sex, they
do not develop their reproductive organs, yet continue to grow.
One way to stock a monosex pond is to separate the fish one by one
according to sex during the breeding season. Often, at this time, fish
change color, and it is easier to sort fish by sex. Then the fish can
be grown to a larger size.
In another method, people have been trying to obtain fish of all one sex
by putting two different species of tilapia into a pond. When these fish
breed, they produce either a monosex culture or a sterile hybrid. Three
crosses do now produce 100% male offspring.
Crosses of Tilapia which Produce 100% Male Offspring:
MALE CROSSED WITH FEMALE
Tilapia macrochir X Tilapia nilotica
Tilapia mossambica X Tilapia nilotica
Tilapia hororum X Tilapia mossambica
There are no crosses that produce 100% female offspring as yet. Males
are preferred because they continue to grow during the breeding season,
when there are no females present -- even though they (the males) continue
to build their nests in preparation for mating.
Monosex culture is a valuable method of pond culture, but is usually
difficult to do: the hybrid crosses are very new; hand-sorting fish by
sex causes many of the fish to die from stress. Even if the fish are
sorted without stressing them, one fish of the opposite sex that
accidentally finds its way into the pond can ruin the whole monosex
culture. So monosex culture is generally not practiced by small-scale
fish farmers.
THE MORE-THAN-ONE-POND OPERATION A farmer who has a larger
area to work with might wish to consider having two or three small ponds.
Perhaps two ponds would be diversion ponds, and the third a barrage
pond fed by a spring. Perhaps the farmer has room for only two barrage
ponds. He does not want to keep eggs and fry in the ponds because it is
harder to protect eggs and fry in barrage ponds. This does not mean he
cannot breed fish. He can keep eggs and fry in an oil drum, washtub,
or anything else as long as the water is clean and contains plenty of
oxygen.
With three ponds, one pond can be the rearing pond in which fingerlings
are raised to market size; one can be used to keep brood stock; and the
third, and perhaps the smallest, can be used as a nursery pond where the
eggs hatch and the fry grow to fingerling size. If the farmer does not
plan to breed fish, then he can use all three ponds as rearing ponds.
He should not do this, however, without thinking ahead to the harvest
and making plans for marketing the fish he will grow, or preserving the
fish for sale or use later.
<FIGURE>
12p31.gif (437x437)
The major difference between a large farm operation and a small one may
be only the number of ponds. Three ponds is enough to have a full-fledged
operating fish farm which includes breeding, selling fry and fingerlings
to other farmers, and raising fry and fingerlings to market and brood
size. Once the farmer is a skilled pond manager, these ponds should do
well and provide a good return on his investment.
Until the farmer is experienced, however, it is better for him to start
with small efforts and a smaller operation. Small pond failure is not as
severe. Once the ponds are working well, the farmer can expand and build
more and/or larger ponds. But he should be encouraged to start small.
There are a lot of factors in fish pond management that are learned best
by experience. But a bad experience will discourage, rather than encourage,
the pond owner.
A FINAL WORD ON PLANNING PONDS Good planning is a must for a
successful fish pond operation. It is during the planning process,
before any money or a lot of time and energy is spent, that many problems
can be solved.
The farmer should keep in mind while planning that ponds do not have to
have expensive equipment in order to work well. Far more important than
the equipment are 1) an understanding of the general principles involved,
2) the selection of a fish or fishes that will do well in his pond (see
next section, "Selection of Fish"), and 3) good daily management of the
pond (see section 6, "Managing the Pond").
3 Planning: Selection of Fish
The farmer now has a firm idea of his site and the types of ponds it is
possible for him to build. He also should know what he wants to do with
his ponds -- raise fish for food or run a fish-marketing business. Now
he must consider very carefully what type or types of fish he is going
to raise in his ponds. The success of the pond depends upon choosing
the fish that will grow best in the type of ponds and conditions that a
farmer is planning.
The following pages give some: 1) general information on characteristics
of fish, and 2) detail about certain fish which have proved to be good
pond fish and why. This information should serve as a guide to a farmer
trying to decide which fish will do best in his ponds.
Characteristics of Fish
The major body parts of all fish perform the same functions, and they
are located in about the same places on any different fish's body. But
the size, shape, and color are often different, and these differences
help tell the fish apart. Knowing how a healthy fish looks is important.
All fish have a tail consisting of the caudal peduncle and the caudal
fin. The fish's fins help it steer through the water and hold it
upright in the water. Often a sick fish cannot steer or flops over on
its side. Other fins on the body include:
* Pectoral -- usually located on the sides of the fish behind
the head.
* Pelvic -- usually located towards the rear of the body where
the hips would be if the fish were a four-legged animal.
* Dorsal -- runs along the top of the fish. May be single or
double. The second dorsal fin is sometimes called the soft dorsal
fin.
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* Anal -- usually located right behind the aral vent (anus) on
the rear bottom end of the fish.
Most fish have eyes, but even with eyes fish cannot see very well.
All fish have gills. The gills are covered by a flap called the
Operculum. The gills are extremely important. Fish take in water
through their mouths. The water is then passed through the gills
which remove the oxygen and nutrients from the water. The water
is then passed outside of the body of the fish through the gill slits.
It is possible to tell a lot about a fish's health and eating habits by
looking at its gills. Fish with many, many feathery gill rakers and
few if any teeth eat the smaller foods in the pond. Fish with few and
larger gill filaments eat the larger particles from the pond. Healthy
gills are a bright red color. If the farmer sees fish with gills that
do not have this healthy red color, or have white spots all over, for
example, he will know that fish is not healthy and should not be bought
or placed in his pond. Or if the fish is already in his pond, he knows
he must take steps to get rid of the disease before it troubles more fish.
Other identifying parts that all fish have are the mouth, the genital
openings (to reproductive organs), and the lateral line. The lateral line
is a small line of nerve cells which runs along the length of the body
about midway on the side of the body. Sometimes the lateral line is
covered by a layer of scales; sometimes it is a different color than the
rest of the body. In any case, the lateral line is an area of sensitivity
that helps the fish feel pressure and temperature changes in the water
around it.
Some fish, like catfish, also have barbels, small projections that hang
down from the sides of the mouth. Barbels help the catfish sense its
surroundings, find food, and attract small fish to the catfish so that
it can eat them.
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When a farmer breeds fish he will want to be able to tell the difference
between male and female fish. This can be difficult with some fish.
However, some fish change color in the breeding season (tilapia, for
example), so they are easy to identify by sex. Some fish can be classified
according to the color and size of their genitals. The separation
of fish by sex is best learned by actual experience in the pond.
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When the farmer goes to buy fish, he must already know what healthy fish
look like. It is very important that he be as familiar as possible with
each of the fish he decides to raise. He must know the characteristics
of that fish and its life cycle, its eating and breeding habits, etc.
The farmer who begins any fish pond enterprise without having this kind
of information is inviting failure. And if it is a new venture, it is
particularly important that the farmer's first effort be as successful
as possible.
The Life Cycle of Fish
Fish start life as fertilized eggs. The eggs grow and then hatch into
small fish, called fry. The fry are attached to the yolk sac which is
the leftover part of the egg they hatched from. The yolk sac provides
food for the fry during the first few days after hatching.
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After the yolk sac is gone, the fry searches for food in the water. All
fry eat the tiny suspended and swimming plants and animals called plankton
in the water. Plankton are hard to see, but if a farmer puts some
of his pond water into a glass container and holds it up to the light so
that the light shines through the water, he can see the tiny plankton
floating in the water. The length of the fry stage depends upon the
species of fish. Usually a fish is a fry at least until the yolk sac is
absorbed. Fry range from 2mm to 30mm in length. This growth process can
take 2 to 6 or 8 days depending upon the type of fish.
As the fry grow bigger, they are called fingerlings. They are called
fingerlings because at this stage of the growth cycle, they are about the
size of a person's finger. Fingerlings vary in size -- from 4-1Ocm.
Above 10cm, the fish is better called a post-fingerling. The adult fish
ranges in size; some can be as large as 2m long and weigh 22kg. An adult
fish is a fish which is sexually mature.
Fingerlings have different eating habits from fry; they are now much
bigger and can eat larger pieces of food. As fingerlings, the fish begin
to show that they like certain foods better than other foods. Each kind
of fish chooses its own kind of food, depending upon his needs and what
is available. For example, a carp fry will eat plankton; as a fingerling,
the carp eats pieces of decayed matter and insect larvae; as an adult
the carp will eat plankton, decayed matter, insect larvae, worms, snails,
and almost anything that is on the bottom of the pond. Common carp, for
example, are called "bottom feeders," because they eat food from the bottom
of the pond.
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The food preference does not always
change as the fish grows. Some fish,
like the silver carp, eat plankton
their whole lives. When the fish
reach adult size, they will sexually
mature in the right conditions.
Brood fish are sexually mature fish
which are chosen as good fish to
breed (spawn), produce eggs and
begin the whole cycle again. This
is called the life cycle of a fish.
Knowing how the fish in the pond
grow, and the foods they require at
each stage in the life cycle, is very
important for good pond management.
Choosing Pond Fish
Choosing fish to grow in ponds can be difficult. A good pond fish has
certain characteristics which help it grow successfully in ponds. There
are some fish which will not adapt to pond conditions and cannot be used
in pond culture. A pond is very different from a natural waterway:
* There is usually no water flowing through a pond. Some fish
need to live where there is quite a bit of current in the
water, rather than in a quiet pool of water.
* The food that is already in the pond is all that is available
to the fish, unless extra food is put in by the farmer.
* There is only a certain amount of water and pond area in which
to move about.
There are many fish that do grow well in ponds. Some of these are fish
grown locally; some are fish grown in other parts of the world.
Many governments today are introducing exotic fish species (these are
kinds of fish not native to that country) into fish pond programs.
They do this for three reasons:
* Some Introduced fish grow better and faster than native fish.
* Some introduced fish are preferred by people for eating (over
local fish).
* The offspring of a cross between a local fish and an introduced
fish sometimes grow faster and taste better than either of the
parent fish (this is called hybrid vigor).
But exotic fish must be watched and used very carefully. They must not
escape into local waters. Some exotic fish which escape create problems
in natural waters when they begin to compete with local fishes for food.
Also, introduced fish can carry diseases or parasites that are fatal to
native fishes.
There are certainly a number of fish in the natural waterways of your
area which will grow well in ponds. Native (local) fish are usually
easier to use because they are adjusted to local water and climate
conditions.
If at all possible, farmers should be encouraged to start their ponds
using a tested pond fish which is locally available and is well-liked
by people in the area. It can be a fish from the list given here or
one chosen from a list prepared in your area. The important points
are that the farmer be able to sell any fish he wishes to sell, that
the fish can grow in ponds, and that there is brood stock available
locally.
Fish Used in Pond Culture
Here are some characteristics that good fish for pond culture will have.
Certainly it may not be possible for a farmer to determine whether a
certain fish has all these characteristics right away, particularly for
those local fish not discussed in detail here or those newly introduced
to pond culture. But good pond fish all have certain characteristics:
the more certain a farmer can be that the fish he chooses to raise fit
these descriptions, the more sure he can be of his success. Good pond
fish are:
* available locally
* able to reproduce (breed) naturally in your area.
* able to live in a confined space (the pond).
* able to find the right foods in ponds.
* fast-growing.
* relatively free of parasites and diseases.
* known and liked as a food fish in the area.
Some fish that fit these criteria for good pond fish and are now grown
in ponds all over the world are named here. Though they all are grown
in ponds, each has certain characteristics which mean that it will grow
better in some kinds of ponds better than other ponds. Of course, these
fish are not the only fish that can be used in ponds. But they are named
here because they have been tested in ponds, and they can grow well under
pond conditions. All of these fish are warm water fish.
SCIENTIFIC AND COMMON NAMES OF FISH USED IN POND CULTURE
Please note: Each fish has a scientific name which is
always the same. The common name, however, can be different
from one country to the next. It is a good idea for anyone
who works with fish to know the scientific name.
Genus - species Common name
1. Anguilla japonica eel
2. Aristichthys nobilis bighead carp
3. Barbus gonionotus tawes
4. Carassius auratus goldfish
5. Carassius carassius crucian carp
6. Catla catla catla
7. Chanos chanos milkfish
8. Cirrhina molitorella mud carp
9. Cirrhina mrigala mrigal
10. Clarias batrachus catfish
11. Clarias macrocephalus catfish
12. Ctenopharyngodon idellus grass carp
13. Cyprinus carpio common carp
14. Helostoma temmincki kissing gourami
15. Heterotis niloticus -
16. Hypophthalmichthys molitrix silver carp
17. Labeo rohita rohu
18. Mugil cephalus mullet
19. Mylopharyngodon piceus black carp
20. Osphronemus goramy gourami
21. Serranochromis robustus -
22. Tilapia macrochir tilapia
23. Tilapia melanopleura tilapia
24. Tilapia mossambica tilapia
25. Tilapia nilotica tilapia
26. Trichogaster pectoralis snakeskin gourami
27. Trichogaster trichopterus three-spot gourami
Following is specific information on some of the more popular pond fish.
COMMON CARP
The common carp, Cyprinus carpio, is a favorite warm water pond fish.
Common carp are used as a pond fish because they:
* spawn easily in ponds.
* do not get sick easily.
* tolerate wide ranges of temperature and pH (factors of water
quality discussed in detail later).
* eat all kinds of food, from zooplankton to decaying plants.
* have a very good growth rate.
* accept supplementary foods.
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Common carp generally are a grey-green color. However, they also can be
gold, yellow, orange, pink, blue, green, or grey. They spawn all year
round in warm waters, and they can be made to spawn by the pond owner if
they do not spawn naturally. Common carp are good to eat when they are
cooked properly. They can be grown in ponds by themselves (monoculture)
or in ponds with Chinese or Indian carp (polyculture).
Some of the yields gotten in various countries by stocking common carp in
monocultures are shown in the following table.
Yields,
Country Culture methods kg/hectare
Czechoslovakia Growth in ponds with ducks 500
Guatemala Intensive culture in ponds 4,000
India Natural growth in ponds 400
Growth in ponds with management 1,500
Indonesia Intensive culture in ponds 1,500
Japan Intensive culture in ponds 5,000
Nigeria Commercial culture with
fertilization and feeding 371-1,834
Philippines Intensive culture in stagnant water 5,500
United States Intensive pond culture with
inorganic fertilization 314
Source: Bardach, et al (1972)
Conclusion: Common carp are a very easy fish to breed, keep, and harvest,
so a fish pond that relies on common carp will probably do well. Common
carp are a good fish for a farmer to use for his first effort. With good
management, common carp will continue to produce healthy eggs and fry
until they are too old (above 5 years of age).
TILAPIA
The Tilapia genus (family Cichlidae) contains at least 14 species, which
are all good pond fish. The color of the fish differs only slightly
depending upon species; tilapia are generally dark brown to black in
color. The most common species grown in ponds is the Tilapia mossambica,
also called the Java tilapia. It has been introduced throughout the world
and is easy to find in most places. Tilapia:
* are hardy fish, resistant to disease.
* breed easily in ponds.
* grow rapidly.
* taste good.
* can withstand wide temperature ranges.
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Tilapia are herbivorous: some species eat higher plants; some eat
phytoplankton. Both the Java tilapia and the Nile tilapia (Tilapia
nilotica) do well in very enriched waters (waters polluted by sewage).
All tilapia have slightly different eating habits, depending on the
species.
Tilapia reproduce every month or so, once they become sexually mature.
They then take very good care of their own eggs and fry in ponds. If
the farmer plans to breed and raise fry, this fish is a good choice
because the fish themselves take care of the fry at a stage where many
fish of other species die easily. The major problem with raising tilapia
in fish ponds is that they become sexually mature at a small size, and
begin to reproduce instead of to grow further. It may be necessary to
separate the tilapia by sex before they are old enough to reproduce. Or
it may be necessary to introduce catfish into the pond to control the
population of small fish.
Conclusion: Tilapia species have many possibilities for pond culture.
Their fast growth rate, ease of breeding, good taste and hardy bodies
make them a good choice, particularly for the first-time fish farmer.
CHINESE CARPS
Other kinds of carp, besides the common carp, often are grown in ponds.
Most commonly used are the Chinese carps. Some of these are:
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* Silver carp (Hypophthalmichthys molitrix). This fish eats
phytoplankton, but will accept rice bran and bread crumbs.
The silver carp gets its name from its silver color. It has
very small scales.
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* Bighead carp (Aristichthys nobilis). This fish feeds mainly
on zooplankton. It is a dusky green color on top which fades
to a pale green color on the abdomen. It also has small scales.
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* Grass carp (Ctenopharyngodon idellus). This fish is an
herbivore and eats water vegetation (but also will eat
almost anything). The grass carp is also silver-colored,
but has a darker grey area running along the top of the body.
It grows larger in size and has larger scales than a silver
carp.
Other chinese carps like the black carp (Mylopharyngodon piceus) and the
mud carp (Cirrhina molitorella) are bottom feeders. This difference in
eating habits is very important in fish pond culture. It is the reason
why polyculture, or growing a number of fish species in one pond can be
successful. When one kind of fish is stocked alone in a monoculture,
the foods in the water not eaten by that type of fish are wasted. In a
polyculture of the above three species of Chinese carp, for example,
three kinds of food are being eaten.
The following table gives some examples of polyculture mixes and of how
many fish of each kind can be stocked in a pond. For example, Pond I is
stocked with silver, bighead, grass and common carp.
STOCKING RATES OF CHINESE CARPS IN PONDS
3 TO 7 METERS DEEP IN KIANGSU PROVINCE, CHINA
Weight of Number of Yearlings per hectare
Species Yearlings, grams
I II III IV
Silver and
bighead carp 500 4,500 4,500 9,000 9,000
Grass carp 500 600 - 3,000
Black carp 500 - 450 3,000
Common carp 200 200 200 200 200
TOTAL: 5,300 5,150 12,200 12,200
Source: Bardach, et al (1972)
The preceding table shows polyculture mixes: as you can see, common carp
can also he used in polyculture with Chinese carp. Chinese carp are
grown in ponds because they grow well in polycultures, and they are very
good to eat. The silver carp grows faster and is tastier (according to
some farmers) than common carp. The grass carp is most often used to
control weeds in the pond. In fact the grass carp does a better job of
weed control than do chemicals. The grass carp is perhaps the most interesting
of the Chinese carp and is now being studied by scientists in
many countries to find better ways of breeding it in ponds.
A farmer might run into problems raising Chinese carp -- if he does not
look into his local situation very well. Farmers will have to have a
source of Chinese carp fry from a government hatchery or a local breeder
before trying to raise Chinese carp. The carp only breed once a year,
and then, in most cases, only with help from man. Also, Chinese carp are
very susceptible to diseases. Then, because they are delicate fish, they
must be handled very carefully, or they will be injured.
Conclusion: A farmer just beginning a fish pond probably would not want
to breed Chinese carp, but he certainly should be familiar with these
fish and how they might help his ponds. For example, even two or three
large grass carps placed in a pond with many fish of one other species,
could be valuable for keeping a pond balanced.
INDIAN CARP
There is one last group of carp often cultured in ponds. These are the
Indian carp. Indian carp are further divided into minor and major carp.
The major carp of India are the catla (Catla catla), the rohu (Labeo rohita),
and the mrigal (Cirrhina mrigala). The minor carp are the reba, the bata,
the sandkohl, and the nagendram fish. The Indian major carp will not
spawn in standing water, so special ponds are built in India to provide
a flow of water for these fish, who must have running water in which to
spawn. The Indian carp can be made to spawn by man, but this is a difficult
process (see "Managing Brood Stock"). However, there seems to be
no reason why the Indian carp cannot be spawned in ponds in places where
ponds can be constructed to provide constantly running water.
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Conclusion: A farmer who has only a small pond should not try to breed
Indian carp. Indian carp can be grown in polycultures with common carp,
but are not as good or fast growing in ponds as the Chinese carp.
Indian carp are also susceptible to many diseases. This is a fish for
an experienced fish farmer who is interested in, and able to, experiment.
GOURAMI
The gourami (Osphronemus goramy) is a very good pond fish. It is
originally from Indonesia, but now is grown all over Southeast Asia.
Gourami possess an accessory air-breathing organ, which means that they
can survive in waters that are low in dissolved oxygen. This makes it'
an important fish in areas where the temperature remains high and there
is little water for certain periods of the year. Gourami spawn all year
round in warm water conditions. Gourami:
* spawn easily all year round in warm waters.
* taste good.
* are easy to breed.
* accept a variety of foods.
* are hardy.
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Conclusion: Gourami are good fish for a first-time fish farmer. And
they are certainly a fish to be considered very thoughtfully by farmers
who live in areas that remain very hot and dry for periods of the year.
The gourami is used to these conditions, and there are other pond fish
which would not do well at all under these conditions.
CLARIAS CATFISH
Clarias catfish are found throughout Asia, India, and Africa, as well as
the Middle East. The species most often used as pond fish are Clarias
macrocephalus and Clarias batrachus. Clarias macrocephalus is preferred
for its good taste; Clarias batrachus grows faster.
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These catfish have accessory air-breathing organs; they can even crawl
out of ponds to look for food. Because they can live in shallow ponds,
these catfish are sometimes used in culture with rice (see paddy culture).
They are scavengers, which means they will eat just about anything.
However, they prefer to eat worms, snails, and other fish. They are
often used in polycultures with tilapia where they serve as predators on
the very small tilapia. They will eat supplementary foods, and give very
high production in ponds. In Thailand, Clarias catfish yield about
97,000kg/ha when they are fed supplementary foods. These catfish are
hardy: they sometimes get external parasites, but these do not kill the
fish.
Conclusion: The catfish are another good fish to be raised in areas
where high heat and long dry spells are found. They are good to eat,
easy to keep, and can be used in ponds in a number of ways. Certainly
a farmer who already cultures paddy rice might be interested in considering
adapting his paddy to catfish culture.
TAWES
The common name tawes is applied to three species of fish -- Barbus
gonionotus, Puntius javanicus, and Puntuis gonionotus. These fish
usually are used in fish ponds for vegetation control, in polycultures
with Chinese carp. Tawes are able to spawn all year round, but they
most often spawn in the rainy season. Tawes need well-oxygenated water
with a strong current to spawn. Tawes feed on soft water plants, but will
also take rice bran. There is not a great deal known about the tawes at
present, but it can be used in polycultures when the grass carp is not
available.
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Conclusion: A farmer starting a polyculture certainly might be interested,
in using this fish. However, first-time fish farmers with limited space
would not want to try breeding this fish.
HETEROTIS NILOTICUS
The Heterotis niloticus spawn easily in ponds. The mature fish will
build a grass-walled nest in the weeds at a pond's edge and spawn inside
this nest. They spawn when water is low and very warm, at the end of
the dry season. The mature fish feed only on plankton, but in a pond
they will accept supplementary food. This fish has a swim bladder which
can serve as an accessory air breathing organ.
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Conclusion: There is not yet a great deal known about the Heterotis
niloticus as a pond fish. But it seems that it is a good choice of fish
for warm climates and warm waters. A farmer who lives in such a climate
might find raising, and even breeding, this fish quite easy -- particularly
in a very well-fertilized pond.
OTHER GOURAMIS
These are the snakeskin gourami (or Sepat Siam -- Trichogaster pectoralis),
the three-spot gourami (Trichogaster trichopterus), and the kissing
gourami (Helostoma temmincki). All of these fish taste good. And they
breed easily in well-oxygenated, warm water. They do require a pond which
has a good growth of vegetation (particularly Hydrilla verticillata).
<FIGURE>
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Conclusion: In a pond situation such as that outlined above, these
gouramis are easy to breed and raise. They are a good fish to use in
polycultures with other gouramis, tilapia, and common carp.
MILKFISH CULTURE
The milkfish (Chanos chanos) can be raised in freshwater even though it
is primarily a brackishwater fish, and will not breed in ponds. The fry
are caught along the shoreline at breeding season (the rainy season) and
transferred to freshwater ponds. Milkfish culture is done for the most
part in the Philippines and in some other Southeast Asian countries, like
Indonesia and Taiwan.
Adjusting (acclimatizing) the fry from the saltwater to the freshwater
pond is hard to do; many fish die if the adjusting process is not done
well. Therefore, milkfish usually are cultured in brackishwater ponds
only; the use of milkfish in freshwater ponds is not widespread. Milkfish
feed on a complex of bottom algae, and, recently, it is reported
they also feed on phytoplankton. Milkfish are prized for their beauty
and their good taste, though they have many, many small bones.
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Conclusion: This is not a fish for the first-time fish farmer. In fact,
it is not a good choice for any farmer unless he has a saltwater pond; is
interested in trying to acclimatize the fish to a freshwater pond; or can
buy milkfish from a source that has them already in a freshwater pond.
EEL CULTURE
Eels (Anguilla sp.) have been cultured in Japan and Taiwan for years.
Eels are very much a luxury food and are not normally grown alone in ponds
outside of these two countries. The eels are grown in ponds in polyculture
with other fishes and are particularly useful in polyculture
with species of tilapia because they eat the smaller tilapias. The eels
used in Taiwan (Anguilla japonica) spawn in the sea and the fry (called
elvers) swim upstream and are collected by dealers. Eels must be fed
supplementary feeds like pellets made of trash fish.
Conclusion: It is not recommended that farmers work with eels because
they must be fed protein and are not very efficient converters of food.
Also, eels cannot be bred in fish ponds.
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OTHER POND FISH
Some other fish grown in ponds are the goldfish (Carassius auratus), the
crucian carp (Carassius carassius), and Serranochromis robustus. Any of
these fish can be grown in polycultures with Chinese, common carp, and
tilapia.
Conclusion: The use of one of these fish in a pond stocked with other,
more important fishes, results in an increase in yields of both species.
In polycultures these species can utilize other food sources and also
act as predators and weed controllers.
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One other fish species used in freshwater ponds is the striped mullet
(Mugil cephalus). Like the milkfish, the mullet is primarily a saltwater
fish, and its fry are collected as they swim upstream. Recently the
mullet has been made to spawn by man, but this is difficult to do because
mullet are very sensitive to handling. However, mullet can survive in
wide temperature ranges and are herbivores, so some farmers may want to
try mullet.
A CLOSING NOTE ON FISH
All these fish have been and are now being cultured in fish ponds around
the world. However, as stated before, they are not the only fish which
can be grown in ponds. In every area there are a number of fish in
natural waters that could be grown in fish ponds. So you might find it
a good idea to experiment with local fish in your ponds, to find those
fishes that might be available to farmers in your area for use in their
ponds. It is better for an extension worker to do the experimenting
than it is to have a farmer risk wasting his time or money, or even more
importantly, risk failure. If a farmer fails, he may not want to try
again.
4 Fish Pond Construction
Construction of a large pond can be very expensive if labor is hired,
machines are used, and expensive equipment is rented. For example, in
the Philippines, a one-hectare pond having two concrete gates and walls
3m high x 3m wide recently cost US$1,522.56. Another pond, about 100m
x 25m, with only a Rivaldi valve cost about US$680.
An interesting fact about fish pond construction is that whether the
pond is large or small, expensive or inexpensive, ponds are all very
much the same. A larger, more expensive pond will not necessarily be
a better pond.
Here is an example of a good beginning for a new and small fish farmer:
A "backyard" fish pond was planned and sited very carefully
by a farmer. The pond was dug by the farmer and constructed
with bamboo pipes for water inlets and outlets. The construction
itself cost no money. The farmer's only expense was a
supply of fingerlings purchased from a nearby market. This
fish pond, managed by the farmer and his family, produced
enough fish for the family and some extra income from fish
sold or bartered for goods needed by the farmer. The family
ate well and suffered no major illnesses during the year.
Next year, the farmer plans to add another pond and to produce
more fish for market. He will add a Rivaldi valve or a wooden
monk to this new pond, because either of these will make ongoing
management somewhat easier, now that there will be two
ponds to manage (The bamboo pipe sometimes got clogged. This
was no problemn to correct when there was only one pond. But
it would take up needed time in a two-pond operation).
Whichever the farmer chooses, the valve or the monk, he will
make it himself with materials found locally, using money from
the sale of his fish.
This farmer began his operation well. He started small and
worked into a larger operation. However, even for the larger
fish farm, he planned an expansion which was within his means.
This kind of careful planning increases the farmer's chances of
success -- and yours. And the scope of the project is something
he can undertake on his own. He gained the knowledge and
experience that he needs to expand his operation.
The following section presents a range of ideas for constructing fish
ponds. The farmer can pick a combination of construction possibilities
which best fit his own needs and resources.
IMPORTANT: Stress that the "right" way in any situation is the way
which:
* the owner can afford
* the owner can manage easily
* fits the owner's needs most completely
Construction should begin only after careful planning such as that
outlined in the preceding sections on "Planning."
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A fish pond has three main parts: the walls, the water inlet, and the
drainage system. Walls are also called dams, dikes, levees, or bunds.
This manual uses "walls." Whatever they are called, walls hold the water
in the pond. They can be built using soil taken from inside the pond,
or they can be built with soil taken from another place. They must be
strong enough to withstand the pressure of all the water inside the pond:
water constantly pushes against the walls. They must also be water-tight
(impermeable), so the pond does not leak.
The water inlet, located above the pond water level, is used to let water
into the pond and is closed off after the pond is filled.
The drainage system is used to empty the water from the pond when the
farmer is ready to harvest the fish.
There are many ways of making inlet and drainage systems: the most
important criterion is that they work. But the walls are especially
important: they are all that keep the fish inside the pond. The walls
must be built carefully.
Pond construction follows the same principles whether the pond is a
single backyard pond or part of a large fish hatchery. These are the
steps in pond construction:
* Survey the land
* Mark out the area of the pond
* Measure and mark out the walls
* Excavate the pond bottom, if necessary
* Build the drainage system
* Build the water inlet
* Build the walls
* Seal the pond bottom and walls
Each of these steps will be discussed in detail in the following pages.
Survey the Land
The first step in the construction of a fish pond is marking the area of
the proposed pond. If the site chosen is a natural slope, the first
thing to be done is to find out where the main wall will be built. The
main wall should be marked off at the lower end of the pond, where the
pond will be the deepest and the slope the greatest. This is where the
pond's drainage system will be put. If the pond is to be on a flat area,
the pond bottom itself must be made with a slope so the pond will drain.
This is done by digging one end deeper than the other end. Remember:
the main wall is always at the deeper end.
DETERMINING THE SLOPE
Even flat ground usually has some kind of slope, although it may be very
little and hard to see. So, before constructing the pond, the land is
surveyed to find out which way the land slopes and what that slope is.
There are a number of ways which can be used to determine slope. The
way outlined here probably would not be used by many farmers if they
were building a pond on their own, but this is an accurate method of
determining slope and should be encouraged if at all possible.
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