Fish
species need to be provided enough nutritious food in order to attain
marketable sizes in a short period of time under culture conditions. The
nutrients that should be included in fish feeds include:
1.
Protein for body building
2.
Fat for normal functioning of the body and for energy
3.
Carbohydrates for energy
4.
Mineral salts for bone structure and body functions
5.
Vitamins for good health.
But
sufficient nutrient availability in a feed alone can not ensure optimum
production performance. Better results can be obtained when fish are fed
correctly using the right techniques that ensure all the fishes have easy
access to the provided feeds, feed should be based on the nutritional needs of
fish and avoiding the excess feed in the fish pond . Feeding fish correctly
means:
1. Quality:
giving feed of the correct nutritional quality for the specified age of fish,
2. Size: feeding the right feed size for easy
consumption,
3. Quantity:
feeding the correct amounts
4. Timing:
feeding at the right times each day.
So, particular
quality and quantity of feed are important factors to fed the fish but there
are some problems with feed and feeding like,
1.
problems with the fish feeds themselves and
2.
problems related to the fish feeding techniques that the farmers
employ.
Food of fish
There
are three types of food used in fish ponds:
A
.Natural food.
B.
Supplementary feeds.
C.
Complete feeds.
1.
Natural food: It
is found naturally in the pond. It may include detritus, bacteria, plankton,
worms, insects, snails, aquatic plants and fish. Their abundance greatly
depends on water quality. Liming and fertilisation in the fish pond provide a
good supply of natural food to the fish.
2.
Supplementary feeds:
These are feeds regularly distributed to the fish in the pond. They usually
consist of low costplantbased foods like rice grain, rice branetc and some
locally available terrestrial plants and
kitchen wastes also act as supplementary feeds.
3.
Complete feeds:
They are also regularly distributed. They are carefully prepared by mixing some
selected ingredients that contain all the necessary nutrients for the fish to
grow well. These feeds are form which the fish are easy to eat and digest for
fish. These feeds are quite expensive.
Production
Systems Based on Food
According
to the type of food given to the fish, the system of fish production can be
categorised into three types:
Extensive: this
fish productionsystem that uses small inputs of labour, fertilisers and capital
relative to the land area being used. Here fish depends entirely on natural
food.
Semi-intensive:
fish production depends on both natural food and supplementary feed, here more
fish may be reared in the pond.
Intensive:
fish production depends entirely on complete feed and the stocking rate no
longer depends on food availability but on other factors such as water quality.
Natural
food
Natural
fish foods present in a fish pond are very diverse and usually consist of a
complex mixture of plants and animals. Main features of the natural food are:
a)
They range from microscopic to relatively large size.
b)
They may be alive or dead (detritus) and available from bacterial
decomposition.
c)
They are generally present in various parts of the pond:
1.
Near the shore example: rooted high plants
2.
Floating in the water example: plankton
3.
On the surface of or within the bottom (benthic material or
benthos) example: worms, insect larvae and snails
4.
Covering the surface of submerged objects (biological cover)
5.
Swimming around such as aquatic insects, frogs and fish
(nekton).
Supplementary Feeds
Profitable
fish farming requires regular supply of sustained and balanced food for fish
growth. To ensure sustained growth, artificial food has to be supplemented with
the natural food. There are several reasons for supplement the natural foods available
within the pond with artificial feedstuffs originating from outside
the pond, for example:
1.
when natural foods become insufficient to feed fish
that is essential for good growth
2.
to raise more fish in pond to produce a higher crop and
still have good growth.
The
more use of supplementary feeds, an extensive system is changed to a semi-intensive
system of production.
Selection
of Supplementary Feed
When deciding on the use of supplementary feeds on a fish
farm following points should be
considered:
1.
good nutritional values: with high protein and
carbohydrate content and low fibre
content
2.
well accepted by the fish
3.
cheap in price: for a given food quality, the lower the
cost it is considered as better
4.
available most of the fish-growing season
5.
minimum additional cost for transport, handling and
processing
6.
easy to handle and store.
Example of Supplementary
Feeds
Many kinds of materials may be used as
supplementary feeds for fish such as:
1. terrestrial plants: grasses, legumes,
leaves and seeds of leguminous shrubs and tree, fruits, vegetables
2. aquatic plants: water hyacinth, water
lettuce, duckweed
3.
small terrestrial animals: earthworms, termites, snails
4. aquatic animals: worms, tadpoles,
frogs, trash fish
5.
rice: broken,
bran, hulls
6.
wheat: middling’s, bran
7.
maize: gluten feed, gluten meal
8.
extracted oil from mustardseeds, coconut, groundnut, sunflowerseeds, soybeanseeds etc
9.
sugar
cane: molasses, filter-press cake, bagasse
10. coffee
pulp
11. cottonseeds
12. brewery wastes
and yeast
13. kitchen wastes
14. Slaughter
house wastes: offal, blood, rumen contents
15. silkworm pupae
16. manure: chicken droppings, pig manure
Classification of Supplementary Feeds
Based on moisture
content supplementary
feedstuffs are classified in two groups:
1. Dry
feedstuffs such as cereals and cakes are easier to store, to transport
and to distribute to the fish. They contain about 10 % moisture.
2. Wet
feedstuffs such as blood, rumen contents, molasses and brewery wastes
require special treatment before feeding for example mixing with dry
feedstuffs to absorb part of the moisture or drying to improve
storage life.They contain about 30-50% moisture. This form is found to be more
palatable and better digested for some species, thus giving better results in
fish health.
Based on nutrientssupplementary
feedstuffs are classified in three groups:
Group A.
It comprises
proteins. Proteins are broken downinto different amino-acids which are used
for growth, reproduction, repairs and secretion processes in fish. Chief
sources of protein are animal by-products, oil-bearing seeds and their
processed cakes. Juveniles and brood stock fish require more proteins than
adult ones.
Group B.
It comprises
carbohydratessuch as starches, sugars and cellulose. Carbohydrates provide the
energy to the fish for maintenance and living activities. Chief sources of carbohydrateare cereals and molasses.
To obtain best
results, use simple mixtures of various feedstuffs to provide fish
with the additional proteins and good carbohydrates required. A high proportion
of fibrous materials should be avoided to feed the fish.
Size of Feed
It is important to adapt the size of the
feedstuff particles to the mouth size of the fish to reduce feed losses
and maximise feed utilisation. Depending on the size of the fish, preparation
may involve different processes, such as: drey feed stuffs are crushed or
grinned to make available for juvenile fish and for herbivorous fish plant
materials are chopped into small pieces.
The feed particles
should not be finer than necessarybecause nutrients are more easily dissolved
into the water thus nutrients loss takes place and there are more chances that
they will decompose in the water. moreover it is difficult for fish to feed
fine particles
Quantity
of Feed
The rate of food
conversion in fish depends on the quality of supplementary feed, stocking
density of fish, size and age of the fish stock, environmental factors and the
method of feeding. The quantity of feed required by using food conversion
ratios (FCR) for the feeds involved. Typical food conversion ratios range
from 8 to 15 kg of feed material per kg of fish produced. Example: The
estimated food conversion ratio for the supplementary feeds available is 6:1.
In the case above, a 200 to 300 kg production will require (200 to 300) x 6 = 1
200 to 1800 kg of supplementary feeds.
When
doing this following points should be taken into account.
1.
The
better the quality of the feed, the less
need of the feed.
2.
Food
requirement of small fish is more thanthe larger ones.
3.
If
there is plenty of natural food, less use of supplementary feed.
4.
If
the fish stocking rate is low, less supplementary feed should be used
and rely more on natural food.
5.
More
food is required in warm water than in cooler water.
6.
The
total quantity of supplementary feeding to be given daily to the fish in a
particular pond is usually expressed as a percentage of the total weight
or biomass (B), of fish present. This percentage is called the daily
feeding rate (DFR).
7.
The daily
feeding rate varies as explained above with such factors as the following.
a) Species and
individual fish size.
b)
Species and water temperature.
c)
Species and amount of natural food present. It should be
remembered that it takes a few years for the natural production level of a new
pond to stabilise.
Time of Feeding
1.
Under
normal rearing conditions, it is best to feed fish at least once a day,
usually for six days a week. In low temperatureconditions it is better to feed
after two to three days and juvenile fish should be fed more often.
2.
The
best feeding time of the day is early morning, as water temperature and
dissolved oxygen content start increasing or in late afternoon i.e, few hours
before the sunset.
3.
In
some cases, using demand feeders feeding time and amount are
determined directly by the choice of the fish feed is supplied when the fish
are hungry.
Checking on Feed Utilisation
It is necessary to
check regularly on feed utilisation during
(a) Before
feeding- to check whether there is any feed left over from the
previous meal. To do this a light scoop made of fine-mesh metal netting mounted
on a long handle can be used.
(b) During
feeding- to observe how actively fish eat. Good appetite of fish indicates its
good health and better water quality.
(c) Every 15 to
30 days- to check on the new fish biomass present in the pond and to adjust the
daily feeding ration accordingly. Feed utilisation is checked during the last
15 to 30 day period by calculating the food conversion ratio for this
period.
(d) At the end
of the production cycle- to check on feed utilisation by calculating the food
conversion ratio for this particular cycle.
Stopping the Feeding
Several occasions are
there when it is necessary to stop feeding the fish such as:
1. Water temperature: too low or too high
2.
Dissolved oxygen: when its content is limited
3.
Particular day of adding manure in the pond
4.
Incidence of epidemic disease in the pond
5.
Fish should not be fed for two or three days before
stressing handling activities such as: sorting or grading them,
transporting them alive, their final harvest, marketing them.
Precautions
(a) The smaller the fish,
the frequency of feeding should be more.
(b) Distribution of
dry feeds should be more and often in comparison to the moist feeds.
(c) In any one
feeding, no more than 3 percent of the total fish weight should be distributed.
(d) The feeding
frequency should be reduced when temperature of water falls down.
(f) The feeding cost
should be checked to make sure it is not excessive compared to the yields
obtained.
References
1. https://www.scribd.com/document/103320009/Chapter6-Feeds-and-Feeding-the-Fish
2.https://www.fao.org/fishery/docs/CDrom/FAO_Training/FAO_Training/General/x6709e/x6709e10.htm
3. https://www.fishkillflea.com/how-much-agriculture-goes-into-fish-feed-in-the-usa
