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Air Breathing Fishes-578

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Air Breathing Fishes-578 Powered By Docstoc
					                            Air Breathing Fishes
                                     Booklet No. 578
                           Fisheries and Aquaculture: FACS-24
Content
Preface
I.     Introduction
II.    Adaptations for Air Breathing
III.   Cultivable Species
IV.    Species wise Description
V.     Pond Requirement
VI.    Breeding
VII.   Rearing Schedule
VIII. Conclusion

Preface

        Air breathing fishes are a group of fishes that can be reared by people who do not have
good ponds with fresh water. They spawn easily under the natural conditions and can be easily
multiplied at the growers level. People who have poor and limited resources can adopt rearing
of these fishes to generate some additional income as well as supplementary protein.

Dr. K. T. Chandy, Agricultural & environmental Education

I. Introduction

       Generally all the fishes live and feed in water and uses oxygen dissolved in water
through the gills. However there are some fishes that can not only live in poorly oxygenated
water but can also live out of water for a considerable time. Such fishes possess special organs
by which they can breathe the oxygen from the air unlike all other fishes.

        In fact there are two kinds of air breathing fishes: one type takes oxygen from the air as
supplementary to what is dissolved in the water the other type is the one which by nature
breathes air from atmosphere. The latter will be drowned if they are kept inside the water for
long time.

        There are several species of air breathing fishes belonging to different orders and
families. But by virtue of their common adaptation to aerial respiration they are generally
grouped together and are collectively known as air breathing fishes.

        They are mainly found in the tropical areas and are of great importance to people who
have very poor resources and rearing facilities for other types of fish culture. In a country like
India where small and marginal farmers are in majority, who may have only the waste water
collected from their bath rooms, kitchen and roof of the house and their animal sheds, rearing of
the air breathing fishes is a very good way of getting the much needed protein.

       Air breathing fishes are also suitable to the rural and tribal areas where we can always
find pools and ponds of stagnant water here and there and near the households. Rearing the air
breathing fishes may be the best way of using these idly lying pools and ponds. Generally these
pools and ponds are breeding places of mosquitoes. By rearing the air breathing fishes the
mosquitoes can be controlled as these fishes prey on them.
II. Adaptations for Air Breathing

        The air breathing fishes acquired their characteristic behavior out of necessity as the
waters in which they lived were very poor in quality and the oxygen dissolved in it was very low.
Hence during the history of evolution these fishes developed several adaptations to live in the
poor quality water. These adaptations are mainly physiological and behaviouristic. They may be
through development of aerial respiratory organs, modifications of blood functions, changes in
food and feeding habits, specialized reproductive behaviour and parental care instincts for
better survival in the adverse conditions and environment.

         When the oxygen content decreases and the level of carbon dioxide increases in the
water the fish comes up to the surface and gulps air for respiration. The frequency of surface
trips for aerial respiration depends on the quality of water in terms of oxygen and carbon dioxide
content. Greater the carbon dioxide or lesser the oxygen content in the water greater will be
frequency of the surface trips made by the fishes for air breathing.

        Living in such adverse conditions the fish become hardy in course of evolution. The
blood is modified to withstand the acidic conditions created by higher carbon dioxide in the pond
water and blood plasma in the body. The haemoglobin in the body of such fishes continues to
bind oxygen even when carbon dioxide percentage in the blood is more than 1.5 and up to 3 per
cent. The oxygen binding capacity of the blood in these fishes is higher than the other fishes.
For example Heteropneusteus possess 400 % more haemoglobin than many other fishes such
as carps.

        Some of the air breathing fishes are known to travel from one place to another in search
of shallow waters and protective vegetation. They prefer shallow waters and protective
vegetation: shallow waters because for air breathing only shorter surface trips are needed and
protective vegetation be- cause they can raise their young ones safely under the cover of
vegetation.

        Different species of these fishes have modified their existing organs or have developed
special organs for air breathing. In some the skin, in others the swim bladder, in a few the gills
and in few others the stomach or the intestine or an altogether new organ has taken up
respiratory function. To facilitate the under- standing of the modifications and developments in
the air breathing fishes, Table 1 will prove to be very helpful.

    Table 1: Nature of aerial respiratory organs in some of the common air breathing fishes

   Sl.No    Fish (common name)          Nature of aerial respiratory organs
   1        Clarias batrachus           Lying oppositely to the gills, under each gill cover in
            (magus)                     the form of a pair of tree like dendrite organs. They
                                        are tufts of epithelial outgrowths from the gill arches
                                        and are supplied with a net work of fine blood
                                        vessels
   2        Heteropneustes fossils      Developed on either side of pharynx as a
            (Singh)                     diverticulum’s excavating the lateral body muscles
                                        and extending almost up to the tail end, in the form
                                        of a hollow, tubular lung which retains air and
                                        diffuses it to the blood
   3        Anabas restudies (kopi      Developed in the form of rosette shaped structure
            or kiwi)                    made of a number of concentrically arranged shell-
                                       like plates with wavy edges. These are outgrowths
                                       from the bronchial arches and are richly supplied
                                       with fine blood vessels
   4        Channa spp. (murrels or    Developed as hollow pouches on the roof of mouth
            snakeheads)                on either side of the palate having a large number of
                                       nodules or papillae richly supplied with blood
                                       vessels. They help in retention and diffusion of
                                       gases
   5        Notopterus spp.            Swim bladder is adapted to function as the aerial
            (featherbacks)             respiratory organ. The main portion of the swim
                                       bladder lying in the abdominal portion of the body
                                       cavity bifurcates into two lateral branches like tubes.
                                       Each of these extends beyond the abdomen into the
                                       trunk, penetrates the muscle, where a series of 14
                                       to 15 blind pouches with finger-shaped processes
                                       are met with. These are supplied with profuse
                                       supply of blood capillaries and recall the
                                       appearance of bronchii and alveoli of mammalian
                                       lung
   6        Pangasius pangasius        Swim bladder is adapted to function as the organ for
            (pangas)                   aerial respiration. The fish has a spacious three-
                                       chambered swim bladder. The ventral wall of the
                                       anterior chamber has a small aperture leading by a
                                       slender pneumatic duct, into the oesophagus on its
                                       dorsal aspect. The anterior chamber; the largest of
                                       the three occupies almost half the anteriodorsal
                                       aspect of the abdominal cavity while the middle
                                       chamber extends upto anal region and the rear one,
                                       which is in the form of a slender tube, extends
                                       beyond the abdomen into the trunk. The inside of all
                                       the three chambers is thrown into convoluted ridges
                                       enclosing small spaces. They are richly supplied
                                       with fine anastomosing blood capillaries
   7        Amphipnuous cuchia         Consists of a pair of sacs growing out of the pharynx
            (mud eel or cuchia eel)    above gills. The gills themselves are rudimentary
                                       and the fish has evidently lost all its power of
                                       aquatic respiration. It comes to the surface of water
                                       at frequent intervals to inhale air into its lungs which
                                       are very similar to those of frogs

III. Cultivable Species

        There are several species of air breathing fishes belonging to different orders and
families. Some of them are valued for their taste and nutritive quality. Table 2 gives the names
of seven air breathing fishes that are recommended for rearing. Theses fishes are known by
different names in different languages. For the benefit of various language groups in our
country, names of these fishes in regional languages are also given along with the scientific
names.
        Among these Clarias, Heteropneustes and Anabas are relished more in the north-
eastern states. They are very popular for their nourishing and recuperative properties and are
recommended as dietary ingredients for sick and convalescent. From ancient times people
know that consumption of these fishes improve the haemoglobin content in the blood. They are
popular for their lean meat quality, the easily digestible fat content and the presence of several
essential amino- acids making them ideal food for invalids. The Channa spp are much
appreciated in the peninsular India especially in Andhra Pradesh and Karnataka. Catfish
(Pangasius- pangasius) is known for its creamy white flesh which people in India like very much.
All the air breathing fishes are generally sold in the market alive and they are also known as live
fishes.

                    Table 2: Cultivable species of air breathing fishes in India

  Sl.No Local      Clarias        Hetero-    Anaba     Chann     Chann     Chann    Pangasius
        names      batra-chus     pneu-      s         a         a         apunct   pangasius
        in                        stes        Testu    maruli    striatu   atus
                                  fossils    -         us        s
                                             dineus
  1       Assam    Magus          Singee     Kai       Haal      -         Haal,    Pangas,
                   Mahgur         Sheene                                   shawl    ponga
                                  e
  2       West   Magus            Singh      Kopi      Sal       Shol      Taki     Pungas
          Bengal Mahgur                      Koyee     Ajal                Lata     Panghra
                                                                                    Pungwas
  3       Bihar    Mangur         Singh      Kabai     Bhor      Soura     Carai    Jellum
                   Manguri                   Kavai     Pumur                        Periasi
                   Mongri                    Kawai     i                            Pangash
                   Maungra                                                          Pangsa
                                                                                    Pangash
                                                                                    Payas
  4       U.P      Mangur         Kama-      Kawai     Sol       Girai     Girai    Payas
                                  chasing              Saur                         Piyasi
                                  hi                   Cajri
                                  Bitchu
                                  Talia
                                  Singee
  5       Punjab Magus            Lahoord    -         Kubra     Sowl      Duloor   -
                 Kugga            Nullie               h         Dhoali    a
                                                       Sawal     Carrod    Daula
                                                       Dowla     h
                                                       h
  6       Orissa   Magurah        Singee     Kou       Saal      Sola      Coriss   Jalang
                   Maguro         Singh                                    a        Pangas
  7       A.P      Marpoo         Ingilaye   -         Poom      Korra     Matta-   Chholuva-
                   Marpulu        e                    ee--nu    meenu     gudisa   jella
                                  Mapujell             Phool     Korra     Burada   Bankra jella
                                  a                    a-        mata      -matta
                                  Marpu                chapa
                                                       Phjool
                                                       mural
  8       Tamil    Masarai        Thaylee    Senna     Aviri    -         Korava    Coola-
          Nadu     Karu-ppu-      Thali-     l         Puver              patti     kellete
                   ktheli         meen       Pauni-    al                           Manga-
                                             eypre                                  keluthi
                                             Panai-                                 Aie
                                             eerike-
                                             ndai

  9       Kerala   Muzhi          Kahree     Undee     Chaer    Sowra     Kayich    -
                   Mazhu          meen       collee    uve      h         al
                   Yerrivahlay    Kadu       Antikal   Veeral   Veralu    Arraca
                   Musi           Moyya      lai       Curuv    Kauna     n
                                  Kari       Karipp    a        n
                                             idi       Bral
  10      Karnat   Halimeena      Kappeth    -         Hoovi    Poolik    Korava    -
          aka                     ede                  namuri   uchi      Kuchi
                                  Kappers              Madinj   Koochi    Belikko
                                  hode                 i        namari    rava
                                  Seruva               Aviu
                                  Sinimee
                                  n
  11      Mahar    Magus          Shengali   Kopi      Kalam    Sohr      Maral     -
          ashtra                  Bitchuka             oral     Mangs
                                  machi                         ha
  12      Comm     Walking        Stinginh   Climbi    Giant    Stripp    Spotte    pungas
          on       catfish        catfish    ng        murrel   ed        d
          name                               perch     snake    murrel    murrel
          in                                           head     Stripp    Spotte
          Englis                                                ed        d
          h                                                     snake     snakeh
                                                                head      ead

IV. Species Wise Description

       The salient features in terms of the biological and cultural aspects of various cultivable
species are given as follows.

A. Clarias spp
        Clarias spp belongs to Clariidae family are widely distributed covering the whole of
Africa, southern and western Asia and can be reared in all other tropical countries.

       They are commonly known as cat fish Clarias fuscus is distributed in higher latitudes
also. The important species among them are briefly described here.

1. Clarias batrachus
        This is commonly known as "magur" or "mangur" in most of the Indian languages. This is
the most extensively cultivated species in Asia. It is cultivated in Thailand commercially. Clarias
macrocephalus is very much like the batrachus but different in the occipital growth which is
pointed in the case of C. batrachus and rounded in the C. macrocephalus which is also slow in
growth and scarce in the availability of the frys for culture. Hence C. macrocephalus is not as
popular as the C. batrachus.

        C. batrachus is more important economically in India than all other catfishes. This grows
up to a maximum size of 40 -45 cm in circumference. It attains sexual maturity at the end of the
first year. The male and female can be distinguished only during the breeding season. In the
fully mature state the female looks relatively heavier with its considerably distended abdomen.
The male on the other hand looks slender. In the female the genital papilla is short, oval and slit-
like while in male it is long and pointed. C. batrachus have a spine on each of their pectoral fins.
These spines are said to be slightly poisonous in nature and are used by them to inflict very
painful wounds on their enemies.

        The number of eggs produced by C. batrachus on an average vary from 53 to 511 per
gm of its body weight and ovary weight respectively. Spawning usually takes place during the
rainy season. They migrate into canals and other water bodies for feeding and breeding. During
the rainy season they even cross the land area to reach other water bodies which are not
connected to each other. At that time they literally walk with their strong pectoral fins. Hence
they are called walking fish.

        The eggs are laid in nests which are constructed by the females in the form of horizontal
holes in the embankments about 20 to 25 cm below the water surface. The size of the hole
varies with the size of the cat fish. The deposited eggs stick to the grass roots or soil surface of
the nest itself. The eggs are guarded by the male while the female remains in the vicinity. They
are small, sticky, spherical, yellowish brown or pale or greenish yellow in colour. They hatch
within 18 -24 hours at a temperature varying between 25 to 35 °C. The hatchlings at the time of
hatching measures about 4.5 to 5.8 mm in length.

        For few days after hatching the body of the hatchlings looks compressed side ways and
the head bent downward. Each hatchling possesses a large ovoid yolk sac inherited from the
respective egg from which each one was hatched. Till about five days it is the source of nutrition
for the hatchling. The yolk sac gets absorbed totally by the 5th day. However before that the
hatchling begin to feed on zooplanktonic organisms and later feed on bigger organisms as they
grow into the fry stage. The frys begin to air breath by 10th or 11th day after hatching and by 15-
20 th day the frys acquires the characteristic look of an adult batraches.

        C. batrachus having very poor taste buds swallows almost anything that comes across
its way. They readily take artificial feed also. Hence it is not at all difficult to feed and rear them.
They can be fed with all kinds of things such as low grade marine trash fish, slaughter house
wastes, fish offal, dried silk worm pupae, rice bran, wheat bran, any type of oil cake etc. Insects
can be attracted to the pond by keeping an electric bulb just above the water level closer to the
shore. The insects thus coming to the pond will be eaten by the batrachus. They can be reared
with Anabas and Heteropneustes or even as a substitute to common carp in the Indian as well
as exotic carps in composite fish culture.

       C. batrachus naturally grows in West Bengal and Chotanagpur areas during the
monsoon in the paddy fields, irrigation channels, drainages, field channels, ditches and ponds.
So the frys are collected from the nature though attempts to spawn them artificially is expected
to succeed shortly. C. batrachus can withstand high stocking density and the recommended
stocking density in India is about 50,000 fingerlings per hectare.
        The production potential of C. batrachus is quite high and ranges between 1000 to 7250
kg per ha. in 4.5 to 11.5 months period. The average yield under various situations and
conditions has been 3645 kg per hectare. Under very good conditions of rearing an yield up to
35,000 kg/ ha in 7 months has been recorded. Culture of C. batrachus in a recirculatory filter
pond tried at Barrackpore in West Bengal yielded a production of 21,900 kg/ha in 6.5 months of
growing period. The size of the ponds vary from 0.015 to 0.18 hectare area.

2. Clarias lazera
        This species is more popular in African countries. It has sharp teeth and is said to be
originally noticed in the river Nile. Therefore it is also known as sharp-tooth catfish or Nile
catfish. Clarias anguillaris is another catfish identified as native of Nile region. C. lazera grows
up to 130 cm while the C. anguillaris grows up to only 90 cm in length.

B. Heteropneustes fossilis
        In many parts of India Heteropnewtes foassilis is Known, as "singhi." People easily get
confused between C. batrachus and H. fossilis ownig to the close similarity in their body
structure and colour. The best way to distinguish between them is to observe their dorsal fins. In
batrachus the dorsal fins is bigger and in fossilis they are very small.

        H.foassilis is commonly seen in the ponds, ditches, swamps and marshes and tolerates
slight brackish water too. They are common not only in India but also in Burma, Thai- land,
Pakistan, Bangladesh, Indonesia and Nepal. The maximum recorded size of fossilis 38 cm in
circumference. In this breed the males are smaller than the females. Like C. batrachus,- this fish
also has deadly spines present on the pectoral fins,

       H. fossilis attains sexual maturity by the end of the first year. The spawning season
extends from June to September.

        The number of eggs released varies from 3000 to 45000 per spawn depending on the
size of the fish and the ovary., On an average about 8000 eggs are produced per 100 gm body
weight. The eggs are green or brown in colour and adhesive in nature, They hatch within 18-24
hours depending on the water temperature. The hatchlings measure about 2.72 mm in length
and possesses the usual yolk sac which gets absorbed in four days. But the larvae starts
feeding on the third day itself. In the beginning they feed on zooplanktons and later on they
become omnivorous. They are generally bottom feeders. They have great liking to gastropods
(any mollusks like snails etc.) and it is a wonder how they are able to swallow such big
gastropods.

        H. fossilis can be cultured alone or in combined with other species like Clarias and/or
Anabas. They may be reared intensively or semi-intensively. In the semi-intensive type of
rearing the stocking density is about 60,000 fingerlings per hectare. If sufficient feed is available
their growth rate is 'remarkable. Low grade marine trash fish and rice bran is found to be good
feed. A mixture of rice bran, oil cake and biogas slurry in the ratio of 1:1:1 has been found to
work as a good low cost teed for H. fossilis.

        Under proper management conditions H. fossilis attains an average weight of 60 gm in 6
months. The yield potential assessed as per several experiments in Assam and West Bengal
ranged from 1642 to 7300 Kg/ha in 4 to 11 months period giving an average of 4510 kg/ha, But
in the intensive culture the maximum yield reported from this species amounts to 35000 kg/ha
in seven months.
C.Anabas spp
        This species is known as climbing perch in English and in several Indian languages as
"kawai or koi". it is found in the tropical regions. Under this species Anabas testudineus is a very
hardy fish and is commonly found in the swampy and marshy tracts as well as abandoned pits,
pools and puddles which remain in the process of drying up during summer months. During the
rainy season they also seen prowling about on wetland. It can literally walk over the dry land for
great distances at a stretch using its operculum and pectoral fins. It is priced for its good taste
though it is a moderate size fish. It grows maximum up to 26 cm in size.

        They become mature by the end of first year. Breeding activity becomes very intense
during the rainy season but by the end of the rainy season sudden decrease is observed in the
same. Depending on body weight and the size of the ovary the number of eggs range from 5000
to 35000 per spawning. A female weighing 50 gm produces on an average about 20,000 eggs.
per spawn. The eggs float freely and look yellowish in colour. They hatch between 18 to 24
hours at 27 to 30o C. The hatchling measuring about 1.9 rnm in length, float upside down
position at the surface. Feeding commences from the 2nd day onwards beginning with
zooplanktons and gradually becoming an omnivorous fish though definite preference is shown
to insects. It consumes all kinds of feed of plant and animal origin.

         This species can be cultured singly or in combination with C. batrachus and/or H.
fossilis. It can also be grown with carps in the composite fish culture. However the ponds?
should have high and very steep slope (above 70°) in order to prevent this species from walking
out of the pond during the rainy season. Depending on the level of management in the
monoculture the stocking intensity will vary from 25000 to 50000 young ones per hectare.
Basically the management practices are the same as those for other air breathing fishes
mentioned so far. The average production of this species is about 876 kg/ha in 5 -11 months
period.

      A oligolepis is another species looks exactly like the A testudinus. For all practical
purposes these two species are not distinguishable and hence they are reared together.

D. Channa spp
       There are several species grouped under this genus; however so far only three species
are culturally important. They are: Channa marulius (giant murrel), Channa striatus (stripped
murrel) and Channa punctatus (spotted murrel). Fishes coming under this species is also called
"snakehead" as its head looks like that of the snake. "Sol" or "sal" are two names commonly
found in several Indian languages. The important three species are briefly described as follows.

1. C. marulius (Giant murrel)
        This species is commonly found in the lakes, reservoirs, swamps and rivers. It can grow
up to 120 cm in length and is highly predacious and cannibalistic in its feeding habit. It breeds
usually from March to October. The number of eggs range from 2000 to 40,000 per spawn
depending on the body weight and the size of the ovary The floating type of eggs. are released
in the weed infested marginal areas and are held together by the vegetation. Eggs hatch within
24 hours. Both the eggs and the hatchlings are guarded by both the parents.

2. C. Striatus (Stripped murrel)
        This type of murrels are very commonly found allover India and are very important
economically. It grows up to about 90 cm in length and is highly predatory in habit feeding on
other fishes, frogs, tadpoles, insects and other live micro and macro organisms. The most
advantageous characteristics of this species is that it breeds throughout the year though the
intensity is much more in the rainy season. It becomes sexually mature by the end of first year.
The number of eggs released range from 3000 to 30,000 per spawning.

3. C. punctatus (Spotted muml)
        Compared to other murrels spotted murrel grows only up to 30 cm in length. It is found in
stray ditches and feeds mainly on smaller fishes, insects, shrimps and occasionally mollusks
etc. They mature sexually by the end of the first year. Breeding starts in April and continues till
October. The number of eggs released range from 3000 to 26,000 per spawning depending on
the size of the ovary and the weight of the fish. The eggs hatch within 24 hours and the
hatchling remain under the parental care moving together in search of feed along the edges of
the pond.

4. General cultural practices of murrels
        Murrels are reared mostly in monoculture system. The seed fish is collected tram the
nature an entire batch of hatchlings will be under the parental care and move around in group in
search of feed all along the edges of the pond making ripples on the surface of the water.
Therefore their movements can be noticed from far and the entire lot can he scooped
out of the pond using a fine meshed net in which all types of murrels may be caught.

        The frys of giant murrels can be recognized by its conspicuous orange-yellow
longitudinal band running laterally; from the posterior edge of the orbit to the tip of the caudal fin.
An eye like spot appears on the caudal tm as a light dark spot surrounded by an orange hue.
The fry of C. striatus has a vermilion red body. Laterally there is a bright reddish golden yellow
longitudinal band and a dark band below. Fry of C. punctatus is characterized by the possession
of a bright golden yellow longitudinal band running from the posterior extremity of the orbit to the
caudal base laterally and a yellow line mid-dorsally from snout to the origin of dorsal fin.

         The frys of murrels can be produced through the method of induced breeding. The
recommended stocking rate of murrels in a grow out pond under Indian conditions is 20,000
fingerlings per hectare for C. marulius 30,000 /ha. for C. striatus and 40,000/ha.for C. punctatus
in semi-intensive operations.

       In intensive system the stocking rate for the three species is 40,000/ha, 60,000/ha and
80,000/ha respectively.

        Under the Indian conditions C. marulius attains on an average weight of 350 -400 gm in
6-8 months period of culture C. striatus 250-300 gm and C. punctatus 150-200 gm \ per
individual fish. The total yield from any of these three amount to about 3000 to 4000 kg/ha in
semi-intensive cultural conditions and 6000-8000 kg/ha under the intensive system of
production.

E. Pangasius spp
        The most popular among the species of Pangasius spp is Pangasius pangasius
commonly called "Pangas". This is the common and important species in the Indian river
system. It grows up to 122 cm in length. It breeds in the rivers during the monsoon months and
grows in them feeding on all kinds of things. However this species is known to have preference
for mollusks. Their culture under artificial conditions is yet to be started commercially and hence
we are unable to give details about its growth rate and yield.

V. Pond Requirement
        As already seen the yield of the above described air breathing fishes is quite high under
the natural and even in the poor growing conditions. Their yield can be further increased by
rearing them in ponds with rearing conditions and feeding practices. For this a pond system will
be highly useful. In this part of the booklet we shall deal with the establishment of the
pond for rearing of the air breathing fishes especially in relation with C. batrachus since this
species most yielding and commonly cultivated.

        The ponds may be constructed singly or in multiples. Single ponds are constructed for
the home level and small scale rearing of air breathing fishes. The multiple pond system is
constructed for intensive, commercial rearing. The ponds are constructed with proper plan and
with facilities for recycling and change of water, feeding, breeding, disease control, draining of
the ponds, for harvesting and for performing all other management practices. The ponds are
better constructed in such a way that water can let in from the common channel to each pond
and let out from each pond independently.

        A farm of one hectare area for rearing any or a combination of air breathing fishes may
be established by constructing ten ponds of 0.1 ha each (52x22xl.20 metres length, width and
depth of water) arranged in two parallel rows on a flat land (or any other way depending on the
topography of the land) with water incoming and out-going channels conveniently built on the
sides. The bunds on the outer side of the pond system and the bund between the rows of ponds
should be 5m. wide though the bunds in between the ponds in the same row may be made
small. On these bund vegetable crops, bananas and papayas may be cultivated to obtain
additional income.

      After establishing the ponds they are limed and fertilized with organic manures and
chemical fertilizers which may be done as per soil test. Otherwise we can follow the general'
recommendations prescribed for fish pond liming, manuring and fertilization.

       A month after liming, manuring and fertilization the frys or fingerlings of any desired
species collected from the nature or from some reliable nursery (including one's own) are
stocked at the recommended rate. They are fed sufficiently regularly and the water quality is
maintained. Alter about 11. months they can be harvested, graded and marketed.

      For more details about pond construction the reader is advised to refer the Booklet
No.520, on liming and fertilization in Booklet No. 524 on "Rearing of Carps".

       Another aspect of the pond construction for the air breathing fish is the use of
abandoned and unused water bodies like ditches, water logging areas, marshy places, waste
water collection tanks, sewage collection pools etc. Obviously the oxygen content in these ate
very low and other fishes will not be able to survive in them. Rearing the air breathing fishes is
the best way of utilizing these water bodies. To prepare these water bodies the following points
may be kept in mind.

1. If the area is very big divide it with bunds or partitions into manageable size of ponds
2. It should be sufficiently protected so that the reared fish should not go out.
3. It should be protected from the seasonal floods.
4. Create facilities for easy supervision and management.
5. Select a suitable breed of fish and rear them.
6. If possible manure and fertilize them.
7. If possible provide the fish with additional feed.
8. Introduce sufficient aquatic plants like eichornia, hydrilla, bacopa, Amazon sword plant, water
ferns, ambulia, hygrophia, myriophyllum etc. Most of these aquatic plants are capable of
removing dissolved metallic and other undesirable substances from the water making it more
conducive for fish rearing.

VI. Breeding

        Steady supply of quality frys and fingerlings is an important factor that should be taken
into consideration in order to ensure the success of the rearing of air breathing fishes. The
breeding behaviour of various species of air breathing fishes is different, But there are a number
of things in which we can find some behavioral pattern, based on which we can describe a
general procedure for the breeding of the air breathing fishes. Breeding of the air breathing
fishes is discussed under the following main headings.

1. Egg production
        Egg production of air breathing fishes is generally not a problem as they easily spawn in
the farm ponds. Paired air breathing fish are left in the pond which contains suitable nesting
area in which they can spawn. Spawning ponds are generally 0.25 ha area; but we can have
any size. The rate of stocking the breeding stock range from 50 to 300 per hectare. We can also
spawn them in pens of 3-6 sq metre and one metre deep. In both cases the egg may be left to
hatch in the pond/pen or may be removed for hatching in a hatchery.

         Spawning in the hatchery tanks or troughs of three metre long and 50 cm wide and 30
cm depth can also be accomplished by injecting the females with three doses of acetone dried
fish pituitaries with an average weight of 10 mg or with one dose of human chorionic
gonadotropin, containing 60 - 2200 International Units. The males need not be injected as in the
case of carps, After the spawning by the females the males release their milt in the water near
the spawn and fertilize the eggs. The females lay between 3000 to 20000 eggs depending on
their size. The eggs are hatched within few days depending of the temperature and the species
different. The fertilized egg mass should be placed in the running water and kept in slight motion
for hatching. The movement of the running water will be sufficient. It should also be kept in mind
that for certain air breathing fishes we have not yet developed any artificial spawning method.

2. Fry production
        After the eggs are hatched the hatchlings are kept in the hatchery trough itself or to
another similar trough for hygienic purpose. They are kept in this till their yellow yolk is absorbed
or the fry start feeding. In a trough of 300x50x30 cm size about 10,000 trys may be stocked. In
this trough a water flow at the rate of 20 litres per minute should be maintained in order to
ensure the availability of sufficient oxygen to all frys and to maintain them healthy.

       Once the frys start feeding they may be shifted to the fry pond which may be about 0.5
ha and is stocked at the rate of 100,000 per ha. They are fed with nutritious artificial feed.
However the mortality in the fry production pond may be around 35 per cent. The frys of the
species like pangasius are transferred to the fry pond directly from the hatchery tanks.

VII. Rearing Schedule

        For the benefit of readers who would like to start a system of air breathing fish rearing,
following time schedule may be useful. Along with the fish rearing we can also have cultivation
of the vegetables and banana to enhance the income. Such a system can he set up
permanently so that it becomes a permanent asset to generate regular income. Month wise
operational schedule for the first year is given which of course should he considered tentative.
Relevant modifications may he introduced hy each rearer according to the situation of the place,
climate and other natural resources available.

       The system given here as an example consists of a combination of air breathing fish (C.
batrachus), carp seed growing, banana cultivation, and vegetable cultivation. Instead of C.
batrachus any of the other air breathing fishes described above can be selected for rearing.

First Year
1. Construction of pond/ponds and setting up of the area may be done in the months of April to
May.

2. Filling water in the pond may be done in June.

3. Planting of bananas on the bunds is done in the month of July.

4. Cultivation of kharif vegetable is done in the months July to October.

5. Raising of carp frys and fingerlings during the months: beginning of July to the end of
October. About four months duration from the beginning of rainy season to the stocking of the
air breathing fishes the pond remains idle. During this time carp seeds (frys and fingerlings) can
be raised to gain additional income from the pond. Almost every 15 days a batch of frys can be
raised. But in the case of fingerlings about three months duration is required and hence only
one time we can raise the fingerlings If there are more ponds we can raise as many batches of
frys and fingerlings as there are ponds.

6. Preparation of pond in November introduction of the air breathing fish. This preparation
consists in removal of all structures installed in the pond tor breeding, spawning and raising frys
and fingerlings of the carps, additional manuring, introducing aquatic plants mentioned earlier,
getting feed stock for the air breathing fishes ready, ordering for or collecting of frys and
fingerlings from the natural sources etc.

7. Introduction of fingerlings of the air breathing fish (C. batrachus) in the months: from mid
November to mid December.

8. Cultivation of rabi vegetables from mid November to
end of February.

9. Rearing of the air breathing fishes during the mon~hs
from mid December to mid June in the following year.

10. 'Cultivation of summer vegetable tram the beginning
March to end of June.

11. Harvesting of the air breathing fishes.

Second year
12. Planting of banana in the month of July.

13. Cultivation of kharif vegetable from the beginning of July to mid August.
14. Raising of carp seeds either frys or fingerlings.

       Next in the cycle is preparation for the introduction of the air breathing fishes. Thus the
cycle of various operations goes and on. Under normal conditions the yield amounts to 3000 to
4000 kg/ha. But under better management conditions the yield expected can go up to 6000 lo
7000 kg/ha. The yield under best management and feeding conditions can go up to 10,000 to
15,000 kg/ha (record yield up to 35000 kg/ha has been reported). Experiments have shown that
rearing air breathing fishes can fetch substantial net profit and in a systems approach (having
vegetables, banana or papayas and carp seed raising along with the air breathing fishes) will
enhance the net profit considerably.

VIII. Conclusion

        Rearing of air breathing fishes is very profitable enterprise. Our country is dotted with
many ponds, ditches, channels, small and big tanks that collect waste water tram the villages,
towns and cities or other types of residential areas or industrial areas, waterlogged and marshy
areas. Most of these water bodies are very low in the oxygen content and are unsuitable for the
rearing of other fishes. The best way to use these otherwise unusable water bodies is to culture
air breathing fishes.

        India is the original place for many of the air breathing fishes known in the world. But
somehow importance is given to fishes that are introduced from out side or some selected
fishes and prawns for the commercial culture. We need to enforce a policy encouraging rearing
and consumption of air breathing fishes in our country,

       Its rearing and management practices are very easy compared to all other fishts
recommended for artificial culture. Yield wise the air breathing fishes have excellent and record
performance. Nutritively they are excellent as their blood contain more haemoglobin,

       They are omnivores and hence feeding them is very casy. They are very good
converters of all kinds of house hold and farm waste. Unlike carps and several other
commercially reared fishes air breathing fishes mature by the end of the first year. Therefore
breeding becomes easier. Select the hest male and female air breathing fishes and breed them
in small tanks.

       Perhaps we need a national level programme supported by finance, technical know-how
and marketing facilities to promote the culture of air breathing fishes in our country. Hope this
booklet will facilitate towards that.
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