LIVE
FEED CULTURES FOR MARINE ORNAMENAL FISH
Introduction
The chief live feeds employed are (a)
rotifers (b) copepods (c) Artemia nauplii. Microalgae form the basic
requirement for live feed culture and hence micro algal culture is the first
step in live Feed production. Microalgae constitute the first link in the oceanic
food chain.
· Culture of Artemia
Artemia is commonly called as “Sea
Monkey” or “Brine Shrimp” which thrives in hyper saline waters and is
distributed worldwide. It lives in temperature of >350C, up to 340ppt of
salinity and <1ppm of dissolved oxygen. Decapsulated cysts and freshly
hatched nauplii of Artemia form an ideal diet for prawns/fish juveniles.
Induction of maturity in brood stock prawn can be achieved if they are fed with
reproductively active adult Artemia. Thus, demand for Artemia continues to
increase with the development and progress of aquaculture. It is readily
available in the form of dry cyst containing dormant embryo, which can remain
in viable condition for years if stored properly. The adult Artemia measures
about 10mm in total length. However, in some polyploidy parthenogenetic strains,
grows up to 20mm in length. Artemia has an elongated body, which can be divided
in to head, thorax and abdomen. A pair of antennules, antennae and stalked eyes
is present in the head region. Thorax has eleven pairs of appendages known as
thoracopods. The abdomen ends in a Furca, covered with spine. The life span of
a brine shrimp is about six months. In bisexual strains, male has penis by
which the sperm is transferred into uterus of the female, during copulation.
Fertilization is achieved in the uterus. In the case of parthenogenetic
strains, embryonic development starts directly as soon as the eggs reach the
uterus. The embryos develop in to nauplii or are coated with shell to form
cysts, in the uterus, as per the prevailing environmental conditions. The
liberated cysts are 200-300 microns in size while the newly hatched nauplii
measure 400-500 microns in length.
Taxonomic position
Phylum
Arthropod
Class
Crustacea
Subclass Branchiopoda
Order Anostraca
Family Artemidae
Genus Artemia
Species A.
salina, A. tunisiana, A. francistoma, A. monica, A. persimilis and A. urmiana
Materials required
Artemia cyst,
Scoop net, Sodium Hypochlorite, Sodium thiosulphate, Beaker, Plastic bucket,
Sea water, Freshwater, Hatching jar, Aerator, Focusing light, etc.
Hydration of cysts
The required amount of dry cysts
are put in a container having sea water or freshwater (20 ml of water for every
one gram of cyst), provided with vigorous aeration. In about an hour, the cysts
get hydrated and turn spherical. The hydrated cysts are filtered on 100μm mesh
bolting silk cloth.
Decapsulation of cysts
Decapsulation of
hydrated cysts of Artemia is achieved by treating them with Sodium hypochlorite
(NaOCl) or with commercial bleaching powder, which dissolves/removes the shell.
Hatching of Decapsulated cysts
Decapsulated Artemia cysts are hatched in cylinder or
conical FRP jar of varying capacity (5 – 500 liters) depending on the
requirement. The optimum water quality conditions required for hatching of
decapsulated Artemia cysts are as follows:
Temperature
- 27 – 30 ̊ C
pH - 7.5 – 8.5
Salinity
- 25 – 30 ppt
Light - 1000 lux
Dissolved Oxygen - Saturation point
· Culture of Rotifer
Introduction
Rotifers are commonly called as
wheel animalcules. Among the rotifers Brachionus
sp. became more popular as 'live food' because of its high nutritive value,
small size, worldwide distribution, fast multiplication and easy adaptability
to captive condition. Of the Brachionus
sp., a euryhaline species, B.
plicatilis is widely used as prime live food for the early stages of fish
and shellfish in many aqua hatcheries. It can also be used as a first food for
most of the zooplankton feeding larval stages of fish and invertebrate. Brachionus belongs to the Sub-family
Brachioninae of the Family Brachionidae of the Order Ploima of the Class
Monogononta under the Phylum Rotifera of the animal kingdom. The pelagic,
herbivore rotifer, Brachionus plicatilis
inhabits in a wide range of water bodies such as brackish waters, salt lakes
and backwaters. It occurs in tropical and sub-tropical waters all over the
world. B. plicatilis thrives best
when temperature range is between 22-25°C and salinity between 10 to 15 ppt.
Morphology
Morphologically, it is divisible
into head bearing wheel organ or corona, body forming Lorica and foot
consisting of toes (Fig.). The size of B.
plicatilis varies between 150 to 250 micron in length (without foot) and
100 to 150 micron in width. .
Food and feeding
B. plicatilis is a filter feeder which feeds on particle size of
less than 5 micron in size. It prefers the food items, which are simple in
shape and well suspended in water. It obtains food through ciliated corona. The
most tested and acceptable food for B.plicatilis
is Chlorella sp. and Tetraselmis sp. with the addition of
baker’s yeast. Maintenance of high food concentration helps in producing
maximum yield in the culture system.
Enrichment
In recent days efforts are made to improve
the nutritional status of zooplankton organisms by using omega-3 essential
fatty acids. Microalgae, which are rich in omega--3 fatty acids are fed to the
Brachionus to increase its food value. Different micro particulate and
emulsified formulations are used for boosting with essential fatty acids and
other components. A further improvement of the nutritional quality of
Brachionus can be accomplished with respect to vitamin "C'
supplementation. Ascorbyl palmitate can be used as vitamin C source because of
its stable and lipophilic characteristics and its bioavailability. Apparently
the vitamin "C' inclusion does not result in any effect on the production
nor on the HUFA-content of the Brachionus. Elevated levels of a bioactive
vitamin 'C' source can thus be transferred through the live food chain towards
the finfish and shellfish larvae. This provides an important tool to build up
stress and disease resistance during larviculture in aqua hatcheries.
Maintenance of culture
Regular uninterrupted supply of
Brachionus to the aqua hatcheries needs judicious management. This involves the
risk of bacterial contamination. A large number of antibiotics are in use to
control the bacteria. It may help in lowering the bacterial load, but implies
the risk of building up of antibiotic resistance. A new approach, i.e. use of
probiotics, is being evaluated as a possible prophylactic treatment, i.e. the
addition of beneficial bacteria in the Brachionus culture and larval rearing
tanks of finfish and shellfish.
· Culture of Bloodworms
Blood worms are otherwise called as
Chironomus larvae. The intermediate larval stage of the midge fly is commonly
called blood worms. They belong to the family Chironomidae of the phylum
Arthropoda. They are usually red in color. It is one of the best live food
items for ornamental fishes.
It can be cultured using box made from wood
cement bricks or plastic care should be taken that there are no holes in the
box and they must be placed in a cod place with plenty of shade box dimension should be 1cm ×1cm ×0.3m
depth, prepare a layer of saw dust, sand
and top soil of each 3cm depth. Add about 6 litre of water to keep them moist.
Add cattle dung, poultry, vegetable waste, cereal waste in ratio of 10:1:1:1. One
kilogram worms feed 5-10kg feed. Inoculate 100 small worms per box @ 25 kg wet
weight.
·
Culture of Mosquito Larvae (Maggot)
It comes
under the phylum Arthropoda. They breed in stagnate water bodies. Cow dung is
the medium for culture of mosquito larvae. They can be harvested using scoop
net.
·
Rotten fish and bread soaked in milk was
kept as a substratum to attract flies to it and left for a day at a well
aerated place
·
The next day eggs of house flies were
found over the substratum
·
It takes 24 hrs for the maggot larvae to
hatch from the eggs
· Culture of Infusorians
Infusoria belong to the class Ciliata under the phylum
Protozoa. They serve ideally as starter feed for early stages of ornamental
fishes. The tiny microscopic one celled animalcules like Paramecium are
collectively called Infusoria. They are found in ponds, tanks and ditches. They
can be easily collected with 0.13 mm mesh cloth. A gallon jar with
clean, filtered pond water was filled and a dried banana skin was added .After
two days the skin was soak to the bottom and a heavy bacterial slime covered
the water surface. At that time a very small quantity of old culture water or
old aquarium water was added. After two weeks Infusorians were observed in
evidence as the water clears up and the culture water was used as a source of
food.
Economical Importance of Live feeds:
ü Large
branchiopods are important to the commercial aquaculture industry
ü They
are the rapidly growing food source for farm fish, mollusks, and shrimp
ü Artemia eggs can be stored dry until needed and then
easily hatched in bulk
ü The
size of live feeds makes it a lot easier for consumption and to digest
ü It
also loaded with full of nutrients
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