Rotifers are popularly called as wheel animalcules. They are an important group of live food organisms for use in aqua hatcheries. Brachionus, which is the most known form of all rotifers, serve as an ideal starter diet for early larval stages of many fish and prawn species in marine as well as freshwater. Species of the genus Brachionus (Brachionidae: Rotifera) are well represented in different water bodies worldwide (Pejler, 1977). Depending on the mouth size of the cultured organisms, small (50 to 110 micron length) or large (100 to 200 micron length) rotifers are used. There are about 2,500 species of rotifers have been known from global freshwater, brackish water, and seawater. B. plicatilis is the species used most commonly to feed fish larvae in hatcheries around the world. It is a euryhaline species, small and slow swimming, with good nutritional value. It is well suited to mass culture because it is prolific and tolerates a wide variety of environmental conditions. The rotifer, B. plicatilis and B. rotundiformis, have been indispensable as a live food for mass larval rearing of many aquatic organisms (Maruyama et al., 1997). By way of significant developments in larval rearing technology of fishes, demand for the rotifer is further increasing.

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Use of Rotifer in Aquaculture of Bangladesh
Introduction
Rotifers are popularly called as wheel animalcules. They are an important group of live food
organisms for use in aqua hatcheries. Brachionus, which is the most known form of all rotifers,
serve as an ideal starter diet for early larval stages of many fish and prawn species in marine as
well as freshwater. Species of the genus Brachionus (Brachionidae: Rotifera) are well represented
in different water bodies worldwide (Pejler, 1977). Depending on the mouth size of the cultured
organisms, small (50 to 110 micron length) or large (100 to 200 micron length) rotifers are used.
There are about 2,500 species of rotifers have been known from global freshwater, brackish water,
and seawater. B. plicatilis is the species used most commonly to feed fish larvae in hatcheries
around the world. It is a euryhaline species, small and slow swimming, with good nutritional value.
It is well suited to mass culture because it is prolific and tolerates a wide variety of environmental
conditions. The rotifer, B. plicatilis and B. rotundiformis, have been indispensable as a live food
for mass larval rearing of many aquatic organisms (Maruyama et al., 1997). By way of significant
developments in larval rearing technology of fishes, demand for the rotifer is further increasing.
Aquaculture
Aquaculture, probably the fastest growing food-producing sector, now accounts for nearly 50
percent of the world's food fish. The need to exchange reliable information on all related subjects
is becoming a key issue for the responsible management of aquaculture. FAO (1988) introduced a
definition of aquaculture, which reduces its confusion with capture fisheries: “Aquaculture is the
farming of aquatic organisms, including fish, molluscs, crustaceans and aquatic plants. Farming
implies some form of intervention in the rearing process to enhance production, such as regular
stocking, feeding, protection from predators, etc. Farming also implies individual or corporate
ownership of the stock being cultivated. For statistical purposes, aquatic organisms which are
harvested by an individual or corporate body which has owned them throughout their rearing
period contribute to aquaculture, while aquatic organisms which are exploitable by the public as a
common property resources, with or without appropriate licenses, are the harvest of fisheries”.
Aquaculture in Bangladesh
Bangladesh is a densely populated country of 147 570 square km with a population of 130 million
people. It is fortunate in having an extensive water resource in the form of ponds, natural
depressions (haors and beels ), lakes, canals, rivers and estuaries covering an area of 4.56 million
ha(DoF,2005).
Bangladesh is one of the world's leading inland fisheries producer with a production of 1 646 819
tons during 2003–4, with marine catch total of 455 601 tons and a total production from
aquaculture of 914 752 tons during 2003–4. Bangladesh's total fish production for the year totaled
above 2.1 million tons (DoF, 2005). FAO (2005) ranked Bangladesh as sixth largest aquaculture
producing country with its estimated production of 856 956 tons in 2003 (FAO, 2005).
Aquaculture accounted for about 43.5 percent of the total fish production during 2003–4, with
inland open water fisheries contributed 34.8 percent (DoF, 2005).

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The present per capita annual fish consumption in Bangladesh stands at about 14 kg/year against
a recommended minimum requirement of 18 kg/year; hence, there is still need to improve fish
consumption in the country.
Fisheries in Bangladesh are diverse; there are about 795 native species of fish and shrimp in the
fresh and marine waters of Bangladesh and 12 exotic species that have been introduced. In
addition, there are 10 species of pearl bearing bivalves, 12 species of edible tortoise and turtle,
15 species of crab and 3 species of lobster.
The Ministry of Fisheries and Livestock (MoFL), Department of Fisheries (DoF), Bangladesh
Fisheries Development Corporation (BFDC) and the Bangladesh Fisheries Research Institute
(BFRI) are the main organizations responsible for aquaculture and its development. Universities,
organizations within other ministries and local and international NGOs are also involved in this
area.
Present Status of Aquaculture in Bangladesh
The country’s fish production has nearly doubled over the last decade—thanks to popularity of
fish farming. According to data of Bangladesh Department of Fisheries, farmed fish production
was 2 million tons in 2013-14. This was only 0.8 million tons back in 2001-02.Consequently, the
overall fish production increased spectacularly by around 88 percent during this period. This is
great news for the nation as fish accounts for about 56 percent of Bangladesh’s intake of animal
protein. According to fisheries department, the country produced about 3.5 million tons of fish in
the 2013-14. Of this, 2.9 million tons came from farms and catches from various Inland water
sources, and 0.6 million tons were from the sea. A decade back, the total fish production stood at
1.9 million tons—majority of it came from various inland water sources.

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This rise in fish culture is due to increase in high quality fish feed and seed production, and
widespread induced breeding technology, the department says. Another reason that boosted fish
production is the Jatka Conservation project that imposed a ban on Hilsa fishing.
The most dominant source of fresh water fish in the country is the several thousand ponds in the
villages, comprising of about 0.4 million hectare area that produce half of the Inland water fish.
One-quarter fish comes from flood plains.
Water area for Inland fisheries comprises of approximately 4.7 million hectares across the country.
Dhaka division tops fish production with claiming 28 percent of the stake; followed by Chittagong,
Khulna and Rajshahi ranging between 13 percent and 20 percent. Rangpur contributes the least
with just 5 percent production.
As per the Food and Agriculture Organisation (FAO), global fish production was 158 million tons
in 2012 and per capita fish consumption was 19.2 kg. Annual consumption of fish and fish products
in Bangladesh was 12 kg/per person in 2010, with Chittagong having highest annual consumption
of about 17 kg/per person. In Bangladesh, about three fourth of consumed fish are fresh water fish,
among which Pangas, Rui, and Tilapi tops our chart. Pangas farming has become an established
agro-processing industry in the country over the last decade. Pangas is most easy to produce due
to its short culture-cycle, high growth rate and unselective feeding habit. It also has good resistance
to diseases. These characteristics are somewhat also present in Tilapia.

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Export of fish and fish products increased by 86 percent from 2001-02 and reached 77,000 tons in
2013-14.
Rotifers in Bangladesh
Many species of rotifers have been identified from different types of freshwater bodies in
Bangladesh. Brachionid rotifers seem to be predominant and the common species recorded are
Brachionus diversicornis, B. falcatus, B. quadridentatus, B. calyciflorus, B. havanensis and B.
forficula. The other common genera in Bangladesh are Keratella, Monostyla, Lecane, Lepadella,
Filinia, Trichocerca, Polyarthra, etc.
Importance of Rotifers
As a live food, rotifers are the perfect size (105-160 micrometers in width) for many species of
fish larvae that are cultured commonly. For rotifers to be nutritionally suitable for fish larvae, they
must be "enriched", fed with various combinations of microalgae or commercially prepared
products. Once enriched, rotifers are an excellent hatchery food for many species of larval fish.
The nutritional value of rotifers for larval fish depends on the rotifers' food source. Researchers
have determined that highly unsaturated fatty acids (HUFAs) are essential for the survival and
growth of finfish larvae. Rotifer feeds containing DHA, 22:6n-3, docosahexaenoic acid, and EPA,
20:5n-3, eicosapentaenoic acid, can be valuable, with DHA the more essential for marine fish
larvae. Depending upon their food source, rotifers are about 52 to 59 percent protein, up to 13
percent fat, and 3.1 percent n-3 HUFA.
Biology and Life History
The life span of rotifers has been estimated to be between 3.4 to 4.4 days at 25°C. Generally, the
larvae become adult after 0.5 to 1.5 days and females thereafter start to lay eggs approximately
every four hours. It is believed that females can produce ten generations of offspring before they
eventually die.
The life cycle of Brachionus plicatilis can be closed by two modes of reproduction. During female
parthenogenesis the amictic females produce amictic (diploid, 2n chromosomes) eggs which
develop and hatch into amictic females. Under specific environmental conditions the females
switch to a more complicated sexual reproduction resulting in mictic and amictic females.
Although both are not distinguishable morphologically, the mictic females produce haploid (n
chromosomes) eggs. Larvae hatching out of these unfertilized mictic eggs develop into haploid
males. These males are about one quarter of the size of the female; they have no digestive tract
and no bladder but have an over-proportionated single testis which is filled with sperm. Mictic
eggs which will hatch into males are significantly smaller in size, while the mictic fertilized eggs
are larger and have a thick, faintly granulated outer layer.

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Figure 1. Parthenogenetical and sexual reproduction in Brachionus plicatilis (modified from Hoff and
Snell, 1987).
These are the resting eggs that will only develop and hatch into amictic females after exposure to
specific environmental conditions. These can be the result of changes in environmental conditions
eventually creating alternations in temperature or salinity or changing food conditions. It should
be emphasized that the rotifer density of the population also plays an important role in the
determination of the mode of reproduction. Although the mechanism is not completely understood,
it is generally believed that the production of resting eggs is a survival strategy of the population
through unfavorable environmental conditions such as drought or cold.

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Strain Differences
Only a few rotifer species belonging to the genus Brachionus are used in aquaculture. Brachionus
plicatilis is a cosmopolitan inhabitant of inland saline and coastal brackish waters. It has a lorica
length of 100 to 340 mm, with the lorica ending with 6 occipital spines.
However, for use in aquaculture, however, a
simple classification is used which is based on
two different morphotypes, namely Brachionus
rotundiformis or small (S-type) rotifers
and Brachionus plicatilis or large (L-type)
rotifers. The differences among the two types
can be clearly distinguished by their
morphological characteristics: the lorica length
of the L-type ranging from 130 to 340 mm
(average 239 mm), and of the S-type ranging
from 100 to 210 mm (average 160 mm).
Moreover, the lorica of the S-type shows
pointed spines, while of the L-type has obtuse
angled spines.
Figure 2 : Brachionus rotundiformis (S-type) and Brachionus plicatilis (L-type) (modified from
Fu et al., 1991).
Who uses rotifers?
Rotifer is used in-
• Finfish hatcheries
• Ornamental fish breeders
• Shrimp hatcheries
Uses of Rotifer in Larviculture
The successful use of rotifer in commercial hatchery operations of red sea beam (Pargus major)
encouraged investigations in the development of mass culture techniques of rotifer. Twenty years
ago, rotifer was first used in larviculture feeding. Fingerling production is one of the many
challenges faced by those interested in promoting industrial production of emerging marine and
fresh water species. In spite of huge efforts to use artificial feeds, the of fish larvae during the
primary nursing phase still depends heavily on natural food. Live feeds include Rotifers, Artemia
and other tiny organisms are often the enhancing larval production. These live foods are used in
larviculture of carps, catfish and shrimp. Though there is not enough study on rotifer culture in
Bangladesh. The benefits they are getting is discussed below.

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Brachionus plicatilis
B. plicatilis is the species used most commonly to feed larval fish in hatcheries in Bangladesh. It
is a euryhaline species, small and slow swimming, with good nutritional value. It is well suited to
mass culture because it is prolific and tolerates a wide variety of environmental conditions.
Brachionus calyciflorus
The freshwater rotifer B. calyciflorus is widely used in aquaculture as a live food to raise larvae of
many species during the first two weeks of exogenous feeding. No other live food has been developed
for larval feeding that can replace rotifers. The two types of protease enzymes in rotifers assist fish
larvae to digest them. Weight, rearing environment and feeding protocol are among the key factors
affecting the migration and fishery returns of fish fingerlings produced by artificial breeding programs
for the purpose of restocking and rehabilitation of stocks.
Brachionus angularis
Brachionus angularis is a cosmopolitan freshwater rotifer. Its potential use as live food for small-
mouthed freshwater fish larvae. In the past, there was less demand for small live food in freshwater
aquaculture, but the demand in recent years has been increasing for several reasons. Ornamental
freshwater fishes that produce small larvae which require small planktonic rotifers for fry
production. This rotifer is used in Bangladesh for Larvae culture.
Now, In Bangladesh; Different hatchery owners prefer different rotifer spp. For feeding their
freshwater larvae. Sometimes they use rotifer as live capsule by enriching rotifer with different
nutrient. As rotifer is a highly nutritive for freshwater fish larvae, hatchery owners of Bangladesh
are used this for better survival of fish larvae.
Uses in Catfish
Larval nutrition and live feed culture like Artemia and rotifers is one of the most important and
obligatory matter for successful fish culture. Feeding with live prey for fish larvae are most
essential because during first few days of their life they have no complete develop digestive tract,
especially their digestive enzymes. Moreover, live increases feeding by predatory larvae, resulting
reduce cannibalism of some species like Clarius gariepinus the enhancing larval production.
Clarius gariepinus is generally considered as predator or omnivorous and also commercially
important fish for aquaculture because they are able to tolerate to extreme environment conditions
and worldwide demand. Awaiss and Kestemont studied the suitability of the freshwater rotifer
Brachionus calyciflorus as starting food for the larviculture of African catfish. Rotifer also acts as
an important food for stinging catfish Heteropnuestes fossilis in their early larval stage of life.
Uses in Shrimp Culture
Now-a-days rotifers are used as replacement of Artemia in shrimp culture. In some coastal shrimp
hatcheries of Bangladesh rotifers are used as successful larvae feed. Many marine fish hatcheries
incorporate rotifers in their larval diets because rotifers are smaller than Artemia. With shrimp,

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Artemia is usually introduced in the Mysis stage, but most species can survive on rotifers from
earlier stages. The success of extensive penaeid larvae rearing systems using rotifers in areas where
Artemia and enrichment diets are prohibitively expensive or unavailable indicates that they are an
alternative worth considering.
Producers of Rotifers
Hatcheries equipped with modern facilities produce rotifers for their culture operations to prevent
mass mortality of species that fetch high market value. The larval stages of stinging catfish
popularly known as shing and African catfish are very sensitive. Therefore, culture operation of
these two species is not easy because of appropriate feed. Live feed like Artemia and rotifer can
overcome the problem. Bangladesh Fisheries Research Institute (BFRI) and live feed laboratories
from different public universities are aiming to disseminate the effective and efficient technique
of culturing rotifers and other live feed organisms.
Problems associated with Rotifer Culture
The culture of rotifer needs intensive care and the environment should be friendly. Inexperienced
personnel can ruin up the whole operation. Therefore, they need to be trained up to run the culture
successfully. There is another problem concerning rotifer culture. Food of rotifer is important.
They feed on phytoplankton like Chlorella sp. Before setting up rotifer culture, farm owners
should consider set up phytoplankton culture. And establishment of advanced live food laboratory
is essential.
Prospects of Rotifer Culture in Bangladesh
Artemia is widely used in different hatcheries across Bangladesh. If there is any 2nd choice that is
rotifer. Bangladesh is a culture based fish producing country. The environment exists here is
suitable for rotifer culture. To produce huge number of fish fry, live food like rotifer is essential to
provide balanced nutrition in their larval stage and prevent mass mortality.
Conclusion
There are about 2000 rotifer species all requiring moisture and most of them inhabit freshwater
(around 1950 species). Most rotifers are free swimming and form an important part of the
freshwater zooplankton. This types of Rotifers are highly nutritive food for larvae culture. So, we
need to put great emphasize for rotifer culture in Bangladesh. Then we can make more profit in
aquaculture.

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References
Pejler, B., 1977. On the global distribution of the family Brachionidae (Rotifera). Arch. Hydrobiol.
Suppl., 53: 255–307.
Maruyama, I., Nakao, T., Shigeno, I., Ando, Y., Hirayama, K., 1997. Application of unicellular
algae Chlorella vulgaris for the mass culture of marine rotifer Brachionus. Hydrobiologia, 358:
133-138.