A comprehensive account of research activities
of Aqua Research Lab
- Carp Culture
The Carp species like Catla catla (catla), Labeo rohita (rohu), Cirrhinus mrigala
(mrigal), Cyprinus carpio (common carp), Hypophthalmichthys molitrix
(silver carp) and Ctenopharyngodon idella (grass carp) are extensively
used in composite culture in India. So far there is no
research based development package for these species. Hence, we attempted to
generate knowledge for larviculture, giving emphasis on larval nutrition and
hatching, poorly developed larvae are highly susceptible to environmental
stress. Use of excess amount of artificial diets and fish excreta result into
deterioration of water quality within the fish culture system. Discharge of
this water into the natural environment leads to the environmental degradation.
This results into ban on coastal zone aquaculture by honorable Supreme Court of
India. In order to maintain optimal environmental conditions for the tiny, sensitive
larvae as well as for adult fishes a suitable “Aquahouse’’ has been designed
and constructed in the Department of Zoology with the financial support
of I.C.A.R., India. The Aquahouse is made of polycarbonate sheet, which helps
to maintain the temperature the most critical factor for growth (Fig. 1). It
also helps to avoid fluctuations of temperature during hot summer/severe
winter. This is most effective for broodstock maintenance and for the culture
of high-valued and endangered species.
Fig. 1. Aquahouse (front view)
Water quality plays a major role in the sustainable development of aquaculture.
Feeding of fish with protein rich diets leads to water quality deterioration in
terms of higher ammonia and nitrite levels. To overcome this problem and to maintain
water quality we tested recirculating system. In the recirculating system
the same water is repeatedly used for long time after treatment. In the
recirculating system, we used biological filters that converted the harmful
ammonia and nitrite to less
toxic nitrate and thus succeeded to use the same water for a long time. Various types of biological filters like
pebbles filter, earthen pot filter and plant filter (hydroponic system) were
used separately or in different combinations (Fig. 2). These reduce ammonia,
nitrite (most critical factors of fish growth), phosphate and COD levels in the
culture systems (Sharma and Chakrabarti, 1997, 2000). More than 90%
survivals of carp larvae were found in this recirculating system. The growth
was also faster. In hydroponic system, money plant Pothos spp.
(ornamental plant), Lemna major (duck weed, used as raw material for
artificial diet preparation of fish) and Trapa spp. (singhara, fruit
producing plant) were used as filter bed materials. Thus, the farmers in
addition to fish may harvest other useful plant product, which will supplement
with additional income. Water requirement for per unit fish production in
recirculating system without filtration unit was 1.5 to 2.5-fold higher than
recirculating system with filtration unit (Sharma and Chakrabarti, 1997, 1998).
Fig. 2. Innerside of the Aquahouse showing three sets of recirculating systems. PFS = pebbles filter system, HS = hydroponic system, EPFS = earthen pot filter system, S = temperature sensor, T = fish culture tank.
Optimization of stocking density is essential to make
the system cost-effective and commercially viable. Indian major carps Catla
catla, Labeo rohita and Cirrhinus mrigala spawns were
cultured under different stocking densities. It appears that the stocking
density can be raised up to 8,333/m3. This is 8-fold higher
than traditional nursery in India (Sharma and Chakrabarti,
1998, 2003; Sharma et al., 2004). The duration of culture period to get
fingerling size is also less than traditional culture system.
Digestive Physiology of Carps
3.1 Scenario during ontogenesis
A comprehensive analysis of the ontogenic changes occurring during early life
stages of the fish is essential for the formulation of artificial diets.
Information on the digestive physiology of fish during ontogenesis will ensure
fish culturists to develop proper feeding strategies for a particular species.
Amylase and proteolytic activities were determined in Indian major carps Catla
catla, Labeo rohita and Cirrhinus mrigala and common carp Cyprinus
carpio during ontogenic development in relation to natural diet
(Chakrabarti and Sharma, 1997; Kumar and Chakrabarti, 1998; Rathore et al.,
2005). Amylase activity was very low during transition period from endogenous
to exogenous feeding. Enzyme activity increased with age in these species.
Bands of various molecular weights appeared during ontogenic development. All
these bands expected to correspond to serine proteases with some evidence of
increasing proteolytic enzyme activity with the age of fish. High
molecular weight bands appeared during early ontogeny and low molecular bands
appeared in the later stage of development.
3.2. Ultrastructure study
Ultrastructure study of the digestive system showed progressive changes in microvilli,
microfilament bundles and secretary granules along with age (Kumar et al.,
2000). Ultrastructural study of three different regions of intestine of Cyprinus
carpio showed variations. The microvilli increase the digestive and
transportive surface and are the structural basis of the processes of membrane
digestion. The presence of the granular cytoplasm and minute vacuoles on the
apical halves covered by a thin brush-border of columnar epithelial cells of
the intestinal mucosa in the present study justified the absorptive function of
the cells of anterior region .
Morphological changes happening in the digestive system of Catla catla during
ontogenic development had been documented by Chakrabarti and Singh (2009,
unpublished, communicated). The digestive system was simple and straight up to
8th day. Slightly folding was found in 9 DAH catla. Marked folding of the
digestive system was found from day-10. Coiling started from day-19 onwards.
3.3. Digestive enzymes in adult carps
Characterization of digestive proteases and their efficiency to hydrolyses the proteins of different food
ingredients were conducted in three carps Catla catla, Labeo
rohita and Hypophthalmichthys molitrix (Kumar et al.,2007
). The amount of various proteolytic enzymes varied
significantly (P < 0.05) in these species. All enzyme extracts, except
catla digestive tissue, displayed bell-shaped pH profiles; catla digestive
tissue sample had a broad pH activity curve. The effects of various protease
inhibitors on enzyme activity showed that enzymes were mainly serine-proteases. Several protein bands ranging from 15.3 to 122.3 kDa were found in enzyme molecular weight of proteases ranged from 22.1-92.7, 25.3-91.2, 21.4-852, 21.7-91.2 and
25.6-90.9 kDa for catla digestive tissue, catla gut contents, rohu digestive
tissue, rohu gut contents and silver carp digestive tissue, respectively. Several trypsin and chymotrypsin-like enzymes were observed from each
enzyme extract. In vitro digestibility study of various feedstuffs like
casein, soybean meal, Silver Cup and Chilean fishmeal showed that all enzyme
preparations, except for rohu digestive tissue, had higher degree of hydrolysis
for casein than other protein feedstuffs. Enzyme preparations from silver carp
digested all feedstuffs more adequately in comparison to other carps.
3.4 Role of live food in larviculture
Role of various types of food in carp larviculture as
well as in the maintenance of water quality had been evaluated. Comparative
studies were performed to evaluate the effects of live food and artificial
diet/ refrigerated-plankton food with Cyprinus carpio (Sharma and
Chakrabarti, 1999) and Catla catla (Sharma and Chakrabarti, 2009). Feeding
of Cirrhinus mrigala larvae with artificial diets varying in quantity of
protein (30, 40 and 50%) revealed that incorporation of 40% protein in
artificial diet was optimum for growth and survival of larvae (Chakrabarti and
4.1. Culture and biochemical composition
One of the major obstacles for the advancement of intensive aquaculture of finfish
is the acceptance of diets during early life stages. Larval nutrition relies on
feeding with live food during the first few days. Monoculture of Ceriodaphnia
cornuta by using organic manures shows that the lower dose of organic
manures can be used to obtain faster peak, whereas the application of higher
dose helps in the production of larger number of Ceriodaphnia cornuta,
which sustains longer duration (Srivastava et al., 2006).
Phospholipid fraction is extremely critical for the larval growth. The commonly available Phosphatidic acid
(PA), Phosphatidylethanolamine (PE), Phosphatidylcholine (PC),
Phosphatidylserin (PS), Phosphatidylinositol (PI) and Cardiolipin (CAR) were
quantified in Daphnia carinata by NMR technique (Srivastava et al.,
2009). Protease activities and their class structure
had been studied in Daphnia carinata (Kumar et al., 2005). SDS-PAGE
showed that the molecular weight of various activity bands ranged from 16.3 to
- Stimulating the Immunity and Disease Resistance of Carps
Disease outbreaks are major obstacles in successful aquaculture. Immunostimulation is
one of the important areas. Achyranthes aspera has immunostimulating
property. Achyranthes aspera enhances the immunity of Catla catla (Rao
and Chakrabarti, 2005a), Labeo rohita (Rao et al., 2004; Rao and
Chakrabarti, 2004b) and Cyprinus carpio (Rao and Chakrabarti, 2005).
Achyranthes aspera increased disease resistance of Labeo rohita
against bacterial infections (Rao et al., 2006).
Effects of UV-B Radiation on Aquatic Ecosystem
A significant reduction in stratospheric
ozone has been observed over the last decade. Ozone reduction enhances the
amount of ultraviolet-B radiation reaching the earth surface. The exposure to
high levels of UVR can result in severe lesions of most of the exposed organs
and tissues like eye and skin. Ultrastructural study of the skin, eyes and gills
of various species of UV-B radiated fishes like ayu Plecoglossus altivelius,
Catla catla catla showed
marked changes. The exposure of the fish to the radiation resulted in the
destruction of microridges in the epidermis and exposed neuromast cells of the
skin. Domed protrusions were also more common in the skin of UV-B radiated fish
than in the control fish. The appearance of mucus in both groups was different.
In the control skin the mucus was spread over a wide area whereas in the
treated fish the mucus was concentrated in a small area. The anastomozing
structures of the microridges of the eyes were lost in UV-B radiated fish and
the microridges themselves were fewer in number, fragmented, and aggregated.
Mucus cells, prominently visible in the control fish, were distorted in the
treated fish. Cell contours were irregular in UV-B radiated fish and cell to
cell contacts had been lost in this group (Sharma et al., 2005, Sharma
and Chakrabarti, 2006).
A freshwater medusa, Limnocnida indica Annandale, 1912 was observed in a lake having free
connection with the river Yamuna in Delhi. The occurrence of medusae influenced the
planktonic population in the lake (Sharma and Chakrabarti, 2000). An
attempt has been made to assess the impact on water quality of diverse
anthropogenic activities on east and west bank of river Yamuna in Delhi, from Palla to Okhla Barrage, both
biologically as well as chemically. Biological life was observed to be more
affected on east bank of the river than on west bank, probably due to heavy
anthropogenic influence on east bank. Favourable habitat at upstream of the
barrage supports more biological life than downstream. Biomonitoring gives an
overall health of the water body, which cannot be done by chemical analysis
alone (Anand et al., 2002).
Recirculation technology will receive more attention as it offers opportunities for captive
markets and safe applications with genetically modified organisms (GMOs) as
absolute guarantees can provide to prevent escapees. This is a solution to the
problem of land and water scarcity. The discharge of recirculating system water
into the environment is safe. This will solve the problem of our coastal zone aquaculture.
This is an eco-friendly system.
The knowledge of lipid and digestive enzyme profiles of fish food organisms,
generated in the present study may assist in the formulation of age-specific
feed for fish and shellfish.
Age-related changes in the diversity and quantity of digestive enzymes appear to represent
evolutionary adaptations to the different natural diets and nutritional
requirements of distinct life-history stages. All these information will help
to develop a package for carp larviculture.
Recommendations for larviculture in Aquahouse
- Aquahouse is made of polycarbonate acrylic sheet which is good for maintaining optimum temperature for survival and growth of larvae
- Fishes reared in Aquahouse escape infection suffers less mortality and can be maintained by recirculating system.
- Pebbles, pieces of earthen pots and hydroponics like money plant, Trapa are highly effective in reducing levels of ammonia, phosphate and COD and these are cost-effective. Hydroponics also supplements farmers net returns
- The optimum stocking density of Indian major carps is 8,000/m3.
- Care should be taken in feeding of carp larvae up to 15 days due to poor digestive enzyme activities.
- Organic manures like cow dung, poultry droppings, and mustard oil cake, increase zooplankton population.
vIncorporation of Achyranthes aspera in the normal feed of larvae substantially the immunity of carps against several diseases.
- During developmental stage of the larvae the size of the foods should ranged from 100µm to 300µm.