Living with Wetlands: A Case Study from the Wetlands ( Beels ) of Barpeta District, Assam - Aquatic Ecosystem: Biodiversity, Ecology and Conservation - page 322

level of the wetlands is absolutely perfect for
high yield of fi shes since total alkalinity below
20.0 mg/l is indicative of poor production and
above 20.0 mg/l does not appear to infl uence pro-
ductivity. Total hardness in the studied wetlands
shows very productive range of 12-32.0 mg/l,
since TH below 15.0 mg/l is indicative of unpro-
ductive water. The fl uctuations of water tempera-
ture between 21.0 and 25.0 °C during summer
facilitate high growth rate of fi shes by inducing
tropical eutrophic condition. Suitable bottom soil
condition and high water quality are essential
ingredients for successful freshwater pisciculture.
Four ecological groups of phytoplankton
encounter with the wetlands to form the produc-
tive area. Three species, viz., Volvox sp ., Dinobryon
sp. and Microcystis sp., produce high abundance.
These three species contribute to the appreciable
density. High abundance of Microcystis sp. and
Dinobryon sp . indicates a productive water condi-
tion favourable for fi sh growth. Outburst of Volvox
species is a surplus chlorophycean biomass which
is not properly utilized by the grazers. Signifi cant
absence of Euglenineae and Bacillariophyceae of
some wetlands affects the overall fi sh productivity
of the wetlands. Considering the observed plank-
ton volume (0.7-7.5 ml/100 l) against 10 ml/m 3
prescribed plankton volume for excellent culture
of Indian major carp species, the studied wetlands
proved to be highly productive water for fi sh
culture.
Zooplankton productivity in the wetlands was
contributed by three important groups, namely,
Rotifera, Copepoda and Cladocera. These three
groups exhibit signifi cant growth and show rich-
ness in productivity. Due to the presence of
healthy growth of planktonic crustacean and roti-
fer, the individual growth rate of Catla catla and
Hypophthalmichthys molitrix is signifi cantly
high. Emergence of fl oating macrophytes,
namely, Eichhornia crassipes is not encouraged
in the wetlands due to its active participation in
the removal of water by transpiration in eutrophi-
cation and for preventing entry of sunlight to the
lower column of water. However, the submerged
vegetation recorded in the wetlands is helpful for
balancing the ecosystem. Some major fi shes like
grass carp and even rohu are directly dependent

upon Hydrilla, Vallisneria and Nias, while Catla
feed on the decomposed biomass of these vegeta-
tions. Most of the fi sh species recorded in the
wetlands are found to be dependent upon the sub-
merged macrophytes. However, the occurrence
of Euryale ferox may create a lot of problems for
fi sh culture. All macrophytes take part in recy-
cling of nutrients in the wetlands.
The annual fi sh yield record collected from
the abounding fi shermen community of the wet-
lands shows that the fi sh productivity remains at
3,500-4,200 kg/year. Considering the total wet-
land water area, the fi sh production with natural
stocking is high. The total production of the
major fi sh group includes Indian major carps and
exotic carps that constitute 55 %, intermediate
fi sh group 25 % and the minor fi sh group 18 %.
The record shows that the remaining 2 % is con-
stituted by Macrobrachium sp . The record of fi sh
growth obtained from the old fi sherman commu-
nity indicates that some fi sh species were pre-
dominant during past which are not found in the
present wetlands. These fi shes are N. nandus, G.
chapra, A. mola and S. bacaila . On the other
hand, according to the fi shermen, some other
fi shes, namely, L. rohita, C. catla, N. chitala, H.
molitrix and C. idella , show very good growth in
the wetlands. From their perspective, even com-
mon carp ( Cyprinus carpio ) and Cirrhinus mrig-
ala could show better growth in culture.

Conclusions

In the background of overall scenario, piscicul-
ture at global level clearly depicts the economic
potentials in Barpeta and Paka-Betbari develop-
mental blocks of Barpeta district of Assam. The
importance of pisciculture is increasing day by
day with the increasing population. However,
land to man ratio is decreasing. It is, therefore,
inevitable to utilize the water resources for food
production. The land with low-lying character
found in the form of natural reservoir which is
not used for agriculture can be used for piscicul-
ture. There is certainty of catching fi sh from the
cultured waters. Because of the presence of
favourable geo-environmental condition for