248
( Clarias mossambicus, C. batrachus ) are
air-breathing fi shes capable of migrating
overland. A few temperate zone fi sh are also
able to migrate overland, e.g. the eel
( Anguilla anguilla ) which shows some
respiratory gas exchange through the skin.
Amongst the mammals, the water vole
( Arvicola amphibius ) of northern Europe
and North American muskrat ( Ondatra
zibethicus ) are both herbivores. They often
graze heavily on Phragmites, Typha, etc.,
reed swamp. It may be noted here that the
reed swamp provides cover and refuge particularly for nesting water birds. Tropical
reed swamps also support large herbivorous
mammals.
11. Fish is a signifi cant component amongst the
wetland biota. On a global scale, fi sh constitutes almost half of the total number of vertebrates in the world. They live in almost all
conceivable aquatic habitats. Approximately
21,723 living species of fi sh have been
recorded out of 39,900 species of vertebrates.
Of these, 8,411 are freshwater species and
11,650 are marine. In India, there are c 2,500
species of fi shes, of which c 930 live in
freshwater (FW) and c 1,570 are marine.
Zoogeographically, FW fi sh have been classifi ed differently by different workers.
12. Seventy species of fi shes belonging to 49
genera under 24 families and 11 orders have
been recorded in Sone Beel, the biggest
wetland in Assam. Also, 57 species of fi shes,
belonging to 28 genera, 17 families and 9
orders, have been recorded in Chatla Haor.
Further, 24 species of fi shes from Puneer
Haor, 24 species from Rupairbala Anua, 13
species from Baskandi Anua, 7 species from
Fulbari Anua, 22 species from Sibnarayanpur
Anua and 42 species of fi shes from Kurti
Beel of Tripura have been recorded.
13. Unhappily, certain exotic fi shes like Cyprinus
carpio, Hypothalmichthys molitrix, Ctenopharyngodon idellus and Oreochromis mossambicus are introduced in the natural and
cultivated wetlands by the fi sh farmers in
many Asian countries. These exotic fi shes
generally replace the indigenous fi shes.
14. Concomitant to above, Australia and NZ
have been islands, separated from the other
continents, for such a long time that they have
a very distinctive fauna. Many of the animals
found in their lakes are quite different
from those found elsewhere. Further, in the
Australian waters, at least 25 species of fi sh
have been introduced.
15. Fish in our studied wetlands in India are common to those found in many wetlands in Asia
and Africa. Some are near the limits of their
geographical distributions. Crossocheilus burmanicus are at the northern limits, while Tor
khudree are near the southern limits. Adult
Wallago attu, Sperata seenghala, etc., could
be keystone piscivore with an ability to limit
the abundance of forage fi sh. Some of the
carps are effective zooplanktivores, which are
capable of changing the size and species
composition of zooplankton communities.
16. At present, the fi sh assemblages in marshes
generally have a dwindling species richness
as compared to other lentic bodies of the
region having almost similar morphometry.
In some of the wetlands where sport fi shery
is active, the fi sh population structures refl ect
the effects of exploitation in the form of fi shing and sports. Effect of high fi sh densities
could also be depicted in the anomalous
growth rate, feeding behaviour, etc., of the
fi shes. In some wetlands, strong competition
amongst different species could also shape
diets through resource partitioning. Prey
resources and, thus, the community structure
of the lower trophic levels in these wetlands
refl ect the effects of intense predation pressure by fi shes.
17. In contrast to the above, the minnow population introduced in certain lentic bodies in
Europe and America during 1985 declined
much more rapidly than could be accounted
for by direct predation by known numbers
of largemouth bass in the waterbody.
Introduction of Clarias gariepinus in some
wetlands in Northeast India during the late
1990s had accelerated the total predation
rate and had changed the composition of
the prey community.
15 Wetland Flora, Plankton, Productivity, Fauna and Fishes
( Clarias mossambicus, C. batrachus ) are
air-breathing fi shes capable of migrating
overland. A few temperate zone fi sh are also
able to migrate overland, e.g. the eel
( Anguilla anguilla ) which shows some
respiratory gas exchange through the skin.
Amongst the mammals, the water vole
( Arvicola amphibius ) of northern Europe
and North American muskrat ( Ondatra
zibethicus ) are both herbivores. They often
graze heavily on Phragmites, Typha, etc.,
reed swamp. It may be noted here that the
reed swamp provides cover and refuge particularly for nesting water birds. Tropical
reed swamps also support large herbivorous
mammals.
11. Fish is a signifi cant component amongst the
wetland biota. On a global scale, fi sh constitutes almost half of the total number of vertebrates in the world. They live in almost all
conceivable aquatic habitats. Approximately
21,723 living species of fi sh have been
recorded out of 39,900 species of vertebrates.
Of these, 8,411 are freshwater species and
11,650 are marine. In India, there are c 2,500
species of fi shes, of which c 930 live in
freshwater (FW) and c 1,570 are marine.
Zoogeographically, FW fi sh have been classifi ed differently by different workers.
12. Seventy species of fi shes belonging to 49
genera under 24 families and 11 orders have
been recorded in Sone Beel, the biggest
wetland in Assam. Also, 57 species of fi shes,
belonging to 28 genera, 17 families and 9
orders, have been recorded in Chatla Haor.
Further, 24 species of fi shes from Puneer
Haor, 24 species from Rupairbala Anua, 13
species from Baskandi Anua, 7 species from
Fulbari Anua, 22 species from Sibnarayanpur
Anua and 42 species of fi shes from Kurti
Beel of Tripura have been recorded.
13. Unhappily, certain exotic fi shes like Cyprinus
carpio, Hypothalmichthys molitrix, Ctenopharyngodon idellus and Oreochromis mossambicus are introduced in the natural and
cultivated wetlands by the fi sh farmers in
many Asian countries. These exotic fi shes
generally replace the indigenous fi shes.
14. Concomitant to above, Australia and NZ
have been islands, separated from the other
continents, for such a long time that they have
a very distinctive fauna. Many of the animals
found in their lakes are quite different
from those found elsewhere. Further, in the
Australian waters, at least 25 species of fi sh
have been introduced.
15. Fish in our studied wetlands in India are common to those found in many wetlands in Asia
and Africa. Some are near the limits of their
geographical distributions. Crossocheilus burmanicus are at the northern limits, while Tor
khudree are near the southern limits. Adult
Wallago attu, Sperata seenghala, etc., could
be keystone piscivore with an ability to limit
the abundance of forage fi sh. Some of the
carps are effective zooplanktivores, which are
capable of changing the size and species
composition of zooplankton communities.
16. At present, the fi sh assemblages in marshes
generally have a dwindling species richness
as compared to other lentic bodies of the
region having almost similar morphometry.
In some of the wetlands where sport fi shery
is active, the fi sh population structures refl ect
the effects of exploitation in the form of fi shing and sports. Effect of high fi sh densities
could also be depicted in the anomalous
growth rate, feeding behaviour, etc., of the
fi shes. In some wetlands, strong competition
amongst different species could also shape
diets through resource partitioning. Prey
resources and, thus, the community structure
of the lower trophic levels in these wetlands
refl ect the effects of intense predation pressure by fi shes.
17. In contrast to the above, the minnow population introduced in certain lentic bodies in
Europe and America during 1985 declined
much more rapidly than could be accounted
for by direct predation by known numbers
of largemouth bass in the waterbody.
Introduction of Clarias gariepinus in some
wetlands in Northeast India during the late
1990s had accelerated the total predation
rate and had changed the composition of
the prey community.
15 Wetland Flora, Plankton, Productivity, Fauna and Fishes