672
aquaculture in the 3rd World Countries , which,
signifi cantly, emphasises ‘ polyculture ’, i.e. the
growing of fi sh and agricultural crops together .
Introduction of new fi sh species and hybridisation may not always prove to be benefi cial.
32.3.3.1 Fishing Regulations
A more traditional means by which the fi shery
managers have cared for their resource is the
practice of imposing restrictions on the anglers,
e.g. managers may close a specifi c area from
fi shing (‘ closed area ’), forbid fi shing during a
particular season when fi sh are more vulnerable
(‘ closed season ’), restrict the number (‘ creel
limit ’) or restrict the size of the fi sh (‘ size limit ’).
Sometimes, people working in the fi eld and
the anglers unite in order to call for stricter regulations on a fi sh species.
32.4 Habitat Protection
Fishery managers are slowly beginning to realise
that many of the traditional management techniques would not be required, if fi shery habitats
are protected in the fi rst place . As such, fi shery
managers are starting to make a transition from a
quickfi x solution used in the lake stream, reservoir, pond, etc., to longer - term solution for fi nding
ways and means to prevent problems from occurring in the fi rst place.
32.5 Fish Disease Management
Despite the high biotic potential of the wetlands,
the fi shes in them sometimes suffer from diseases
due to various reasons. One such disease found
in freshwater fi shes recently is the Epizootic
Ulcerative Syndrome (or EUS) which has been
sweeping the fi shes in epidemic form on a semiglobal scale from Australia to Asia since 1972.
As a typical case, among the fi shes of Sone
Beel, there have been large-scale mortalities since
1988, due to EUS, affecting about 70 % of the fi sh
population (Kar and Dey 1988b ). The exact aetiological agent is still not very clearly known.
Investigations conducted in India (Kar and Dey
1988a , b , 1990 ; Kar et al. 1993 , 1995 , 2006 , 2007a , b ;
Das et al. 1990 ; Kar and Das 2011 ; Kar 1990 , 2007 ,
2010 , 2012 ) and elsewhere in the world (FAO
1986 ; Roberts et al. 1992 ) have revealed that factors such as organic pollution of water and soil and
radioactive and heavy-metal contaminations may
not be responsible for the disease. Although opportunistic bacteria and fungi have been isolated from
the diseased fi shes, they are considered to be only
secondary infectants, in view of their close association with the fi shes in water since ancient times.
As such, a primary viral aetiology has always been
suspected. Recently, virus-like particles have been
isolated in tissue culture from diseased Clarias
batrachus (Kar et al. 1993 , 1995 ). And attempts
are being made to identify them. Viruses causing
similar kinds of disease, isolated elsewhere (Frerichs
et al. 1986 ; Ahne et al. 1988 ), are thought to be
belonging to Rhabdovirus group. Furthermore, the
outbreak of the EUS fi sh disease has been found to
be strongly correlated with changes in the environment, in which the total alkalinity (TA) of the water
has been found to act as a ‘stress factor’ (Kar et al.
2007a , b ), enabling the virus to infect the fi sh body.
Lime has been found to be useful to some extent in
controlling the spread of EUS.
32.6 Prospects for the Future
The freshwater fi sheries have tremendous potential in Asia and India , in general and in Assam , in
particular, if their management is done in an
effective way. Over the past century, only a few
fi sheries management techniques have been
evolved, such as fi sh culture, stocking and predator control.
It is obvious that new techniques, specially the
right attitude towards management , need to be
developed to meet the challenges of the future.
32.7 Leasing and Management
of Public Waterbodies
This is an important aspect of utilisation of public
properties as common property resources. It could
be quite sensible and justifi able to use a common
32 Fisheries Scope in the Wetlands and Enhancement Methods
aquaculture in the 3rd World Countries , which,
signifi cantly, emphasises ‘ polyculture ’, i.e. the
growing of fi sh and agricultural crops together .
Introduction of new fi sh species and hybridisation may not always prove to be benefi cial.
32.3.3.1 Fishing Regulations
A more traditional means by which the fi shery
managers have cared for their resource is the
practice of imposing restrictions on the anglers,
e.g. managers may close a specifi c area from
fi shing (‘ closed area ’), forbid fi shing during a
particular season when fi sh are more vulnerable
(‘ closed season ’), restrict the number (‘ creel
limit ’) or restrict the size of the fi sh (‘ size limit ’).
Sometimes, people working in the fi eld and
the anglers unite in order to call for stricter regulations on a fi sh species.
32.4 Habitat Protection
Fishery managers are slowly beginning to realise
that many of the traditional management techniques would not be required, if fi shery habitats
are protected in the fi rst place . As such, fi shery
managers are starting to make a transition from a
quickfi x solution used in the lake stream, reservoir, pond, etc., to longer - term solution for fi nding
ways and means to prevent problems from occurring in the fi rst place.
32.5 Fish Disease Management
Despite the high biotic potential of the wetlands,
the fi shes in them sometimes suffer from diseases
due to various reasons. One such disease found
in freshwater fi shes recently is the Epizootic
Ulcerative Syndrome (or EUS) which has been
sweeping the fi shes in epidemic form on a semiglobal scale from Australia to Asia since 1972.
As a typical case, among the fi shes of Sone
Beel, there have been large-scale mortalities since
1988, due to EUS, affecting about 70 % of the fi sh
population (Kar and Dey 1988b ). The exact aetiological agent is still not very clearly known.
Investigations conducted in India (Kar and Dey
1988a , b , 1990 ; Kar et al. 1993 , 1995 , 2006 , 2007a , b ;
Das et al. 1990 ; Kar and Das 2011 ; Kar 1990 , 2007 ,
2010 , 2012 ) and elsewhere in the world (FAO
1986 ; Roberts et al. 1992 ) have revealed that factors such as organic pollution of water and soil and
radioactive and heavy-metal contaminations may
not be responsible for the disease. Although opportunistic bacteria and fungi have been isolated from
the diseased fi shes, they are considered to be only
secondary infectants, in view of their close association with the fi shes in water since ancient times.
As such, a primary viral aetiology has always been
suspected. Recently, virus-like particles have been
isolated in tissue culture from diseased Clarias
batrachus (Kar et al. 1993 , 1995 ). And attempts
are being made to identify them. Viruses causing
similar kinds of disease, isolated elsewhere (Frerichs
et al. 1986 ; Ahne et al. 1988 ), are thought to be
belonging to Rhabdovirus group. Furthermore, the
outbreak of the EUS fi sh disease has been found to
be strongly correlated with changes in the environment, in which the total alkalinity (TA) of the water
has been found to act as a ‘stress factor’ (Kar et al.
2007a , b ), enabling the virus to infect the fi sh body.
Lime has been found to be useful to some extent in
controlling the spread of EUS.
32.6 Prospects for the Future
The freshwater fi sheries have tremendous potential in Asia and India , in general and in Assam , in
particular, if their management is done in an
effective way. Over the past century, only a few
fi sheries management techniques have been
evolved, such as fi sh culture, stocking and predator control.
It is obvious that new techniques, specially the
right attitude towards management , need to be
developed to meet the challenges of the future.
32.7 Leasing and Management
of Public Waterbodies
This is an important aspect of utilisation of public
properties as common property resources. It could
be quite sensible and justifi able to use a common
32 Fisheries Scope in the Wetlands and Enhancement Methods