International Journal of Marine Science 2015, Vol.5, No.23 1-13
11
(IAS). Occurrence of exotic Sucker catfish,
Pterogoplichthys multiradiatus
, native to the South
American drainages, capable of tolerating pollution,
through their air breathing ability was observed from
their studies.
It negatively affects the periphyton
feeding and bottom spawning fishes. Similar
situations may be replicated in water bodies like
Vembanad backwater, where economically valuable
bottom spawners such as
Etroplus suratensis
occur.
Krishnakumar et al., 2011 reported the unscientific
and illegal farming of the invasive African Catfish
Clarias gariepinus
, in the surrounding area of
Vembanad estuary resulted in the escape and spread of
the species into this system. The study noted that the
species begins to dominate in the fish population and
it turn can be invasive in near future.
The barrage
played a significant role in the variation of the physico
– chemical parameters of the southern part of
Vembanad estuarine system. T
he marine fish and
prawns reproduce in the saline waters of sea and
migrate to the estuary after completing their pelagic
development (Suja and Mohammed, 2010). The
commercially important species in estuarine area were
Mugil sp.,
Chanos chanos,
Tachysurus
sp.,
Etroplus
suratensis, Macrobrachium rosenbergii
, and
Scylla
serrata,
but many of these species have now getting
vanished from the area, while others have become a
rarity. The native fish species such as
Horabagrus
brachysoma
and
Hyporhamphus xanthopterus
of
Vembanad estuary were vulnerable and other species
suffered a decline in both numbers and distribution
(Asha et al 2014). The operation of Thaneermukkom
barrage and its impact on the breeding migration of
Macrobrachium rosenbergii
was reported by Kurup
and Harikrishnan, (2000). The landing of
M.
rosenbergii
was declined over a period of several
years and it was estimated to have declined from 429t
in 1960 to 57.69t in 2012 (Asha et al 2014).
4 Conclusion
The fishery in Vembanad estuarine system is facing
tremendous pressure due to the aging
Thaneermukkom barrage as well as its faulty
construction along with non-synchronized opening
and closing of the barrage. This has affected the tidal
rhythm and fishery patterns of the estuary that
maintained the hydro-biological balance in the
ecosystem. From the CCA analysis it could be
concluded that depth, temperature, pH and salinity
invariably had significant bearing on the diversity,
distribution and fishery production in the southern and
northern sectors of Vembanad estuary. The northern
part exhibited a euryhaline fish species structure as
compared to stenohaline grouping in the southern
sectors of the estuary. So, effective steps are to be
initiated for co-ordinating the proper management of
the Thaneermukkom barrage, so that the life cycle
processes of the fishery are not affected. Recently
Govt. of Kerala has initiated measures to replace
damaged shutters of the barrage as well as opening the
reclaimed areas by fixing with shutters for proper
functioning and connectivity of the wetland system.
However further studies are necessary to understand
the effects of such renewed changes on the fishery on
a long term basis.
Authors contribution
SBN is the supervisor of the project. CVA, RIC, PSS and SBN
made significant contributions to experimental design, data
analysis and interpretation and also involved in manuscript
drafting.
Acknowledgments
The authors are grateful to the Head, Department of Marine
Biology, Microbiology and Biochemistry, Cochin University of
Science and Technology for providing necessary facilities to
carry out the work. This study forms a part of the research
project “Ecosystem Based Monitoring and Modelling of the
Vembanad Kol Wetland in Kuttanad, Kerala, India” funded by
Ministry of Environment and Forests, Govt. of India and the
authors are thankful for the financial support. A special thanks
is extended to all those who helped with field sampling.
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