International Journal of Marine Science 2015, Vol.5, No.23 1-13
1
Research Article Open Access
Environmental factors structuring the Fish assemblage distribution and
Production potential in Vembanad estuarine system, India
C. V. Asha , R. I. Cleetus, P. S. Suson, S. Bijoy Nandan
Department of Marine Biology, Microbiology & Biochemistry, School of Marine Sciences, Cochin University of Science and Technology, Fine Arts Avenue,
Kochi-682016, Kerala, India
Corresponding author email
International Journal of Marine Science, 2015, Vol.5, No.23 doi: 10.5376/ijms.2015.05.0023
Received: 03 Jan., 2015
Accepted: 10 Mar., 2015
Published: 09 Apr., 2015
Copyright
©
2015
Asha et al., This is an open access article published under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Preferred citation for this article:
Asha et al., 2015, Environmental factors structuring the fish assemblage distribution and production potential in Vembanad estuarine system, India,
International Journal of Marine Science, Vol.5, No.23 1-13 (doi
Abstract
Vembanad wetland system, a Ramsar site on the West coast of India is the largest estuarine system, renowned for its rich
fishery diversity and endemicity. In 1976, to regulate salinity intrusion into the Vembanad estuarine system, the Thannermukkom
barrage was constructed across the estuary dividing it into fresh water dominated southern and a northern region dominated with
brackish water, which has grossly altered the eco-biology of the region. In this context, the influence of environmental factors on fish
assemblage structure has been poorly recognised in Vembanad estuarine system mainly for effectively implementing proper
management and conservation measures. Information on fish assemblage in relation to environmental parameters collected from
February 2012 to January 2013 is reported in this contribution. Estimates of annual average fishery production indicated a catch of
4774.46 t in the estuary, in which 10.1% and 89.9% was contributed by southern and northern zones respectively
.
Seventy four
species of finfishes, eleven species of shell fishes were identified for the study period. Multidimensional scaling and canonical
correspondence analysis significantly demarcated the spatio – temporal variation of fish species distribution and observed a strong
correspondence between fish assemblage and environmental variables. Depth, temperature, pH and salinity were the most important
parameters explaining the variation in fish assemblage composition and abundance in Vembanad estuarine system. The aging
Thaneermukkom barrage and its faulty operation reduced the tidal flushing altering the circulation and mixing process, especially in
the southern part of estuary. This influenced the hydrological characteristics leading to a decline in estuarine fishery and its
production potential.
Keywords
Environmental factors; Fish assemblage; Ramsar site; Vembanad wetland system
Introduction
In an aquatic environment, understanding the
dynamics of fish population and species distribution in
response to environmental factors are essential.
Variation in the abundance and composition of fish
species in an ecosystem provide the basic idea for
implementing the ecosystem – based fisheries
management. For the evaluation of environmental
variables on organisms, fishes are important because
they participate in multiple trophic levels in aquatic
community and are having long life span and are
easily sampled. Estimation of fish assemblage
structure has high value in estuarine quality
assessment.
Species assemblage is an important
ecological unit that interact trophically and respond to
environmental and habitat conditions
(Craig and
Bosman, 2013).
Fish communities of coastal estuarine
environment possess a mixture of euryhaline species
adapted to brackish environments, along with true
marine and fresh water species. Therefore, the
diversity of fish species in estuaries are very high and
are composed of marine, estuarine, freshwater and
migrating species (Henderson, 1988; Lobry et al.,
2003). Biological condition of aquatic environment is
important because fishes react with external aquatic
environmental parameters. It leads to shift in the
assemblage composition of fish species. Fish
assemblages are recognized as sensitive indicators of
habitat degradation, environmental contamination and
overall ecosystem productivity. The fish assemblages
in the estuarine systems are typically dynamic,
reflecting the changing environmental conditions in
which they are exposed (Tremain and Adams, 1995;
Able and Fahay, 1998; Idelberger and Greenwood,
