The impact of a permanent weir (bund) construction on the ecology and fish species diversity of Muriyad wetland is studied. As this wetland area remains 0.5-1 meter below the mean sea level, rice cultivation   is carried out   after dewatering the fields,   and construction of temporary bunds. Permanent weirs are constructed for mitigating the risk of crop loss and reduce the recurring expenditure for annual bund construction. It is    carried out with a view to increase the rice production by   growing an additional crop during the summer season.   However, these interventions have drastically altered the natural hydrological cycle of the wetland.  

Muriyad wetland also supported a good number of economically important fish species. The present study indicates that the species richness of the fish has come down.   Some of the once abundant species of fishes like   W allago attu and Heteropneustes fossilis have become rare. Increased irrigation facilities allowed the farmers to use high yielding varieties of rice. The concomitant use of large quantities of fertilisers and pesticides resulted in the contamination of water. Even though rice production has increased significantly,   the developmental activities have diminished several other major functions and values of this natural wetland.

*Department of Zoology, Christ College;
** Department of Geology Christ College;
Irinjalakkuda,
Kerala.
Phone: 0488-828711.
E-mail: kurishinkal@yahoo.com