Kanhirapuzha reservoir with a total area of 515 ha is in the category of small reservoirs «1000ha) as per the records of the GovernrnentofIndia(Sugunan, 1995). Its storage capacity is 70.82 mm’ draining water from 70 square kilometre catchment area spreading in the eastern slope of Western Ghats. This is a perennial reservoir storing water round the year and the release of water even during summer does not decrease the water level drastically.
Reservoirs receive nutrient input from the allochthonous sources, which often determine the water quality, nutrient regime and the basic production potential. Particulate matter originating from within and the surrounding landscape of the stream is an important basal resource to fluvial food webs.
The major determinant of reservoir productivity, mean depth of this reservoir is 13.75 m indicating it as a moderate deep basin in which bottom region does not lie in the euphotic zone thus showing less productivity. Based on rainfall the seasons of this region can be broadly classified as rainy (June- November) and dry (December – May). The morpho-edaphic index (MER) is the most widely used index of potential fish production in reservoirs. This is a metric expression derived by dividing lake’s total dissolved solids (mg/l) or its conductivity by its mean depth in meters. Estimation of potential fish production made through MEI can be used for calculating the stocking densities of fish fingerlings in inland reservoirs (Welcomme, 1976).
Morphological features of the reservoir
The morphological data was collected from the Irrigation Department, Government of Kerala. The fisheries data were obtained from the Office of the Deputy Director of Fisheries, Palakkad region. For lirnnological and biological studies, pertinent samples were collected monthly from July 2007 to June 2009 except for few months (June & October 2008) when wind in the reservoir was too strong, combined with flash flood. Sampling and analysis of water, soil, biotic communities and primary production were carried out following standard methods (APRA, 1980; Bose, 1998). Water and plankton samples were collected every month for 2007- 2009 spatially at five sites, lentic (site- S1), confined (site-S2), lotic (site-S3), intermediate(site-S4) and between hillocks (site- S5)and at surface, 1m, 2m, middle and bottom of the reservoir.
- Central Inland Fisheries Research Institute, Barrackpore