e - poz 2 - Central Institute of Brackishwater Aquaculture
e - poz 2 - Central Institute of Brackishwater Aquaculture
e - poz 2 - Central Institute of Brackishwater Aquaculture
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INvISTGATIONS ON THE FISHERY ECOLOGY OT VEMBANAO M -- A REVIEWMost <strong>of</strong> the research on the ecology and fisheries <strong>of</strong> the Vembanad lake wereconducted during the preimpoundment phase, i.e., before the commissioning <strong>of</strong>the Thanneermukkom barrage. The Cochin backwaters and its incoming riversconstituttng the northem wing <strong>of</strong> the Vembanad lake have been the major area <strong>of</strong>Interest to the researchers. Due to this, the literature based on studies extendingup to the southern tip <strong>of</strong> the lake near Alleppey is rather few (Fig.2).An account on the formative history <strong>of</strong> the Vemba~d lake has been presented byMenon (1913) and Rasalam and Sebastian (1976). Gopalan (1976) has presented acomprehensive account <strong>of</strong> the history <strong>of</strong> reclamation and the consequentshrinkage <strong>of</strong> the backwaters, especially the Vembanad backwaters. Similarly,under the IndaDutch Collaborative Research Project on the Water Balance Study<strong>of</strong> the Kunanad Region, various aspects <strong>of</strong> the ecology and fisheries <strong>of</strong> Vembanadldke wt?re investigated and reported (Anon., 1989).WATER QUALITY : Several studies have been conducted on the various physlcclchemical aspects <strong>of</strong> the Cochin estuary in a fisheries perspective. Balakrishnan(1957) was one <strong>of</strong> the earliest to study the surface salinity <strong>of</strong> the Ernakulamchannel, attributed to the rapid salinity fluauations,due to the influence <strong>of</strong> tide.George and Kartha (1963) recorded the surface salinity <strong>of</strong> Cochin backwaters Inrelation to the tidal regime. Josanto (1971) analysed the bonom salinitycharacteristics and the factors that influence the saltwater penetration in theVembanad lake extending from the Cochin bar mouth to Alappuzha.Hydrological features in relation to salinity distribution were also studied by a fewmore workers. These include the work <strong>of</strong> Cherian (1967) Qasim and Gopinathan(l969), Ramamirtham et a/. (1986,1987l and Wellershaus (1 971).SEDIMENT AND NUTRIENTS : The nature <strong>of</strong> sediment and the distribution anddynamics <strong>of</strong> nutrients like nitrate, nitrate ammonia, phosphate and silicate in theVembanad lake particularly in the Cochin backwater system has been a major area<strong>of</strong> research by several authors. Sankaranarayanan and Quasim (1969) andSankaranarayanan and Panampannayil (1979) concentrated their research on the