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INvISTGATIONS ON THE FISHERY ECOLOGY OT VEMBANAO M -- A REVIEWMost of the research on the ecology and fisheries of the Vembanad lake wereconducted during the preimpoundment phase, i.e., before the commissioning ofthe Thanneermukkom barrage. The Cochin backwaters and its incoming riversconstituttng the northem wing of the Vembanad lake have been the major area ofInterest to the researchers. Due to this, the literature based on studies extendingup to the southern tip of the lake near Alleppey is rather few (Fig.2).An account on the formative history of the Vemba~d lake has been presented byMenon (1913) and Rasalam and Sebastian (1976). Gopalan (1976) has presented acomprehensive account of the history of reclamation and the consequentshrinkage of the backwaters, especially the Vembanad backwaters. Similarly,under the IndaDutch Collaborative Research Project on the Water Balance Studyof the Kunanad Region, various aspects of the ecology and fisheries of Vembanadldke wt?re investigated and reported (Anon., 1989).WATER QUALITY : Several studies have been conducted on the various physlcclchemical aspects of the Cochin estuary in a fisheries perspective. Balakrishnan(1957) was one of the earliest to study the surface salinity of the Ernakulamchannel, attributed to the rapid salinity fluauations,due to the influence of tide.George and Kartha (1963) recorded the surface salinity of 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 of Cherian (1967) Qasim and Gopinathan(l969), Ramamirtham et a/. (1986,1987l and Wellershaus (1 971).SEDIMENT AND NUTRIENTS : The nature of sediment and the distribution anddynamics of nutrients like nitrate, nitrate ammonia, phosphate and silicate in theVembanad lake particularly in the Cochin backwater system has been a major areaof research by several authors. Sankaranarayanan and Quasim (1969) andSankaranarayanan and Panampannayil (1979) concentrated their research on the
nutrient regimen in the water and sediment phases of Cochin backwaters inrelation to other environmental features. Murthy and Veerayya (1972) gave adetailed account d the phosphorous content in the sediments of the Vernbanadlake. Eswara Prasad (1982) has described the. sediment features of m e prawnfarming a- adjacent to the Vembanad lake. A similar study in the prawn fieldsin and around Cochin backwaters is also presented by Aravindakshan et a/. (1992).Purandara and Dora (1987) had studied the textural characteristics and organicmatter of the near shore and surface sediment samples of the Vembanad lakebetween Azhikode in the North and Alappuzha in the South. One majorcontribution was by Sarala Devi (1989) and Sarala Devi et a/. (1992) on thetemporal and spatial distribution of the particulate organic carbon and particulatematter in Coch~n backwaters, especially in the lower reaches of the Periar rlver.Seralathan et a/. (1993) analysed and presented their findings on the features of thesediment and the distribution of organic carbon in the Cochln harbour area. .PLANKTON : One major area of ecological investiagtions in the Vembanad lakewas the qualitative and quantitative distribution of the plankton populat~on.Studies have been conducted on the variation and distribution of phytoplanktonand the factors affecting its production. One of the earliest report In this contextwas of George (1958) who has given an account of the general.composrtlon of theolankton from the Cochin backwaters. Subseauent important contribut~ons were;hose of Qasim and Reddy (1967) on the conientratio" of chlorophyll, Qas~m etal. (1969) on the organic production, Qasim et al. (1974) on the contribut~on ofmicroplankton and the nannoplankton, Gopinathan (1972) on the planktonbiomass, Gopinathan et a/. (1974), and Joseph and Pilla~ (1975) on the total cellcounts and the spatial and temporal distribution of the phytoplankton, .Quantitative and qualitative cmpos~tion of plankton In Vembanad lake extend~ngfrom Cochin to Alappuzha has been investigated by several authors (Devassy andCopmathan 1970, Devassay and Bhattathiri 1974, Kumaran and Raz 1975,Gopalakrlshnan et a/. 1988). The phytoplankton were exclusively studled byGopinathan (1972) in the Cochin backwaters where he reported the presence of62 species of Bacillariophyceae, 24 species of Dinophyceae, 3 specles ofMyxophyceae and 2 species of Cilioflagellates.
Page 2 and 3: Ecology and Fisheries Investigation
Page 4: The Vembened take on the south-west
Page 7 and 8: The lakc had already been reclatd c
Page 9 and 10: from the orig~nal marine environmen
Page 11: of this century. The current lwei o
Page 14 and 15: The project was implemented partial
Page 16 and 17: The barrage at Thanneerrnukkom acro
Page 21 and 22: Several literatures are available o
Page 23 and 24: ECOLOGICAL INVESTffiATtONS WRING 19
Page 25 and 26: so.
Page 28 and 29: The sediment texture showed that sa
Page 31 and 32: summer. The pure saline forms that
Page 33 and 34: eporxd by Nair et al. (1983) was di
Page 35 and 36: lhJm md tabqodr Onty m spxlcr m6emd
Page 37: A view of the endangered fish speci
Page 41 and 42: Urcrobrachium rosenbergir 57 930 47
Page 43 and 44: The study reveals that the Thanneen
Page 45 and 46: BIBLIOGRAPHY ON VEMBANAD LAKEAnon.
Page 48 and 49: m,T.R. Mii(l. Y. nd Wli, C. M. 1984
Page 50 and 51: Smlathan, P., MccoJuMkr~y, N. I., r
Page 52: I. E-. Mu. bid. E d.I. lndln FWI. A

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