Some aspects of prawn ecology in Cochin backwaters

V.T. Paulinose, T. Balasubramanian, P.N. Aravindakshan, P.G. Menon, M.K. Kutty

Abstract



Prawn population of a large perennial tidal pond and three other connected smaller ponds in the Cochin backwaters were studied in relation to the environment occurring in these ponds. While the large pond afforded a more stable environment greater human influence in the smaller shallower ponds made their environment more fluctuating and less conductive for the growth of prawns although nutrient and primary productivity levels were generally high in these ponds. All the ponds were rich in oxygen and nutrients especially phosphorus. Primary production during the premonsoon months was considerably lower than during the monsoon months, chlorophyll a values often being less than 20 mu g/l whereas the monsoon values were as high as 300 mu g/l in Pond 2. The monthly growth of Penaeus indicus in cages ranged from 19.0-30.4 mm during the January-February period but it decreased considerably during the second month. Smaller ponds being shallow with about 2 m depth at the deepest portion, high temperature and salinity during premonsoon months seem to have directly affected the growth. Probably, the growth was also indirectly affected by temperature particularly in Pond II by promoting decomposition of rich organic matter leading to reducing conditions

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