Jayasree P S creator Raman N N (Guide) text xx Panangad Department of Fishery Hydrography, College of Fisheries 2009 9999 monographic und

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129 Present study was carried out in the prawn filtration pond of the College of Fisheries adjacent to Cochin backwater to find out the seasonal variation of macrobenthos and to correlate them with the seasonal variation in hydrographical parameters and sedimentary characteristics of the pond. Fortnightly samples for hydrographical parameters, sedimentary characteristics and biological studies were collected during the period from October 2007 to September 2008. Hydrographical parameters like salinity, water temperature, turbidity, pH, total alkalinity, hardness, nutrients, dissolved oxygen, primary production, chlorophyll – a and transparency were observed. Polychaetes, tanaids, amphipods, bivalves and gastropods were the benthic groups obtained. Prawn juveniles and cumaceans encountered very rarely, during the study period were grouped as ‘others’. Among these gastropods, tanaids and polychaetes were the dominant forms. In the culture field, benthic populations were maxi mum during post monsoon months and showed a decreasing trend during pre monsoon and with the onset of monsoon it further decreased. Gastropods were the most dominant group observed during pre monsoon, forming 80% of total macrobenthos. Tanaids were the second major group and they were the dominant group during the post monsoon period forming 54% of total macrobenthos. Polychaetes were the third major group and constituted 35% of total macrobenthos during monsoon season and they were the second maximum during that period. In the culture field benthic abundance was found to be mainly influenced by substratum characteristics. Among the different hydrographical parameters studied for seasonal variation, water temperature, pH, primary production and chlorophyll were found to be significantly different. Among the sedimentary characteristics studied for seasonal variation, sediment pH was found to be significantly different. MFSc 639.2 JAY/ST PG http://krishikosh.egranth.ac.in/handle/1/5810043174 http://krishikosh.egranth.ac.in/handle/1/5810043174 140128 20220323110110.0