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Open Water Farming of Pearlspot Etroplus suratensis (Bloch) in Low-Volume Cage 
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Pages: 839-847 Authors: K.G. PADMAKUMAR, P.S. MANU, L. BINDU Date: 2009/10/25 Hits: 530 |
Abstract
Pearlspot, Etroplus suratensis (Bloch) seeds of size 6.0-50.0 g were stocked at 200 m-3 in low-volume cages of size 2 m3 in open waters of mean depth 2 m and moderate water flow (> 0.05 m.second-1) in Vembenad lake, on the south west coast of India. The fish was fed with ‘Higashi’ brand commercial sinking pellets of 20% crude protein. Average fish production was 26.76+9.308 (range 17.80-44.40) kg.2 m-3 in 205.3 + 60.983 days. The stocked fish exhibited absolute growth rate of 0.50-0.90 g.day-1 and maximum survival from 45 to 100%. The fish was observed to attain an average size of 163.76 + 40.214g and a maximum size of 350-480 g at harvest. The specific growth rate ranged from 0.27 to 0.76% day-1. Maximum production was achieved in cages with highest stocking density (230 m-3), and the over all food conversion ratio was 3.52. Length–weight relationship indicated the general well-being of the cage-reared fish compared to that from natural catches. Net cages stocked with pearlspot were almost devoid of fouling and mesh clogging algae as the fish was observed to feed on the filamentous algae attached to the cage structure. These observations indicate the role of pearlspot as a ‘scraping’ species. Higher concentration of organic carbon in sediments and nutrients, especially nitrates in waters just under the cages indicates the essential need for restricting nutrient loading from cages to below the environmental carrying capacity.
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