J. Rajasekharan Nair, P.M. Sherief-1998
Asian Fisheries Science, 10(3): 179-187
Abstract:
The study was designed to arrive at an experimentally-determined application factor for fixing tentative water quality criteria for phenol in tropical freshwaters. Larval rohu Labeo rohita (14-18 mm total length, 118-139 mg wet weight) were subjected to static lethal bioassay. The 24-h LC50 value was found to be 32 mg/l at 29 +/- 1 C. Juvenile rohu (26-33 mm total length, 226-273 mg wet weight) were exposed to sublethal phenol concentrations (0.1, 0.5, 2, 5 and 10 mg/l) for 28 d at 29 +/- 1 C without aeration. Treatment media were replaced everey 48 h. Fish were fed a pelleted diet at 6% wet body weight per day. Rohu exposed to 5 and 10 mg/l phenol showed significantly lower mean wet weight gain, specific growth rate, food conversion efficiency, and dry matter and protein digestibility. These fish also had higher moisture content, and lower protein, lipid and ash contents, as body nutrients were depleted. Juveniles exposed to the lower phenol concentrations of 0.1, 0.5 and 2 mg/l were not significantly different from the control. The maximum allowable toxicant concentration for juvenile rohu was 3.16 mg/l, indicating an application factor of 0.10.
(College of Fisheries, Kerala Agricultural University, Panangad P.O., Cochin - 682 506, India)