Abstract
Microalgae Chlorella vulgaris was cultured in sugar mill wastes to produce rotifer Brachiomus longispina and rearing of Clarias batrachus post larvae were trialed for 28 days using cultured rotifer as live food in laboratory condition in the Department of Aquaculture between November, 1999 and January 2003. Chlorella vulgaris was cultured in different inorganic media enriched with 10% sodium acetate, Bold basal medium with 10% sodium acetate (BBMAC), N:P:K (1.0:1.0:0.5) with 10% Na acetate (NPKAC1), N:P:K (1.0:1.5:0.5) with 10% Na acetate (NPKAC2) and Bold basal medium (BBM) as control. Then Chlorella vulgaris was cultured in different media prepared from inexpensive sugarmill wastes and byproducts such as sugar mill effluent medium (SMEM), press mud medium (PMM), normal molasses medium (NMM) and red sugar medium (RSM) with a control medium as BBM to find out optimum dose and finally mass culture of C. vulgaris was done in optimum dose of SMEM and PMM with NPK as control medium. Sugar mill wastes used for algae culture showed very promising result in respect to cell growth, chlorophyll a, specific growth rate (SGR) of cell and chlorophyll a and total biomass during the study. Among different media of SMEM, PMM, NMM and RSM, maximum growth of C. vulgaris were found in SMEM 50% PMM1.0 g/l, NMM1.0 g1 and RSM0.4 g showed significantly (P<0.01) higher growth of C. vulgaris than that cultured in BBM as control. Mass culture of C. vulgaris showed that maximum cell growth obtained in PMM1.0 g followed by SMEM 50% and NPK. The proximate composition analysis of Chlorella vulgaris grown in the above said media in most cases showed significantly (P<0.01) higher crude protein and lipid content than C. vulgaris cultured in BBM. Chemical composition of sugar mill wastes and by-product indicated that press mud contained significantly (P<0.05) higher crude protein and lipid than molasses and red sugar. Brachionus longispina fed on Chlorella vulgaris grown in PMM1.0 g, SMEM 50% and NPK showed that highest density of the rotifer was found on 10th day than those rotifer fed on C. vulgaris grown in PMM1.0 g followed by those grown in SMEM 50% and NPK. Brachionus longispina fed on C. vulgaris grown in PMM10 g contained significantly (P<0.01) higher crude protein (61.40%) than those cultured in other treatments. But lipid content of B. longispina was found significantly higher (P<0.01) when fed on C. vulgaris grown in SMEM50% than that of B. longispina fed on C. vulgaris cultured in PMM10 g and NPK as control. A 4 days old Clarias batrchus post larvae was treated for 28 days using Brachionus longispina as live food with five treatments containing 80 larvae/10 litre of water in the laboratory aquaria. Maximum survival (57.92%) was obtained in treatment V where initially the post larvae fed only on rotifer and then supplemented with Moina and artificial diet for two weeks showed also significantly (P<0.05) higher weight and length gain than other treatments. In the control treatment I, C. batrachus post larvae was provided with artificial diet (50% protein) showed significantly (P<0.05) least growth in respect to survival (37.5%), length and weight gain. From the experiment, it is concluded that suitable microalgae culture may be established using inexpensive agroindustrial wastes such as sugarcane industry wastes. Rotifer or other commercially important zooplankton raising may be promoted fed on cultured microalgae for post larval rearing of cat fishes/fin fishes using as live food organism for aquaculture development to the fore.