Comparison of the effects of trash fish and pelleted diets in Clarias grow-out operations
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The environmental characteristics of four ponds and the production performance of Clarias in the ponds was investigated in response to the application of two feeds from November 1980 to March 1981. Each of the 800 m2 ponds was stocked with 20,000 fry, averaging 6.8 g; trash fish was applied in two ponds and a pelleted diet in the other two. After 5 months 26% of the Clarias fed on trash fish survived; they had attained an average weight of 94.2 g at the rate of 0.61 g/day. The survival rate of C larias fed a pelleted diet was 22%; the fish reached an average weight of 86.2 g in 5 months at the rate of 0.55 g/day. Corresponding net yields for the period were 0.434 and 0.279 kg/m2. Water quality conditions were comparable in each pond throughout the grow-out period with the exception that BOD values in ponds fed on trash fish averaged 8.4 g O2/m3/day is opposed to 6.9 g O2/m3/day in ponds where pelleted food was used. Chemical adversities were not as pronounced as recorded in similar culture operations. The difference was attributed to relative low stocking densities and to frequent water exchanges in the study ponds. The high mortality, slow growth and outbreaks of disease was related to the relatively low water temperatures and the amplitude of change which occurred through the culture period.