Abstract

Growth of the mudfish, Clarias anguillaris in of treated and untreated domestic sewage was investigated. Six weeks old fingerlings obtained from Delta State University, Asaba Campus Research Farm were used and the study lasted for 14 weeks. Fingerlings were kept in stock tank containing 10, 000 cm³ bore hole water and allowed to acclimate for two weeks. The stock tank was well aerated and fingerlings fed twice daily at the rate of 4% body weight with poultry mash in a daily renewal static bioassay system. The stock (0%- control) was then diluted with bole hole water serially to give 25, 50, 75 % strength of the treated and untreated domestic sewage and 100 % into which 10 fingerlings each were introduced. Weekly measurement of growth parameters of fish total length and weight were taken. The condition factor (k) was calculated. Increase in fish total length and weight in control, treated and untreated domestic sewage was observed. Growth of fish was significantly higher (P<0.05) in the treated domestic sewage than in the untreated. There was no significant (P>0.05) difference in total length of fish in all concentrations of treated domestic sewage as compared with controls. However, fish in 100% concentration of domestic sewage had a slower increase in total length than fish in other treated concentrations. Weight gain in C. anguillaris was higher in the 50% but not significantly (P>0.05) higher than other concentrations of treated domestic sewage. The increase in fish weight in the untreated domestic sewage was not significantly (P>0.05) different in all the treatments but was significantly (P<0.05) lower than that of fish in the control. Condition factor of C. anguillaris in both the treated and untreated domestic sewage varied and decreased except for fish in 100% treated domestic sewage which was observed to have an increase in the value of the condition factor from 3.76g cm^-3 to 4.73g cm^-3. Untreated domestic sewage water showed a higher turbidity, biochemical Oxygen Demand (B.O.D), alkalinity and nitrate composition of than treated sewage which had higher oxygen content and was clearer in appearance than the untreated. Microbial analysis shows the presence of Escherichia fecalis, Streptococcus fecalis and Enterococcus fecalis in untreated sewage with ciliated protozoans in both treated and untreated sewage. This study has shown that treated domestic sewage is best for healthy fish growth with reduced risk of transfer of pathogens.

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