Effect of Water Chemistry on Growth Performance of Some Freshwater Fish Exposed to Some Heavy Metals Mixture

Abstract

This studied was conducted to evaluate the correlation between water physico-chemical parameters and the growth performance of two fish species viz . Ctenopharyngodon idella and Hypophthalmichthys molitrix . Fish were exposed to sub-lethal (1/3rd of LC 50 ) concentrations of metal mixture under controlled laboratory condition for 90 days. All physical and chemical parameters were determined twice a day through out experimental period. Water pH (7.25), total hardness (225 mg/L as CaCO 3 ) and temperature (30℃) of water were kept constant during each trail for fish. Correlation and regression analyses were computed to find-out relationships among various parameters defined for this study. During growth periods of 90 day, both fish species were monitored weekly for their increase in average wet weights (g), fork and total lengths (mm), specific growth rate, condition factor, feed intakes and feed conversion efficiency. No fish species showed any mortality during the entire period of growth trails under chronic stress of metal mixture. The relationships among all phyisco-chemical and growth parameters were investigated after 90-day growth trail. The obtained results showed that physico-chemistry of metal mixture stressed media exerted significant effect on both fish growth. Significantly better feed intake increased the ammonia production and excretion by both fish resulting fish weight increments positively non-significant correlated with contents of stressed media and also cause significant effect on growth of fish. Total ammonia content of test media exhibited significantly direct relationship with dissolve oxygen. However, calcium showed significantly inverse correlation with magnesium by the both fish species. It is also concluded that not only toxicity of metals but also the deficiency of consumed oxygen cause frequent deaths of fish in water due to biological decomposition of heavy metals.