Impact of physico-chemical variables of test media on growth performance of metal stressed major carps

Growth responses of catla catla,labeo rohita and cirrhina mrigala were determined,separately,under chronic exposure of mixture of metals (fe+zn+pb+ni+mn) at sub-lethal concentrations (1/3rd of lc 50) for 12 weeks (01-06-2010 to 01-09-2010). fish were kept under constant water temperature,ph and total hardness of 30°c,7 and 200mg/l,respectively. the physico-chemical parameters were monitored on daily basis throughout test period. the relationships among growth parameters of fish and water quality characteristics of metal mixture (mm) stressed media were computed by using correlation method. physico-chemistry of the test media (water) used for different treatments exerted significant impacts on fish growth,feed intake,condition factor and feed conversion efficiency(fce) of fish also. significantly better feed intake enhanced the ammonia (nh3) production and excretion by the fish resulting into non-significantly positive relationship of fish weight increments with contents of the test media. significantly higher feed intake resulted in excessive excretion of nh 3 by the fish to cause significant impact on its growth. sodium (na) and potassium (k) showed significantly positive correlation with ammonia concentrations of the test media,indicating excessive release of na and k by the fish under stress of mm that resulted in significantly more excretion of nh3 by the fish. copyright 2012 zoological society of pakistan.