IMPACT OF CHRONIC EXPOSURE TO HEAVY METAL MIXTURES ON SELECTED BIOLOGICAL PARAMETERS OF FRESHWATER FISH SPECIES

Heavy metal contamination usually causes depletion in feed utilization in fish, and such disturbance may result in reduced metabolic rate and hence causing reduction in their growth. The present study assessed theharmful effect of sub-lethal concentrations of four different heavy metal mixturesi.e., Mix-I (Mn+Ni), Mix-II(Mn+Ni+Pb), Mix-III (Mn+Pb+Zn+Fe), and Mix-IV (Mn+Ni+Pb+Zn+Fe) on five fish species including Labeorohita, Catla catla,Cirrhinamrigala, Hypophthalmichthys molitrix, and Ctenopharyngodonidella.The experiment was carried out in triplicatefor each species separately in glass aquarium for 12 weeks. The results showed a significant(p < 0.001)effect on the treated group as compared to the control group. The average weight gain was as C. catla>L. rohita>C. mrigala>C. idella>H. molitrix. The condition factor was as C. idella>C. mrigala>L. rohita>C. catla>H. molitrix. Similarly, the feed intake also reduced significantly (p>0.001) in the treated group, and the feed conversion efficiency showed significant (p>0.05) effect of metal mixtures on fish metabolism and growth activity. The current study concluded that the studied heavy metals are toxic to different fish species, even at sub-lethal concentrations, and affect different biological parameters of fish growth. Keywords:heavy metals; chronic exposure;freshwater fishes;growth performance; feed conversion efficiency