Long term effects of lead (Pb) toxicity on the growth performance, nitrogen conversion ratio and yield of major carps

One group of three fish species, Catla catla, Labeo rohita and Cirrhina mrigala, was exposed to sub-lethal concentrations of lead (Pb), separately, in aquaria for 30 days while other was kept un-stressed as a control. After exposure period both stressed and control fish were shifted to earthen ponds to rear, separately, for six months to study their growth, nitrogen conversion ratio (NCR) and yield at final harvest. Statistical analysis of the research data showed significant effects of fortnights, species and treatments on wet weights, fork and total lengths of three fish species. Among three fish species C. mrigala gained maximum weigh of 53.76 +- 7.39 g that varied significantly ( P<0.05) from that of L. rohita (41.7 +- 9.48 g) but non-significantly from the weight gains of C. catla (52.65+-9.40 g). Fork and total length increments were observed significantly (P<0.05) higher in C. mrigala Followed by that of C. catla and L. rohita. Fish stressed at sub-lethal level of Pb showed significantly (P<0.01) lower weights, fork and total lengths as compared to the control fish. Fortnights (P<0.05), species, treatments and the interaction (species x treatments) exerted significant (P<0.05) effects on NCR. On the basis of this investigation, it was concluded that sub-lethal metal (lead) exposure to the fish at fingerling stage had long term effect on growth (weight, fork and total length gains), NCR and yield of fish when cultured in grower ponds. (author)