Effect of Lethal and Sub-lethal Concentrations of Heavy Metal (Zinc) on Opercular Beat Frequency (OBF) in Cyprinus carpio var. communis

In the present investigation, the acute and sublethal toxicity of a grey list heavy metal (Zinc) on the juvenile of Common carp (Cyprinus carpio) was evaluated to determine its effect on the Opercular beat frequency (OBF) under laboratory conditions. The fish was exposed to varying levels of the toxicant (2.12mg/L; 4.25mg/L and 8.50 mg/L) for 96 hrs using static bioassay. Opercular beat frequency (OBF) in exposed fishes initially increased at 6 hr and 12 hr time interval compared to the control followed by a gradual decrease at later time points (48, 72 and 96 hour time intervals) that reflected a mild inhibitory effect. The operculum beat frequency was significantly (P< 0.05) affected by the exposure and concentration indicating an impaired respiratory function. A decline or alteration in OBF suggests respiratory stress, which is a direct marker of toxic effects. This study gives clear insight into how zinc toxicity impair basic life-sustaining functions in fishes. These findings highlight the potential of opercular beat frequency as a sensitive bioindicator for assessing sublethal respiratory stress in fish exposed to heavy metal contaminants like zinc.