EFFECT OF SUBLETHAL CONCENTRATION OF FORMALIN ON HAEMATOLOGICAL AND BIOCHEMICAL PARAMETERS OF Oreochromis niloticus

Formalin has long been used for traditional treatment of fish ectoparasites, even though it is a highly toxic compound. Besides this, formalin is a one of the major constituent of plywood mill effluent. Perumbavoor, Ernakulam (district) of Kerala is one of the major plywood industrial belt and hundreds of plywood factories have been working in a limited area. All these plywood factories are discharging effluents directly into the nearby water bodies without any proper treatments. Hence a detail study is necessary to evaluate the impact of formalin on aquatic organisms especially fishes. In this ground a study was undertaken to evaluate haematological and biochemical changes resulting from the exposure of Oreochromis niloticus to sub lethal concentrations of formalin (1/80th (0.175 ml), 1/70th (0.2 ml) and 1/50th (0.28 ml) dilution of LC50 of formaldehyde) for a period of 20hrs, 100hrs and 300 hrs. It is noted that with an increase in the concentrations and exposure period, the total count of RBC, haemoglobin, PCV, MCH, MCHC and MCV decreased as compared to that of the control. The WBCs count increased with increase in concentration and exposure period. Blood Glucose level showed an increasing trend with dosage and exposure time. Total Protein, Globulin and Albumin were lower in exposed fish as compared to control. The changes observed in this study indicated that haematological and biochemical parameters can be used as an indicator of formalin related stress in fish. The current work emphasized the necessity to regulate the discharge of formaldehyde from domestic and industrial sources into aquatic system. A very mild concentration (0.37 ml) is preferable for the control of parasitic infection in aquaculture; otherwise it may affect the health of fishes and finally human being.