Impact of Mercury Containing Industrial Effluent on the Changes in Clinical Symptoms, the Brain Somatic Index and Hepato Somatic Index of fresh water fish, Oreochromis mossambicus, Peters

Zoology

Emissions of effluent from various industries into water bodies are having detrimental effects on aquatic species like fish. High percentage of mortality of fish due to the action of the effluent might be due to the pathological changes. The present investigation was designed to study the effect of effluent of a chlor-alkali industry on a fresh water fish, Oreochromis mossambicus, Peters and its toxicological significance. The MAC value of the effluent was found to be 6.41 ml/l for 30 days and to be on the safer side 6.0 ml/l was considered for 28 days of the exposure for sub-lethal toxicological studies. The LC10, LC50, LC100 values after 28 days were recorded. It has been observed that all the exposed fishes appeared lethargic after exposure to the effluent. The major clinical symptoms such as inappetance and ataxia appeared immediately after exposure. At higher concentration, the exposed fish showed loss of equilibrium, gradual onset of inactivity, erratic swimming with irregular collision to the inner glass wall of the aquarium were observed. Infection of eyes, exophthalmia and involusions of test fish were observed, when compared to control fish. Autopsy studies revealed that the liver and brain of exposed fish were congested, pale and tender. The liver somatic index and brain somatic index decreased (r = -0.989, p :S. 0.001 and r = -0.934, p :s 0.001) with the increase in exposure period, when compared to control fish (r = 0.897, p :S. 0.05 and r = 0.946, p :S. 0.0 1). The percent inhibition of BSI and LSI increased in exposed fish with the increase in exposure period. The control fish remained clinically healthy throughout the period of experiment indicate the percent decrease in BSI & LSI in exposed fish when compared to control fish. The percent decrease of BSI, increased. With the increase in exposure period except on 28th day of exposure and a maximum decrease of 14.46 % was recorded on 21 set day of exposure. In case of LSI, a similar trend was observed but here the index decreased maximum by 32.24 %, when compared to control fish, after 28 days of exposure. When the fish was transferred to toxicant free medium, no recovery was marked, rather percent decrease increased up to 27.81 % was recorded in BSI, whereas, further depletion in LSI was marked. A maximum of 44.3 % decrease on 14th day & 39.4 % decrease on 28th day of recovery was marked. The two ways analysis of variance ratio test based on the data related to BSI and LSI of control and exposed fish. No significant difference between rows and columns was observed, BSI data indicate the existence of significant difference between rows, LSI data and non-significant difference between columns, When the exposed fish were transferred to toxicant-free tap water, no significant recovery in their activity was observed.

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