Mass mortality of fish in the Visakhapatnam harbour

Abstract

Mass mortality of fish was observed in the Visakhapatnam Harbour, which receives both industrial and domestic effluents from installations located in its environs, on 4 different occasions which was preceded by sudden climatic and hydrographical changes in the environment. Mortality was localized in one arm of the harbour which receives the effluents from an oil refinery and a fertilizer factory. Mortality might have been caused by the sudden discharge of large quantities of acids and sulphur dioxide which brought out conditions favourable for emanation of free CO₂ in abnormal quantities. The mortality was also believed to have been caused by asphyxiation due to lowered oxygen tension and presence of abnormal quantities of free CO₂ which was supported by the data collected on one occasion (29 Sept. 75).