Effect of mining activities on the clam fisheries and bottom fauna of Goa estuaries

Abstract

Comparison of two clam beds and associated benthic fauna, in Mandovi and Cumbarjua canal estuarine system of Goa, India, severely affected by massive inputs of mining rejects, revealed that, in less than 10 years (1972-73 to 1982-83), high biotic variability induced by increasing environmental stress has caused irreversible ecosystem instability. Reduced dissolved oxygen concentration; high suspended solids and blanketing of bottom deposits by mining rejects, has resulted in more than 70% reduction in clam production; near extinction of resident fauna and the appearance of a low diversity bottom fauna, comprising of tolerant but vagrant species. Ever increasing entry of mining rejects, which has reduced the healthy and highly productive estuarine environment of 1972-73, into an impoverished biotope, in less than 10 years, unless prevented will result in the total extinction of estuarine life in the near future