A summary of the impact of acid rain on atlantic salmon (Salmo salar) in Canada

Abstract

Within the present North American range of Atlantic salmon, severe acid rain effects are limited to the Southern Upland area of Nova Scotia. In the Southern Upland, long range transport of H2SO4 has caused many rivers to decline in pH to the point where their Atlantic salmon stocks have been destroyed or much diminished. Chemical records show a declining pH trend in N.S. rivers since the early 1950s. Eighty % of the annual variation in H+ concentration can be accounted for by a multiple linear regression model on excess sulphate, total Al and organic anions. It is technically feasible to restore the acidified salmon habitat by the addition of limestone; the total cost of mounting a liming program to restore the lost habitat has been estimated at $4.75 × 106 yr−1. The pre-acidification Atlantic salmon production capacity of the Southern Upland was estimated from physical habitat surveys and tag return data to be about 45 000 fish yr−1. Acidification has caused a 50% decline to the current production level of about 23 000 fish yr−1. The costs of the liming program, when compared to the economic benefits of the anticipated salmon enhancement, are economically unjustifiable. The eradication of salmon from such large regions will hinder future programs to reestablish the species in their former range when pollution of the atmosphere is eventually brought under control. Present plans are for a small liming program to establish a series of refuges for the preservation of nuclei of native salmon stocks.