The effects of acidification on Scandinavian freshwater fish fauna

Abstract

Acidification of freshwaters have inflicted a m ajor perturbation on Scandinavian aquatic ecosystems as indicated by severe regional loss of fish populations. This decline was first noted in the early 1920s but became particularly severe after W orld W ar II in the 1950s and 1960s. In southern Norway regional dam age is now docum ented in an area of 33000 km ² , 13000 km ² of which are devoid offish. Several m ajor southern salmon rivers are now barren. In Sweden more than 2500 lakes are docum ented to be affected. This corresponds to 3 -4 % of the total lake surface area. An additional 6000 lakes are assumed to be affected by acidification. Population losses are also found in thousands of kilometres of running w ater as well as in salmon and seatrout rivers on the southwest coast. This paper describes the early observations, chronology of this decline and reviews possible causes and mechanisms. The acidification and the associated loss of fishstocks over vast areas is apparently the most devastating change recorded for the fish fauna of Scandinavia