Ecological effects of acidification on tertiary consumers. Fish population responses

Acidification effects fish populations in various ways, dependant on several factors of biotic and abiotic nature. The most important abiotic factor is water quality and its variability through season and during episodes. Among important biotic factors are fish species, development stages and spawning strategy. Also the specimens residence at time of toxic water and their ability to seek areas of better quality (refuges), are of main importance. For inland populations, reproduction failure seems to be the most important factor for population losses. Which lifestage being most affected might, however, differ from one population to another, even among the same species. Eggs and. alevins have been considered to be the most sensitive stages, although high mortality of postspawners have been reported from several lakes. Anadromous species, like Atlantic salmon, have stages of development that are particularly sensitive to changes in water quality. These stages are connected to physiological changes when preparing for change in salinity (smoltification and return from sea). Unfortunately these physiological changes coincides with the most critical environmental periodes; spring melt and autumn rain.