Mortality in perch population in a Baltic pulp mill effluent area

Perch were captured between 1983 and 1985 in the coastal area affected by effluents from the Norrsundet pulp mill on the Bothnian sea to calculate their mortality, and compared with reference stock from Aland. Pooled data from the 4 most exposed stations (Area I) had a mean annual mortality of 0.62 compared with the 2 more distant stations (Area II) in which the mortality was 0.34. The mortality in the fin-damaged fish was higher than in all the other studied stock.