Effects of a Bleached Pulp Mill Effluent on Growth and Gonad Function in Baltic Coastal Fish

Abstract

Growth and reproductive capacity in perch (Percafluviatilia L.) and roach (Rutilusrutilus (L.)) were studied during 1983, 1984 and 1985 in a coastal area of the Bothnian Sea affected by bleached pulp mill effluents. Comparative investigations were made at a mill producing unbleached pulp. In perch exposed to bleachery effluents effects were observed on length increase rates, somatic condition factors and on gonad development. The fraction of fishes displaying inhibited gonadal recrudescence was high close to the mill, and the size of developing gonads was comparatively small. Growth was faster in exposed fishes, in young-of-the-year as well as in older fish. Effects on length growth could be distinguished as far back as in 1975. Energy storage, expressed as the condition factor, was highest in exposed fishes. The effect pattern was more diffuse in roach, but examples of reduced gonad growth were noted. In conclusion, these studies provided evidence for changes in the energy allocation system in fish exposed to a bleached pulp mill effluent.