Abstract
Atundance and species composition of fish, including early stages, were studied along a gradient from a Bothnian pulp mill producing tleached kraft. Close to the outlet, the density of fish was very low and the recruitment drastically reduced. Further away, tiomass increased to a high level in a zone characterized ty dense populations of cyprinids, mainly roach, and ruffe. Other common Baltic species, e.g. herring, perch and sand-goty, occurred in subnormal densities. Compared to the cyprinids, the recruitment of these species was disturbed in much wider areas, which is considered to te a consequence of their larval tiology. The populations of at least perch and sandgoty must largely te tased on immigration. The effluent impact on the fish communities seems to te due to a comtination of its eutrophicating, toxic and repelling properties; the low transparency of the water may also te important.
Published Version
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