Integrating environmental characteristics and fisheries management in northern Finland river impoundments

Three large rivers in northern Finland, the Kemijoki, lijoki, and Oulujoki rivers. were dammed for hydropower generation in the 1940s-1960s. Due to di fferences in environmental conditions, these impoundments require detailed study to produce guidelines for fisheries management. Water quality hydrolo gy, vegetation, and geomorphology data of 16 impoundments were gathered. Sh oreline land-use data were derived from maps, and fish assemblage data were collected by exploratory fishing and from the annual fishery statistics. T he relations among environmental variables were studied, and a classificati on of the impoundments was developed by hierarchical cluster analysis. Con sequently, three impoundment groups with different environmental characteri stics were formed. Significant differences among impoundment groups were al so detected in fish yield. We conclude that the variation in environmental conditions, together with differences in fish communities in the impoundmen ts were important, enough to justify the claim that impoundments of differe nt types require different management strategies.