Development and intercalibration of methods in nordic freshwater fish monitoring

A working group on freshwater fish sampling initiated by Finnish, Norwegian and Swedish participants developed and inter-calibrated methods for use in fish studies in Finland and Scandinavia. Differences in sampling methods and problems related to the ageing of fish were considered. A common standardized multi-mesh gill-net was developed for monitoring freshwater fish. Attempts were also made to increase the comparability of age determination of fish performed in the 3 countries. Results from comparative analyses of age determinations of 3 freshwater fish species often found in lakes subject to acid precipitation in the Nordic countries were examined.