Undersökning av lekområden för mal (Silurus glanis) i Båven

In Sweden, the Wels catfish (Silurus glanis) is a protected species and exist in only three known water systems in the country. With spawning habitats being destroyed by human activities, it is important to know more about the Swedish catfish’s reproductive behaviour and habitat preferences in order to protect the species. In this report, catfishes tagged with transmitters was tracked using radio telemetry, day and night for two weeks in Lake Båven during the spawning period. Habitat data on the depth, bottom hardness and vegetation was collected in known and potential spawning areas in the lake using an echo sounder. Habitat preference analysis indicated depth and bottom hardness as important factors when catfishes chose spawning habitat. The analysis did not indicate vegetation to be important. Habitat data from spawning positions of tagged catfishes was used to identify other sites suitable for reproduction in nearby areas. Home range during spawning was calculated for two catfishes and was found to be 1.05 and 1.35 ha. Based on this information and the identified sites suitable for spawning, the total available spawning habitat in the study area was found to be enough for 12 to 15 catfishes. This is relatively few, and indicates that additional spawning sites would benefit the population