Swimming performance of the European minnow

Maximum sustained swimming speeds of the European minnow were examined using increased velocity tests in a swim-speed chamber. Maximum sustained swimming speed for the size class 50–64 mm was 10.4 ? 4.0 cm s–1 (mean ? SD), for the size class 65–79 mm 14.2 ? 4.8 cm s–1, and for the size class 80–105 mm 16.0 ? 5.6 cm s–1. Similarly sized minnows were able to maintain considerably higher speeds in a raceway. For instance, individuals of the largest size class could maintain a swimming speed of 34 cm s–1 for at least 25 min. Hence, the maximum swimming capacity of the fish was highly underestimated using the increased velocity test in the swim-speed chamber. The unintentional distribution of minnows by man to new watersheds is considered a critical environmental problem in Norway, because of their potential to develop high densities in communities with low diversity. Recorded high swimming speeds indicated minnows' capability to spread further upstream when introduced to new water systems, and that their swimming and jumping abilities must be taken into account when constructing migration barriers to prevent further spreading. High swimming speeds could also indicate minnows' potential for competing with salmonids not only in lakes but also in riverine environments.