Data of morphological and trophic divergence of lake and stream minnows (Phoxinus phoxinus)

I studied the divergence pattern of the European minnow (Phoxinus phoxinus), a common freshwater fish that has received little attention despite its large distribution. In many Scandinavian mountain lakes, European minnows are considered as being invasive and were found to pose threats to the native fish populations due to resource competition. Minnows were recently found to show phenotypic adaptations in lake versus stream habitats, but the question remained if this divergence pattern is related to differences in resource use. I therefore studied the patterns of minnow divergence in morphology (i.e., using geometric morphometrics) and trophic niches (i.e., using stomach content analyses) in the lake Ånnsjön and its tributaries to link the changes in body morphology to the feeding on specific resources. In August 2018, minnows were caught from three lake locations (L1, L2, L3; Figure 1) using gill nets (1 × 10 m with 6 mm mesh size), which were exposed for up to 12 hr. Furthermore, minnows were collected from three different slow-flowing tributaries that were less than two km away from the lake: downstream Stor Klockbäcken (location S1), downstream Sjöviksbäcken (location S2), and downstream Kvarnbäcken (location S3) (Figure 1). In the streams, minnows were caught using an electrofishing approach and killed with an overdose of benzocaine. Fish were frozen to −20°C and transported to the laboratory at Uppsala University. In total, 279 minnows were analyzed, 158 from the lake locations (L1: 52, L2: 52, L3: 54), and 121 in the streams (S1: 50, S2: 50, S3:21). In the laboratory, fish were thawed and subsequently individual length (to the nearest mm) was taken. See Morphological and trophic divergence of lake and stream minnows (Phoxinus phoxinus) by Scharnweber (2020) for furhter methodological information. The dataset was originally published in DiVA and moved to SND in 2024.