Present status of the North American Umbra pygmaea (DeKay, 1842) (eastern mudminnow) in Flanders (Belgium) and in Europe

The eastern mudminnow Umbra pygmaea (DeKay, 1842) originates from the eastern part of the United States of America and was transferred to Europe already at the beginning of the 20th century. This paper summarizes the current distribution in Europe and adds an extended dataset of eastern mudminnow records in Flanders (Belgium). The core of the European distribution seems to be the southeast of The Netherlands and the northeast of Flanders. Eastern mudminnow is established in lotic waters in Flanders and was found on 76 locations over the last 15 years. Neutral pH and high oxygen concentrations positively correlate with the presence of eastern mudminnow. The abundance of U. pygmaea decreases significantly with an increase of the number of fish species. The length-frequency distribution shows a peak at 7.0 cm and total length of U. pygmaea specimens varies between 3.4 and 13.7 cm. The overall length-weight relationship for all U. pygmaea specimens in Flanders shows a positive allometric growth. Fulton’s condition factor for all eastern mudminnow specimens caught in Flemish rivers is 1.22. Assessment of U. pygmaea on its potential invasiveness in Flanders results in a low to medium risk.