Opmars van de Kesslers grondel in Nederland

In 2007 two unidentified fishes were caught in the river Waal, which turned out to be Neogobius kessleri. This is a Ponto-Caspian species which is colonising Central and Western-European rivers since a decade. In 2005 this species was caught in the upper Rhine in Germany and in 2006 in the lower part of the German Rhine. In 2008 Neogobius kessleri has been caught at many sites in the larger Netherlands rivers from the German border till the western site ‘Hollands Diep’. Almost all locations are characterised by the presence of large stones or a worn out river soil. At one site the species was found in a shallow stagnant water body covered with Nuphar lutea. Neogobius kessleri is hard to catch by dip-netting, because the fish hides between stones and can’t be reached. Electrofishing is a far more suitable method. The habitat were Neogobius kessleri is found looks very similar to suitable habitat of Cottus perifretum. At most locations where Neogobius kessleri was caught, no Cottus perifretum could be found, although this species was expected. This gives rise to the assumption that Neogobius kessleri might be a competitor for Cottus perifretum.