Consumption of amphipods by littoral fish after the replacement of native Gammarus roeseli by invasive Dikerogammarus villosus in Lake Constance

The Ponto-Caspian amphipod Dikerogammarus villosus (Sowinski) invaded Lake Constance, Central Europe (47°39'N, 9°18'E,)in 2002 and within four years had colonized the entire littoral zone of the upper lake basin, replacing the formerly dominantspecies Gammarus roeseli Gervais. Fifteen fish species were sampled from six littoral sites in the upper lake basin in 2005 and 2006, and their stomach contents were compared with samples taken prior to the replacement of G. roeseli by D. villosus. Three zoobenthivorous fish species (European eel Anguilla anguilla (L.), Eurasian perch Perca fluviatilis L., and burbot Lota lota (L.)), which had regularly consumed G. roeseli, included D. villosus immediately into their diet in similar proportions. Shifts in amphipod consumption have thus not been detected, whereas effects of the invasive amphipod on the macrozoobenthos community, which on their part might affect the food base of littoral fish, require detailed study