Trophic Interactions Between Invasive Round Goby ( Neogobius melanostomus ) and Native Burbot ( Lota lota ) in the Lower Oder River, Germany

ABSTRACT

The invasive round goby ( Neogobius melanostomus ) has become widespread in European rivers, raising concerns about trophic interactions with native benthic fishes. We investigated dietary composition and trophic niche characteristics of native burbot ( Lota lota ) and invasive round goby in the Lower Oder River to assess the extent of resource overlap and potential trophic interactions between the two species, using stomach‐content and stable‐isotope (δ ¹³ C and δ ¹⁵ N) analyses of fish muscle and liver tissues. At the invaded site, both species consumed benthic prey resources, particularly amphipods. Smaller burbot and round goby showed partial overlap in prey use, whereas larger burbot increasingly shifted towards piscivory. Direct predation of round goby by burbot was rare, as round goby was detected in the stomach contents of only one burbot. Stable‐isotope analyses showed low overlap between the muscle isotopic niches of burbot and round goby. Overlap increased after accounting for body size, suggesting that size‐related differences in resource use contributed to the observed isotopic separation. Overall, our results indicate partial trophic overlap between invasive round goby and native burbot in the Lower Oder River, with the greatest similarity in prey use occurring among smaller individuals. These findings provide a baseline for the current trophic relationship between the two species. Seasonal and long‐term studies are needed to determine whether the strength and direction of these interactions change over time.