The invasive round goby Apollonia melanostomus (formerly Neogobius melanostomus) has negatively affected benthic fish communities throughout the Great Lakes. In this study, we compared the sensory physiology and behavior of three native species-slimy sculpin Cottus cognatus, spoonhead sculpin C. ricei, and logperch Percina caprodes-with those of the round goby to determine the mechanisms that allow the round goby to dominate native fish. The reaction and strike distances of the four species were examined during predator-prey trials using natural amphipod prey Gammarus spp. under varying light intensities (0-130 lx) to compare input from the mechanosensory lateral line and visual systems. Trials in the dark (0 lx) indicated that the sculpins and the round goby had similar lateral line sensitivity. However, all three native species had a significant advantage in reaction and strike distance over the round goby at higher light intensities. Interspecific resource competition was assessed by pairing a round goby with a native fish in an artificial stream. Round gobies gained significantly more weight than the native fishes during all trials. Slimy sculpins were able to maintain their weight in the presence of the round goby; however, spoonhead sculpins and logperch lost a significant amount of weight during the trials. These experiments indicate that although the round goby does not possess an inherent sensory advantage, it can dominate resources and outcompete native fish. Thus, round gobies may pose risks for a wide variety of native benthic fishes.
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We thank Tom Hrabik, Michael Lynch, and Jamie Sloan for insightful comments on the manuscript. We are grateful to Dennis Pratt, Daniel Yule, Lori Evrard, and Lynn Wright for providing research animals, and Celeste Lindquist and Nicole Siegler for field assistance. Funding was provided by Visualization and Digital Image Laboratory at the University of Minnesota, Duluth. This work is the result of research sponsored by the Minnesota Sea Grant College Program supported by the NOAA office of Sea Grant, U.S. Department of Commerce. The U.S. Government is authorized to reproduce and distribute reprints for government purposes, not withstanding any copyright notation that may appear hereon. This paper is journal reprint No. 542 of the Minnesota Sea Grant College Program.
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