A field observation of rotational feeding by Neogobius melanostomus

Video documentation was obtained of the invasive benthic fish, Neogobius melanostomus, the round goby, feeding on crushed dreissenid mussels at a depth of 12 m in Georgian Bay of Lake Huron, Canada. Gobies used rotational or twist feeding to tear away particles from crushed mussels. At least 43 examples of this feeding maneuver occur in the video. Up to 120 round gobies/m2 were visible at a time in the video. Mean standard length of gobies was 37 mm. Mean standard length of fish exhibiting twist feeding was larger, 48 mm. Mean size of intact mussels in visible clusters was about 10×20 mm, a size which exceeds the gape width of the largest gobies observed in the video. Gobies are known to use twisting to wrest small attached mussels from the substrates which can be crushed by their pharyngeal teeth. We surmise the behavior observed in the video is an opportunistic manifestation of this inherent behavioral adaptation to exploit a temporary windfall of food.