Ecomorphology of Round Goby, Neogobius Melanostomus , Predation on Zebra Mussels, Dreissena Polymorpha

Invasive round goby, Neogobius melanostomus, in the North American Great Lakes, exhibit a diet shift from soft-bodied native prey to hard-bodied invasive zebra mussels, Dreissena polymorpha, at 60-70 mm SL. To feed on zebra mussels attached to substrate via byssal fibers, round gobies use oral jaws to remove zebra mussels and pharyngeal jaws to process. Jaw design and performance may limit the ability of round gobies to feed on zebra mussels. Computer calculated bite force of round gobies correlated to the byssal fiber attachment strength of zebra mussels demonstrates that smaller N. melanostomus are not capable of removing D. polymorpha of substantial size to primarily feed on them. Examination of pharyngeal musculature and dentition concluded that molluscivorous round gobies demonstrated characteristics adapted for eating hard-bodied prey, which were absent in non-molluscivorous round gobies. Results demonstrate the relationship of morphology and performance of round goby jaws to its ontogenctic diet shift.