Analysis food habits and pharyngeal morphology of round gobies (Neogobius melanostomus) in Fairview Gravel Pit (Erie Co., PA)

The round goby (Neogobius melanostomus) is a non-native fish from the Ponto-Caspian region of Eurasia that has successfully colonized the North American Great Lakes. It has received considerable attention in terms of its ecological role and impacts to the ecosystems it has invaded. Round gobies possess robust, molar-like pharyngeal structures that are well-suited to crushing hard-bodied prey such as dreissenid mussels, which comprise a large portion of their diet when present. Published work from our laboratory described pharyngeal morphology of round gobies from sites where dreissenids are present (Presque Isle Bay) and absent (Fairview Gravel Pit) and found more robust pharyngeal structures in gobies from Presque Isle Bay. That analysis, however, was limited to linear and area measurements, and only qualitatively described site and goby-size-related differences in pharyngeal shape. This study was designed to quantify food habits and pharyngeal morphology of 21 round gobies from the Fairview Gravel Pit that ranged in size from 43 to 108 mm total length (TL). Stomach contents were identified to broad taxonomic levels to determine if food habits changed in terms of composition of hard-bodied prey as round gobies increased in length. Lower pharyngeals were dissected, fixed in 10% formalin, cleared, and stained, then photographed. Shapes were assessed through geometric morphometric analyses of pharyngeal outlines. Ongoing work with this sample of round gobies will characterize the intestinal microbiome to determine if the microbiome changes with fish length and food habits.