Spatio-temporal description of spottail shiner (Notropis hudsonius) fatty acid profiles in Lake Michigan's southern basin

Abstract

On-going ecosystem alterations within Lake Michigan have drastically transformed species interactions and food-web assembly. Description of trophic interactions across broad spatial regions is likely necessary to fully appreciate the structure of this emerging food web. Spottail shiners, Notropis hudsonius, are numerically abundant in the nearshore zone of Lake Michigan, but their trophic interactions are under-described. To that end, we described fatty acid profiles of spottail shiner through spring, summer, and fall across western and eastern shorelines of Lake Michigan's southern basin. Fatty acids, used as dietary tracers, suggested a shift from benthic-based diets in spring to more pelagic-associated diets in summer and a reversal in fall. When time lag of fatty acid accumulation is accounted for in interpretations, diets likely follow spring plankton and summer/fall benthic invertebrate maxima. Fatty acid profiles also indicated differences in diet composition based on geographic location, with benthic tracers more prevalent among spottail shiner inhabiting the western shoreline. These interpretations were generally supported by stomach content data, with high Chironomidae consumption in spottail shiners from western waters. The presence of Coleoptera, Hymenoptera, and Odonata in spottail shiner stomach contents throughout the lake highlights its reliance on nearshore and potentially inshore areas. This study offers one of the most spatially broad depiction of spottail shiner foraging habits in Lake Michigan.