Do Syntopic Crayfish Partition Trophic Resources? New Insights From Stable Isotopes and Stomach Contents

Stable isotope analyses provide a useful tool to examine the trophic ecology of omnivorous crayfish species. Here, we examined the diets of syntopic crayfish species throughout the eastern side of Oklahoma using the natural abundances of ¹³C and ¹⁵N isotopes and by quantifying stomach contents. We aimed to (1) elucidate whether syntopic crayfish species partition their food resources, (2) determine if potential resource partitioning is site-specific or consistent across localities, and (3) assess the functional and trophic roles of crayfish in streams located in eastern Oklahoma. In accordance with other studies, our stable isotope profiles and mixing models indicate that crayfish are omnivorous and occupy a trophic level between other invertebrate consumers and benthic fishes. Additionally, we found strong support for differences in isotopic signatures among syntopic species. Stable isotope mixing models suggested that larger bodied crayfish species feed more on detritus and fine particulate organic matter, whereas smaller bodied species feed more on macroinvertebrates and fish. Stomach content analysis largely supported the results from the mixing models. Our results suggest that resource partitioning may be a key factor allowing multiple species to inhabit the same location, despite the omnivorous nature of crayfish species.