Trophic ecology of the North American crayfish genus Barbicambarus Hobbs, 1969 (Decapoda: Astacoidea: Cambaridae): evidence for a unique relationship between body size and trophic position

Knowledge regarding the trophic ecology of a species is invaluable in conservation planning. Trophic ecology of crayfishes, however, is largely generalized across taxa, with a significant lack of species-specific data. Two such data deficient species are the bottlebrush crayfishes, Barbicambarus cornutus (Faxon, 1884), and the Tennessee bottlebrush crayfish, Barbicambarus simmonsi Taylor & Schuster, 2010. To obtain data on the trophic position of these species, we collected specimens of the two sympatric species and representative food groups in the Green River system in Kentucky, USA and the Shoal Creek drainage in Tennessee and Alabama, USA during the summer of 2013. We aimed to analyze the trophic position and diet of both species through stable isotope and gut content analyses. Our work indicates that the two species of Barbicambarus occupy a higher trophic position than other sympatric species of crayfishes, possibly occupying a higher-level functional role as predator within their respective systems. Gut content analyses showed no clear evidence of a higher-level predator diet, but did include tissues of animals at a higher trophic level. The stable isotope analysis showed a significant increase in trophic level with increasing size, a pattern not seen in any other species in this study. These results indicate Barbicambarus species have a trophic ecology that differs from those reported in the literature for other crayfish species.