Date of Award
Master of Science
Black Carp (Mylopharyngodon piceus) is an invasive fish species native to Asia that has become increasingly abundant within the Mississippi River Basin during the past decade. Originally introduced to control snails that are an intermediate host for trematode parasites of fishes in aquaculture ponds, Black Carp are now present in several rivers in the U.S. and represent a potential threat to threatened and endangered mussel populations. Black Carp have historically been classified as molluscivores; however, a recent study that examined gut contents of Black Carp collected from the Mississippi River Basin indicated that Black Carp are opportunistic consumers that prey upon a wide variety of invertebrates and are flexible in their feeding modes. Despite the potential for Black Carp to compete with native riverine fish species for invertebrate prey, only one published study has compared Black Carp trophic position with that of native fishes in a small portion of the Black Carp’s invaded range. Therefore, the objectives of this study were to assess trophic overlap between Black Carp and two fish species native to the Mississippi River Basin using isotopic niche analysis and gut contents analysis. Dorsal muscle tissue samples were collected from Black Carp, Freshwater Drum (Aplodinotus grunniens), and Blue Catfish (Ictalurus furcatus) and analyzed for δ13C and δ15N to assess each species’ isotopic niche. Freshwater Drum and Blue Catfish gut contents were also removed and analyzed and compared to published Black Carp stomach contents data. Gut contents analysis indicated differences in diet composition between Black Carp and the two native fish species. Chironomidae had the highest frequency of occurrence (67%) and percent of taxa by number (47%) for Freshwater Drum. Trichoptera had the highest frequency of occurrence (58%) and percent of taxa by number (30%) for Blue Catfish, and Gastropoda had the highest frequency of occurrence (16.5%) of any specific prey taxa for Black Carp. Black Carp showed low isotopic niche overlap (≤47%) with both native species when muscle tissue δ13C and δ15N data from all fish collection locations were combined and when assessment of isotopic niches was restricted to the subset of locations where all three species were collected. Isotopic niche overlap was also low (10-48%) between Black Carp and both native species when isotopic niches were compared at individual collection locations. Intraspecific isotopic niche overlap among fish collection locations was highly variable (0-69%) within each of the three species, highlighting the need to assess interspecific isotopic niche overlap by collection location. Broad isotopic niches exhibited by Black Carp in the Mississippi River and tributaries are indicative of substantial trophic diversity among individuals and use of multiple basal energy sources, consistent with a recently published study which found that Black Carp diet composition differed among individuals and that Black Carp consumed a variety of invertebrates, including non-benthic taxa.
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