Stable isotope analysis spills the beans about spatial variance in trophic structure in a fish host - parasite system from the Vaal River System, South Africa.

Stable isotope analysis offers a unique tool for comparing trophic interactions and food web architecture in ecosystems based on analysis of stable isotope ratios of carbon (C/C) and nitrogen (N/N) in organisms. were collected from six sites along the Vaal River, South Africa and were assessed for ectoparasites and endoparasites. (Copepoda), and (Cestoda), and larval sp. (Nematoda) were collected from the gills, intestine and mesenteries, respectively. Signatures of δC and δN were analysed in host muscle tissue and parasites using bulk stable isotope analysis. Variable stable isotope enrichment between parasites and host were observed; and the host shared similar δN signatures and endoparasites being depleted in δC and δN relative to the host. Differences in stable isotope enrichment between parasites could be related to the feeding strategy of each parasite species collected. Geographic and spatial differences in enrichment of stable isotopes observed in hosts were mirrored by parasites. As parasites rely on a single host for meeting their nutritional demands, stable isotope variability in parasites relates to the dietary differences of host organisms and therefore variations in baseline stable isotope signatures of food items consumed by hosts.