The influence of diet composition and tissue type on the stable isotope incorporation patterns of a small‐bodied southern African minnow Enteromius anoplus (Cypriniformes, Cyprinidae)

Rationale In trophic ecology, the use of stable isotope data relies on the general understanding of isotope turnover rates and diet‐to‐tissue discrimination factors (DTDFs). Recent studies on the application of stable isotope data have shown that isotope turnover rates and DTDFs can be influenced by many factors, including diet composition and tissue type. This study investigated the influence of diet composition and tissue type on stable isotope incorporation patterns in a small‐bodied African minnow, the chubbyhead barb Enteromius anoplus. Methods The isotopic incorporation patterns of carbon (δ13C values) and nitrogen (δ15N values) into white muscle and caudal fin tissues of the chubbyhead barb were examined using two isotopically different diets. Controlled‐diet stable isotope feeding trials using a fishmeal‐based diet (diet 1) and a soya‐based diet (diet 2) were conducted over a 180‐day period for the chubbyhead barb. Results The two diets had contrasting isotopic incorporation patterns: diet 1 was associated with progressively high δ13C and δ15N values, whereas diet 2 was associated with progressively low δ13C and δ15N values over time for both muscle and fin tissues. The δ13C turnover rates were similar for both tissues (56 and 61 days), whereas the δ15N turnover rates differed between fin and muscle tissue in both diets (diet 1 = 4 and 130 days, and diet 2 = 72 and 300 days, respectively). The DTDFs were similar for both tissues in diet 1 (Δ13C: −3.96 to −2.62‰, Δ15N: 1.98 to 2.61‰) and diet 2 (Δ13C: 4.05 to 5.24‰, Δ15N: 8.45 to 9.69‰). Conclusions These results suggest that fin tissue can potentially be used as an alternative for muscle tissue in food web studies with a reasonable level of error. The isotopic turnover rate and DTDFs estimates for E. anoplus, however, require consideration of diet composition because different diets may differ in their isotopic incorporation patterns.