We conclude that niche SCA and niche SIA do not provide comparable estimates of dietary niche, at least for the three predator species examined. TA) were often correlated however, we did not observe any statistically significant correlations between niche SCA and liver/muscle tissue niche SIA (i.e., Levins' vs. Within-technique comparisons for niche SCA and niche SIA metrics (i.e., SEA vs. Model species were three large-bodied sharks: white (Carcharodon carcharias), dusky (Carcharhinus obscurus), and scalloped hammerhead (Sphyrna lewini). We tested this hypothesis by comparing commonly used dietary niche estimates derived from stomach contents (niche SCA: Levins', Shannon-Wiener's, and Smith's), with those estimated using stable isotopes of liver and muscle tissue. In theory, dietary niche estimates derived from fast turnover rate tissues (e.g., blood plasma and liver) may augment stomach content-derived estimates more agreeably than slower turnover rate tissues (e.g., muscle or fin).
An underlying assumption of this approach is that stable isotopes accurately reflect the dietary breadth of a species over a temporal duration defined by tissue-specific isotopic turnover rates. Calculation of dietary niche characteristics using stable isotopes has become a popular approach to understand the functional role of taxa across food webs.
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