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Fin‐icky samples: an assessment of shark fin as a source material for stable isotope analysis
Author(s) -
Hussey Nigel E.,
Chapman Demian D.,
Donnelly Erin,
Abercrombie Debra L.,
Fisk Aaron T.
Publication year - 2011
Publication title -
limnology and oceanography: methods
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.898
H-Index - 72
ISSN - 1541-5856
DOI - 10.4319/lom.2011.9.524
Subject(s) - fin , fish fin , dorsal fin , carcharhinus , biology , pelagic zone , population , reef , ecology , fishery , fish <actinopterygii> , materials science , demography , sociology , composite material
Analyzing stable isotopes (SI: δ 15 N and δ 13 C) in a new tissue requires rigorous testing before its general application in examining aspects of animal ecology. Shark fin provides a novel, minor invasive source material, which is important considering the conservation status of many large sharks. Fin, however, is not a single tissue but composed of multiple tissues, primarily skin and cartilage. This may complicate the interpretation of SI, as fin can be sampled from multiple fins and different regions of a fin from an individual. Here, we examined the variation in δ 15 N and δ 13 C with sample location on the anal fin of Caribbean reef sharks ( Carcharhinus perezi ). Values of δ 15 N and δ 13 C were highly correlated across sampling locations indicating that mean population or size class fin SI data would be reliable. At the individual level, large variation in δ 15 N and δ 13 C between anal fin sampling locations indicates that the varying proportional contributions of tissues would complicate individual level analyses. For three pelagic shark species, dorsal fin δ 13 C values were consistently higher than δ 13 C muscle tissue values, identifying tissue‐specific diet discrimination factors. This would confound multiple tissue studies that assume that SI values across tissues will be equal if the animal is in equilibrium with its diet. Proposed sampling protocols for fin material will negate many of these issues, but caution is warranted for comparisons of SI data between shark fin and other tissues or across species until the isotope dynamics of fin have been experimentally validated.