Amino acid N-15 trophic enrichment factors of four large carnivorous fishes

作者：Hoen Danielle K^*; Kim Sora L; Hussey Nigel E; Wallsgrove Natalie J; Drazen Jeffrey C; Popp Brian N

来源：Journal of Experimental Marine Biology and Ecology, 2014, 453: 76-83.

DOI：10.1016/j.jembe.2014.01.006

• Amino acid
• Crimson snapper
• Elasmobranch
• Stable isotope
• Trophic enrichment factor
• Trophic position

Ecosystem-based fisheries management strategies require knowledge of trophic relationships. Trophic position (TP) estimates from compound specific nitrogen isotopic analysis of amino acids (AA-CSIA) show promise as the method can disentangle confounding factors associated with changing delta N-15 values at the base of the food web, but it has yet to be tested in many organisms. This novel technique requires two empirically determined biological parameters: 1)13, the difference in delta N-15 values between glutamic acid (glu) and phenylalanine (phe) in primary producers and 2) trophic enrichment factor (TEF), the N-15 enrichment of glu and phe at each trophic step. Values of beta (3.4%circle.) and TEF (7.6%circle.) have been suggested for animals in aquatic environments: however recent observations indicate that TEF values may be variable, particularly among elasmobranchs where urea retention may alter nitrogen isotope fractionation between glu and phe. To test these uncertainties, we determined TEF values for three species of sharks, sand tiger (Carcharias taurus), lemon (Negaprion brevirostris), and leopard sharks (Triakis semifasciata), and one teleost species, opakapaka (Pristipomoides filamentosus) grown on controlled and well characterized diets for durations ranging from three (T. semifasciata) to over five years (P. filamentosus). TEF values for both elasmobranchs and opakapaka were similar to 2%., significantly lower than TEFs previously reported. These results do not support the hypothesis that urea retention lowers N-15 trophic enrichment between glu and phe in elasmobranchs. Rather, isotopic enrichment factors may be primarily driven by differences in dietary protein quality, leading to distinct TEFs for herbivores (similar to 7.6%.) and carnivores (%26lt;7.6%circle.). We propose a method to calculate TP which integrates different TEF values for herbivores and carnivores. Published by Elsevier B.V.

• 出版日期2014-4