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Uncertainties associated with trophic discrimination factor and body size complicate calculation of δ 15 N‐derived trophic positions in Arapaima sp.
Author(s) -
Jacobi Cristina Mariana,
Villamarín Francisco,
Jardine Timothy D.,
Magnusson William Ernest
Publication year - 2020
Publication title -
ecology of freshwater fish
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 55
eISSN - 1600-0633
pISSN - 0906-6691
DOI - 10.1111/eff.12553
Subject(s) - trophic level , biology , ecology , predation , isotope analysis , food web , trophic state index , food chain , nutrient , phytoplankton
Abstract Stable isotope ratios of nitrogen (δ 15 N) have been used to estimate trophic position (TP) of organisms due to the predictable enrichment of nitrogen‐15 in consumer tissues relative to their diet. We explored estimates of trophic position using liver and muscle δ 15 N and stomach content analysis in a broad size range of Arapaima sp. from Amazonian floodplain lakes. Estimates of TP based on liver δ 15 N were more closely related to the stomach content data than estimates based on muscle δ 15 N, possibly because of the higher turnover of nitrogen in liver. Total length and season explained most of the variation in TP values estimated from δ 15 N, showing that they have more effect than prey trophic position on δ 15 N values. The TP estimated by identification of stomach content was 3.6 and was unrelated to the size of the arapaima. This highlights the need for a better understanding of the factors that affect values of δ 15 N and stomach content analysis is still needed to unravel the trophic ecology of predatory fishes.