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Trophic size‐structure of sailfish Istiophorus platypterus in eastern Taiwan estimated by stable isotope analysis
Author(s) -
Tsai C.N.,
Chiang W.C.,
Sun C.L.,
Shao K.T.,
Chen S.Y.,
Yeh S.Z.
Publication year - 2014
Publication title -
journal of fish biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.672
H-Index - 115
eISSN - 1095-8649
pISSN - 0022-1112
DOI - 10.1111/jfb.12290
Subject(s) - trophic level , biology , isotope analysis , δ13c , pelagic zone , stable isotope ratio , δ15n , isotopes of nitrogen , ecology , zoology , physics , quantum mechanics
To examine trophic dynamics over different size classes, an isotopic study of sailfish Istiophorus platypterus life‐history stages was carried out. Samples were collected from eastern Taiwan and the South China Sea during April 2009 and February 2012. A total of 263 samples (111–245 cm, lower jaw fork length, L LJFL ) were examined for changes in trophic structure in relation to L LJFL by using stable isotope analysis of carbon ( δ 13 C ) and nitrogen ( δ 15 N ). The δ 15 N values for I. platypterus ranged from 7·51 to 14·19‰ (mean ± s.d . = 12·06 ± 1·16‰) and the δ 13 C values ranged from −22·04 to −15·48‰ (mean ± s.d . = −17·62 ± 1·10‰). The δ 15 N values were positively dependent on L LJFL ( r 2 = 0·377), whereas δ 13 C were negatively dependent on L LJFL ( r 2 = 0·063). There were significantly different seasonal changes in nitrogen and carbon isotopic concentration, but no significant differences in concentrations between eastern Taiwan and the South China Sea were reported. The trophic level ( T L ) of each L LJFL class was correlated, starting from 2·84 T L for size class I ( L LJFL < 140 cm) and reaching 5·03 T L for size class VI ( L LJFL > 221 cm). The mean ± s.d . T L was 4·43 ± 0·19 for all samples. The results reveal that I. platypterus occupies a wide range of trophic levels and different size classes occupy different trophic positions in the pelagic ecosystem.