Trophic size‐structure of sailfish Istiophorus platypterus in eastern Taiwan estimated by stable isotope analysis. Issue 2 (22nd January 2014)

• Record Type: Journal Article
• Authors: Tsai, C.‐N.; Chiang, W.‐C.; Sun, C.‐L.; Shao, K.‐T.; Chen, S.‐Y.; Yeh, S.‐Z.
• Is Part Of: Journal of fish biology. Volume 84:Issue 2(2014)
• Page Start: 354
• Page End: 371
• Publication Date: 2014-01-22
• Subjects: Fishes -- Periodicals; Fishes -- Great Britain -- Periodicals; 597
• DOI: 10.1111/jfb.12290
• Languages: English
• ISSNs: 0022-1112

Abstract

<abstract abstract-type="main" id="jfb12290-abs-0001"> <title> <x xml:space="preserve">Abstract</x> </title> <p id="jfb12290-para-0001">To examine trophic dynamics over different size classes, an isotopic study of sailfish <italic>Istiophorus platypterus</italic> 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, <italic>L</italic><sub>LJFL</sub>) were examined for changes in trophic structure in relation to <italic>L</italic><sub>LJFL</sub> by using stable isotope analysis of carbon (δ<sup>13</sup>C) and nitrogen (δ<sup>15</sup>N). The δ<sup>15</sup>N values for <italic>I. platypterus</italic> ranged from 7·51 to 14·19‰ (mean ± <sc>s.d</sc>. = 12·06 ± 1·16‰) and the δ<sup>13</sup>C values ranged from −22·04 to −15·48‰ (mean ± <sc>s.d</sc>. = −17·62 ± 1·10‰). The δ<sup>15</sup>N values were positively dependent on <italic>L</italic><sub>LJFL</sub> (<italic>r</italic><sup>2</sup> = 0·377), whereas δ<sup>13</sup>C were negatively dependent on <italic>L</italic><sub>LJFL</sub> (<italic>r</italic><sup>2</sup> = 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 (<italic>T</italic><sub>L</sub>) of each <italic>L</italic><sub>LJFL</sub> class was correlated, starting from 2·84 <italic>T</italic><sub>L</sub> for size class I (<italic>L</italic><sub>LJFL</sub> < 140 cm) and reaching 5·03 <italic>T</italic><sub>L</sub> for size class VI (<italic>L</italic><sub>LJFL</sub> > 221 cm). The mean ± <sc>s.d</sc>. <italic>T</italic><sub>L</sub> was 4·43 ± 0·19 for all samples. The results reveal that <italic>I. platypterus</italic> occupies a wide range of trophic levels and different size classes occupy different trophic positions in the pelagic ecosystem.</p> </abstract>