Intra‐species variability in foraging strategies may be common, which has significant implications for efforts to understand and manage enigmatic species like the whale shark Rhincodon typus. The ecological relevance of differences in tissue isotopes within and between individuals in the context of foraging however depends on understanding tissue turnover times and carbon (Δ¹³C) and nitrogen (Δ¹⁵N) discrimination, which can vary with physiology, metabolism, and diet quality. Here, we examine isotope dynamics in captive R. typus as a basis for enhanced ecological insights into wild populations of the world's largest fish and other enigmatic species. A variable diet, principally consisting of two krill (Euphausia pacifica and Euphausia superba) provided an average of 48 ± 20 MJ/d (mean ± SD), or 2.7 ± 1.3 times basal metabolic requirements. On this diet, in agreement with allometric relationships, large body sizes (3,000–4,000 kg) were matched by slow plasma and cartilage turnover rates (empirically derived as 9 months and 3 yr, respectively), which provide tissue‐specific limits on the timescales over which we can isotopically detect diet changes in this species. Average diet‐to‐tissue discrimination showed significant variation between tissues (plasma and cartilage), and among growing and fasting individuals (Δ¹³C range, 1.5 to 5.5‰; Δ¹⁵N range, −0.1 to 2.9‰). Assimilation rates increased with temperature and were higher for the smaller E. pacifica (15 ± 2 mm) than E. superba (48 ± 2 mm). Growth significantly lowered both Δ¹⁵N_plasma and Δ¹⁵N_cartilage, with inappetence markedly reducing Δ¹⁵N_plasma and Δ¹³C_plasma, as well as significantly altering blood biochemistry. Captive findings facilitated the first robust multi‐tissue growth‐ and nutrition‐corrected isotope analysis of a wild R. typus population, suggesting individual foraging specialization on low trophic level mid‐ocean or coastal prey. Long‐term fasting during ocean‐basin‐scale migrations may be common and such metabolic effects should be carefully quantified when isotopically assessing intra‐species foraging differences. The metabolically constrained multi‐tissue, multi‐isotope approach described can facilitate ecological insights that are indispensable for effective conservation and management of globally threatened, but poorly understood, species by identifying differences in key foraging areas and target prey within and between individuals.

中文翻译：

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使用多组织，多同位素方法增强对世界上最大鱼类觅食专业化的认识

种内觅食策略的变异性可能很常见，这对于努力理解和管理诸如鲸鲨Rhincodon typus之类的神秘物种具有重要意义。在组织差异的生态相关性内和在然而觅食的上下文中的个体之间同位素取决于理解组织周转时间和碳（Δ ¹³ C）和氮（Δ ¹⁵ N）鉴别，其可以与生理学，代谢和饮食变化质量。在这里，我们研究了圈养鼠伤寒沙门氏菌的同位素动态，以此作为增强对世界最大鱼类和其他神秘物种的野生种群的生态洞察力的基础。可变饮食，主要由两个磷虾（Euphausia pacifica）组成和Euphausia superba的平均代谢能力为48±20 MJ / d（平均±SD）或2.7±1.3倍。在这种饮食中，与异速关系密切一致，大体重（3,000–4,000公斤）与缓慢的血浆和软骨周转率（分别根据经验得出分别为9个月和3年）相匹配，这为时标提供了组织特定的限制。通过它我们可以同位素检测该物种的饮食变化。平均饮食到组织鉴别表现出组织（等离子体和软骨），以及生长和空腹个体间之间（Δ显著变化¹³ ℃范围内为1.5〜5.5‰，;Δ ¹⁵ N档，-0.1〜2.9‰）。同化率随温度的升高而增加，较小的E. pacifica的同化率更高（15±2毫米）比E. superba（48±2毫米）。生长显著降低两个Δ ¹⁵ Ñ_血浆和Δ ¹⁵ Ñ_软骨，与食欲不振显着减少Δ ¹⁵ Ñ_血浆和Δ ¹³ Ç_等离子体，以及显著改变血液生物化学。圈养发现促进了第一鲁棒多组织生长-和野生的营养校正同位素分析R. typus人口，这表明在低营养水平的海洋中部或沿海猎物上进行个体觅食专长。海洋盆地规模迁徙期间长期禁食可能很常见，当同位素评估种内觅食差异时应仔细量化这种代谢作用。所描述的受代谢限制的多组织，多同位素方法可以通过识别关键觅食区和目标捕食者之间以及个体之间的差异来促进生态学见解，这对于有效保护和管理全球受威胁但知之甚少的物种是必不可少的。