Abstract

Restricted to low-productivity environments near their thermal maxima, larval tunas may be threatened by warming global temperatures, yet our understanding of how they are constrained is limited. We examined blackfin tuna (Thunnus atlanticus, presumptive) diet and growth in the context of their prey and predators in the Straits of Florida in 2 years with contrasting summer conditions: low temperature (26.7–28.3°C)–high prey and high temperature (28.4–29.0°C)–low prey. In the cooler, high-prey conditions, larvae had 30% faster growth (0.45 mm d⁻¹), fuller guts from predominantly feeding on calanoid copepods, and were 10× more abundant, dominating the larval fish assemblage. In contrast, in warm, low-prey conditions fewer, younger, and slower-growing (0.35 mm d⁻¹) T. atlanticus fed predominantly on nauplii and had less full guts. Modelling individual growth across years revealed that growth peaked at an optimum of 28.5°C (5°C below known thermal maxima in the field) and high densities of predators selectively consumed slower-growing larvae. Low-prey availability may reduce the thermal optima of larvae, as growth and survival are diminished when low prey and high temperature coincide. Our results illustrate the importance of considering food web dynamics with temperature when predicting the response of organisms to ecosystem variability, particularly ongoing climate change.

中文翻译：

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有些人喜欢它，饥饿的金枪鱼不喜欢！温度和浮游生物食物网动力学对热带金枪鱼幼虫生长和饮食的影响

摘要

幼体金枪鱼只能在接近其最高温度的低生产率环境中受到全球温度升高的威胁，但是我们对它们如何受到限制的理解是有限的。我们在2年的夏季条件下对比了佛罗里达海峡中的黑鳍金枪鱼（Thunnus atlanticus，推测性）的饮食和生长情况，并对比了夏季情况：低温（26.7–28.3°C）–高猎物和高温（ 28.4–29.0°C）–低猎物。在凉爽，高产的条件下，幼虫的生长速度加快了30％（0.45 mm d ^-1），主要来自于cal类co足类动物，因此肠道更加饱满，并且幼体的数量增加了10倍，成为幼体鱼群的主要组成部分。相反，在温暖，低捕食的条件下，生长的时间更短，更年轻，更慢（0.35 mm d ^-1）T.atlanticus主要以无节幼体为食，饱腹感较弱。对多年的个体生长进行建模后发现，生长的最适峰值温度为28.5°C（比已知的田间最高温度低5°C），高密度的捕食者有选择地消耗了生长较慢的幼虫。当低猎物和高温同时发生时，低猎物的可获得性可能会降低幼虫的热最佳状态，因为其生长和生存能力会降低。我们的结果表明，在预测生物体对生态系统变异（尤其是持续的气候变化）的响应时，考虑温度影响食物网的重要性。