Department of Biological Sciences, California State University Long Beach, Long Beach, California, United States of America.
School of Statistics, University of Minnesota, Minneapolis, Minnesota, United States of America.
PLoS One. 2022 Jun 9;17(6):e0268914. doi: 10.1371/journal.pone.0268914. eCollection 2022.
White sharks (Carcharodon carcharias) are the largest shark species to display regional endothermy. This capability likely facilitates exploitation of resources beyond thermal tolerance thresholds of potential sympatric competitors as well as sustained elevated swim speeds, but results in increased metabolic costs of adults, which has been documented in different studies. Little, however, is known of the metabolic requirements in free-swimming juveniles of the species, due to their large size at birth and challenges in measuring their oxygen consumption rates in captivity. We used trilateration of positional data from high resolution acoustic-telemetry to derive swim speeds from speed-over-ground calculations for eighteen free-swimming individual juvenile white sharks, and subsequently estimate associated mass-specific oxygen consumption rates as a proxy for field routine metabolic rates. Resulting estimates of mass-specific field routine metabolic rates (368 mg O2 kg-1 h-1 ± 27 mg O2 kg-1 h-1 [mean ± S.D.]) are markedly lower than those reported in sub-adult and adult white sharks by previous studies. We argue that median cruising speeds while aggregating at nearshore nursery habitats (0.6 m s-1 [mean ± S.E = 0.59 ± 0.001], 0.3 TL s-1) are likely a feature of behavioral strategies designed to optimize bioenergetic efficiency, by modulating activity rates in response to environmental temperature profiles to buffer heat loss and maintain homeostasis. Such behavioral strategies more closely resemble those exhibited in ectotherm sharks, than mature conspecifics.
白鲨（Carcharodon carcharias）是显示区域内温血的最大鲨鱼物种。这种能力可能有助于利用潜在共生竞争者的热耐受阈值以外的资源，以及维持较高的游泳速度，但会导致成年鲨鱼的代谢成本增加，这在不同的研究中都有记录。然而，由于它们出生时体型巨大，以及在圈养中测量其耗氧量的挑战，因此对于该物种自由游动的幼鲨的代谢需求知之甚少。我们使用来自高分辨率声学遥测的位置数据三边测量法，从地面速度计算得出十八条自由游动的幼年白鲨的游泳速度，然后估计相关的比耗氧量作为现场常规代谢率的替代指标。由此得出的比耗氧量（368mg O2 kg-1 h-1 ± 27mg O2 kg-1 h-1 [平均值 ± S.D.])明显低于以前的研究报告的亚成体和成年白鲨的比耗氧量。我们认为，在近岸育苗栖息地聚集时的中位数巡航速度（0.6m s-1 [平均值 ± S.E. = 0.59 ± 0.001]，0.3TL s-1）可能是一种旨在优化生物能量效率的行为策略的特征，通过调节活动率来响应环境温度曲线，以缓冲热量损失并维持体内平衡。这种行为策略更类似于那些在冷血鲨鱼中表现出的策略，而不是成熟的同类。
