Gallagher Austin J, Skubel Rachel A, Pethybridge Heidi R, Hammerschlag Neil
Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL, USA.
Fish Ecology and Conservation Physiology Laboratory, Department of Biology and Institute of Environmental Science, Carleton University, Ottawa, ON, Canada.
Conserv Physiol. 2017 Feb 14;5(1):cox002. doi: 10.1093/conphys/cox002. eCollection 2017.
Evaluating how predators metabolize energy is increasingly useful for conservation physiology, as it can provide information on their current nutritional condition. However, obtaining metabolic information from mobile marine predators is inherently challenging owing to their relative rarity, cryptic nature and often wide-ranging underwater movements. Here, we investigate aspects of energy metabolism in four free-ranging shark species ( = 281; blacktip, bull, nurse, and tiger) by measuring three metabolic parameters [plasma triglycerides (TAG), free fatty acids (FFA) and cholesterol (CHOL)] via non-lethal biopsy sampling. Plasma TAG, FFA and total CHOL concentrations (in millimoles per litre) varied inter-specifically and with season, year, and shark length varied within a species. The TAG were highest in the plasma of less active species (nurse and tiger sharks), whereas FFA were highest among species with relatively high energetic demands (blacktip and bull sharks), and CHOL concentrations were highest in bull sharks. Although temporal patterns in all metabolites were varied among species, there appeared to be peaks in the spring and summer, with ratios of TAG/CHOL (a proxy for condition) in all species displaying a notable peak in summer. These results provide baseline information of energy metabolism in large sharks and are an important step in understanding how the metabolic parameters can be assessed through non-lethal sampling in the future. In particular, this study emphasizes the importance of accounting for intra-specific and temporal variability in sampling designs seeking to monitor the nutritional condition and metabolic responses of shark populations.
评估捕食者如何代谢能量对保护生理学越来越有用，因为它可以提供有关其当前营养状况的信息。然而，从活动的海洋捕食者那里获取代谢信息具有内在的挑战性，这是由于它们相对稀少、生性隐秘，且经常在水下大范围活动。在这里，我们通过非致命性活检采样测量三个代谢参数[血浆甘油三酯（TAG）、游离脂肪酸（FFA）和胆固醇（CHOL）]，来研究四种自由游动鲨鱼物种（n = 281；黑鳍鲨、公牛鲨、护士鲨和虎鲨）的能量代谢方面。血浆TAG、FFA和总CHOL浓度（以毫摩尔每升计）在种间存在差异，并且随季节、年份变化，在一个物种内也随鲨鱼体长而变化。TAG在活动较少的物种（护士鲨和虎鲨）的血浆中最高，而FFA在能量需求相对较高的物种（黑鳍鲨和公牛鲨）中最高，CHOL浓度在公牛鲨中最高。尽管所有代谢物的时间模式在物种间各不相同，但似乎在春季和夏季出现峰值，所有物种的TAG/CHOL比值（一种状况指标）在夏季呈现出明显的峰值。这些结果提供了大型鲨鱼能量代谢的基线信息，并且是未来理解如何通过非致命采样评估代谢参数的重要一步。特别是，本研究强调了在旨在监测鲨鱼种群营养状况和代谢反应的采样设计中，考虑种内和时间变异性的重要性。
