Abstract：
Levels of dissolved oxygen in open ocean and coastal waters are decreasing (ocean deoxygenation), with poorly understood effects on marine megafauna. All of the more than 1000 species of elasmobranchs (sharks, skates, and rays) are obligate water breathers, with a variety of life-history strategies and oxygen requirements. This review demonstrates that although many elasmobranchs typically avoid hypoxic water, they also appear capable of withstanding mild to moderate hypoxia with changes in activity, ventilatory responses, alterations to circulatory and hematological parameters, and morphological alterations to gill structures. However, such strategies may be insufficient to withstand severe, progressive, or prolonged hypoxia or anoxia where anaerobic metabolic pathways may be used for limited periods. As water temperatures increase with climate warming, ectothermic elasmobranchs will exhibit elevated metabolic rates and are likely to be less able to tolerate the effects of even mild hypoxia associated with deoxygenation. As a result, sustained hypoxic conditions in warmer coastal or surface-pelagic waters are likely to lead to shifts in elasmobranch distributions. Mass mortalities of elasmobranchs linked directly to deoxygenation have only rarely been observed but are likely underreported. One key concern is how reductions in habitat volume as a result of expanding hypoxia resulting from deoxygenation will influence interactions between elasmobranchs and industrial fisheries. Catch per unit of effort of threatened pelagic sharks by longline fisheries, for instance, has been shown to be higher above oxygen minimum zones compared to adjacent, normoxic regions, and attributed to vertical habitat compression of sharks overlapping with increased fishing effort. How a compound stressor such as marine heatwaves alters vulnerability to deoxygenation remains an open question. With over a third of elasmobranch species listed as endangered, a priority for conservation and management now lies in understanding and mitigating ocean deoxygenation effects in addition to population declines already occurring from overfishing.
摘要：
公海和沿海水域的溶解氧水平正在下降（海洋脱氧），对海洋大型动物的影响知之甚少。所有1000多种弹枝(鲨鱼，溜冰鞋,和光线)是强制性的水呼吸器，有各种生活史策略和氧气需求。这篇综述表明，尽管许多弹性膜通常避免缺氧水，随着活动的变化，它们似乎也能够承受轻度至中度的缺氧，通气反应，循环和血液学参数的改变，和g结构的形态改变。然而,这样的策略可能不足以承受严重的，进步,或延长的缺氧或缺氧，其中厌氧代谢途径可以在有限的时间内使用。随着气候变暖，水温升高，放热弹性膜将表现出升高的代谢率，并且可能难以忍受甚至与脱氧相关的轻度缺氧的影响。因此,在温暖的沿海或表层浮游水域中，持续的低氧条件可能导致弹性分支分布的变化。与脱氧直接相关的弹性膜的大量死亡率很少被观察到，但可能被低估了。一个关键的问题是，由于脱氧导致的缺氧扩大，栖息地体积的减少将如何影响弹性鱼和工业渔业之间的相互作用。延绳钓渔业每单位努力捕捞受威胁的中上层鲨鱼，例如,与邻近的区域相比，已经证明高于氧气最小区域，常氧地区,并归因于鲨鱼的垂直栖息地压缩与增加的捕捞努力重叠。海洋热浪等复合压力源如何改变脱氧的脆弱性仍然是一个悬而未决的问题。超过三分之一的弹枝物种被列为濒危物种，现在，保护和管理的优先事项是理解和减轻海洋脱氧效应，以及过度捕捞已经造成的种群减少。
