Climate change is anticipated to have multiple consequences for aquatic ectotherms. Warming temperatures, for example, are predicted to reduce body size in many fish species. Smaller sizes may be caused by physiological constraints associated with respiration, life-history responses to faster growth and concomitant earlier age at maturity, and interactive effects of fishing and climate change on evolution. Here, using a phylogenetically broad dataset of 100 marine species, we explore how natural mortality might respond to a 10% reduction in asymptotic length (L_∞). We find that this decrease in size (predicted to be associated with a 1 °C ocean temperature increase) is likely to exacerbate natural mortality (M) for most marine fishes, albeit not all, on Canada’s Scotian Shelf. Across all bony fishes (Actinopterygii), the median proportional increase in natural mortality is 10.5%; limited data suggest that chondrichthyans are less affected. Smaller-bodied fish species experienced greater absolute increases in M than larger-bodied species. Among commercially exploited species for which sufficient data are available, M is predicted to increase by 0.14 for Atlantic mackerel (Scomber scombrus), 0.08 for Silver hake (Merluccius bilinearis), 0.04 for Atlantic herring (Clupea harengus), and 0.02 for Atlantic cod (Gadus morhua) and Pollock (Pollachias virens). The present study offers a simple means of exploring the mortality consequences of reduced body size hypothesized to result from globally warming water temperatures, thus contributing a potential tool for climate-change vulnerability assessments of marine fishes.

预计气候变化将对水生变温动物产生多重后果。例如，预计气温升高会减少许多鱼类的体型。较小的尺寸可能是由与呼吸相关的生理限制、对更快生长和伴随的较早成熟年龄的生活史反应以及捕鱼和气候变化对进化的交互影响造成的。在这里，我们使用 100 种海洋物种的系统发育广泛数据集，探索自然死亡率如何对渐近长度 ( L _∞ )减少 10% 做出反应。我们发现这种尺寸的减小（预计与海洋温度升高 1°C 相关）可能会加剧自然死亡率（M) 对于加拿大苏格兰大陆架上的大多数海洋鱼类，尽管不是全部。在所有硬骨鱼（Actinopterygii）中，自然死亡率的中位数比例增加为 10.5%；有限的数据表明软骨鱼类受到的影响较小。体型较小的鱼类比体型较大的鱼类经历了更大的M绝对增加。在有足够数据可用的商业开发物种中，预计大西洋鲭鱼 ( Scomber scombrus ) 的M增加 0.14 ，银鳕鱼 ( Merluccius bilinearis )增加0.08 ，大西洋鲱 ( Clupea harengus ) 增加0.04，大西洋鳕鱼 ( Clupea harengus ) 增加 0.02 Gadus morhua ) 和 Pollock ( Pollachias virens）。本研究提供了一种简单的方法来探索假设由全球变暖的水温导致的体型减小的死亡率后果，从而为海洋鱼类的气候变化脆弱性评估提供了一个潜在的工具。