National Research Council Postdoctoral Fellow for Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla Shores Drive, La Jolla, CA, 92037, USA.
Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla Shores Drive, La Jolla, CA, 92037, USA; Southall Environmental Associates, Inc., Soquel Dr., Aptos, CA, 95003, USA.
Curr Biol. 2021 Jul 26;31(14):3174-3179.e3. doi: 10.1016/j.cub.2021.04.067. Epub 2021 Jun 3.
Whales are now largely protected from direct harvest, leading to partial recoveries in many previously depleted species. However, most populations remain far below their historical abundances and incidental human impacts, especially vessel strikes and entanglement in fishing gear, are increasingly recognized as key threats. In addition, climate-driven changes to prey dynamics are impacting the seasonal foraging grounds of many baleen whales. In many cases these impacts result directly in mortality. But it is less clear how widespread and increasing sub-lethal impacts are affecting life history, individual fitness, and population viability. We evaluated changes in body lengths of North Atlantic right whales (NARW) using aerial photogrammetry measurements collected from crewed aircraft and remotely operated drones over a 20-year period (Figure 1). NARW have been monitored consistently since the 1980s and have been declining in abundance since 2011 due primarily to deaths associated with entanglements in active fishing gear and vessel strikes. High rates of sub-lethal injuries and individual-level information on age, size and observed entanglements make this an ideal population to evaluate the effects that these widespread stressors may have on individual fitness. We find that entanglements in fishing gear are associated with shorter whales, and that body lengths have been decreasing since 1981. Arrested growth may lead to reduced reproductive success and increased probability of lethal gear entanglements. These results show that sub-lethal stressors threaten the recoveries of vulnerable whale populations even in the absence of direct harvest.
鲸鱼现在在很大程度上受到直接捕捞的保护，这导致了许多以前资源枯竭的物种的部分恢复。然而，大多数鲸鱼种群的数量仍然远远低于其历史数量，而人类的偶然影响，特别是船只撞击和渔具缠绕，正日益被认为是关键威胁。此外，受气候驱动的猎物动态变化正在影响许多须鲸的季节性觅食地。在许多情况下，这些影响直接导致死亡。但是，间接和日益增加的亚致死影响如何影响鲸鱼的生活史、个体健康和种群生存能力，目前还不太清楚。我们使用载人飞机和远程操作的无人机在 20 年期间收集的航空摄影测量测量结果，评估北大西洋露脊鲸（NARW）的体长变化（图 1）。自 20 世纪 80 年代以来，NARW 一直受到持续监测，自 2011 年以来，由于与主动渔具缠绕和船只撞击相关的死亡，其数量一直在减少。高比例的亚致死伤害和关于年龄、大小和观察到的缠绕的个体信息，使这一群体成为评估这些广泛存在的压力源对个体健康可能产生的影响的理想选择。我们发现，渔具缠绕与鲸鱼体型较小有关，而且自 1981 年以来，体长一直在减少。生长停滞可能导致繁殖成功率降低，以及被渔具缠绕致死的概率增加。这些结果表明，即使没有直接捕捞，亚致死压力源也会威胁到脆弱鲸鱼种群的恢复。
