Kershaw Joanna L, Ramp Christian A, Sears Richard, Plourde Stéphane, Brosset Pablo, Miller Patrick J O, Hall Ailsa J
Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, St Andrews, UK.
Mingan Island Cetacean Study, Saint Lambert, QC, Canada.
Glob Chang Biol. 2020 Dec 24. doi: 10.1111/gcb.15466.
Climate change has resulted in physical and biological changes in the world's oceans. How the effects of these changes are buffered by top predator populations, and therefore how much plasticity lies at the highest trophic levels, are largely unknown. Here endocrine profiling, longitudinal observations of known individuals over 15 years between 2004 and 2018, and environmental data are combined to examine how the reproductive success of a top marine predator is being affected by ecosystem change. The Gulf of St. Lawrence, Canada, is a major summer feeding ground for humpback whales (Megaptera novaeangliae) in the North Atlantic. Blubber biopsy samples (n = 185) of female humpback whales were used to investigate variation in pregnancy rates through the quantification of progesterone. Annual pregnancy rates showed considerable variability, with no overall change detected over the study. However, a total of 457 photo-identified adult female sightings records with/without calves were collated, and showed that annual calving rates declined significantly. The probability of observing cow-calf pairs was related to favourable environmental conditions in the previous year; measured by herring spawning stock biomass, Calanus spp. abundance, overall copepod abundance and phytoplankton bloom magnitude. Approximately 39% of identified pregnancies were unsuccessful over the 15 years, and the average annual pregnancy rate was higher than the average annual calving rate at ~37% and ~23% respectively. Together, these data suggest that the declines in reproductive success could be, at least in part, the result of females being unable to accumulate the energy reserves necessary to maintain pregnancy and/or meet the energetic demands of lactation in years of poorer prey availability rather than solely an inability to become pregnant. The decline in calving rates over a period of major environmental variability may suggest that this population has limited resilience to such ecosystem change.
气候变化已导致全球海洋在物理和生物方面发生变化。顶级捕食者种群如何缓冲这些变化的影响，进而最高营养级具有多大的可塑性，在很大程度上尚不清楚。在此，我们将内分泌分析、2004年至2018年期间对已知个体进行的长达15年的纵向观察以及环境数据相结合，以研究顶级海洋捕食者的繁殖成功率如何受到生态系统变化的影响。加拿大圣劳伦斯湾是北大西洋座头鲸（Megaptera novaeangliae）的主要夏季觅食地。利用雌性座头鲸的鲸脂活检样本（n = 185），通过定量孕酮来研究怀孕率的变化。年度怀孕率显示出相当大的变异性，在研究期间未检测到总体变化。然而，总共整理了457条有/无幼崽的经照片识别的成年雌性目击记录，结果显示年度产犊率显著下降。观察到母鲸 - 幼鲸对的概率与前一年的有利环境条件有关；通过鲱鱼产卵群体生物量、哲水蚤属丰度、总体桡足类丰度和浮游植物水华规模来衡量。在这15年中，约39%已识别的怀孕未成功，平均年度怀孕率分别比平均年度产犊率高出约37%和23%。综合这些数据表明，繁殖成功率的下降至少部分可能是由于雌性在猎物可获得性较差的年份无法积累维持怀孕所需的能量储备和/或满足泌乳的能量需求，而不仅仅是无法怀孕。在一个主要环境多变的时期产犊率下降，可能表明该种群对这种生态系统变化的恢复力有限。
