Population Dynamics Branch, Northeast Fisheries Science Center, National Oceanic and Atmospheric Administration, United States Department of Commerce, Woods Hole, Massachusetts, United States of America.
Division of Biological Monitoring and Assessment, Bureau of Marine Science, Department of Marine Resources, State of Maine, West Boothbay Harbor, Maine, United States of America.
PLoS One. 2021 Jul 21;16(7):e0253914. doi: 10.1371/journal.pone.0253914. eCollection 2021.
The northern shrimp (Pandalus borealis Krøyer) population in the Gulf of Maine collapsed during an extreme heatwave that occurred across the Northwest Atlantic Ocean in 2012. Northern shrimp is a boreal species, and reaches its southern limit in the Gulf of Maine. Here we investigate proximate causes for the population collapse using data from fishery-independent surveys, environmental monitoring, and the commercial fishery. We first examined spatial data to confirm that the decline in population estimates was not due to a major displacement of the population, and then tested hypotheses related to fishing mortality and shifts in predation pressure. Fishing mortality may have contributed but could not explain the magnitude of the decline or the disappearance of pre-exploitable size individuals. Stomach contents analysis and biomass trends revealed no new fish predators of shrimp. However, longfin squid (Doryteuthis pealeii Lesueur) was unique among all species in showing time-series biomass peaks during spring, summer and fall of 2012, and spatial overlap with northern shrimp was unusually high in 2012. Longfin squid is a voracious and opportunistic predator that consumes crustaceans as well as fish. We hypothesize that the warmer temperatures of 2012 not only led to expansion of longfin squid distribution in Gulf of Maine, but had differential effects on migration phenology that further increased spatial overlap with northern shrimp. The weight of our evidence suggests that longfin squid predation was likely a significant factor in the collapse of northern shrimp in the Gulf of Maine.
2012 年，西北大西洋发生极端热浪，缅因湾的北方长额虾（Pandalus borealis Krøyer）数量锐减。北方长额虾是一种北方物种，其分布范围的最南端可达缅因湾。本研究利用渔业独立调查、环境监测和商业渔业数据，调查了这次种群崩溃的近因。我们首先检查了空间数据，以确认种群数量的减少不是由于种群的大规模迁移，然后测试了与捕捞死亡率和捕食压力变化有关的假设。捕捞死亡率可能起了作用，但无法解释数量下降的幅度或可开发个体的消失。胃内容物分析和生物量趋势表明，没有新的鱼类捕食虾类。然而，2012 年，长枪乌贼（Doryteuthis pealeii Lesueur）是唯一一种在春季、夏季和秋季都表现出时间序列生物量峰值的物种，并且与北方长额虾的空间重叠度在 2012 年异常高。长枪乌贼是一种贪婪且机会主义的捕食者，它既吃甲壳类动物，也吃鱼类。我们假设，2012 年较高的温度不仅导致长枪乌贼在缅因湾的分布范围扩大，而且对其迁徙物候学产生了不同的影响，进一步增加了与北方长额虾的空间重叠度。我们的证据表明，长枪乌贼的捕食很可能是缅因湾北方长额虾数量崩溃的一个重要因素。
