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首页> 外文期刊>Ecological Applications >New hypothesis helps explain elasmobranch 'OutBurst' on Georges bank in the 1980s
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New hypothesis helps explain elasmobranch 'OutBurst' on Georges bank in the 1980s

机译：新的假设有助于解释1980年代Georges银行的弹性分支“ OutBurst”

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摘要

Regime shifts are a feature of many ecosystems. During the last 40 years, intensive commercial exploitation and environmental changes have driven substantial shifts in ecosystem structure and function in the northwest Atlantic. In the Georges Bank-southern New England region, commercially important species have declined, and the ecosystem shifted to one dominated by economically undesirable species such as skates and dogfish. Aggregated abundance indices indicate a large increase of small and medium-sized elasmobranchs in the early 1980s following the decline of many commercial species. It has been hypothesized that ecological interactions such as competition and predation within the Georges Bank region were responsible for and are maintaining the "elasmobranch outburst" at the heart of the observed ecosystem shift. We offer an alternative hypothesis invoking population connectivity among winter skate populations such that the observed abundance increase is a result of migratory dynamics, perhaps with the Scotian Shelf (i.e., it is an open population). Here we critically evaluate the survey data for winter skate, the species principally responsible for the increase in total skate abundance during the 1980s on Georges Bank, to assess support for both hypotheses. We show that time series from different surveys within the Georges Bank region exhibit low coherence, indicating that a widespread population increase was not consistently shown by all surveys. Further, we argue that observed length-frequency data for Georges Bank indicate biologically unrealistic population fluctuations if the population is closed. Neither finding supports the elasmobranch outburst hypothesis. In contrast, survey time series for Georges Bank and the Scotian Shelf are negatively correlated, in support of the population connectivity hypothesis. Further, we argue that understanding the mechanisms of ecosystem state changes and population connectivity are needed to make inferences about both the causes and appropriate management responses to large-scale system change.
机译：政权转移是许多生态系统的特征。在过去的40年中，密集的商业开发和环境变化推动了西北大西洋生态系统结构和功能的重大转变。在Georges Bank南部的新英格兰地区，重要商业物种已减少，生态系统已转移至一种由经济上不受欢迎的物种（例如溜冰鞋和dog鱼）主导的物种。总体丰度指数表明，随着许多商业物种的减少，1980年代初中小规模的弹性分支增加了。有人假设，乔治斯银行地区内部的竞争和捕食等生态相互作用是造成并维持着观察到的生态系统转变核心的“弹枝突突”的原因。我们提供了另一种假设，该假设在冬季滑冰种群之间引起了种群连通性，因此观察到的丰度增加是迁徙动态的结果，也许是斯科特架子所致（即是开放种群）。在这里，我们严格评估冬季滑冰的调查数据，以评估这两种假设的支持。冬季滑冰主要是1980年代乔治·班克斯（Georges Bank）滑冰总数量增加的原因。我们显示，乔治银行区域内不同调查的时间序列显示出较低的连贯性，表明并非所有调查都始终显示人口的普遍增加。此外，我们认为观察到的乔治银行的长频数据表明，如果人口封闭，生物学上不切实际的人口波动。两项发现均不支持弹性分支爆发假说。相比之下，Georges Bank和Scotian Shelf的调查时间序列呈负相关，以支持人口连通性假设。此外，我们认为需要了解生态系统状态变化和种群连通性的机制，才能对大规模系统变化的原因和适当的管理对策进行推断。

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