Center for Stock Assessment Research and Department of Applied Mathematics and Statistics, Jack Baskin School of Engineering, University of California, Santa Cruz, CA 95064, USA.
Proc Natl Acad Sci U S A. 2011 Apr 26;108(17):7075-80. doi: 10.1073/pnas.1100334108. Epub 2011 Apr 11.
A central and classic question in ecology is what causes populations to fluctuate in abundance. Understanding the interaction between natural drivers of fluctuating populations and human exploitation is an issue of paramount importance for conservation and natural resource management. Three main hypotheses have been proposed to explain fluctuations: (i) species interactions, such as predator-prey interactions, cause fluctuations, (ii) strongly nonlinear single-species dynamics cause fluctuations, and (iii) environmental variation cause fluctuations. We combine a general fisheries model with data from a global sample of fish species to assess how two of these hypothesis, nonlinear single-species dynamics and environmental variation, interact with human exploitation to affect the variability of fish populations. In contrast with recent analyses that suggest fishing drives increased fluctuations by changing intrinsic nonlinear dynamics, we show that single-species nonlinear dynamics alone, both in the presence and absence of fisheries, are unlikely to drive deterministic fluctuations in fish; nearly all fish populations fall into regions of stable dynamics. However, adding environmental variation dramatically alters the consequences of exploitation on the temporal variability of populations. In a variable environment, (i) the addition of mortality from fishing leads to increased temporal variability for all species examined, (ii) variability in recruitment rates of juveniles contributes substantially more to fluctuations than variation in adult mortality, and (iii) the correlation structure of juvenile and adult vital rates plays an important and underappreciated role in determining population fluctuations. Our results are robust to alternative model formulations and to a range of environmental autocorrelation.
生态学中的一个核心和经典问题是，是什么导致种群数量出现波动。了解波动种群的自然驱动因素与人类开发之间的相互作用，对保护和自然资源管理至关重要。为了解释波动现象，提出了三个主要假说：（i）物种间的相互作用，如捕食者-猎物相互作用，导致波动；（ii）强烈的非线性单物种动态导致波动；（iii）环境变化导致波动。我们将一个通用的渔业模型与来自全球鱼类物种样本的数据相结合，以评估其中两个假说，即非线性单物种动态和环境变化，如何与人类开发相互作用，影响鱼类种群的可变性。与最近的分析结果相反，这些分析结果表明，捕鱼通过改变内在的非线性动态来驱动波动增加，我们的研究表明，单物种非线性动态本身，无论是在存在还是不存在渔业的情况下，都不太可能导致鱼类的确定性波动；几乎所有的鱼类种群都处于稳定动态的区域。然而，添加环境变化会极大地改变开发对种群时间可变性的影响。在一个多变的环境中，（i）来自捕鱼的死亡率的增加会导致所有被研究的物种的时间可变性增加，（ii）青少年的补充率变化对波动的贡献远远大于成年死亡率的变化，（iii）青少年和成年关键率的相关结构在确定种群波动方面起着重要而被低估的作用。我们的结果对替代模型公式和各种环境自相关都是稳健的。
