Non-stationary driver-response relationships are increasingly being recognized by scientists, underlining that a paradigm shift out of conventional stationary relationships is crucial. Japanese sardine (Sardinops melanostictus, Clupeidae) is a typical small pelagic fish in the northwestern Pacific with considerable fluctuations in productivity, bringing about great economic and ecological concerns. Numerous studies suggest that the population dynamics of Japanese sardine is an integrated process affected by multiple density-dependent, fishing and climatic drivers. However, little has hitherto been done to incorporate the non-stationary effects of multiple drivers, impeding progresses in understanding the population dynamics and in developing management strategies. In this study, we adopted variable coefficients generalized additive models to reveal the non-stationary effects of density dependence, fishing pressure and climatic conditions on the population dynamics of Japanese sardine. Results suggest that the dynamics of Japanese sardine from 1976 to 2018 could be divided into four periods: the 1980s when suitable climatic conditions from strong Siberian High pressure system sustained high abundance; the 1990s when negative density-dependent effects and degrading climatic conditions due to temperature increase led to population collapse; the 2000s when negative triple effects, particularly high fishing pressure, restricted the population increase; and the 2010s when favourable climatic conditions with re-strengthening Siberian High pressure system accompanied by low fishing pressure contributed to the population recovery. The study highlights that precise identifications of population status and climatic conditions are helpful to achieve good trade-offs between resource exploitation and protection and to facilitate ecosystem-based management for Japanese sardine fisheries.

中文翻译：

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多个驱动因素对日本沙丁鱼（Sardinops melanostictus，Clupeidae）动态的非平稳影响

科学家越来越多地认识到非固定的驾驶员反应关系，强调从传统的固定关系中转变范式是至关重要的。日本沙丁鱼（Sardinops melanostictus, Clupeidae)是西北太平洋典型的中上层小型鱼类，生产力波动较大，带来极大的经济和生态问题。大量研究表明，日本沙丁鱼的种群动态是一个综合过程，受多种密度依赖、渔业和气候驱动因素的影响。然而，迄今为止，很少有人将多个驱动因素的非平稳效应纳入其中，这阻碍了对人口动态的理解和制定管理战略的进展。在这项研究中，我们采用可变系数广义加性模型来揭示密度依赖性、捕捞压力和气候条件对日本沙丁鱼种群动态的非平稳影响。结果表明，日本沙丁鱼的动态从 1976 年到 2018 年可分为四个时期：1980 年代，西伯利亚高压系统带来的适宜气候条件持续高丰度；1990 年代，由于温度升高，负密度依赖效应和气候条件恶化导致人口崩溃；2000 年代，负面的三重影响，特别是高捕捞压力，限制了人口增长；2010 年代，有利的气候条件和重新加强的西伯利亚高压系统伴随着较低的捕鱼压力有助于人口恢复。