Essington Timothy E, Moriarty Pamela E, Froehlich Halley E, Hodgson Emma E, Koehn Laura E, Oken Kiva L, Siple Margaret C, Stawitz Christine C
School of Aquatic and Fishery Sciences and
School of Aquatic and Fishery Sciences and.
Proc Natl Acad Sci U S A. 2015 May 26;112(21):6648-52. doi: 10.1073/pnas.1422020112. Epub 2015 Apr 6.
Forage fish support the largest fisheries in the world but also play key roles in marine food webs by transferring energy from plankton to upper trophic-level predators, such as large fish, seabirds, and marine mammals. Fishing can, thereby, have far reaching consequences on marine food webs unless safeguards are in place to avoid depleting forage fish to dangerously low levels, where dependent predators are most vulnerable. However, disentangling the contributions of fishing vs. natural processes on population dynamics has been difficult because of the sensitivity of these stocks to environmental conditions. Here, we overcome this difficulty by collating population time series for forage fish populations that account for nearly two-thirds of global catch of forage fish to identify the fingerprint of fisheries on their population dynamics. Forage fish population collapses shared a set of common and unique characteristics: high fishing pressure for several years before collapse, a sharp drop in natural population productivity, and a lagged response to reduce fishing pressure. Lagged response to natural productivity declines can sharply amplify the magnitude of naturally occurring population fluctuations. Finally, we show that the magnitude and frequency of collapses are greater than expected from natural productivity characteristics and therefore, likely attributed to fishing. The durations of collapses, however, were not different from those expected based on natural productivity shifts. A risk-based management scheme that reduces fishing when populations become scarce would protect forage fish and their predators from collapse with little effect on long-term average catches.
饵料鱼支撑着世界上最大的渔业，但它们在海洋食物网中也起着关键作用，将能量从浮游生物传递给较高营养级的捕食者，如大型鱼类、海鸟和海洋哺乳动物。因此，除非采取保障措施避免将饵料鱼消耗到危险的低水平，否则捕鱼可能会对海洋食物网产生深远影响，而在这种低水平下，依赖饵料鱼的捕食者最为脆弱。然而，由于这些鱼类种群对环境条件敏感，区分捕鱼和自然过程对种群动态的影响一直很困难。在这里，我们通过整理占全球饵料鱼捕获量近三分之二的饵料鱼种群的时间序列，来识别渔业对其种群动态的影响，从而克服了这一困难。饵料鱼种群崩溃具有一系列共同和独特的特征：崩溃前数年捕鱼压力大、自然种群生产力急剧下降以及对降低捕鱼压力的滞后反应。对自然生产力下降的滞后反应会大幅放大自然发生的种群波动幅度。最后，我们表明，崩溃的幅度和频率大于根据自然生产力特征预期的水平，因此可能归因于捕鱼。然而，崩溃的持续时间与基于自然生产力变化预期的持续时间并无不同。一种基于风险的管理方案，即在种群稀少时减少捕鱼，将保护饵料鱼及其捕食者免于崩溃，同时对长期平均捕获量影响不大。
