Abstract An important decrease in small pelagic fish condition and size has been observed in the most productive ecosystem of the Mediterranean Sea, the Gulf of Lions, since 2008, leading to an important fishery crisis. Previous studies suggested bottom-up control to be the most probable cause for these changes. Here, we investigate whether an environmental change might have caused such a situation. In the absence of zooplankton time series, this study aims at describing temporal changes in key abiotic factors for the planktonic and fish production of the Gulf of Lions, such as SST, meso-scale fronts, wind-induced coastal upwelling, river discharge, water stratification and deep convection and then at understanding potential link on Chl-a concentration as well as small pelagic fish populations. Our results indicate that the environmental conditions have broadly changed in the Gulf of Lion, with a major change in the mid-2000s, affecting the Chla concentration (which showed a regime shift in 2007), but also the SST, the upwelling and frontal activities, the Rhone river discharge (and particularly the N and P nutrients inputs) as well as the deep winter convection. Those changes could have affected the plankton production and consequently the small pelagic fish community that displayed similar patterns of variations as the environmental conditions.

中文翻译：

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狮子湾环境和小型远洋鱼类群落的伴随变化

摘要 自 2008 年以来，在地中海最具生产力的生态系统狮子湾中观察到小型中上层鱼类的状况和大小显着下降，从而导致了重大的渔业危机。先前的研究表明，自下而上的控制是这些变化的最可能原因。在这里，我们调查环境变化是否可能导致这种情况。在没有浮游动物时间序列的情况下，本研究旨在描述狮子湾浮游和鱼类生产的关键非生物因素的时间变化，例如海温、中尺度锋、风引起的沿海上升流、河流流量、水分层和深层对流，然后了解 Chl-a 浓度以及小型远洋鱼类种群的潜在联系。我们的结果表明，狮子湾的环境条件发生了广泛变化，在 2000 年代中期发生了重大变化，影响了 Chla 浓度（在 2007 年显示出制度转变），但也影响了海温、上升流和锋面活动、罗纳河排放（尤其是 N 和 P 养分输入）以及冬季深层对流。这些变化可能会影响浮游生物的生产，从而影响小型中上层鱼类群落，它们显示出与环境条件类似的变化模式。罗纳河排放（尤其是 N 和 P 养分输入）以及冬季深层对流。这些变化可能会影响浮游生物的生产，从而影响小型中上层鱼类群落，它们显示出与环境条件类似的变化模式。罗纳河排放（尤其是 N 和 P 养分输入）以及冬季深层对流。这些变化可能会影响浮游生物的生产，从而影响小型中上层鱼类群落，它们显示出与环境条件类似的变化模式。