The Eocene/Oligocene (E/O) boundary (~33.9 million years ago) has been described as a state change in the Earth system marked by the permanent glaciation of Antarctica and a proposed increase in oceanic productivity. Here we quantified the response of fish production and biodiversity to this event using microfossil fish teeth (ichthyoliths) in seven deep-sea sediment cores from around the world. Ichthyolith accumulation rate (a proxy for fish biomass production) shows no synchronous trends across the E/O. Ichthyolith accumulation in the Southern Ocean and Pacific gyre sites is an order of magnitude lower than that in the equatorial and Atlantic sites, demonstrating that the Southern Ocean was not a highly productive ecosystem for fish before or after the E/O. Further, tooth morphotype diversity and assemblage composition remained stable across the interval, indicating little change in the biodiversity or ecological role of open-ocean fish. While the E/O boundary was a major global climate-change event, its impact on pelagic fish was relatively muted. Our results support recent findings of whale and krill diversification suggesting that the pelagic ecosystem restructuring commonly attributed to the E/O transition probably occurred much later, in the late Oligocene or Miocene.

始新世/渐新世（E / O）边界（约3,390万年前）被描述为地球系统的状态变化，其特征是南极洲永久性冰河化和拟议的海洋生产力增加。在这里，我们使用来自世界各地的七个深海沉积物核心中的微化石鱼齿（鱼鳞石）来量化鱼类生产和生物多样性对这一事件的响应。鱼鳞石的蓄积率（代表鱼类生物量的生产）在整个E / O中没有同步趋势。南部大洋和太平洋回旋区的鱼鳞石堆积量比赤道和大西洋的低，数量级低，这表明在E / O之前或之后，南部大洋不是鱼类的高产生态系统。进一步，在整个时间间隔中，牙齿的形态类型多样性和组合组成保持稳定，这表明开放海洋鱼类的生物多样性或生态作用几乎没有变化。尽管E / O边界是全球主要的气候变化事件，但其对远洋鱼类的影响相对较小。我们的结果支持了鲸鱼和磷虾多样化的最新发现，这表明通常归因于E / O转变的远洋生态系统重组可能发生在晚渐新世或中新世晚期。