The California Current Ecosystem has experienced variable climate regimes, hypoxia, and marine heatwave events that have the potential to impact groundfishes and their associated fisheries. Using bottom trawl survey data collected by NOAA Fisheries, we assessed changes over the last four decades in northern California Current continental shelf (≤200 m) groundfish assemblage composition, species' presence, and relationships to environmental and habitat variables. We focus on the currently understudied continental shelf area, due to its ecological and economic importance, especially after the recent opening of historically important areas to trawling. We found a temporally consistent separation in groundfish assemblages between depth zones based on NMS analysis using species found in over 1% of samples, with shallow, mid-, and deep shelf groupings. Grain size, species richness, and diversity were associated with assemblage composition. Then, focusing on petrale sole, rex sole, lingcod, arrowtooth flounder, sablefish, English sole, Pacific sanddab, and Dover sole, we examined what factors impact groundfish presence and abundance on the shelf. Bottom temperature, sediment characteristics, and depth were correlated with abundance for all species. These results corroborate previous work indicating recent reductions in presence of hypoxia-intolerant species. Shallow-water groundfishes known to tolerate warmer water and low dissolved oxygen concentrations exhibit reductions offshore, possibly a result of low recruitment. There have been significant spatiotemporal changes in the shelf groundfish populations over the past several decades, and while assemblage composition over most of the shelf remains consistent, single species distributional shifts may impact access to target species in newly reopened areas.

中文翻译：

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气候、海洋学和栖息地对北加州洋流大陆架底层鱼类分布和丰度的影响

加利福尼亚洋流生态系统经历了多变的气候状况、缺氧和海洋热浪事件，这些事件有可能影响底层鱼类及其相关渔业。我们使用美国国家海洋和大气管理局渔业收集的底拖网调查数据，评估了过去四年在加利福尼亚北部当前大陆架 (≤ 200 m) 底层鱼类组合组成、物种存在以及与环境和栖息地变量的关系的变化。我们关注目前尚未得到充分研究的大陆架区域，因为它具有生态和经济重要性，特别是在最近对具有历史意义的区域开放拖网捕捞之后。基于 NMS 分析，我们使用超过 1% 的样本中发现的物种，在浅层、中层、和深货架分组。颗粒大小、物种丰富度和多样性与组合组成有关。然后，我们重点研究了petrale鞋底、rex鞋底、lingcod、箭齿比目鱼、sablefish、英国鞋底、Pacific sanddab和Dover鞋底，研究了哪些因素会影响架子上底层鱼类的存在和丰度。底部温度、沉积物特征和深度与所有物种的丰度相关。这些结果证实了之前的工作，表明最近缺氧不耐受物种的存在减少了。已知能够耐受较温暖的水和低溶解氧浓度的浅水底层鱼类在近海表现出减少，这可能是低补充的结果。在过去的几十年里，陆架底层鱼类种群发生了显着的时空变化，