Abstract Urban nearshore ecosystems are built environments that differ structurally and functionally from the natural ecosystems they replace. Eco-engineering offers the ability to enhance these ecosystems by reducing the impacts of shoreline modification. Recent studies have linked shoreline armoring and pier shade—common features of modified shorelines—to lower foraging rates, altered distribution patterns, and increased predation risk for juvenile salmon. The 2017 replacement of the Elliott Bay seawall in Seattle, WA, USA incorporated novel eco-engineering design elements, including glass light penetrating surfaces (LPS) in overwater structures, an elevated seafloor, and textured substrates in the seawall face to enhance nearshore habitat for juvenile Pacific salmon (Oncorhynchus spp.) migrating from natal streams to the ocean. To examine the effectiveness of seawall eco-engineering, we used snorkel surveys to assess changes in juvenile salmon spatial distribution and foraging patterns during peak outmigration (March–August), and measured ambient light penetration before and after seawall replacement. Overall, we found that juvenile salmon were distributed more evenly across a spatial mosaic of habitats following eco-engineering. LPS enhanced ambient light penetration in nearshore under-pier habitats, and juvenile salmon use of these habitats increased concurrently. Salmon densities under piers tended to be greatest at low tides, indicating that light availability may mediate selective habitat use. Feeding rates at sites immediately adjacent to the seawall increased both between and under piers following habitat enhancement. Our findings suggest that the elevated light levels facilitated by LPS, in concert with physical enhancements that provided more complex shallow water habitat, temper the negative effects of pier shade and shoreline armoring on juvenile salmon.

中文翻译：

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作为鲑鱼栖息地的海堤：生态工程改善太平洋鲑鱼幼鱼的分布和觅食

摘要 城市近岸生态系统是在结构和功能上与它们所取代的自然生态系统不同的建成环境。生态工程能够通过减少海岸线改造的影响来增强这些生态系统。最近的研究将海岸线装甲和码头遮荫（改良海岸线的常见特征）与较低的觅食率、改变的分布模式和幼年鲑鱼的捕食风险增加联系起来。2017 年更换美国华盛顿州西雅图的埃利奥特湾海堤采用了新颖的生态工程设计元素，包括水上结构中的玻璃透光面 (LPS)、升高的海底和海堤面的纹理基材，以改善近岸栖息地幼年太平洋鲑鱼 (Oncorhynchus spp.) 从出生的溪流迁移到海洋。为了检验海堤生态工程的有效性，我们使用浮潜调查来评估迁徙高峰期（3 月至 8 月）幼鲑鱼空间分布和觅食模式的变化，并测量海堤更换前后的环境光穿透。总的来说，我们发现在生态工程之后，幼鲑鱼在栖息地的空间镶嵌中分布更均匀。LPS 增强了近岸码头下栖息地的环境光渗透，同时这些栖息地的幼鲑鱼使用量增加。码头下的鲑鱼密度在退潮时往往最大，这表明光照可能会调节栖息地的选择性使用。随着栖息地的改善，紧邻海堤的地点的喂食率在码头之间和码头下方都增加了。