The American Eel Anguilla rostrata is a catadromous fish found in rivers along the East Coast of North America. American Eel populations have declined throughout their range for several reasons, including habitat fragmentation caused by damming, which hinders access to much of their historic lotic habitats. This study examined differences in abundance and size structure across river segments divided by nine dams in the Bronx River, New York, a heavily urbanized system. American Eels were sampled via multipass electrofishing at nine sites over the course of 3 years. American Eels 250 mm TL or larger were implanted with passive integrated transponder tags to estimate survival and movements. Estimates of abundance were calculated for electrofishing data using the Huggins closed-capture model. Density was estimated based on area surveyed, abundance data, and estimated weights of American Eels. Eel mops were used to evaluate the presence and relative abundance of different life stages of American Eels (glass, elver, and small yellow phases). Our results showed decreased abundance in upstream areas, with a corresponding increase in average size. Density, by weight, was consistent among sites. Tagging data showed minimum apparent survival of up to 0.29 and only a single movement between dammed segments, demonstrating high site fidelity. Eel mop sampling revealed that although glass- and elver-stage American Eels were common downstream, relative abundance decreased rapidly above the first dam. These results suggest that the Bronx River American Eel population is structured by physical barriers to passage, density-dependent limitations, high stationariness, and high apparent survival.

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美国鳗鱼在大坝城市河流中的丰度和分布

美国鳗鲡Rostrata是在北美东海岸的河流中发现的一种流域鱼类。由于多种原因，美国鳗鱼的数量在整个范围内都在下降，其中包括大坝造成的栖息地破碎化，这阻碍了人们进入其大部分历史悠久的水生栖息地。这项研究检查了纽约布朗克斯河（一个高度城市化的系统）中被九个大坝划分的河段在丰度和大小结构上的差异。在 3 年的时间里，美国鳗鱼在 9 个地点通过多通道电捕鱼进行了采样。美国鳗鱼 250 毫米 TL 或更大的被植入无源集成转发器标签，以估计生存和运动。使用 Huggins 封闭捕获模型计算了电捕鱼数据的丰度估计值。密度是根据调查面积、丰度数据估算的，和估计美国鳗鱼的重量。鳗鱼拖把用于评估美洲鳗不同生命阶段（玻璃、精灵和小黄色阶段）的存在和相对丰度。我们的结果显示上游地区的丰度降低，平均大小相应增加。密度，按重量，在站点之间是一致的。标记数据显示最小表观存活率高达 0.29，并且在拦阻段之间只有一次移动，表明现场保真度高。鳗鱼拖把采样显示，虽然玻璃阶段和幼鳗阶段的美国鳗鱼在下游很常见，但在第一个大坝上方的相对丰度迅速下降。这些结果表明，布朗克斯河美国鳗鱼种群的结构是通过物理障碍、密度依赖性限制、高稳定性和高表观存活率。鳗鱼拖把用于评估美洲鳗不同生命阶段（玻璃、精灵和小黄色阶段）的存在和相对丰度。我们的结果显示上游地区的丰度降低，平均大小相应增加。密度，按重量，在站点之间是一致的。标记数据显示最小表观存活率高达 0.29，并且在拦阻段之间只有一次移动，表明现场保真度高。鳗鱼拖把采样显示，虽然玻璃阶段和幼鳗阶段的美国鳗鱼在下游很常见，但在第一个大坝上方的相对丰度迅速下降。这些结果表明，布朗克斯河美洲鳗鱼种群的结构是通过物理障碍、密度依赖性限制、高稳定性和高表观存活率。鳗鱼拖把用于评估美洲鳗不同生命阶段（玻璃、精灵和小黄色阶段）的存在和相对丰度。我们的结果显示上游地区的丰度降低，平均大小相应增加。密度，按重量，在站点之间是一致的。标记数据显示最小表观存活率高达 0.29，并且在拦阻段之间只有一次移动，表明现场保真度高。鳗鱼拖把采样显示，虽然玻璃阶段和幼鳗阶段的美国鳗鱼在下游很常见，但在第一个大坝上方的相对丰度迅速下降。这些结果表明，布朗克斯河美国鳗鱼种群的结构是通过物理障碍、密度依赖性限制、高稳定性和高表观存活率。