Diadromous fish use both freshwater and marine habitats to complete their life cycles, but dams restrict those connections, and as a result, many populations are historically low across their range. The Penobscot River, Maine, USA, once had large populations of diadromous fish and has recently been the focus of large restoration projects. Our objective was to assess the river restoration impacts in the estuary using mobile, multi-frequency echosounders (SIMRAD EK60 split-beam 38 and 120 kHz) to construct a time series of fish distribution using metrics of fish length and fish density, both seasonally and pre-restoration (2012–2014) versus post-restoration (2015–2019). Seasonally, fish size was the smallest in summer, while density and biomass were greater as compared to spring and fall. Between pre- and post-restoration years, fish length did not differ, and with a median of 4.7 cm, median density increased from less than 0.5 fish m⁻² to greater than 1 fish m⁻². Fish biomass was approximately three times greater in post-restoration years where it ranged 23 to 316 mt per survey than pre-restoration years where it ranged from 9 to 114 mt per survey. These patterns are consistent with a system undergoing restoration of migratory fish where larger adult fish migrate in the spring and their juveniles in the summer and fall. This study demonstrates the ecological impacts of river restoration on its estuary by quantifying multiple metrics (fish biomass, density, and size).

产海鱼类利用淡水和海洋栖息地来完成它们的生命周期，但水坝限制了这些联系，因此，许多鱼类在其分布范围内的数量处于历史低位。美国缅因州的佩诺布斯科特河曾经盛产大量的淡水鱼，最近成为大型恢复项目的焦点。我们的目标是使用移动式多频回声测深仪（SIMRAD EK60 分波束 38 和 120 kHz）评估河口河流恢复影响，并使用鱼类长度和鱼类密度（季节性和季节性）指标构建鱼类分布的时间序列。恢复前（2012-2014）与恢复后（2015-2019）。从季节上看，夏季鱼类体型最小，但密度和生物量均高于春季和秋季。在恢复前和恢复后的年份之间，鱼的长度没有差异，中位数为4.7厘米，中位数密度从小于0.5条鱼m ^-2增加到大于1条鱼m ^-2。恢复后年份的鱼类生物量约为恢复前年份（每次调查 9 至 114 吨）的三倍，每次调查范围为 23 至 316 吨。这些模式与正在恢复洄游鱼类的系统一致，其中较大的成鱼在春季迁移，幼鱼在夏季和秋季迁移。本研究通过量化多个指标（鱼类生物量、密度和大小）来论证河流恢复对其河口的生态影响。