Movement, delays, and survival of hatchery Atlantic Salmon Salmo salar smolts were evaluated through the Piscataquis River, a tributary of the Penobscot River in Maine, USA. We explored the effects of the river’s four dams (Guilford, Dover, Browns Mill, and Howland dams) from 2005 to 2019. During this period, the downstream-most dam (Howland Dam) transitioned from full hydropower generation to seasonal turbine shutdowns and later was decommissioned with the construction of a nature-like fish bypass in 2016. We estimated survival through open-river reaches and at each dam using acoustic telemetry (n = 1,611). Dams decreased survival, with per-river-kilometer (rkm) apparent survival averages of 0.972, 0.951, and 0.990 for Guilford, Dover, and Browns Mill dams compared to a per-rkm survival of 0.999 for open-river reaches. Turbine shutdowns increased survival at Howland Dam (to around 0.95), which was further increased by the nature-like fish bypass (0.99). We used radiotelemetry in 2019 (n = 75) and demonstrated that approximately one-third of the fish used the bypass, while the remaining fish used alternative routes. Smolts successfully passing the three upstream dams had lower apparent survival through Howland Dam than smolts that were released upstream of Howland Dam. Although smolts passing Browns Mill Dam had high survival, the dam caused extended delays, with median delay times surpassing 48 h in most years. Most of the delays caused by Browns Mill Dam occurred after fish had passed the dam and may indicate a sublethal effect of passage. Overall, while survival through Howland Dam has improved, passage and delays at the three upstream dams in aggregate represent a critical impediment to the effective use of the high-quality spawning habitat found upstream.

中文翻译：

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美国缅因州皮斯卡塔奎斯河中大西洋鲑鲑的迁徙，存活和延迟

孵化场大西洋鲑鲑的迁徙，延误和存活情况通过美国缅因州Penobscot河的支流Piscataquis河评估了鲑鱼的鲑鱼。我们研究了2005年至2019年这条河的四个水坝（吉尔福德，多佛，布朗斯米尔和霍兰德水坝）的影响。在此期间，最下游的水坝（霍兰德水坝）从完整的水力发电过渡到季节性的涡轮机停工，后来又关闭了于2016年因建造类似大自然的鱼道而退役。我们使用声遥测技术估算了开阔河段和每个大坝的生存率（n = 1,611）。大坝降低了生存率，吉尔福德，多佛和布朗斯米尔大坝的平均每公里生存率分别为0.972、0.951和0.990，而裸河段的平均每公里生存率仅为0.999。涡轮机关闭增加了Howland大坝的存活率（至0.95左右），而自然界中的鱼类绕行则进一步提高了存活率（0.99）。我们在2019年使用了无线电遥测（n = 75），并证明大约有三分之一的鱼使用了旁路，而其余的鱼则使用了替代路线。成功地通过三个上游大坝的牡蛎通过Howland大坝的表观存活率比在Howland大坝上游释放的鲑鱼低。尽管经过布朗斯磨坊大坝的软体动物存活率很高，但大坝造成了延误，在大多数年份中，中位延误时间超过了48小时。布朗斯米尔水坝造成的大多数延误发生在鱼通过水坝之后，这可能表明通过是致命的。总体而言，尽管通过Howland大坝的生存得以改善，但三个上游大坝的通行和延误总计严重阻碍了有效利用上游发现的高质量产卵栖息地。