The consequences of dam passage for downstream-migrating American eel in the Penobscot River, Maine

Matthew A. Mensinger; Erik J. Blomberg; Joseph D. Zydlewski

doi:10.1139/cjfas-2020-0402

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The consequences of dam passage for downstream-migrating American eel in the Penobscot River, Maine

Matthew A. Mensinger·Erik J. Blomberg·Joseph D. Zydlewski

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Abstract

American eel ( Anguilla rostrata ) often pass hydropower dams during adult spawning migrations. We conducted a 4-year acoustic telemetry study that characterized passage risks through two dams (West Enfield and Milford) in the Penobscot River, Maine, USA. We released tagged fish ( n = 355) at two sites, estimated survival and delay under variable river conditions, and compared performance among dammed and free-flowing river sections. Survival rates (standardized per river kilometre, rkm) were lower at West Enfield (Φ rkm = 0.984 ± 0.006 SE) and Milford (Φ rkm = 0.966 ± 0.007 SE) compared with undammed River sections (Φ rkm = 0.998 ± 0.0003 SE). Cumulative mortality was 8.7% (4.4 km) and 14.2% (5.5 km) through dammed sections and 8.7% throughout the rest of the river (58.1 km). Fish that already passed an upstream dam incurred higher downstream mortality compared with individuals without passage experience. Additionally, fish endured long delays at dams, and >10% of fish were delayed >24 h. Low flows exacerbated the risk of mortality and delay. These results offer evidence for direct, latent, and sublethal consequences of dam passage for migrating eels.

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Canadian Journal of Fisheries and Aquatic Sciences Article

Source-reported bounding extent: 44.94341743150153° to 45.24298649437894° latitude; -68.69064331054688° to -68.59176635742188° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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Matthew A. Mensinger, Erik J. Blomberg, Joseph D. Zydlewski. 2021. The consequences of dam passage for downstream-migrating American eel in the Penobscot River, Maine. https://doi.org/10.1139/cjfas-2020-0402

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