Energetic Impacts of Passage Delays in Migrating Adult Atlantic Salmon
For any migratory organism, habitat connectivity is critical for population stability. Structures that impede movement between necessary habitats can be damaging to population persistence. In riverine systems, dams act as migratory barriers, altering ecosystems and delaying, injuring, or otherwise i...
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DigitalCommons@UMaine
2021
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| Online Access: | https://digitalcommons.library.umaine.edu/etd/3468 https://digitalcommons.library.umaine.edu/cgi/viewcontent.cgi?article=4511&context=etd |
| Summary: | For any migratory organism, habitat connectivity is critical for population stability. Structures that impede movement between necessary habitats can be damaging to population persistence. In riverine systems, dams act as migratory barriers, altering ecosystems and delaying, injuring, or otherwise impairing migratory fish movement into essential habitat. Critically endangered Atlantic salmon (Salmo salar) populations in Maine have been on the decline since the 1800s. Because most Atlantic salmon rivers are now highly dammed systems, hydropower dams have been cited as causal to the decline in returning adult populations. Previous studies have demonstrated that Atlantic salmon experience substantial delays below dams while moving upstream, but current state of knowledge with respect to metabolic costs and fitness outcomes for delayed Atlantic salmon provides no clear quantification of risk associated with this delay. I sought to understand consequences of delay in the context of an increased thermal experience below dams. With my collaborators, I have documented that water temperatures below surface-release dams remain several degrees warmer throughout peak summer months than water temperatures in upstream sections of river. Thus, adult Atlantic salmon experiencing delays below dams will be subject to warmer thermal experiences than if they had moved rapidly to upstream sections of river. As ectotherms, ambient water temperatures directly impact physiological processes, but salmonids generally have a narrow optimum temperature range. As waters warm to outside that range, metabolic processes become more energetically costly. That excess energy use might manifest itself in reduced individual reproductive success, or in the case of Atlantic salmon, a decrease in population iteroparity rates. In Chapter 1, we quantified the energetic cost of dam-mediated delays of adult migrating Atlantic salmon using HOBO temperature loggers, temperature-logging radio tags, and a Distell Fish Fatmeter as a noninvasive surrogate for ... |
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