Characterizing predation risk during Atlantic salmon smolt migration
Salmon populations across the globe have incurred substantial declines over the last 50 years with many on the verge of extinction. Among these, the Gulf of Maine Distinct Population Segment of Atlantic salmon (Salmo salar) has declined by > 95%, and was subsequently listed under the Endangered S...
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DigitalCommons@UMaine
2024
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| Online Access: | https://digitalcommons.library.umaine.edu/etd/4046 https://digitalcommons.library.umaine.edu/context/etd/article/5108/viewcontent/D_Mensinger_Matthew_Aug24.pdf |
| Summary: | Salmon populations across the globe have incurred substantial declines over the last 50 years with many on the verge of extinction. Among these, the Gulf of Maine Distinct Population Segment of Atlantic salmon (Salmo salar) has declined by > 95%, and was subsequently listed under the Endangered Species Act in 2000. Once inhabiting rivers throughout New England, Maine is the last place in the United States where sea-run adults return to spawn each spring. The majority of these fish return to the Penobscot River, which has been the focus of intense restoration and research efforts over the last two decades. The smolt stage of the salmon life cycle, when salmon migrate from freshwater to the marine environment, is a period of low survival. During migration, smolts incur high mortality as they negotiate impoundments, salinity differences, and novel predators in route to marine entry. Since 2005, researchers from the National Oceanic and Atmospheric Administration, University of Maine, and U.S. Geological Survey have tagged over 5,000 smolts to better characterize the risks incurred by smolts that move through the Penobscot River. These studies have revealed areas of elevated mortality and movement patterns that may be indicative of predation. High levels of predation, especially if beyond natural levels, can be a limiting factor in population recovery. However, beyond anecdotal accounts and evidence from other systems, there remains a critical knowledge gap in the understanding of smolt predation risk in this system. In this study, we used novel methods to quantify predation rates, identify smolt predators, and describe relationships between predation risk and environmental, seasonal, and individual influences during smolt migration in the Penobscot River. We tagged smolts with acid-sensitive acoustic predation transmitters with temperature sensors (n=270) from 2021–2023 to quantify predation rates and identify predator taxa. Tagging studies were paired with the use of Predation Event Recorders to capture ... |
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