Selection and scour of brown trout spawning gravels along a geomorphic gradient of the Logan River, Utah
Location
Eccles Conference Center
Event Website
http://water.usu.edu/
Start Date
3-30-2011 10:30 AM
End Date
3-30-2011 10:35 AM
Description
A decrease in exotic brown trout (Salmo trutta) abundance with increasing elevation may be caused by unfavorable abiotic conditions, including scour and displacement of brown trout fry during spring floods. In 2009 and 2010, we investigated relationships between the geomorphic template and selection and scour of brown trout spawning gravels within study reaches along an elevational gradient of the Logan River, Utah. Across reaches, densities of spawning adults demonstrated a strong positive relationship with gravel availability. A comparison of egg burial versus scour depths suggested that scour of not-yet-emerged fry in spring 2009 was near 35%, compared to 3 % in 2010, due to a longer 2009 flood duration. However, scour depths did not increase with increasing elevation and/or reach shear stress. Although a preference for microsites with low shear stress helps protect fry from scour, high scour depths may cause mortality of a significant percentage of incubating fry at all elevations during high flood years. Mortality could be greater at high elevations, where emergence is more closely timed with the spring flood event, potentially limiting brown trout abundance.
Selection and scour of brown trout spawning gravels along a geomorphic gradient of the Logan River, Utah
Eccles Conference Center
A decrease in exotic brown trout (Salmo trutta) abundance with increasing elevation may be caused by unfavorable abiotic conditions, including scour and displacement of brown trout fry during spring floods. In 2009 and 2010, we investigated relationships between the geomorphic template and selection and scour of brown trout spawning gravels within study reaches along an elevational gradient of the Logan River, Utah. Across reaches, densities of spawning adults demonstrated a strong positive relationship with gravel availability. A comparison of egg burial versus scour depths suggested that scour of not-yet-emerged fry in spring 2009 was near 35%, compared to 3 % in 2010, due to a longer 2009 flood duration. However, scour depths did not increase with increasing elevation and/or reach shear stress. Although a preference for microsites with low shear stress helps protect fry from scour, high scour depths may cause mortality of a significant percentage of incubating fry at all elevations during high flood years. Mortality could be greater at high elevations, where emergence is more closely timed with the spring flood event, potentially limiting brown trout abundance.
https://digitalcommons.usu.edu/runoff/2011/Posters/26