Adult Rainbow Trout Habitats Selection in the Henry's Fork of the Snake River, Idaho
Location
Hager-Lubbers Exhibition Hall
Description
The Henry’s Fork is a high-elevation, 4th-order, groundwater-dominated river with notable seasonal changes in aquatic habitat. Previous fisheries research has focused on factors limiting the rainbow trout population. As a result, management and restoration were directed toward increasing recruitment. With current population numbers now equal to historical highs, our research focus has shifted to adult rainbow trout ecology and behavior. Field work during the summers of 2013 and 2014 was conducted in order to quantify available aquatic habitat and link trout position to environmental variables. Detailed habitat surveys indicate that macrophyte cover substantially increases throughout the summer and is a strong determinant of other in-stream habitat characteristics. Paired logistic regression shows that adult rainbow trout prefer greater depths. Water levels are highly dependent on macrophyte abundance at the reach scale, and available trout habitat increases through this interaction. However, when macrophyte abundance is high, adult trout show secondary preference for localized areas of lower macrophyte cover but otherwise show no selectivity for macrophyte cover, velocity, or substrate size. Future management strategies aimed at conserving the Henry’s Fork’s naturally reproducing rainbow trout population should consider the influence of primary production on habitat suitability.
Adult Rainbow Trout Habitats Selection in the Henry's Fork of the Snake River, Idaho
Hager-Lubbers Exhibition Hall
The Henry’s Fork is a high-elevation, 4th-order, groundwater-dominated river with notable seasonal changes in aquatic habitat. Previous fisheries research has focused on factors limiting the rainbow trout population. As a result, management and restoration were directed toward increasing recruitment. With current population numbers now equal to historical highs, our research focus has shifted to adult rainbow trout ecology and behavior. Field work during the summers of 2013 and 2014 was conducted in order to quantify available aquatic habitat and link trout position to environmental variables. Detailed habitat surveys indicate that macrophyte cover substantially increases throughout the summer and is a strong determinant of other in-stream habitat characteristics. Paired logistic regression shows that adult rainbow trout prefer greater depths. Water levels are highly dependent on macrophyte abundance at the reach scale, and available trout habitat increases through this interaction. However, when macrophyte abundance is high, adult trout show secondary preference for localized areas of lower macrophyte cover but otherwise show no selectivity for macrophyte cover, velocity, or substrate size. Future management strategies aimed at conserving the Henry’s Fork’s naturally reproducing rainbow trout population should consider the influence of primary production on habitat suitability.