Were Bull Trout Successfully Reintroduced into the Wallowa River?

Whether reintroductions can be effective recovery actions for bull trout is unclear. Bull trout in the Wallowa River (Grande Ronde River subbasin, Oregon) have been considered extirpated since the 1950’s.  In 1997, 600 bull trout (70-380 mm in fork length) from the Imnaha River subbasin (Oregon) were introduced into the Wallowa River.  We evaluated 1) whether pure bull trout are currently present in the Wallowa River and, if so, 2) their most likely source.  From 2010-2013, 119 char were captured, and had tissue collected on which genetic analysis was performed.  The majority of these fish (71.4%) were pure bull trout, but first generation hybrids with brook trout were also observed.  The Wallowa bull trout were more similar to bull trout from the Imnaha River subbasin than to bull trout from the Grande Ronde River subbasin.  Wallowa River bull trout also exhibited evidence of a recent bottleneck, consistent with the translocation of fish in 1997.  The genetic diversity of these fish was low, possibly suggesting a small population size.  The 1997 reintroduction appears to have resulted in successful spawning, natural reproduction and recolonization of bull trout, however, genetic diversity remains low and the size of the population is unknown.