Data from a 4-year capture and transport program were used to assess translocation as a management strategy for two long-lived, federally endangered catostomids in the Upper Klamath Basin, Oregon. Lost River (Deltistes luxatus) and shortnose (Chasmistes brevirostris) suckers, two species endemic to the Klamath Basin, were translocated from Lake Ewauna to Upper Klamath Lake in each of 4 years (2014–2017) in an effort to augment existing spawning populations in Upper Klamath Lake. Lake Ewauna, downstream of Upper Klamath Lake and connected to it by the Link River, has small populations of Lost River and shortnose suckers. Upper Klamath Lake has the largest remaining population of Lost River suckers and one of the largest remaining populations of shortnose suckers. Adult suckers were captured in Lake Ewauna, tagged with passive integrated transponder (PIT) tags, and translocated to the Williamson River, a spawning tributary that flows into Upper Klamath Lake. We monitored initial success of translocation efforts with encounters from remote PIT tag antennas and physical recaptures.

A total of 659 suckers were translocated from Lake Ewauna to the Williamson River (40 in 2014, 384 in 2015, 172 in 2016, and 63 in 2017). All individuals that were translocated were assumed to be one of the endangered taxa, but recaptures indicated that some translocated suckers were misidentified and were instead Klamath largescale suckers (Catostomus snyderi), a non-listed species that is also endemic to the Upper Klamath Basin. Other recaptures of translocated individuals revealed conflicts in species identification between the two endangered taxa as well. Due to species identification conflicts, we analyzed translocated individuals by cohort (year of translocation) and sex only. Specifically, we documented encounters of translocated individuals at spawning locations and throughout the Upper Klamath Lake watershed, analyzed frequency of return to spawning sites, assessed fidelity to spawning sites, and monitored migration timing over three full years (2015, 2016, and 2017). Remote PIT tag antennas at 11 sites and 5 physical capture locations were part of a monitoring network to re-encounter translocated individuals. In contrast to other years of the study, high flows in the Williamson River in 2017 prevented the installation of a river-wide weir and upstream trap with associated PIT-tag antennas that routinely detect large numbers of tagged fish. As a result, re-encounter probabilities in 2017 were expected to be lower than 2015 and 2016.