Bringing Pacific Lamprey Back to the Tucannon River With Artificially-Propagated Larvae
Abstract
The Confederated Tribes of the Umatilla Indian Reservation (CTUIR) have implemented a reintroduction program for Pacific Lamprey (Entosphenus tridentatus) in the Columbia River Basin due to population declines of this species throughout its historic range. Artificial propagation, a new frontier in restoration research for Pacific Lamprey, is one method that is supporting CTUIR reintroduction efforts in the Tucannon River, WA. In 2021 and 2022, CTUIR released approximately 850,000 artificially-propagated Pacific Lamprey prolarvae into the Tucannon River and tracked them in the wild using genetics. Objectives were to confirm the following:
1) Artificially-propagated (AP) larval lamprey can survive in the wild.
2) AP survivors can grow continuously across years and distribute downstream of release locations.
3) Genetic parentage assignments would match known cross records, and offspring locations would be observed nearest to their release group location.
In 2021 and 2022, twelve female and eighteen male lampreys were tissue sampled and cross-fertilized in the lab. The resulting larvae were reared to a minimum of 30 days post-fertilization. AP larvae were released into the Tucannon River in 2021 (n = 471K) and 2022 (n = 387K). Crosses were isolated into two release treatments (staggered release vs direct release) that were released at two sites in the Tucannon River. Prior to the first release of AP lamprey, no Pacific Lamprey were detected in the Tucannon River upstream of river kilometer 14 (Index 4) during electrofishing and eDNA surveys. Post-release electrofishing at multiple index sites in 2023 provided data on presence and distribution of AP survivors. Genetic analysis was conducted on all sampled larvae to determine whether they were AP offspring.
Of the 262 larval lampreys collected in 2023, only four “failed” to genotype. While larvae occurred at seven index sites, no AP fish were identified in the lower river (far from AP release sites). AP larvae were collected from the upper Tucannon River near larval release locations. Of the larvae successfully genotyped in survey samples from the AP release sites, 100% were assigned to one or two AP parents. Moreover, most of the fish were assigned to both parents, increasing the credibility of assignments.
Genetic parentage assignment indicated that AP Pacific Lamprey released into the Tucannon River survived and grew at rates of approximately 30 mm/yr for up to two years in the wild (SY21 average length = 102mm; SY22 avg length = 61mm). The crosses conducted in the laboratory were consistent with crosses identified from field collections and revealed that both direct and staggered release methods worked. However, contrary to expectation, AP larvae did not disperse far downstream in their first few years of life. Future years of results from genetic marking experiments will hopefully help to refine release methodology and specifically: 1) confirm AP survive to advanced life stages, 2) understand effects of density on emigration and transformation, and 3) provide information on Tucannon River carrying capacity for this species.
Authors
Citation
Seilo, Z., A. Jackson, A. Maine, M. Moser, J. Weaskus, K. Moses-Conner, P. Sheoships, G. Silver, and J. Hess. 2025. Bringing Pacific Lamprey back to the Tucannon River with artificially-propagated larvae. Oregon American Fisheries Society Meeting, February 27 – 28, 2025. Bend, OR.