Pacific Lamprey Translocations to the Snake River Boost Abundance of All Life Stages

Abstract

The Pacific Lamprey Entosphenus tridentatus is an anadromous fish that has severely declined in the Snake River basin. In 2007, the Nez Perce Tribe initiated translocation of adults to this region from the main-stem Columbia River and has continued the translocations to this day. These actions are aimed at restoring larval abundance along with holistic habitat improvements. We performed parentage and sibship analyses with 260 single-nucleotide polymorphism loci to monitor productivity of translocated lamprey over a decade (2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018). These results provide the first direct evidence that translocations boosted larval abundance, increased juvenile production in the interior Columbia River (~3% in 2017 and 2018), and demonstrated successful migration to the Pacific Ocean. Per capita juvenile production from Snake River adult lamprey translocations out-performed that of their volitionally migrating counterparts in the interior Columbia River, demonstrating that translocating adults to suitable habitats increased overall productivity. We projected that the translocations may eventually return enough adult offspring to the Columbia River to replace the annual take of adults for translocations, despite many adults likely returning to other basins. These translocations are also restoring Pacific Lamprey to historical areas where they had been nearly extirpated, which has impactful benefits both culturally and ecologically. Further, this study provided an unprecedented volume of data that has redefined key biological attributes, including timing of life stage transformation (average of 6.7-year-old juveniles), larval growth rates (~22 mm/year for the first 4 years), ocean duration (average of 5.1 years), dispersal (~3% of Snake River-origin adults that return to the Columbia River will divert to the Willamette River), and life span (median age of postspawn adults was 12.9 years). We even quantified a new biological phenomenon of delayed spawning, which occurs at low rates (~9%) in nature. These data provide an opportunity to monitor ongoing translocation efforts and inform adaptive management to aid species recovery.

Broad‐scale eDNA sampling for describing aquatic species distributions in running waters: Pacific lamprey Entosphenus tridentatus in the upper Snake River, USA

“…Curves are conditioned on the median value of the third covariate not depicted in a panel and are truncated to avoid extrapolation beyond conditions that occurred within the study area stream network access to and availability of suitable upriver and tributary spawning habitat is not limiting Pacific lamprey populations in this region (Clemens et al, 2017). Insufficient time has passed, however, to test this hypothesis using returns of offspring from translocated adults because the generation time for Pacific lamprey in this basin may exceed 15 years (Hess et al, 2022).…”

“…We were also uncertain about which life stage may have produced the positive detections. Although all such locations plausibly supported larval forms, some of the detections may also have resulted from recently translocated, naturally returning or overwintering adults, decaying carcasses following spawning or downstream‐migrating juveniles (Dawson et al ., 2015; Hess et al ., 2022), although this was immaterial for the delineation of occupied habitat. Finally, eDNA‐based detection of Pacific lamprey, while regarded as very high, may still fail to detect this species when it is present and warrant repeat sampling at a site (Burian et al ., 2021).…”

“…Pacific lamprey in the interior Columbia River basin exhibit a complex life history that may take well over a decade to complete (Clemens et al ., 2017; Hess et al ., 2022). All known populations are anadromous and consist of relatively large‐bodied, stream‐maturing adults (Hess et al ., 2014; Parker et al ., 2019) that spawn in late spring to early summer in low‐gradient streams or rivers, often in locations that also host spawning populations of Pacific salmon and steelhead ( Oncorhynchus spp.…”

“…Similar structures blocking access to historically occupied habitat on the Lemhi River and upper Salmon River have also been removed in the last few decades, but there has been no evidence of recolonization (IDFG, 2011). In Idaho, recent sampling indicated that indigenous populations of Pacific lamprey remained in the Snake, Salmon and Clearwater Rivers (IDFG, 2011; McIlraith et al ., 2015; Hess et al ., 2022), and in Oregon and Washington wild populations were believed to be present in the Imnaha and Grande Ronde Rivers (U.S. Fish and Wildlife Service, 2004).…”

“…In early summer, most adults are released in headwater tributaries or upper river main stems, where traditional ecological knowledge affirmed their historical presence (Tod Sween, Nez Perce Tribe, and Aaron Jackson, Confederated Tribes of the Umatilla Indian Reservation, personal communications). These adults presumably spawn shortly thereafter, although seasonal access issues occasionally led to stocking at other times, and some adults may have overwintered and spawned the following year (Hess et al ., 2022).…”