Project Background

Sturgeon species across the globe face many threats to their continued survival in the wild including pollution, habitat degradation resulting from impoundments and water diversions, insufficient river flows, historical overfishing, and lack of access to spawning grounds. White sturgeon (Acipenser transmontanus, hereafter WS), are not federally listed in the United States, however, several population segments are state-listed as threatened and the Kootenai River population is listed as endangered. White sturgeon are also listed as endangered under the Canadian Species at Risk Act, and several populations of white sturgeon rely on conservation hatcheries for continued survival in the wild. Molecular genetics can help answer questions about white sturgeon biology that are difficult to answer using traditional survey techniques and can facilitate improvements in hatchery protocols to more effectively support the re-establishment of a self-sustaining wild population.

Upper Columbia River White Sturgeon: Estimating Number of Spawners (Ns)

Anthropogenic alterations to the Upper Columbia River have caused a complete lack of larval persistence in its population of WS, leading the Canadian government to list them as an endangered population. To mitigate this problem, conservation aquaculture programs rear larvae and release them as juveniles, at which point they have a high survival rate in the wild. While larvae were initially obtained by spawning adults in captivity, our previous research found that collecting fertilized eggs and larvae from the wild following natural spawning events captures significantly greater genetic diversity from the adult spawning population. This method has since comprised the basis of WS conservation aquaculture in the Upper Columbia River.

The period of captivity to which each year class is subjected while being raised in the hatchery provides a unique opportunity to easily obtain genetic samples that are representative of the wild breeding adult population. We are using 13 microsatellite markers as well as a newly developed panel of 325 single nucleotide polymorphism (SNP) markers to conduct population genetic analyses. Our primary aim is to estimate the number of spawning adults (Ns) in the Upper Columbia population, which is achieved through progeny array reconstruction with the program COLONY. An additional question we aim to address is whether larvae are drifting from the Canadian segment of the river downstream into the American segment, where individuals of this population are no longer afforded governmental protection. Samples from individuals collected in the American river segment matching to sibling groups from the Canadian river segment would confirm larval movement across international borders. Our results will help inform conservation and management plans, both in Canada and the United States.

Graduate Student Peter Johnson.

Snake River White Sturgeon: Estimating Number of Spawners (Ns)

            A major tributary of the Columbia River, the Snake River is impacted by numerous impoundments that divide the river into segments with white sturgeon populations connected by limited downstream migration. Recent studies in the Hells Canyon reach of the Snake River suggest a lack of juvenile recruitment, compounded by extremely slow growth and delayed age-at-maturity for adults, may be contributing to low population numbers in this reach. One potential driver of low juvenile recruitment is a low Ns, but determining Ns using traditional survey techniques is challenging due to their preference for spawning in deep and turbulent waters. We will address this question using genetics by estimating Ns based on the genetic diversity of their offspring. Our preliminary results using 13 microsatellite markers suggest that there are approximately 108-175 adult spawners represented by WS larvae collected in 2017. To further refine this estimate we will be using a recently developed SNP panel to examine if an increased number of genetic markers will help us to narrow our estimate for Ns. We will also be examining the potential effects of river flow on Ns. We collected samples during a high-water year (2017) and a more typical year in terms of river flow (2018) and our estimates of Ns from these two years will help us begin to understand how river flow might affect spawning success.

Anticipated Results: How will our work help WS conservation?

The results from this work will help us refine our estimates of the number of spawning adults in the Hells Canyon reach of the Snake River, which will improve our understanding of recruitment limitation and illuminate potential effects of river flow on Ns. Our Ns estimates will help inform decisions about potential translocations from other reaches of the Snake River, as well as providing evidence for consideration in flow regime decisions. This work will also allow us to better evaluate the genetic diversity within the Hells Canyon reach; smaller Ns values can lead to inbreeding depression and low genetic diversity, which means the population is more vulnerable to loss of individuals and further erosion of genetic diversity during stochastic events. Taken together, the results from this work will help inform genetic management of WS within the Hells Canyon reach of the Snake River, and will also contribute to our understanding of threats to the genetic health of WS populations across their range.

Graduate Student Aviva Fiske.