The Influence of Metal Contamination on the Fishery of the Upper Clark Fork River, Montana, USA

Authors' Names

Taylor Gold QuirosFollow

Presentation Type

Oral Presentation

Category

STEM (science, technology, engineering, mathematics)

Abstract/Artist Statement

Historical mining and mineral processing have led to heavy metal contamination in the flood-plain of the Upper Clark Fork River of western Montana. This contamination has acted as a long-term stressor on the river and its inhabitants, the effects of which can be seen in changes in fish populations along the river's gradient of decreasing metal concentration with distance from the mining source. Understanding the relationships between stressors and ecological responses is essential for management and restoration goals pertaining to ecosystems negatively affected by anthropogenic activities. This study analyzed population distribution of salmonid species based on long-term monitoring and recent community composition surveys. Historical salmonid monitoring shows an unusual pattern in population density; instead of low trout density near metal-filled headwaters, lowest populations densities are located far downstream. At the headwaters, a previously strong relationship between trout recruitment and minimum flow during hatching (r² = 0.461, p = 0.003, n = 15, 2000-2019) has weakened significantly over the past three years, suggesting the influence of flow on recruitment is waning. Additionally, Brown Trout populations declined 4.5-fold from 1976 to 2021 at a heavily contaminated upstream site, while downstream populations showed a 2-fold increase in the same time period. Species composition changed very little among sites with communities dominated by Mountain Whitefish and Brown Trout. Along this spatial gradient, ratios of invasive Brown Trout to the native Mountain Whitefish increased from 4:1 to 52:1 between the upper and lower reaches of the river. Combined with the overall decrease in salmonid presence downstream, these findings suggest that the unusual population patterns of salmonids in the Upper Clark Fork River may be strongly influenced by species interactions in addition to environmental metal contamination.

Through close collaboration with the Montana Fish, Wildlife, and Parks Department, results from this study will help inform fisheries management on the UCFR as well as help direct future remediation and restoration efforts. Additionally, this work uses ecology-based methodology to evaluate the influence of anthropogenic stressors on fish communities in an open-canopy mid-order river.

Mentor Name

H. Maurice Valett

Personal Statement

Ecosystems affected by human activity are often described in terms of disturbance: an event occurs, causes damage, and the influence extends past those associated with the event itself. However, the effects of chronic anthropogenic influences (such as pollution) on ecosystems are of increasing and vital relevance to ecosystem function. These chronic ecosystem stressors affect all aspects, abiotic and biotic alike, and fundamentally change ecosystem structure and function. Freshwater systems, despite being vitally important to society, often bear the brunt of anthropogenic pollution as chemicals, trash, and other forms of waste are offloaded at multiple sites along the course of many rivers. Though restoration and management can mitigate these impacts, without a deeper understanding of how long-term stress affects the ecosystem as a whole, these actions often treat symptoms of the damage, and are unable to address the full scope of the harm. Thus, understanding how chronic anthropogenic stressors affect riverine systems is key to both management and restoration goals. Using fish, the top predators of riverine food webs, my research assesses how chronic metal stress has influenced the river at population, community, and ecosystem levels. It is impossible to completely restore what has been harmed, but through hard work and collaboration, we can work to lessen the recovery time for the imperiled ecosystems. Finding ways to shorten this recovery time and mitigate negative anthropogenic influences is the goal of my research, and the reason I became a scientist. I am fortunate enough to be conducting my research with support from the National Science Foundation's Established Program to Stimulate Competitive Research, which has funded the Consortium for Research on Enviornemtnat Water Systems (CREWS). CREWS plays an important role in supporting STEM research and education in Montana. As part of CREWS I have become a member of a network of interdisciplinary scientists that addresses Montana water quality issues and connects them to research at a national level. I have never seen collaboration of this extent, at such a high level of scientific work, and the value of these experiences cannot be overstated. My collaborators across the state, in the academic, public, and private sectors have taught me so much about science, about communication, and about working for something that you believe in. I have been able to pass on what I have learned to both scientific and non-scientific audiences and am committed to contributing to the ongoing work addressing stress ecology, both personally and professionally. This project has given me the skills and capabilities I need to reach these goals.