NSF Proposal: Evaluating SARP Barrier Assessments for Brook Trout

Evaluating the SARP Barrier Assessment Protocol for Brook Trout Passage at Culverts in Southern Appalachian Headwater Streams

Introduction

Road-stream crossings, particularly culverts, are a pressing issue causing habitat fragmentation in Appalachian headwater streams. The Southeast Aquatic Resources Partnership (SARP) has developed a protocol to assess fish passage potential at these crossings, but the protocol’s criteria lack validation with species-specific movement data. This knowledge gap is particularly urgent for Brook Trout, a native species with stringent habitat requirements and limited thermal tolerance.

Brook Trout require connected stream networks to access seasonal habitats for spawning, feeding, and thermal refuge (Stranko et al., 2008). These needs are increasingly constrained as fragmentation from road crossings, timber harvest, and urbanization reduces stream connectivity and increases water temperatures (Eschner & Larmoyeux, 1963; Niles & Hartman, 2021). When culverts interrupt this connectivity, populations may become isolated and more vulnerable to habitat degradation and climate stress (Chadwick & McCormick, 2017; Meisner, 1990). Although Brook Trout can leap vertically up to 3.5 times their body length, their success depends on adequate downstream pool depth and flow conditions (Kondratieff & Myrick, 2006). Many culverts rated as passable by the SARP protocol may lack the hydraulic or geomorphic conditions necessary for successful Brook Trout movement.

This study will ask whether Brook Trout can pass through culverts rated as passable under the SARP assessment protocol. I hypothesize that Brook Trout will exhibit reduced passage success at culverts with shallow pools or high flow velocity, even when these culverts are considered passable by structural design standards. Understanding this discrepancy is crucial for enhancing connectivity assessments and effective habitat restoration strategies.

Methods

To test this hypothesis, I will use a field-based observational approach. Study sites will be located in Southern Appalachian headwater streams on U.S. Forest Service lands. All selected culverts will have existing SARP assessments and be scored as passable. At each site, I will install paired Passive Integrated Transponder (PIT) tag antenna arrays on the upstream and downstream sides of the culvert. A sample of resident Brook Trout will be captured, PIT-tagged, and released within the stream reach. To assess directionality and ensure detection from both entry points, some tagged individuals will be released upstream of the culvert while others will be released downstream.

Antennas will operate continuously for at least four months, with the option to extend this period to six months if resources permit. This time frame is designed to capture seasonal movements, including low-flow conditions in late summer and potential upstream movements during the fall spawning period. The antennas will record all tagged fish that move past detection points.

While movement in both directions will be recorded, the primary focus of this study is upstream passage. Most culverts create barriers to upstream movement due to outlet drops, shallow downstream pools, or high velocities. Downstream movement, by contrast, is generally less restricted. A successful passage event will be defined as a fish detected at one antenna and then subsequently at the other, in a sequence consistent with upstream or downstream movement.

To understand how physical culvert conditions affect movement, I will collect field measurements including outlet drop, downstream pool depth, culvert slope, flow velocity, and substrate composition. These measurements will be taken during site visits using a flow meter and other standard tools. While this approach does not provide continuous flow data, nearby USGS stream gauges located downstream in the same watersheds will offer practical context. These gauges record continuous flow and can help estimate the general flow regime during the study period. Budget constraints limit the feasibility of installing continuous monitors at the study sites themselves. 

I will use generalized linear models to examine whether passage events correlate with physical features and to evaluate whether SARP scores predict actual movement outcomes. This study addresses the need identified by Raleigh (1982) and Isaak et al. (2015) for validating habitat-specific movement and planning strategic connectivity under climate change scenarios.

Intellectual Merit and Broader Impacts

This project will provide the first empirical validation of the SARP culvert passability protocol using data on Brook Trout movement. This species is ideal for testing passage assumptions because of its sensitivity to habitat fragmentation, sedimentation, and thermal stress (Eschner & Larmoyeux, 1963; Stranko et al., 2008). The study addresses a clear ecological and conservation gap by testing whether culvert design metrics predict actual biological outcomes. This research contributes to the understanding of stream connectivity, the impacts of barriers, and how fish behavior interacts with human infrastructure.

The project's broader impacts are promising. Results will inform land managers, restoration practitioners, and regional conservation planners. If Brook Trout fail to pass culverts considered structurally passable, it will highlight the need to revise assessment protocols or include more biological criteria. Over time, culverts may degrade and lose passability, so this study may also support reassessment timelines or long-term monitoring strategies. Findings could lead to better culvert inventories, improved prioritization of barrier replacements, and more effective conservation of cold-water stream habitats. In addition to conservation goals, improved connectivity supports recreational fisheries by maintaining healthy, self-sustaining populations. With Brook Trout representing both a cultural icon and a bioindicator species, their successful conservation has implications for broader aquatic biodiversity and watershed health.

References

Chadwick, J., & McCormick, S. (2017). Upper thermal limits of growth in Brook Trout and their relationship to stress physiology. Journal of Experimental Biology, 220(21), 3976–3987.

Eschner, A. R., & Larmoyeux, J. (1963). Logging and Trout: Four Experimental Forest Practices and Their Effect on Water Quality. The Progressive Fish-Culturist, 25(2), 59–67.

Hudy, M., Thieling, T. M., Gillespie, N., & Smith, E. P. (2008). Distribution, status, and land use characteristics of sub-watersheds within the native range of Brook Trout in the eastern United States. North American Journal of Fisheries Management, 28(4), 1069–1085.

Isaak, D. J., Wenger, S. J., Peterson, E. E., Ver Hoef, J. M., Nagel, D. E., Luce, C. H., Hostetler, S. W., & Dunham, J. B. (2015). The cold-water climate shield: Delineating refugia for preserving salmonid fishes through the 21st century. Global Change Biology, 21(7), 2540–2553.

Kondratieff, M. C., & Myrick, C. A. (2006). How high can Brook Trout jump? A laboratory evaluation of Brook Trout jumping performance. Transactions of the American Fisheries Society, 135(2), 361–370.

Marschall, E. A., & Crowder, L. B. (1996). Assessing population responses to multiple anthropogenic effects: A case study with Brook Trout. Ecological Applications, 6(1), 152–167.

Meisner, J. D. (1990). Effect of climatic warming on the southern margins of the native range of Brook Trout (Salvelinus fontinalis). Canadian Journal of Fisheries and Aquatic Sciences, 47(6), 1065–1070.

Niles, J., & Hartman, K. (2021). Riparian timber harvest intensity affects the diets of Appalachian Brook Trout. Transactions of the American Fisheries Society, 150(4), 490–502.

Raleigh, R. F. (1982). Habitat suitability index models: Brook Trout. U.S. Fish and Wildlife Service, Western Energy and Land Use Team.

Stranko, S. A., Hilderbrand, R. H., & Morgan, R. P. (2008). Brook Trout declines with changes in land cover and temperature in Maryland. North American Journal of Fisheries Management, 28(4), 1223–1232.