Evaluating Novel Approaches For Improving Anadromous Fish Passage In Coastal Rivers

Author

Aaron BunchFollow

Date of Award

5-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Forestry and Environmental Conservation

Committee Chair/Advisor

Dr. Troy Farmer

Committee Member

Dr. Dennis DeVries

Committee Member

Dr. Heather Evans

Committee Member

Dr. Brandon Peoples

Committee Member

Dr. Todd Petty

Abstract

Few of the world's rivers remain free-flowing for over 1000 km, significantly impacting anadromous fish populations due to dam-induced habitat fragmentation. Three partial migration barriers (low-head dams) on North Carolina's Cape Fear River (USA)—lock and dam 1 (LD1), lock and dam 2 (LD2), and lock and dam 3 (LD3)—impact American shad Alosa sapidissima, Atlantic sturgeon Acipenser oxyrinchus oxyrinchus, and striped bass Morone saxatilis populations. Mitigation strategies to pass fish upstream have included conservation locking, nature-like fishway construction, and environmental flows (e-flows). This study introduced a novel e-flow (dam submergence flow), tested acoustic double-tagging techniques for tracking American shad at multiple spatial scales, assessed fish-flow relationships using spatiotemporal core space use data at LD1 for all species, and evaluated passage using acoustic telemetry and multistate models for American shad and striped bass, as well as environmental DNA for Atlantic sturgeon. Our findings suggest that dams were submerged at approximately 17,000 ft³/s. Double-tagged American shad in the treatment group with attached tags and revised tagging and handling protocols did not differ from the control group, and we recommend this approach. Fish exhibited changes in space use patterns following a modification to the nature-like fishway and showed a strong response to changing flow fields and flow magnitudes. American shad and striped bass showed a preference for the route with the highest attraction flow. American shad passed more often and quicker than striped bass, while tagged Atlantic sturgeon did not pass during the study. Flow generally enhanced passage probabilities for American shad and striped bass, especially at LD2 and LD3 compared to LD1. eDNA signaled passage of untagged Atlantic sturgeon above LD1 and LD2. To mitigate impacts, conservation locking should be conducted at all LDs in order to pass fish upstream during low-moderate flow periods, and lockage timing should align with the species-specific requirements. Given the evolutionary importance of flow regimes and habitat connectivity for anadromous fishes, management should aim to preserve riverine systems' natural functions, while considering human needs. A collaborative approach among managers, scientists, conservationists, and other stakeholders is essential for improving anadromous fish populations in this complex social-ecological system.

Recommended Citation

Bunch, Aaron, "Evaluating Novel Approaches For Improving Anadromous Fish Passage In Coastal Rivers" (2024). All Dissertations. 3576.
https://tigerprints.clemson.edu/all_dissertations/3576

Author ORCID Identifier

0000-0002-1855-5616