Date of Award

Fall 2026

Abstract

Anadromous river herring, including alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis) provide critical ecosystem services across freshwater, estuarine, and marine habitats on the Atlantic coast. Population declines in recent decades have led to research and management efforts to improve adult survival and increase access to spawning habitats, primarily focusing on the freshwater phase of migration via barrier removal or remediation projects. Comparatively less research and management effort have investigated post-spawning movement behaviors and habitat usage, which may provide insight into developing successful management strategies. We used telemetry methods to assess barrier passage and track movements of adult river herring across freshwater and estuarine environments in the Bellamy River and Great Bay, New Hampshire, USA. In spring 2025, we tagged 120 individuals with PIT tags, 50 of which also had acoustic telemetry tags, including both sexes and both river herring species, at several freshwater sites in the Bellamy River, which were monitored with two PIT antennas and 27 acoustic telemetry receivers from May-June 2025. We found no evidence of upstream passage of two dam removal sites in the Bellamy River, likely arising from a combination of poor passage conditions (e.g., high flow conditions experienced in 2025) and adverse tagging effects (i.e., fallback). River herring tracked with acoustic telemetry resided in the study area for 15.4 ± 1.9 (SE) days, including usage of tidal and estuarine habitats for several weeks. 30% of acoustic tagged individuals made multiple upstream migrations, potentially indicative of oscillation behavior between estuarine and riverine habitats, and four individuals strayed to other rivers. Females were found to have significantly reduced apparent survival (12%) compared to males (52%). Analysis of movement timing indicated a preference for nighttime movements and an avoidance of low tides, which may be reflective of behavioral predator avoidance. Together, these results suggest that adult river herring display complex movement behaviors following exit from freshwater, including a reliance on estuaries, and that adult movement behaviors are system-specific, influenced by both abiotic and biotic drivers. Future river herring research should investigate drivers of outmigration survival and identify other systems in which within season straying and oscillation behavior may be adaptive for survival and reproduction. Management efforts should ensure suitable estuarine habitats are available for adult river herring during the migratory period.

Document Type

Master's Thesis

First Advisor

Nathan B Furey

Second Advisor

Remington Moll

Third Advisor

Matthew Ogburn

Department or Program

Biological Sciences

Degree Name

Master of Science

Download

Share

COinS