Activity Patterns of Anadromous Fish below a Tide Gate: Observations from High?Resolution Imaging Sonar

The construction of dams and tide gates on waterways has altered the physical structure many coastal, estuarine, freshwater systems. These changes have come at a cost to fish populations, most notably diadromous species, which rely connectivity between marine anthropogenic structures can direct effects migrating fish, such as blocking passage, or more subtle effects, changing movement patterns. This study used high-resolution Adaptive Resolution Imaging Sonar examine behavior Striped Bass Morone saxatilis, large coastal predator, Alewife Alosa pseudoharengus Blueback Herring aestivalis (collectively known river herring), are forage below gate River in Wellfleet, Massachusetts, during herring spring spawning run. were persistently present downstream exhibited strong diurnal tidal Activity was highest night ebb tides. During peak outflow periods, observed milling dam scour pool, indicating delayed upstream passage. migration primarily associated with daytime incoming Downstream-migrating nighttime hours. While it documented that provided impediment migration, their effect predator could pose an additional challenge herring, further complicating recovery efforts. Due prevalence obstructed waterways, studying around is important understanding full range impacts these systems under varying ecological conditions relationships.