Restoring Connectivity in Coastal Wetlands to Enhance Northern Pike Spawning Habitat in a Large Regulated River

Recent habitat and connectivity loss in the St. Lawrence River system is primarily attributed to water level regulation and the spread and dominance of invasive hybrid cattail (T. X glauca).  Lack of access and wetland changes have influenced spawning habitat for potadromous fishes such as northern pike (Esox lucius), a top littoral predator in the system.  We examine if an amphibious excavator can be used to reconnect habitats via channel creation by linking main channels with their remnant meadow marsh areas to enhance fish spawning habitat.  The response of fish and riparian spawning habitat including wetland vegetation and seed bank response, predatory macroinvertebrates, temperature (ºC), dissolved oxygen (mg/L) and fish access given water levels (mASL) were compared among sites with connectivity enhancements to natural reference sites.  Exposed floodplain sediments following excavation showed a positive response of beneficial native plants indicating seed bank viability.  Use by 13 fish species was documented in created channels and northern pike production was observed with greatest success during periods of higher spring water levels.  We conclude that connectivity enhancements show a positive initial success for fish and their critical habitat but projects are constrained by the system-wide effect of water level regulation.  Continued investigation is needed to address longer-term vegetation succession and fish population-level responses.