Evaluation of Nature-Like Fishways at Two Coastal Streams in New England

Nature-like fishway designs have been constructed in Europe and elsewhere with some success, but performance of these designs has not been extensively evaluated for North American species. Evaluating passage of adult anadromous clupeids to their spawning areas is especially important considering their recent dramatic population declines.  Two nature-like fishways in New England were evaluated for passage of alewives (Alosa pseudoharengus) using passive integrated transponder (PIT) telemetry and showed differing results.  At Town Brook in Plymouth, Massachusetts a 32 m long perturbation boulder rock ramp with a 4.2% slope passed 94% of attempting fish with most ascending in under 22 minutes.  At East River in Guilford, Connecticut a 48 m long steppool bypass design with a 7.1% slope passed only 40% of attempting fish with a median transit time of 75 minutes.  At both sites tagged fish passed rapidly downstream through the fishways after spawning. Nature-like designs are suitable for the passage of alewife but further evaluations are required to more precisely identify the influence of vertical drop per pool and specific local hydraulics on behaviors and passage performance for this species.