Session A5 - Designing Sustainable Fish Passage

The design and construction of fish passage--especially fish ladders--for diadromous fish is not new in Maine. At Damariscotta Mills, an original fishway constructed in 1807 has been rebuilt many times, and is currently undergoing another renovation. Other fishways of even more recent construction have fallen into deterioration, or have become ineffective due to the partial or complete failure of dams. The landscape of failed and failing fishways offers important lessons to modern day practioners of fish passage design, including the need to maintain dams and fishways and the need for more sustainable passage design. The NOAA Restoration Center approaches the issue of fish passage sustainability in various ways, including feasibility studies to assess if dam removal is a better option for fish passage, operations and maintenance plans as a requirement of publicly-funded projects, dam inspections and dam repairs by owners as a condition of fishway installation, and more sustainable, low maintenance fish passage designs. Examples of low maintenance designs currently being considered include aluminum baffles (rather than wood baffles) in Denil fish ladders, aluminum stop logs, rock ramp fishways, dam removals, and the replacement of undersized, perched culverts with open bottom arch culverts. Sustainability also requires a realistic assessment of fish passage effectiveness, and the need to diversify fisheries restoration across many watersheds of varying size and habitat quality as a buffer against the failure of individual fishways and the presence of natural barriers. The restoration of diadromous fish in watersheds without dams, especially hydropower dams, should be encouraged as an additional tool for sustainability