Maine's Diadromous Fish Community: Past, Present, and Implications for Atlantic Salmon Recovery FEATURE: ENDANGERED SPECIES

Co-evolved diadromous fishes may play important roles in key life history events of Atlantic salmon (Salmo salar) in northeastern U.S. riverine ecosys- tems. We reviewed available information on the historic and current abundance of alewives (Alosa pseudoharengus), blueback herring (Alosa aestivalis), American shad (Alosa sapidissima), rainbow smelt (Osmerus mordax), and sea lamprey (Petromyzon marinus) for several rivers in Maine. Historically, these diadromous fishes were sub- stantially more abundant and were able to travel much farther inland to spawning and rearing areas in comparison to contemporary conditions. At historic abundance levels, these diadromous fishes likely provided several important functions for Atlantic salmon such as providing alternative prey for predators of salmon (i.e., prey buffering), serving as prey for juvenile and adult salmon, nutrient cycling, and habi- tat conditioning. Restoring the co-evolved suite of diadromous fishes to levels that sustain these functions may be required for successful recovery of the last native Atlantic salmon populations in the United States.