Introduced Fish in Maine
Alewife (Alosa pseudoharengus) Fact Sheet
- Alewife can occur in fresh waters as either historically present/restored anadromous or stocked landlocked forms. The same can be said for several other 'freshwater' fish species (Atlantic salmon, rainbow smelt, and white perch).
- Generally speaking, landlocked and anadromous forms of fish are very different in terms of their behavior and ability to adapt to various aquatic habitats. Although landlocked alewives may move between waterbodies, the population no longer has an inherent ability to migrate to the sea. Conversely, an anadromous alewife does not have the inherent ability to survive and prosper in inland lakes and ponds. Some individual fish may survive for a time, but are not capable of over-wintering, or completing their life cycle wholly in freshwater environments.
- The historical (pre-industrial or pre-dam) natural distribution of alewife in freshwaters is well documented by the Maine Department of Marine Resources and includes all waterways and waterbodies included in the current anadromous fish restoration program - representing all three Maine-New England native and indigenous Alosine- type fishes (alewife, blueback herring, and American shad).
- Anadromous fish populations, including alewife, are indigenous species which were historically an integral part of the freshwater ecosystem to which they are currently being restored. The trophic status of many of these waterbodies have become increasingly eutrophic over the past century. Given that the inherent capacity of anadromous alewives for entrance and departure from natal lakes and ponds are not interfered with (beaver dams, inadequate flow levels), then the lake water quality impact of their temporary seasonal presence should not be of major environmental concern.
- If for any reason (e.g., beaver dams, extended drought, dam regulation, inadequate fish passage) adult post-spawning anadromous alewives are not able to effectively exit from a given waterbody - then they will not survive, but will fall prey to avian and mammalian predators and/or scavengers and ultimately could be an additional source of nutrients to the aquatic ecosystem in which they occur.
Prepared by Dr. David Halliwell, Maine DEP (15 May 2004)
Reviewers: Jim Stahlnecker, Barry Mower, Dana Murch (Maine DEP); Gail Wippelhauser, Nate Gray (Maine DMR); and Merry Gallagher, John Boland (Maine DIFW).