Introduced Fish in Maine

David B. Halliwell (Spring 2005)
Maine Department of Environmental Protection, Augusta

What is an introduced species?
Legal Issues
Acknowledgements
References & Literature Cited
Appendix A: Scientific Nomenclature of Maine’s Introduced Fishes
Appendix B: Historical Annotations for Introduced Maine Fishes
Appendix C: Alewife (Alosa pseudoharengus) Fact Sheet
Appendix D: White perch occurrence in Maine and New England freshwaters

What is an introduced species?
Biologists, and the public in general, use various terms to refer to species that occupy an area or waterbody, some of which are confusing and others that are often mistakenly applied. A general definition for an indigenous fish species is one that naturally inhabits waters within its historic biogeographical range, including all naturally occurring native fish species. In contrast, introduced fishes (alien, foreign, exotic, nonnative, nonindigenous, and transplanted natives: Fuller et al. 1999) are those found to occur in waterbodies (e.g., river drainages, inland lakes, coastal waters) outside of their natural distributions, as a direct result of human intervention.

By these definitions, introduced fishes in Maine (n = 20+) include a large number of established nonnative and native sport (game) and forage (bait) fish species comprising: (1) illegal transplants2 (e.g., black crappie, bluegill, central mudminnow, green sunfish, northern pike, and walleye); and (2) historic legal stockings2 - but also, in many cases, illegally transplanted (e.g., landlocked rainbow smelt, alewife, and white perch; chain pickerel, smallmouth and largemouth bass, and yellow perch). According to an article in the Bangor Daily News (May 13, 2002), Maine Department of Inland Fish and Wildlife fishery biologists have (recently) estimated that "more than 500 illegal fish (introductions) have been made into Maine (inland) waters since 1980, and about half of these species were not native to Maine" (hence, the other one-half are Maine native fishes!).

A third group of 'introduced' fishes comprise highly managed, hatchery-reared, and widely stocked salmonids (i.e., landlocked Atlantic salmon, brook, brown, and rainbow trout, lake trout, and splake - hybrid between lake and brook trout), in addition to introduced landlocked forage populations of rainbow smelt and alewife. Landlocked Atlantic salmon and rainbow smelt (Warner 2001) are truly indigenous to individual lakes in only four separate Maine river drainages: Presumpscot - Sebago Lake; St. Croix - East and West Grand Lake; Penobscot - Sebec Lake; and the Union - Green Lake (Warner and Harvey 1985).

Following is a listing of species within representative groups of introduced fishes occupying Maine waters (see Appendix A for scientific nomenclature). This listing is also applicable to freshwaters throughout New England, with the exception of the Lake Champlain drainage system in western Vermont - which is characterized by a more diverse indigenous fish fauna, as influenced by the richer species pool from the Great Lakes fish fauna (Halliwell et al. 1999).

1. Intercontinental (European and Asian) Origins: Exotic fishes including common carp, goldfish, and rudd, as well as several non-established aquarium-released and sub-tropical fish species (i.e., ide-or golden orfe and giant snakehead).
   
2. Intracontinental (Interstate-Province) Origins: Introduced non-native fishes from adjacent states/provinces include illegally transplanted black crappie, walleye, northern pike, muskellunge, white catfish, bluegill, green sunfish, central mudminnow, and emerald shiner - as well as both legally stocked and illegally transplanted smallmouth and largemouth bass.
   
3. Legally stocked and illegally transplanted (landlocked) native coastal fish species - including white perch, rainbow smelt and alewife, and native inland fish species - including chain pickerel, yellow perch, golden shiner and fathead minnow.
   
4. Another group of freshwater fishes, that may or may not represent possible Maine introductions, comprise the following species: spottail shiner, eastern silvery minnow, and gizzard shad.
   
   Spottail shiner and eastern silvery minnow (primarily larger-river cyprinids), were originally listed by Kircheis (1994) as historically occurring, nonnative bait-fish introductions. Spottail shiner are now very abundant in the lower Kennebec River (personal communication, Nate Gray, Maine DMR), while eastern Silvery minnow have not been further reported from Maine waters. Gizzard shad were only recently found, comprising four adults (2000) in the lower Kennebec River in Waterville (personal communication, Brandon Kulik, KA). The origin of gizzard shad in the Connecticut River (MA) was considered a natural range extension (O'Leary and Smith 1987). Gizzard shad, which now occur in the Merrimack River in Massachusetts, have also been observed in recent years below the lower dam on the Saco River in Maine (Jim Stahlnecker, Maine DEP).
   
5. Other potentially invasive freshwater fishes species, not yet found to occur in Maine, but nevertheless, populating neighboring New England states, include yellow bullhead (Ameiurus natalis) and rock bass (Ambloplites rupestris).

Currently, there are 63 fish species established or populating Maine freshwaters (= 60 reported by Halliwell et al. 1999 + central mudminnow, bluegill and green sunfish), not including walleye, and gizzard shad - which are represented in Maine by only adult fish at this time, with no known natural reproduction occurring. Nearly one-third of Maine’s existing resident fish fauna were introduced from out-of-state, both legally by State/Federal fishery agencies (e.g., smallmouth and largemouth bass, brown and rainbow trout) and illegally by unauthorized introductions (e.g., green sunfish, bluegill, northern pike, muskellunge, and central mudminnow). There are also hundreds of records of both authorized and illegally introduced land-locked populations of native coastal and inland fish species (e.g., primarily white perch, rainbow smelt and golden shiner, but also several records of landlocked alewife, as well as numerous historical transplant records for chain pickerel and yellow perch. Illegal fish introductions to Moosehead Lake include yellow perch (mid-1950's), smallmouth bass (mid-1970's), and white perch (1984) - all of which have become established to the detriment of the wild brook trout fishery (Maine DIFW Lake Report, 2003 update). Introduced fish species inhabit a multitude of inland Maine water bodies statewide as a result of both historical and current legal sport/forage fish stockings and illegal sport/bait fish transplants. The indiscriminate and unauthorized distribution of any fish species, whether they be Maine natives or exotics, must be prevented, at all costs, in order to protect and sustain the biological integrity and future of Maine's valuable aquatic natural resources.

Legal Issues!

The introduction (intentional release) of any fish species (from any source), without a permit from the Maine Department of Inland Fisheries and Wildlife, is a Class E crime, punishable by fines up to $10,000, including jail time and loss of license to fish. A new Maine law took effect on June 23, 2003, which prohibits the transport of all live fish from their natural place of origin - with the exception of legally permitted baitfish species, inclusive of rainbow smelt. A $2,000 reward is offered for information leading to the apprehension of the person or persons responsible for the illegal introduction of fish into any inland water in Maine. This would include releases of unwanted aquarium fish species and the dumping of live baitfish into a foreign waterbody at the end of a day's fishing! The environmentally responsible and acceptable action is to dispose of unwanted bait by leaving on the land or ice to provide food for mammalian and avian scavengers. To report violations of Maine's Fish and Wildlife laws, call Operation Game Thief at 1-800-ALERT-US (1-800-253-7887).

Acknowledgments

Thanks to Peter Vaux (University of Maine, Senator George J. Mitchell Center), Dave Courtemanch and Barry Mower (Maine DEP) and the following fish and wildlife professionals, for their critical review of this paper and as primary sources for Maine freshwater fish status and occurrence information - including Maine DIFW retired (Owen Fenderson and Robert Foye - deceased, Matt Scott, Ken Warner, Fred Kircheis) and active biologists: Forrest Bonney, Dave Boucher, Francis Brautigam, Scott Davis, Phillip deMaynadier, Merry Gallagher, Paul Johnson, Jim Lucas, and Bill Woodward; Maine DMF: Nate Gray and Jim Stahlnecker (past); Brandon Kulik (Kleinschmidt Associates) and Chris Yoder (Midwest Biodiversity Institute). Thanks also to a host of newspaper writers for their active interest and timely reporting of introduced fish related happenings, including: Dwayne Rioux (past), Ken Allen, Joe Rankin, and Jonathan Humphrey (Morning Sentinel and Kennebec Journal); Deirdre Fleming (past), Misty Edgecomb, John Holyoke and Terry Farren (Bangor Daily News), and contributors from the Associated Press, as commonly published in the Portland Press Herald.