Staff | Status | Search | Report | Projects | Prevention | Glossary | Links | Kids


The Great Lakes have a long history of aquatic nonindigenous species (ANS) introductions – both intentional and unintentional. As of 2012, over 180 nonindigenous species have been reported to have reproducing populations in the Great Lakes basin, i.e. lakes Superior, Michigan, Huron, St. Clair, Erie, Ontario, and their connecting channels and water bodies within their respective drainages (Mills et al. 1993, Ricciardi 2001, Ricciardi 2006, Ricciardi unpubl. data). The two most recent ANS reported and verified established in the Great Lakes basin were Hemimysis anomala and Procambarus clarkii.

The number of Great Lakes aquatic nonindigenous species documented in GLANSIS must be interpreted as a minimum. Identification depends on our ability to find, recognize, verify, and document new species, which is, in turn, dependent on our ability to adequately sample the Great Lakes ecosystem.

Species Included in GLANSIS

Species are assessed for inclusion in the database on a case-by-case basis. The present database does not include waterfowl.

The present GLANSIS database consists of three lists:

Inclusion of the Sea Lamprey

The provenance of the sea lamprey in Lake Ontario is unresolved with Smith (1995) and Mandrak and Crossman (1992) arguing that it was non-native and Bailey and Smith (1981), Daniels (2001), and Bryan et al. (2005), among others, arguing that it was native. Regardless of its status in Lake Ontario, virtually all agree that it subsequently spread to the rest of the Great Lakes after the opening of the Welland Canal. We include it in this database because of its historic and present importance as an invader in most of the Basin and its devastating basin-wide impact on Great Lakes fisheries.

Database Structure

GLANSIS functions as a Great Lakes specific node of the USGS NAS national database. Information entered for GLANSIS automatically appears in NAS. GLANSIS provides targeted access to the information – especially collection records – for established Great Lakes nonindigenous species in the NAS Database. Our goal is to eventually complete profiles for all Great Lakes nonindigenous species that meet our criteria for listing (below).

Additional information on aquatic invasive species related to the Great Lakes region that are not included in GLANSIS – e.g., species which have been reported but not established, failed introductions, cryptogenic species for which evidence is considered insufficient (such as Gammarus fasciatus), range expansions within the Great Lakes, and species native to the Great Lakes which have invaded other regions of the U.S. may be available through USGS NAS.

GLANSIS Definitions and Criteria for Listing (Nonindigenous and Range Expansion)

Based on these criteria, the list of aquatic nonindigenous species found via GLANSIS is subject to constant revision.

Geographic criterion: Only species which are established in the Great Lakes basin below the ordinary high water mark -- including connecting channels, wetlands and waters ordinarily attached to the Lakes -- are included in the GLANSIS database. Species which have invaded inland lakes within the Great Lakes basin but not meeting the above geographic criterion are not included in the database.

Aquatic criterion: GLANSIS includes only aquatic species. USDA wetland indicator status is used as a guideline for determining whether wetland plants should be included in the list - OBL, FACW and FAC wetland plants are included in this list as aquatic; FACU and UPL plants are not. In keeping with this criteria, the following upland, facultative upland and terrestrial plants were removed from the list (12/08): Lotus corniculatus, Sonchus arvensis, Sonchus arvensis var. glabrescens, Carex flacca, Epilobium parviflorum, Polygonum caespitosum var. longisetum. Waterfowl, reptiles and mammals spending significant time in and dependent on the water are not currently included, but are being considered for addition to the database.

Nonindigenous criterion: The species included in GLANSIS are those which are considered nonindigenous within the Great Lakes basin according to the following definitions and criteria (based on Ricciardi 2006):

  1. The species appeared suddenly and had not been recorded in the basin previously
  2. It subsequently spreads within the basin
  3. Its distribution in the basin is restricted compared with native species
  4. Its global distribution is anomalously disjunct (i.e. contains widely scattered and isolated populations)
  5. Its global distribution is associated with human vectors of dispersal
  6. The basin is isolated from regions possessing the most genetically and morphologically similar species

Range expansion criterion: The species included in GLANSIS on the range expansion list are those which are considered nonindigenous to a portion of the Great Lakes basin according to the above nonindigenous criterion but which have been identified in the peer-reviewed literature and/or by consensus of expert review to be native to some portion of the basin.

Cryptogenic species are those species that cannot be verified as either native or introduced (after Carlton, 1996). These include species that may have been identified as invasive by one researcher, but for which a literature review reveals conflicting opinions. For example, Paranais frici and Pristina acuminata, listed as nonindigenous by Trebitz et al. (2009), are not considered so by others (Spencer & Hudson 2003, Moroz 1994).

Species that have been identified as cryptogenic are generally not listed, but are being considered for inclusion in a separate list or in the main GLANSIS list with an appropriate identifier.

Many species which have expanded their ranges within the basin (e.g., those native to Lake Ontario which have invaded Lake Superior) are now included in the GLANSIS database under the Species Category 'Range Expanders'. When searching for species nonindigenous to a particular lake or basin (e.g., species nonindigenous to Lake Superior) select nonindigenous + range expanders to ensure inclusion of these species in your search.

Note: Although widely used, the term 'invasive' is vague and subject to widely inconsistent usage. Biologically it is often related to the relative ability of a species to spread and establish in new areas, while legislatively and politically it is used to characterize a nonindigenous species “whose introduction does or is likely to cause economic or environmental harm or harm to human health” (Executive Order 13112, February 1999). Thus, the term 'invasive' has multiple meanings and requires a subjective judgment. We avoid using the term 'invasive', but may use the word 'invader', in the context that a nonindigenous species that has successfully established a reproducing population is an 'invader'. 'Exotic' is a commonly used synonym for 'nonindigenous'.

Established criterion: A nonindigenous species is considered established if it has a reproducing population within the basin, as inferred from multiple discoveries of adult and juvenile life stages over at least two consecutive years. Given that successful establishment may require multiple introductions, species are excluded if their records of discoveries are based on only one or a few non-reproducing individuals whose occurrence may reflect merely transient species or unsuccessful invasions.

Thus common carp, which were first collected in the Great Lakes in 1880, is included in the database. Grass carp, which is not believed to be reproducing in the Great Lakes (and so not established) is not included. While bighead and silver carp eDNA has recently (2009) been reported in southern Lake Michigan, presence of adult reproducing fish has not been verified, so these species are not included in GLANSIS either.

GLANSIS Definitions and Criteria for Listing (Watchlist)

The GLANSIS Watchlist represents a synthesis of research conducted between 1998 and 2010. As a result, it may not fully reflect the effect regulations established during that period have had or will have on vectors of introduction (e.g., ballast water, aquaculture, live food trade, bait). The list provided below is intended to be precautionary; if there is debate about a species probability of invasion (introduction, survival, establishment, and spread) in the Great Lakes, the preference is for inclusion on this list until such doubt is resolved.

Geographic criterion: Lives in a known donor region1 (e.g., rivers adjacent to Great Lakes, inland lakes in the Great Lakes region, western Europe, the Ponto-Caspian region) or in a zone with high specialization, species pool, or climate conditions that match the Great Lakes1.

Aquatic criterion: Within the context of the Great Lakes Aquatic Nonindigenous Species Information System (GLANSIS), the criterion of including only aquatic species is unchanged. USDA wetland indicator status is used as a guideline for determining whether wetland plants should be included in the list OBL, FACW, and FAC wetland plants are included in this list as aquatic; FACU and UPL plants are not. Waterfowl, reptiles, and mammals spending significant time in and dependent on the water are not currently included but are being considered for addition to the database.

Established critireon: NOT already established in the Great Lakes, but assessed as ‘likely’ to become so in peer-reviewed literature. Watchlist-specific criteria:2

  1. A transport vector currently exists that could move the species into the Great Lakes
  2. The species is likely to tolerate/survive transport (including in resting stages) in the identified vector
  3. The species has a probability of being introduced multiple times or in large numbers
  4. The species is likely to be able to successfully reproduce in the Great Lakes
  5. The species has been known to invade other areas


The species has been identified in one or more peer-reviewed scientific publications3 as having high probability for survival, establishment, and/or spread if introduced to the Great Lakes.

A note on climate change - The potential warming of the Great Lakes due to climate change is an important factor to consider in light of potential future invaders. This watchlist includes a few species for which predicted increases in water temperature have led to explicit remarks concerning future invasion probability. Otherwise, species which may be introduced but are not likely to overwinter given the current temperature regime are not included in this list of high probability invaders.

1This list is not comprehensive, as most published studies have been on the Ponto-Caspian region; very little information is currently available for other areas of the world with similar habitats or from which shipping traffic arrives to the Great Lakes (e.g., Asia, Central and South America).

2Species included on this watchlist meet at least three of these five criteria.

3Criteria and methods employed in these peer-reviewed publications vary but are generally consistent with the specified watchlist criteria.


Bailey, R.M., and G.R. Smith. 1981. Origin and geography of the fish fauna of the Laurentian Great Lakes basin. Can. J. Fish. Aquat. Sci. 38: 1539-1561.

Bryan, M.B, D. Zalinski, B. Filcek, S. Libants, W. Li, and K.T. Scribner. 2005. Patterns of invasion and colonization of the sea lamprey. Mol. Ecol. 14: 3757-3773.

Daniels, R.A. 2001. Untested assumptions: the role of canals in the dispersal of sea lamprey, alewife, and other fishes in the eastern United States. Env. Biol. of Fishes 60: 309-329.

Mandrak, N.E., and E.J. Crossman. 1992. Postglacial dispersal of freshwater fishes into Ontario. Can. J. Zool. 70:2247-2259.

Mills, E.L., J.H. Leach, J.T. Carlton, and C.L. Secor. 1993. Exotic species in the Great Lakes: a history of biotic crises and anthropogenic introductions. J. Great Lakes Res. 19: 1-54.

Moroz, T.G. 1994. Aquatic Oligochaeta of the Dnieper-Bug estuary system. Hydrobiologia 278: 133-138

Ricciardi A. 2001. Facilitative interactions among aquatic invaders: is an “invasional meltdown” occurring in the Great Lakes? Can. J. Fish. Aquat. Sci. 58: 2513-2525.

Ricciardi A. 2006. Patterns of invasion in the Laurentian Great Lakes in relation to changes in vector activity. Divers. Distrib. 12: 425-433.

Smith, S. H. 1995. Early changes in the fish community of Lake Ontario. Great Lakes Fishery Commission Technical Report 60, Ann Arbor.

Spencer, D.R. and P.L. Hudson. 2003. The Oligochaeta (Annelida, Clitellata) of the St. Lawrence Great Lakes region: an update. J. Great Lakes Res. 29: 89-104

Trebitz, A.S., J.R. Kelly, J.C. Hoffman, G.S. Peterson, and C.W. West. 2009. Exploiting habitat and gear patterns for efficient detection of rare and non-native benthos and fish in Great Lakes coastal ecosystems. Aquatic Invasions 4: 651-667.


Support for this project has been provided by the NOAA Invasive Species Program (Silver Spring, MD), the NOAA Great Lakes Environmental Research Laboratory (Ann Arbor, MI) and the Great Lakes Fishery Trust (Lansing, MI). The GLANSIS project has received 2010 funding from USEPA under the Great Lakes Restoration Initiative (GLRI) for several improvements.

See Also:

GLANSIS Poster (.pdf)

NOAA-GLERL Technical Memo 161: An Impact Assessment of Great Lakes Aquatic Nonindigenious Species (.pdf)