Species Native to the Region and Great Lakes Basin, but not the Rainy-Lake of the Woods Basin

After the species native to the Rainy-Lake of the Woods Basin were categorized, the database was filtered to identify those species that were native to the Region and Great Lakes Basin, but not the Rainy-Lake of the Woods Basin. This filter resulted in 99 species, including 61 fish species. For most of these species, concern of risk to the ecosystem in the Rainy-Lake of the Woods Basin is low because they have similar climates, predators, and competition from familiar species; therefore, these species are categorized as Low priority for risk evaluation. Additionally, many of these fish have been stocked for sport fishing, are widely used in bait trade, or have expanded their range owing to stream connections including artificial locks and canals. Two species were determined to be High-Approaching priority for risk evaluation: Trachemys scripta (pond slider), and Pectinatella magnifica (magnificent bryozoan). Pond sliders are expanding their range north up the Mississippi River Basin. They are common in aquarium trade and are often illegally released by pet owners (U.S. Geological Survey, 2012). They can outcompete native turtles, and the subspecies Trachemys scripta elegan (red-eared slider) is one of “100 of the World's Worst Invasive Alien Species” (Invasive Species Specialist Group, 2021a). Magnificent bryozoan can develop nuisance populations that foul intake pipes and interfere with fishing nets (Ricciardi and Reiswig, 1994; Wood, 2001). They also are a host species for the salmon parasite (Tetracapsuloides bryosalmonae) that causes proliferative kidney disease (Okamura and Wood, 2002).

Species Native to the Great Lakes Basin, but not the Rainy-Lake of the Woods Basin or the Region

Next, the species list was filtered for those species native to the Great Lakes Basin, but not the Rainy-Lake of the Woods Basin or the Region, resulting in 14 species, including 11 fish. Most of these species are native to the Eastern Great Lakes and have been introduced via purposeful stocking or bait buckets (U.S. Geological Survey, 2012). Three of these species are currently in the Rainy-Lake of the Woods Basin: Lepomis megalotis (longear sunfish), Thymallus arcticus (Arctic grayling), and Salmo salar (Atlantic salmon). Arctic grayling and Atlantic salmon have been stocked in the Rainy-Lake of the Woods Basin, and the longear sunfish is speculated to be native to Minnesota (U.S. Geological Survey, 2012). All but two of the species were categorized as Low priority for risk evaluation for the Rainy-Lake of the Woods Basin. Didymosphenia geminata (rock snot) and Gambusia holbrooki (eastern mosquitofish) are categorized as High-Approaching priority for risk evaluation. Rock snot are stalked diatoms that coat stream substrates and choke out all other vegetation, eliminating food sources for many invertebrates, which in turn decreases prey for fish (Ladrera and others, 2018). Eastern mosquitofish have been shown to displace populations of native fish after introduction for mosquito control. They not only prey on mosquito larvae but also outcompete other native fish by feeding on zooplankton, fish, amphibian eggs, and invertebrates (U.S. Geological Survey, 2012).

Species Native to the Region, but not the Rainy-Lake of the Woods or Great Lakes Basins

Twenty-four species, including 12 fish species, are native to the Region, but not the Great Lakes or Rainy-Lake of the Woods Basin. None of these species are currently in Rainy-Lake of the Woods. These species were all categorized as Low priority for risk evaluation. Many have been transported via bait bucket release, pet/aquarium release, or from range extension through connected water ways (U.S. Geological Survey, 2012). These species have natural predators and competitive species to keep any range expansion limited.

Marine Fish and Crocodilians

The next step in this process was to identify those species that pose a relatively low risk of introduction to the Rainy-Lake of the Woods Basin and therefore would be in the Low priority for risk evaluation category. Species were added to this Low priority for risk evaluation category systematically based on group, proximity, and transportation or spread. The first group that was wholly categorized as Low priority were the 137 marine fish. None of these species have been found in the Rainy-Lake of the Woods Basin according to the available databases and only two were found in the Region or Great Lakes Basin—Platichthys flesus (European flounder) and Lutjanus sebae (emperor snapper). The presence of these two species was due to individual releases from aquariums or ballast, and the species have not been known to reproduce in freshwater (Cooley and others, 2000; U.S. Geological Survey, 2012). Similarly, the seven crocodilian species also were categorized as Low priority for risk evaluation. Caiman crocodilus (common caiman) and Alligator mississippiensis (American alligator) have been recorded in the Region and (or) Great Lakes Basin; however, they were the result of pet releases or escape and these species would not be able to overwinter in the Rainy-Lake of the Woods Basin (U.S. Geological Survey, 2012).

Mammals

The next group to be evaluated and categorized as Low priority for risk evaluation were non-native mammals. A total of four mammals were in this group: Myocastor coypus (nutria), Hydrochoerus hydrochaeris (capybara), Zalophus californianus (California sea lion), and Otaria flavescens (South American sea lion). The only one of these species that was present in the Rainy-Lake of the Woods Basin was the nutria. Although nutria are known to cause a great amount of damage and have high fecundity, several studies have shown nutria have not adapted to overwinter during extended periods of freezing temperatures and, therefore, would likely not survive the climate in the Rainy-Lake of the Woods Basin (Gunderson, 1955; Gosling and others, 1983; Sheffels, 2013).

Species Present in Rainy-Lake of the Woods Basin

The remaining species (1,117) were subsequently evaluated on native status, proximity, transportation or introduction ease, and any extraneous details that may alter the evaluation. The first filtering for these species focused on proximity. Species that are currently (2021) present in the Rainy-Lake of the Woods Basin were identified and totaled 31, including 9 fish and 14 plants. Six of the fish species (all in the family Salmonidae) are intentionally stocked to maintain populations and were categorized as Low priority for risk evaluation. Of the remaining three, Piaractus brachypomus (pirapatinga) are tropical fish that were collected after aquarium releases and unable to survive the winter climate in the Rainy-Lake of the Woods Basin (U.S. Geological Survey, 2012); this species, therefore, was designated as Low priority. Cyprinus carpio (common carp) and Osmerus mordax (rainbow smelt) were introduced into the Region during the 1800s. Because they have been part of the ecosystem in the Rainy-Lake of the Woods Basin for more than a century, they were designated as High-Present priority. Similarly, Phalaris arundinacea (reed canarygrass) and Craspedacusta sowerbyi (freshwater jellyfish) have been present in the Rainy-Lake of the Woods Basin for several decades and categorized as High-Present priority (U.S. Geological Survey, 2012). The remaining species were categorized as Very High-Present priority. These invertebrates and plants are well-known aquatic invasive species including Butomus umbellatus (flowering rush), Lythrum salicaria (purple loosestrife), Dreissena polymorpha (zebra mussel), and Faxonius rusticus (rusty crayfish). Their presence in the Rainy-Lake of the Woods Basin is having a large effect on the ecosystem, including reducing wild rice habitat and displacing native crayfish (Minnesota Department of Natural Resources, 2008, 202114).

Species Present in the Region and Great Lakes Basin, but not in Rainy-Lake of the Woods Basin

There were 190 species on the list that were present in the Region and Great Lakes Basin, but not in the Rainy-Lake of the Woods Basin. These species were evaluated by group starting with the 27 algae. One species (Ulva (Enteromorpha) prolifera) was categorized as Low priority for risk evaluation because it is mostly marine. Two species (Chaetoceros muelleri and Chroodactylon ornatum) have not been reported since the early 1980s and were, therefore, categorized at Moderate priority. The remaining algae were categorized as High-Approaching priority. These species may eventually elevate to Very High priority if their spread accelerates, but most of the species were introduced via ballast and do not currently appear to be spreading quickly (U.S. Geological Survey, 2012).

One amphibian-frog, Xenopus laevis (African Clawed Frog), was on the list. This species may have been originally released from laboratories because they are used frequently in laboratory testing (U.S. Geological Survey, 2012). Occurrences in the Region have been limited to individual collections, so the species was categorized as Low priority for risk evaluation.

Six Annelids-Oligochaetes were on the list, and all were categorized as High-Approaching priority for risk evaluation. Four of these species are in Lake Superior or other basins near the Rainy-Lake of the Woods Basin, and NAS indicates two of these species (Gianius aquaedulci, Potamothrix vejdovskyi) have become the dominant benthic invertebrate species in nearshore areas (U.S. Geological Survey, 2012). Owing to their small size, they may be easily transported unknowingly via wildlife or human activities, which was a determining factor in their categorization.

Three bacteria species are present in the Region and Great Lakes Basin. Based on current risk assessments, Aeromonas salmonicida does not pose a significant environmental risk in the Great Lakes Basin (National Oceanic and Atmospheric Administration, 2019). However, these bacteria affect native and introduced salmon species (National Oceanic and Atmospheric Administration, 2019); therefore, Aeromonas salmonicida was categorized as High-Approaching priority for risk evaluation. Both Renibacterium (Corynebacterium) salmoninarum (bacterial kidney disease) and Piscirickettsia cf. salmonis (muskie pox) can have high infection rates and cause mortality in desirable native fish populations (National Oceanic and Atmospheric Administration, 2019). Bacterial kidney disease is present in adjacent basins and fish culture facilities, which may increase the rate of introduction.

The only bird species currently (2021) on the list for aquatic invasive species present in the Region and Great Lakes Basin, but not the Rainy-Lake of the Woods Basin, is Cygnus olor (mute swan). The mute swan was categorized as Very High-Approaching priority for risk evaluation for several reasons, including its presence in adjacent watersheds, its aggressive nature towards other waterfowl and humans, and its ferocious appetite, which causes uprooting of many aquatic plants including wild rice (U.S. Fish and Wildlife Service, 2019; U.S. Geological Survey, 2019).

The freshwater bryozoan Lophopodella carteri is native to Asia and is thought to have arrived attached to landscaping and greenhouse plants (U.S. Geological Survey, 2012). These bryozoans are able to survive the digestive tract of migratory waterfowl, which may provide a pathway into the Rainy-Lake of the Woods Basin (Bushnell, 1965). Because they can create nuisance encrusting colonies (Ricciardi and Reiswig, 1994), but are not yet present in adjacent watersheds, they are categorized as High-Approaching priority for risk evaluation.

The only nonindigenous Coelenterate-Hydrozoan in the Region and Great Lakes Basin but not in the Rainy-Lake of the Woods Basin is Cordylophora caspia. This species is present in the St. Louis River Basin and likely was introduced from ballast or in aquarium release. Owing to their competition with larva fish for zooplanktonic prey, they have been categorized as Very High-Approaching priority for risk evaluation.

The 20 species in the crustacean groups of amphipods, cladocerans, copepods, and mysid were evaluated together. Many of these species originally were introduced via ballast and are being spread with the assistance of recreational boats and other invasive species (U.S. Geological Survey, 2012; National Oceanic and Atmospheric Administration, 2019). These 20 species, their priority categories, and some simplified comments as to reasoning for the categorization are shown in table 1. These comments are based on information for each species within the databases. Those designated as Moderate priority for risk evaluation are not known to pose significant negative impact based on GLANSIS Risk Assessments (National Oceanic and Atmospheric Administration, 2019). Those in the High-Approaching and Very High-Approaching priority for risk evaluation categories all can pose negative impacts and have been categorized in these two categories mainly owing to the proximity to the Rainy-Lake of the Woods Basin.

Red swamp crayfish (Procambarus clarkii) are native to the Gulf of Mexico Region of the United States and are the only crayfish in the database that is present in the Region and Great Lakes Basin but not in the Rainy-Lake of the Woods Basin. They have been sold in aquaculture and aquarium trade, which has caused their introduction throughout the United States (U.S. Geological Survey, 2012). Red swamp crayfish are generalist feeders that compete with native crayfish, other invertebrates, and fish. Their burrows can destabilize banks, causing erosion and damage to vegetation including rice fields (U.S. Geological Survey, 2012). Because of the numerous possible impacts, red swamp crayfish are designated as Very High-Approaching priority for risk evaluation.

Forty-six fish species are on the list that are not yet present in the Rainy-Lake of the Woods Basin but are present in the Region and Great Lakes Basin. Many of those categorized as Low priority for risk evaluation are stocked sport fish or forage fish, failed warm-water aquarium releases, or cannot survive in the Rainy-Lake of the Woods Basin’s subfreezing climate (U.S. Geological Survey, 2012). The four species designated as Moderate priority for risk evaluation do not pose an immediate risk to the Rainy-Lake of the Woods Basin but have the potential to affect native food webs if introduced. Seven species were designated as High-Approaching priority. Four of these species are in the Duluth, Minnesota, area or Lake Superior; however, their mode of spread historically has been through stream connectivity and release or escape (U.S. Geological Survey, 2012). Therefore, if precautions are taken to educate the public that these species can alter native ecosystems and to help identify the spread, the spread of these species could be minimized (Anderson and others, 2008). The six species in the Very-High Approaching priority for risk evaluation category also are in watersheds adjacent to the Rainy-Lake of the Woods Basin (U.S. Geological Survey, 2012). These six species have had significant negative impact in aquatic systems where they have been introduced, including displacing native species, destroying habitat, and feeding on native fish eggs and larva. All six species are highly fecund species and are adaptable to the climate in the Rainy-Lake of the Woods Basin (U.S. Geological Survey, 2012). The 46 species not yet present in the Rainy-Lake of the Woods Basin but present in the Region and Great Lakes Basin, and comments as to the justification for their categorization, are shown in table 2. These comments are based on information for each species within the databases.

Thirteen mollusks are in the bivalve and gastropod groups summarized in table 3. The two species categorized as Moderate priority for risk evaluation prefer warmer waters than provided by the Rainy-Lake of the Woods Basin (U.S. Geological Survey, 2012); however, climate change may cause increased temperature in the Rainy-Lake of the Woods Basin, which would allow for warmer-water species to become established. The remaining species were categorized as High-Approaching or Very High-Approaching based on their proximity, fecundity, reproductive process, and impacts on ecosystems where they have been introduced.

The 55 plant species present in the Region and Great Lakes Basin, but not the Rainy-Lake of the Woods Basin, vary in their modes of spread and introduction as well as their priority categorization. The species, priority for risk evaluation, and comments as to proximity and reasoning for the categorization are shown in table 4. Six species are designated as Low priority for risk evaluation owing to proximity, climate preference, or questions regarding their native status. Similarly, eight species were designated as Moderate priority for risk evaluation owing to their moderate impact in other introduced areas or their distance from the Rainy-Lake of the Woods Basin. For example, Myosotis scorpioides (forget-me-not) is in proximity to the Rainy-Lake of the Woods Basin but has become naturalized and has had moderate impact on locations where it was introduced. The 24 High-Approaching priority for risk evaluation species could become Very High without oversight of their possible vectors. Lastly, the 16 Very High-Approaching priority for risk evaluation species are either directly adjacent to the Rainy-Lake of the Woods Basin or have successful reproduction and spread via multiple pathways. These 15 species have very invasive tendencies and can outcompete established native and non-native species.

The flat worms group, Platyhelminthes, has seven species in the Region and Great Lakes Basin. Five of these species primarily infect the exotic Eurasian ruffe and were categorized as Moderate priority for risk evaluation; however, they may be elevated to a higher priority for risk evaluation if the ruffe is introduced into the Rainy-Lake of the Woods Basin. Leyogonimus polyoon is the parasite that was responsible for mass avian mortalities in Lake Winnibigoshish, Minn., in 2007 and 2008 (U.S. Geological Survey, 2012). Because of its proximity and possible impact, it was designated as Very High-Approaching priority for risk evaluation. Ichthyocotylurus pileatus has been found in the St. Louis River headwaters and causes mortality in desirable native fish including Perca flavescens (yellow perch), Sander vitreus (walleye), and Percopsis omiscomaycus (trout-perch), as well as come cyprinid species (U.S. Geological Survey, 2012).

The last two groups present in the Region and Great Lakes Basin, but not the Rainy-Lake of the Woods Basin, are protozoans and viruses. All of these species are relatively close to the Rainy-Lake of the Woods Basin and can be transported via multiple pathways (National Oceanic and Atmospheric Administration, 2019). The four species that are ranked as Very High-Approaching have proven to have significant impacts, and in some cases high mortality, on the species they infect including P. flavescens, Micropterus salmoides (largemouth bass), and salmonoid species (table 5).

Species Present in the Region but not in the Great Lakes or Rainy-Lake of the Woods Basin

Currently 46 recorded non-native species are present in the Region but are not present in the Great Lakes or Rainy-Lake of the Woods Basins, with fish (35) accounting for most of the species. This filter was divided into fish species and non-fish species. The non-fish species, their assessment priority, and comments regarding justification for those categorizations are shown in table 6. Of the fish species, 28 were categorized as Low priority for risk evaluation and mostly consist of failed aquarium releases, stocked fish, or those that do not tolerate extended near-freezing temperatures (table 7). Six species of invasive carp are present in the Region; owing to the invasive nature of these species, they were all designated as High-Approaching. Three of these carp are the same species, Mylopharyngodon piceus (black carp), but are diploid, triploid, or undesignated reproductive status.

Species Present in the Great Lakes Basin but not in the Region or Rainy-Lake of the Woods Basin

Forty invasive species have been determined to be present in the Great Lakes Basin but not the Rainy-Lake of the Woods Basin or the Region; nine were fish and 13 were plants. Of the 18 nonfish and nonplant species, two were designated at High-Approaching because they have been found in other assessments to have ecological impacts to native communities (U.S. Geological Survey, 2012; National Oceanic and Atmospheric Administration, 2019) (table 8). The three species categorized as Very High-Approaching are plants that are able to form dense mats and crowd out native species (U.S. Geological Survey, 2012; National Oceanic and Atmospheric Administration, 2019; Agriculture Victoria, 2020). The High-Approaching plant species also are capable of outcompeting native species but are farther away and not as easily transported or spread (U.S. Geological Survey, 2012; National Oceanic and Atmospheric Administration, 2019).

Species Not Present in the Rainy-Lake of the Woods Basin, Great Lakes Basin, or Region

After all species present in the Rainy-Lake of the Woods Basin, the Great Lakes Basin, or the Region were categorized for priority of risk evaluation, the total was 809 species, with the majority being 422 fish species and 142 plant species. Of these species, only three were designated as High-Approaching: Procambarus virginalis (marbled crayfish), Filinia cornuta, and Filinia passa. The marbled crayfish has not yet been found in the wild but is a common aquarium pet (U.S. Geological Survey, 2019). The reason for the elevated priority is that this crayfish is able to produce fertilized eggs via parthenogenesis, which means all marbled crayfish are females and lay eggs that are already fertilized without sperm (U.S. Geological Survey, 2012). Because of this unique ability, even one marbled crayfish released from an aquarium could produce a viable population to become established in the wild. The other two species, Filinia cornuta and Filinia passa, are rotifers that, although not yet present in the Great Lakes Basin, have been found in ballast tanks within the Great Lakes Basin. Nineteen species were designated as Moderate based on either proximity or potential to be introduced as being native to or currently in similar climates as the Rainy-Lake of the Woods Basin. The remaining 787 species are currently categorized as Low priority for risk evaluation. Many of these species are tropical, native to areas within North America, or currently confined to coastal basins; however, they could pose a threat to the Rainy-Lake of the Woods Basin in the future (U.S. Geological Survey, 2012, 2019; National Oceanic and Atmospheric Administration, 2019; Centre of Agriculture and Biosciences International, 202125; University of Georgia - Center for Invasive Species and Ecosystem Health, 2021). All the species not yet found in the Rainy-Lake of the Woods Basin, the Region, or Great Lakes Basin have been determined to be nonindigenous, and those that have probable vectors for introduction may warrant additional attention by stakeholders.