23 American Currents Vol. 41, No. 4 IN SEARCH OF MINNESOTA’S CROSSOVER CONNECTIONS Konrad Schmidt Saint Paul, MN I have always been fascinated with fish distribution. Shortnose Gar Lepisosteus platostomus, Bullhead Minnow How did they get to where they are today? Of course Pimephales vigilax, Pugnose Minnow Opsopoeodus emili- since humans have arrived on the scene, we have played ae, Blackstripe Topminnow Fundulus notatus, Warmouth a major role in spreading species around both intention- Lepomis gulosus, Western Sand Darter Ammocrypta clara, ally through stocking or accidentlly via navigation and and River Darter Percina shumardi) in the Lake Michi- drainage projects. However, a pet peeve of mine is the gan basin. John Lyons (Wisconsin Department of Natural rush to judgment of so many biologists to conveniently Resources and NANFA member) believes at least 15 addi- dismiss new occurrences in drainages or disjunct locali- tional species have crossed this natural flood connection ties as bait-bucket releases. One case in point was the over the last several thousand years rather than just the 1974 discovery of Northern Sunfish (Lepomis peltastes) period following the construction of the navigation canal. in Minnesota from a very isolated lake miles inside the He noted early historical accounts report spring flooding Boundary Waters Canoe Area Wilderness. Access to the of the Wisconsin River flowing down the Fox River for lake is restricted to non-motorized watercraft requiring several days at a time. several long and rugged portages. The initial assumption Crisscrossing Minnesota doing fish surveys for more regarding the origin of this population was an illegal in- than 40 years I have become more and more intrigued troduction; however, the possibility of being a natural with road signs marking continental and drainage divides. occurrence was not ruled out (Phillips et al. 1982). Since then additional specimens have been found mislabeled in museum collections and additional fish surveys revealed the original occurrence is part of a spotty, but natural range through portions of several Great Lakes states and southern Ontario. Nevertheless, the position persists to- day in some circles that the Northern Sunfish is an intro- duced species in Minnesota. Over three decades ago, I received the just released Fishes of Wisconsin (Becker 1983) and immediately dove into the most comprehensive work done to date in the upper Midwest. I eventually read it cover to cover, but one of the most fascinating topics covered was crossover connections where intermittent fish passage corridors can form between drainages during high water periods. Becker listed several possible crossovers, but highlighted the low divide between the Fox and Wisconsin rivers at Portage (Figure 1) where floodwaters were deep enough to float canoes and barges. A navigation canal was completed in 1837 and widened with locks in 1876. This crossover is the suspected source of Mississippi River species (i.e., Figure 1. North American continental divides. http://www. halfwayanywhere.com/trails/continental-divide-trail/what-is- Photos and maps by the author unless otherwise indicated. the-continental-divide-trail/ Fall 2016 American Currents 24 Figure 2. Laurentian divide and crest near Virginia, MN. Figure 3. Laurentian divide near Browns Valley, MN. A few are obvious such as portions of the Laurentian di- 6 number 27). The “alien” species include: Greater Red- vide in northeastern Minnesota where today a range of horse (Moxostoma valenciennesi), Northern Hog Sucker hills, that were once lofty mountains a “billion” years ago (Hypentelium nigricans), Orangespotted Sunfish Lepomis( separate the Great Lakes from the Hudson Bay drainages humilis), Smallmouth Buffalo Ictiobus( bubalus), White (Figure 2). Bass (Morone chrysops), and White Crappie (Pomoxis an- However, more often than not, the landscapes are large nularis). All are indigenous to Minnesota, but this breach lakes or wetlands perched on the cusp of divides showing no is an early warning sign of what is coming and eliminating perceptible rise or fall whatsoever. One example is the same this crossover could become the last ditch effort to stop Laurentian divide to the west on the South Dakota border Asian Carp invading the Hudson Bay basin. In December near Browns Valley, Minnesota. Here, only a highway with a 2015 commercial fishermen caught the first Grass Carp normally stagnant culvert separates the Gulf of Mexico via (Ctenopharyngodon idella) from the Minnesota River near the Minnesota River from Hudson Bay via the Red River New Ulm. This was followed with the first Bighead Carp of the North, but water will flow either way dependent on (Hypophthalmichthys nobilis) in February 2016 at the same which side is higher (Figure 3). location. Six fishes reported north of the divide are assumed This low divide once was the spillway for Glacial Lake not native to the Red River of the North drainage, but Agassiz that drained melt water of wasting glaciers follow- do occur south of the divide in the Minnesota River and ing the last Ice Age and the source of the Glacial River War- may have utilized this crossover connection (see Figure ren. The present day Minnesota River and Mississippi down- 25 American Currents Vol. 41, No. 4 Figure 4. St. Anthony Falls by George Catlin (1796–1872). Figure 6. Minnesota’s major drainages and potential cross- overs (map key in Table 2). num), Northern Hog Sucker, Orangespotted Sunfish, and Stonecat (Noturus flavus) (Hatch et al. 2003). The barrier was restored in 2015 with the closure of the upper lock as a control measure to prevent the spread of Bighead and Silver Carp (H. molitrix), but the jury remains out if the closure was done in time. The second case in point was discovered by accident Figure 5. Freshwater Drum locality at Hatties Hole. Numbers when in 2001 an angler caught a Freshwater Drum (Aplodi- 37 and 38 are possible crossovers between drainages. notus grunniens) at Hatties Hole in the Rainy River on the stream of their confluence are mere trickles in comparison Ontario–Minnesota border. The species had never been to Warren, which cut an enormous valley spanning up to reported from the Lake of the Woods–Rainy River drain- five miles wide and 250 feet deep providing incredibly scenic age, but does occur over a virtually non-existenet divide vistas today (Wikipedia contributors). through a great expanse of flat-as-a-pancake peatlands in There are at least two instances in Minnesota where the Red Lakes, which is in the Red River of North drain- crossovers were created from fairly recent human inter- age. Countless connections of human origin may occur in vention. St. Anthony Falls in Minneapolis (Figure 4) is the general vicinity of crossover 37 (Figure 5). A century the best known. For 10,000 years since the last Ice Age, ago there was a massive effort to drain the peatlands for the falls functioned as a migration barrier with 123 fish- agriculture through a vast system of ditches that cross the es known below the falls, but only 63 above (Eddy et al. drainage at numerous points. They have not been main- 1963). However, since the construction of the Upper and tained in several decades, but most still flow today, provid- Lower St. Anthony navigation locks in 1963 at least eight ing multiple pathways to the Rainy River. There is possibly species have breached the historic barrier and now occur an alternate route from the Roseau River to the west also in the lower Mississippi Headwaters drainage. These in- via ditches at crossover 38. The appearance of Freshwater clude: Blackside Darter (P. maculata), Bullhead Minnow, Drum in the Rainy River is likely not a source of concern. Channel Catfish Ictalurus( punctatus), Flathead Catfish However, it may serve as an early warning of “Barbarians (Pylodictis olivaris), Gizzard Shad (Dorosoma cepedia- at the Gate” since Common Carp (Cyprinus carpio) occur Fall 2016 American Currents 26 Figure 7. Sensitive species: male and female Northern Sunfish (left) and male Least Darter (right). in the Red Lakes south of crossover 37, but remain absent, in drainages. The coordinates listed for crossovers should be for now, in Lake of the Woods drainage. viewed as general localities since multiple potential “passes” In 2013, I used a 500,000 plus record distribution da- often occur in close proximity to each other (Table 2). tabase to produce range maps for all 164 fish species that However, I must emphasize stocking and bait-pail in- occur in Minnesota. Displaying records spatially on a map troductions can never be entirely ruled out. I used a very is an amazing tool that often reveals overlooked occur- arbitrary and subjective “personal hedge filter” to sort the rences missed in routine data queries. Potential crossovers crossovers into confidence levels of primary and secondary surfaced between both continental, and also, watershed based on each species’ relation to human activities. Pri- divides within major drainages. Typically, a crossover mary crossovers involve extremely sensitive fishes which occurred in a watershed’s headwaters where one or more have no history of stocking or exhibit very high mortal- species were common on one side and appeared to “bleed” ity under the crowded conditions in a bait pail. Second- over establishing a beachhead, which more often than not ary crossovers may very well be valid, however, most of remains localized and does not spread. The map’s shaded these species have a history of introductions as game, for- relief background usually revealed a pass (i.e., lakes, wet- age, and/or bait species; transfers from long-defunct fish lands, or valleys) on the divide where suspected connec- rescue programs, or agricultural and navigation projects tions occurred. However, literature searches in other dis- (e.g., American Eel’s, Anguilla rostrata, presence in Lake ciplines such as geology, glaciation, soils, and hydrology Superior via the Welland Canal that bypasses Niagara are mandatory to confirm crossovers existed since the last Falls).