Ictiobus niger (Rafinesque, 1819)
Basis for Listing
Although the Black Buffalo (Ictiobus niger) was known in Minnesota historically from the Mississippi River as far north as Lake Pepin (Phillips and Underhill 1971; Becker 1983), there were no verified records before 1983. Since 1983, however, it has been verified as a part of Minnesota's fish fauna. Specimens have been collected from Pools 4, 7, and 8 of the Mississippi River (Pitlo et al. 1995) and from the lower portions of the Cottonwood River, a tributary of the Minnesota River (Hatch et al. 2003). Southern Minnesota appears to be this species' northern ecological limit (Hatch et al. in preparation). In 1984, when the Black Buffalo was initially designated a special concern species, information on distribution, abundance, preferred habitats, and life history was limited. In 2013, following the completion and analyses of targeted surveys, the status of the Black Buffalo was elevated to threatened.
The Black Buffalo is black on the back, dark green or bronze on the sides, and dull yellow or off-white below. It has a heavy, rounded body, long dorsal fin, conical head, and blunt snout. It has a small ventral mouth, with thicker lips than the similar Bigmouth Buffalo (I. cyprinellus), and a slightly more slender body than the Smallmouth Buffalo (I. cyprinellus) (Hatch et al. in preparation; Lyons et al. 2012). While the average total length of the Black Buffalo is 50.3 cm (19.8 in.) (Becker 1983), the largest recorded in Minnesota was 86.9 cm (34.2 in.) in total length, 51 cm (20 in.) in girth, and weighed over 9 kg (20 lbs.). The species is suspected of hybridizing with both buffalo species, which would make crosses difficult to identify (Lyons et al. 2012).
The Black Buffalo is found in sloughs, impoundments, and both fast- and slow-flowing portions of rivers (Hatch et al. in preparation). In Mississippi River Pool 4, from 1994-2015, 38 of 45 Black Buffalo were found in tailwater zones of dams; 3 in side channel borders; 2 in main channel borders, 1 in backwaters, and 1 in impounded shoreline. Secchi readings (transparency) ranged 27-100 cm (11-39 in.), depths of 1.0-8.0 m (3.3-26.2 ft.) (37 fish at 4.1 m [13.5 ft.] or more), and velocities of 0.0-0.57 m/s (0.0-1.9 ft./s) (41 at 0.29 m/s [0.95 ft./s] or less) (LTRMP 2016).
Biology / Life History
Little information is available on the life history of Black Buffalo in Minnesota, but it is thought to have similar habits to Smallmouth and Bigmouth buffaloes. The species, however, tends to occupy deeper water and areas of faster moving currents than the latter two species. The Black Buffalo's diet includes mollusks, insects, crayfish, duckweed, and algae. The species spawns from April to mid-June (Becker 1983).
Conservation / Management
The Black Buffalo is a rare species that is vulnerable to habitat degradation. There is a potential for significant impacts to this species from dams as a result of hampered fish passage and reduced habitat availability and from navigational maintenance on the Mississippi River. Further research into these threats and potential mitigation options are needed. Additional research needs for the Black Buffalo in Minnesota include life history studies, genetic analysis, identification of habitat guilds, and determination of the extent of its hybridization with Smallmouth and Bigmouth buffalo. Current genetic analyses methods cannot distinguish Black Buffalo from other buffalo species. However, the scope of ongoing research at Tulane University is attempting to solve the impasse (Dr. H. Bart, personal communication).
Conservation Efforts in Minnesota
Recent MN DNR (Proulx 2005; Schmidt and Proulx 2009) and Minnesota Pollution Control Agency (PCA) fish surveys have extended the species range upstream to Minnesota Falls in the Minnesota River and Minneapolis in Mississippi River Pools A, 1, and 2. In 2012, MN DNR fisheries biologists, surveying fish in a commercial catch, reported the first Black Buffalo from the St. Croix River downstream of Bayport (J. Stiras and N. Vanderbosch, personal communication). The recent inception of Minnesota’s Clean Water Legacy Program will eventually yield benefits to Black Buffalo habitats through nutrient and sediment load reductions.