Platygobio gracilis (Richardson, 1836)
Basis for Listing
The inclusion of the Flathead Chub (Platygobio gracilis) in Minnesota’s ichthyofauna is based on a single specimen collected from the Red River of the North near the town of Climax in 1984 (Renard et al. 1986). In Manitoba, it is common in the Assiniboine River, which joins the Red River of the North at Winnipeg. The species occurs from the confluence downstream into Lake Winnipeg but is rare (Stewart and Watkinson 2004). Since 1984, the Red River of the North has been trawled at two stations and electrofished at 18 without success (Hatch et al. in preparation). Both survey techniques have been very effective at sampling the species in the Assiniboine River (D. Watkinson, pers. comm.). Elsewhere, the Flathead Chub is in jeopardy over a large portion of its range.
While it is uncertain whether the Flathead Chub is a native species to the state or was introduced into the Red River of the North, populations are known from Lake Winnipeg and the lower Red River in southern Manitoba, just across the Minnesota-Canada border (Hatach 2015; Schmidt 2016). Because frequent wide lateral flooding of the Red River could connect the southern Manitoba population with Minnesota, it is highly plausible that this minnow has extended its range southward into Minnesota waters. Further survey work is needed to attempt to relocate this species in Minnesota and clarify its distribution. Given its extreme rarity, and until more field data are available, the Flathead Chub was listed as a species of special concern in 2013.
The Flathead Chub is a large minnow, with some adults attaining sizes of 27-32.3 cm (10.6-12.7 in.) total length. Distinguishing characters include a streamlined body, with a depressed head; terminal maxillary barbel; and falcate dorsal, pectoral, and anal fins (Stewart and Watkinson 2004).
Adults prefer mid-channel bottoms of swift flowing large rivers, typically over substrates of gravel and sand. Schools have been observed in scour holes on the downstream side of stumps and boulders. Juveniles occupy shallow riffles along banks over shale, gravel, and silt infill (Stewart and Watkinson 2004).
Biology / Life History
Little information is available on the life history of this species. It is thought to spawn in the spring during high-water because nuptial adults are not found in the summer, when their habitat can be effectively sampled. In Alberta, the species' maximum life span is 5 years (Stewart and Watkinson 2004).
Conservation / Management
The coverage and intesity of sampling effort of 1983-1984, when 41 stations were electrofished over its entire length, has not been repeated in the Red River of the North (Renard et al. 1986). Additional surveys targeting the species are needed in the Red River of the North and lower reaches of large tributary streams. That said, the Red has a deeply incised trough-like channel over most of its length, and this habitat type often exceeds the effective range of electrofishing gear. Missouri trawls should be utilized in future survey efforts as this gear was designed to sample small benthic fishes from deep mid-channel habitats (Herzog et al. 2009).
References and Additional Information
Goldstein, R. M., J. C. Stauffer, P. R. Larson, and D. L. Lorenz. 1996. Relation of physical and chemical characteristics of streams to fish communities in the Red River of the North basin, Minnesota and North Dakota, 1993-95. USGS Water-Resources Investigations Report 96-4427. Minnesota Water Science Center, USGS, Mounds View. viii + 57pp.
Hacker, V. A. 1957. Biology and management of Lake Trout in Green Lake, Wisconsin. Transactions of the American Fisheries Society 86(1):71-83.
Hatch, J. 2015. Minnesota fishes: just how many species are there anyway? American Currents 40(2):10?21.
Herzog, D. P., D. E. Ostendorf, R. A. Hrabik, and V. A. Barko. 2009. The mini-Missouri trawl: a useful methodology for sampling small-bodied fishes in small and large river systems. Journal of Freshwater Ecology 24(1):103-108.
NatureServe. 2013. NatureServe Explorer: an online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington Virginia. <http://www.natureserve.org/explorer>. Accessed 28 May 2013.
Pflieger, W. L. 1997. The fishes of Missouri. Revised edition. Missouri Department of Conservation, Jefferson City. 372 pp.
Phillips, G, L. American Eel Anguilla rostrata (Lesueur, 1817). In J. T. Hatch, G. L. Phillips, K. P. Schmidt, and M. McInerny, editors. The Fishes of Minnesota (in preparation).
Renard, P. A., S. R. Hanson, and J. W. Enblom. 1986. Biological survey of the Red River of the North. Minnesota Department of Natural Resources, Division of Fish and Wildlife, Ecological Services Section, Special Publication No. 142, St. Paul. 60+ pp.
Schmidt, K. 2016b. Curious cases of fish occurrence: minnow mysteries. American Currents 41(2):16?22.
Stewart, K. W., and D. A. Watkinson. 2004. The freshwater fishes of Manitoba. University of Manitoba Press, Winnipeg. 300 pp.