Phenacobius mirabilis (Girard, 1856)
Basis for Listing
The Suckermouth Minnow (Phenacobius mirabilis) is a peripheral species reaching the northern edge of its range in southeastern Minnesota, where it is restricted to the Cannon, Cedar, Root, Upper Iowa, and Zumbro river systems. From 1992-2011, there are 43 records of the species; however, in 37 of those records the total catch was 1-5 specimens, and there have been no large catches (greater than 20 specimens) reported from a single locality since 1966. The species historically occurred in the Mississippi River and several small tributaries, but these populations are likely extirpated. There have been no collections or reports from the Mississippi since 1953, Crooked Creek (1943), Garvin Brook (1964), Rollingstone Creek (1967), Wells Creek (1975), and Pine and Winnebago Creeks (1958). In the Cannon River system, the species once occurred in the mainstream, where the last collection was in 1960. In the Root system, it has been absent from the South Fork Root River and following creeks since the 1940s: Bear, Crystal, Diamond, Lynch, Pine, Rice, Rush, Silver, Torkelson, Trout Run, Upper Bear, and Willow. In the Upper Iowa system, the species has not been reported from Beaver Creek since 1960. In the Zumbro system, it was last reported from the Middle Fork Zumbro River in 1963 (Hatch et al. in preparation). The Minnesota Pollution Control Agency (MPCA) has conducted full community fish surveys in streams where the species occurs from 2004-2011. In the Cannon River system, Suckermouth Minnows were found at only 1 of 122 stations. In the Zumbro system, the species was absent at all 33 stations sampled. In the Root, it was present at 5 of 142 stations. In the Cedar, the species was reported for the first time in the Shell Rock River; however, system-wide it occurred at only 6 of 118 stations. The drastic decline in distribution and abundance, localized extirpations in Minnesota, and conservation status rankings primarily in states on the periphery of the species’ range, prompted listing the Suckermouth Minnow a special concern species in 2013.
The Suckermouth Minnow is a medium-sized minnow that is typically 6.5-10 cm (2.6-3.9 in.) total length, with a maximum of 12.5 cm (4.9 in.). Distinguishing characteristics include an inferior mouth, with fleshy lips and no barbels; a dark lateral stripe; 8 dorsal fin rays; 43-51 lateral line scales, and about 34 scale rows around the body. Breeding males have small tubercles on the head, frontal region of the body, and fins (Lyons et al. 2006). Eddy and Underhill (1974) reported nuptial males develop a bright iridescent blue and silver color.
The Suckermouth Minnow is a pioneer species that rapidly invades disturbed stream habitats and typically becomes extremely abundant. Range extensions in the upper Midwest have been attributed to impacts on streams from the conversion of land for crop production. However, following the species initial dominance, as stream habitats gradually stabilize, abundance noticeably declines, eventually persisting as a minor component of a stream community. Preferred habitats include riffles in low to moderate gradient warm water and highly turbid streams that are 1.0-12 m (3.3-39.4 ft.) wide and 0.6-1.5 m (2.0-4.9 ft.) deep, with primarily gravel substrates (Becker 1983).
Biology / Life History
There is very little life history information available on this species. In Wisconsin, Suckermouth Minnows reach sexual maturity during the second growing season (age class I) and are thought to have a very prolonged spawning season of multiple clutches, which may occur from late May through August. This could be an adaptation to streams exhibiting erratic flow regimes. The maximum lifespan of the species is 3 years. (Hatch et al. in preparation).
Conservation / Management
Basic research needs include a life history study and genetic analyses of stream system populations to determine management of the species as a single or multiple units. However, the most critical information missing at this time is finding the causes of the species' overall decline and localized extirpations. Stream habitat assessments at extant and historic sites should receive the highest priority in future management decisions. However, there is one plausible scenario that ought to be considered: fish survey data prior to the 1940s is extremely sparse, and it is impossible to determine how abundant and widespread Suckermouth Minnows were before the original landscape was converted to agricultural production. Perhaps streams have recovered sufficient channel stability that they no longer support the critical, though currently unknown, requirements of this species.
Conservation Efforts in Minnesota
Although it is uncertain at this time whether the Minnesota DNR's Legacy Program will help or hinder this pioneer species, which prefers disturbed and turbid streams, the program utilizes the Watershed Health Assessment Framework to rank watersheds. This diagnostic tool examines the following metrics: hydrology, geomorphology, biology, connectivity, and water quality. Analysis of these results from watersheds where the species occurs may identify causes of its decline in Minnesota.
References and Additional Information
Becker, G. C. 1983. The fishes of Wisconsin. University of Wisconsin Press, Madison, Wisconsin. 1052 pp.
Eddy, S., and J. C. Underhill. 1974. Northern fishes, with special reference to the Upper Mississippi Valley. Third edition. University of Minnesota Press, Minneapolis, Minnesota. 414 pp.
Lyons, J., P. C. Hanson, E. A. White. 2006. A photo-based computer system for identifying Wisconsin fishes. Fisheries 31(6):269-275.
NatureServe. 2013. NatureServe Explorer: an online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington Virginia. <http://www.natureserve.org/explorer>. Accessed 20 May 2013.
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).
Schmidt, K. P. 2000. Stream survey results for the Gravel Chub (Erimystax x-punctatus), Slender Madtom (Noturus exilis), and Bluntnose Darter (Etheostoma chlorosomum) in southeastern Minnesota. Final report submitted to the Minnesota Department of Natural Resources. 14 pp + figures.
Schmidt, K. P., and N. Proulx. 2009. Status and critical habitat of rare fish species in the Mississippi River from the Coon Rapids Dam to the Iowa border. Final report submitted to the State Wildlife Grants Program, Minnesota Department of Natural Resources. 29 pp.