Hybopsis amnis (Hubbs and Greene, 1951)
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Basis for Listing
The Pallid Shiner (Hybopsis amnis) is a rare species that reaches its northern distribution limit in the St. Croix River drainage of Minnesota and Wisconsin. Two specimens were collected from the St. Croix River north of Taylors Falls in the early 1900s, but subsequent intensive collecting has failed to reveal additional specimens in this drainage. Becker (1983) stated that the range of this species appears to have shrunk since 1930. Given its rarity in the state, the Pallid Shiner was listed as a special concern species in Minnesota in 1984. At the time, information on the species’ distribution, abundance, preferred habitats, and life history was limited. In 2013, following the completion and analyses of targeted surveys, the status of the Pallid Shiner was elevated to endangered.
The Pallid Shiner is a small, slender minnow that reaches a maximum total length of about 65 mm (2.6 in.) in Minnesota and Wisconsin (Hatch et al. in preparation). It is silvery in color and has a thin lateral stripe that extends from its tail through the eye and onto the snout. Its snout is blunt and extends far beyond its upper lip, and its mouth is small and almost horizontal. Its dorsal fin is high and has 8 rays (Eddy and Underhill 1974).
The Pallid Shiner is very similar in appearance to the Pugnose Shiner (Notropis anogenus), Ozark Minnow (N. nubilus), Weed Shiner (N. texanus), Blackchin Shiner (N. heterodon), and Blacknose Shiner (N. heterolepis) (Lyons et al. 2012).
The Pallid Shiner inhabits large- and medium-sized rivers and occasionally streams, often at the downstream ends of sand and gravel bars. It appears to avoid heavily silted habitats but has been collected over substrates ranging from mud, sand and gravel, to rocks. It seems to prefer slow-moving waters but has also been found in habitats with moderate to swift currents (Hatch et al. in preparation). The species rarely enters the mouths of smaller tributary streams (Eddy and Underhill 1974; Becker 1983).
In Mississippi River Pools 4 and 8, fish surveys collected 22 Pallid Shiners from 1989-2014 from the following habitats: backwaters (11 fish), main channel borders (6), and side channel borders (5). Secchi readings (transparency) ranged 31-84 cm (1-2.8 ft.); depths of 0.4-1.4 m (1.3-4.6 ft.); and velocities of 0.0-0.27 m/s (0.0-0.89 ft./s) (LTRMP 2016).
Biology / Life History
The reproduction of the Pallid Shiner has not been studied. As a short-lived minnow (probably a little over 2 years), it is most likely mature at 1-year (Kwak 1991). Males develop tubercles (small hardened breeding growths) on their heads, gill covers, pectoral fin rays, and branchiostegals (Hubbs 1951). Clemmer (1971) suggested that the species breeds from late winter to early spring in the southern part of its range. Its diet and feeding habits are unknown.
Conservation / Management
The Pallid Shiner is a rare species in Minnesota. Its known range in the state is limited to a heavily used portion of the Mississippi River, making it vulnerable to impacts from human activities. It is unknown if its rarity in Minnesota is a result of being at the northern limit of its range, or a result of human impacts, or a combination of both (Hatch et al. in preparation). Additionally, the habitat it occupies is very difficult to sample effectively, which may bias population estimates. Research needs for the Pallid Shiner include Minnesota life history studies, genetic analysis, and identification of habitat guilds.
Iowa DNR Long Term Monitoring Project (LTRMP) biologists reported the species from several stations in Mississippi River Pool 13 near Bellevue in 2014 and 2015. These were the first reports of the species during the program’s 25-year history of intensive sampling with multiple survey equipment and techniques. The suspected source of these recent occurrences is a downstream dispersion from Minnesota and Wisconsin Mississippi tributaries due to an extreme and prolonged period of high stream flows in 2014 (Bowler and Schmidt 2016).
Conservation Efforts in Minnesota
In 2002, the Pallid Shiner was reported from Pool 3 of the Mississippi River. This marked the first time the species had been recorded that far north in Minnesota since the late 1940s. Routine sampling of Mississippi River habitats, including waters surrounding sandbars, should be conducted to determine the status of the species. The Minnesota DNR Division of Ecological Services received a State Wildlife Grant to conduct surveys for rare fish species in the Mississippi River from the Twin Cities to the Iowa border. These surveys were conducted from 2006-2008 (Schmidt and Proulx 2009). The Pallid Shiner was a targeted species but was not collected.
The recent inception of Minnesota’s Clean Water Legacy Program will eventually yield benefits to Pallid Shiner habitats through nutrient and sediment load reductions.