Notropis topeka (Gilbert, 1884)
Basis for Listing
The Topeka Shiner (Notropis topeka) is restricted to small prairie streams that are tributary to the Missouri River in Lincoln, Murray, Nobles, Pipestone, and Rock counties in southwestern Minnesota. Streams in this region lie in an agricultural area used for cultivation and grazing. While it has been suggested that this species is intolerant of siltation, Minnesota observations suggest otherwise (Hatch, in preparation). Survival of the Topeka Shiner is, however, dependent upon careful land management. Once widespread and abundant in portions of Iowa, Kansas, Minnesota, Missouri, Nebraska, and South Dakota, this species now inhabits less than 10% of its original geographic range. For these reasons, the Topeka Shiner was listed as a special concern species in Minnesota in 1984. The species was also designated a federally endangered species by the U. S. Fish and Wildlife Service in1998.
The Topeka Shiner is a small minnow, not exceeding 8 cm (3 in.) in total length. It is silvery in color and has a prominent lateral band that ends in a small black chevron at the base of the tail fin. The snout is blunt and the mouth oblique. The anal fin has 7 rays. Males develop orange-red coloration in their dorsal, anal, and pelvic fins during the breeding season (Hatch 2001). The species is very similar in appearance to the Sand Shiner (N. stramineus), which is a common species associate. However, Topeka Shiners have a conspicuous chevron pointing forward at the base of the caudal (tail) fin.
Topeka Shiners inhabit slow-moving small to midsize prairie streams with sand, gravel, or rubble bottoms. They prefer pool and oxbow areas that are outside main channel courses. These pools are in contact with groundwater and usually contain vegetation and areas of exposed gravel. Groundwater research revealed that the aquifer in the Rock River Valley is thicker than in adjacent tributaries, indicating the species’ preferred off-channel habitats in tributary streams are more vulnerable to water loss from groundwater appropriation for agriculture and municipal uses (Berg et al. 2004). Adult Topeka Shiners exhibited a preference for medium size pools, 60-149 cm (24-59 in.) deep, with velocities less than 30 cm/s (12 ft./s) (Aadland and Kuitunen 2006).
Biology / Life History
The Topeka Shiner typically reaches sexual maturity in its second year. Spawning lasts from mid-May to early July, when water temperatures reach 22°C (71.6°F). During spawning, Topeka Shiners move from the deeper water of overwintering pools to the shallower margins of pools and slow runs. They do not build their own nests but use nests of Orange-spotted Sunfish (Lepomis humilis) or Green Sunfish (L. cyanellus). Males establish small territories around the nest and aggressively defend it from all other fish. The Topeka Shiner feeds at three trophic levels; eating zooplankton, small insects and their larvae, and vegetation (Dahle 2001; Hatch and Besaw 2001).
Conservation / Management
Water quality throughout the Topeka Shiner's range has been degraded by nutrient and pesticide run-off, heavy sediment loading, highway construction, urban development, and dewatering and construction of impoundments. Minnesota and South Dakota populations may be more secure due to availability of off-channel habitat as summer refugia and as low-predator environments (Dahle 2001; Hatch 2001). However, siltation of streams in southwestern Minnesota is still a concern and should be minimized. To protect Topeka Shiner spawning habitat, no in-stream work should be conducted before August 15.
Five genetic studies of Topeka Shiners have been conducted since 1988, though all used different techniques and none were systematic and comprehensive investigations of the species’ entire range. However, the studies do provide some insight to the genetic relationships among Topeka Shiner populations (Cunningham 2015). Significant variation occurs between the Lower Missouri River (Kansas and Missouri) and Upper Missouri River (South Dakota, Minnesota, and Iowa). Populations likewise exhibit significant differences on the watershed level (e.g. Big Sioux, Vermillion, James, and Des Moines). Although far from definitive, the studies further suggest this genetic differentiation also occurs in individual streams. Therefore, future conservation efforts need to focus on maintaining and protecting populations based on stream systems (e.g. Rock, Split Rock, and Pipestone).
Topeka Shiner have been successfully cultured and reared in small aquariums with little difficulty, even in the absence of active sunfish (Lepomis spp.) nests, which has been reported as a common reproductive strategy in streams. Fry hatched in July attained the length of approximately 2.5 cm (1 in) by December. The Missouri Department of Conservation has also cultured the species in a hatchery environment for reintroduction to historical habitats. One unintentional instance of pond culture appears to be a viable third option for maintaining captive populations, if future management needs in Minnesota require stocking sources. A landowner constructed a pond near Luverne, MN that had an intermittent connection to the Rock River. Jay Hatch (University of Minnesota) confirmed the presence of Topeka Shiners in the pond; the species was initially abundant, but vanished shortly after Largemouth Bass (Macropterus salmoides) were detected (Katula 2015).
Conservation Efforts in Minnesota
Until 2008, Topeka Shiner populations in Minnesota and South Dakota appeared stable, but monitoring surveys in Minnesota since that time have revealed a drastic decline in distribution and abundance. This was preceded by serious declines in the 1900s in Iowa, Nebraska, Kansas, and Missouri, where Topeka Shiners are absent from 80% of their historic sites. The Topeka Shiner was consequently afforded protection under the federal Endangered Species Act in 1998 and in June 2004, 372 km (231 mi.) of stream in Iowa and Nebraska and 974 km (605 mi.) in Minnesota were designated as critical habitat for the species.
Thorough Topeka Shiner surveys were conducted in Minnesota from 1997-2001 by the University of Minnesota with funding from the U.S. Fish and Wildlife Service and the Minnesota DNR. Survey results showed greater numbers of individuals and occurrences in Minnesota than in other parts of the species' range. Researchers also found Topeka Shiner numbers to be highest in off-channel habitats. Researchers continue to conduct hydrological and habitat analyses annually and the Minnesota Biological Survey targeted this species during their 2006 and 2007 surveys of southwestern Minnesota. Measures are being taken by the Minnesota DNR and the U.S. Fish and Wildlife Service to protect spawning fish from the impacts of development activities. Portions of several creeks and streams in the Big Sioux River Watershed are designated as critical habitat for the species. In March 2007, the City of Adrian completed the state's first ever Habitat Conservation Plan (HCP) to address potential impacts to Topeka Shiners resulting from increased annual consumption of groundwater at their municipal wellfield.
Presence/absence monitoring surveys have been conducted since 2004 (Nagle 2014; Nagle and Larson 2014). Topeka Shiners were present an average of 76.4% at randomly selected sites from 2004-2010. However, surveys detected a decline in relative abundance at all sites in 2009 and 2010. The lowest presence rate was found in 2010 at 60% of the sites of sampled and continued to decline in 2012 (40%), and 2013 (30%), then rebounded slightly in 2014 (45%).
Fish surveys were conducted at 10 stations in the Missouri River drainage (i.e. Rock, Nobles, and Jackson counties) near the Iowa state line in 2013. Topeka Shiners were found at three stations, with a cumulative catch of five individuals (Schmidt 2013). These surveys also collected the first specimens of Smallmouth Bass (Micropterus dolomieu) in the Rock (Rock County) and Little Rock (Nobles County) rivers. Later data queries found the Minnesota Pollution Control Agency reported the first known occurrences of the species from Little Rock in 2012 and Beaver Creek (Rock County) in 2013. Elsewhere in the Topeka Shiner’s range, the introduction of Largemouth Bass (M. salmoides) has been identified as one factor causing the drastic decline of the species. The impact on Topeka Shiners of a new piscivorous species in their habitats, which are relatively free of predators, is unknown and needs further study.
The recent inception of Minnesota’s Clean Water Legacy Program will eventually yield benefits to Topeka Shiner’s habitats through nutrient and sediment load reductions.