Notropis anogenus Forbes, 1885
Click to enlarge
Basis for Listing
The Pugnose Shiner (Notropis anogenus) is rare throughout its range and is often absent in apparently suitable habitat. While Minnesota remains the center of abundance for this species, at least 17 extirpations have occurred at historical locations in Minnesota (Schmidt in preparation). The species is widely distributed across the north central two-thirds of Minnesota; however, definitive abundance data is insufficient to fully assess status. Becker (1983) believed this species to be “in serious trouble throughout its range,” as it is extremely intolerant to turbidity and siltation. Removal of littoral vegetation from lakes and an increase in turbidity in lakes and streams are linked to its demise in other states. Both these phenomena have occurred at many of the historic Minnesota sites.
In 1996, when the Pugnose Shiner 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 Pugnose Shiner was elevated to threatened.
The Pugnose Shiner is a small, slender minnow with large eyes and a small terminal mouth that is oblique and almost vertical, giving it a distinctive pugnose appearance. They are silvery in color, with a dusky back and a dark lateral band that extends from their, snout through their eye, to a dark wedge-shaped spot on the base of their tail. The species average 4.6 cm (1.8 in.) long. This is the only species of Notropis native to Minnesota that has a heavily pigmented peritoneum (lining of the gut cavity), and their 8-rayed dorsal fin distinguishes them from the Pugnose Minnow (Opsopoeodus emiliae), which usually has 9 or 10 rays (Hatch et al. in preparation).
The Pugnose Shiner is also very similar in appearance to the Pallid Shiner (Hybopsis amnis), Ozark Minnow (N. nubilus), Weed Shiner (N. texanus), Blackchin Shiner (N. heterodon), and Blacknose Shiner (N. heterolepis) (Lyons et al. 2012). Pugnose Shiners have superior, strongly oblique to nearly vertical mouths. The other associated species have terminal mouths, though the Blacknose Shiner may sometimes have a slightly subterminal mouth. Blacknose Shiners have crescent-shaped scales in the lateral stripe, and both Blacknose and Weed Shiners have a lighter zone above the stripe.
The species is a very common associate of both the Blackchin and Blacknose shiners. In the Otter Tail River system of west central Minnesota, it can be found with both species as well as the Weed Shiner.
In Minnesota, the Pugnose Shiner inhabits clear glacial lakes and low gradient small-to-moderate-sized streams in areas of little current. Rooted aquatic plants or muskgrass (Chara spp.) is almost always present and is a more important limiting factor than substrate type. In Minnesota and Wisconsin, the species has been collected over bottoms of sand, gravel, mud, marl, and detritus. In Fish Lake (Le Sueur County) and Little Swan Lake (Todd County), the species migrates into water 1.2-1.8 m (4-6 ft.) deep by mid-May. As summer progresses, they move shoreward into waters 0.9-1.2 m (3-4 ft.) deep. They remain at this depth in the areas of thickest vegetation until late July, when they begin a slow migration back to deeper waters (paraphrased with permission from Hatch et al. in preparation, who cites Becker 1983; Doeringsfeld 1993; Porterfield and Ceas 2012).
Biology / Life History
In Fish Lake (Le Sueur County), both males and females reached sexual maturity at age-1. Younger (age-1) females produce mature eggs later in the season than older females; however, older females will spawn multiple times throughout the season. In 2010–2012, the average size of gravid age-1 females in Fish Lake was 35 mm (1.4 in.) total length. Total egg counts of all age classes from Fish Lake were 130–766, with higher counts coming from larger females. The descriptions of ovaries from both Minnesota and Wisconsin females indicate the production of multiple clutches in this species. The Pugnose Shiner most likely begins spawning in May and continues through July in Minnesota and Wisconsin. In Fish Lake, females with mature eggs were present from 23 May to 23 July. In Wisconsin, gravid females were collected on May 15 in one lake, and females resorbing eggs were collected on August 8 from another lake (Becker 1983). Females collected in June and July were gravid, partially spent, or entirely spent. Water temperatures were 21.1–28.9ºC (70.0-84.0 F) (paraphrased with permission from Hatch et al. in preparation, who cites Becker 1983; Doeringsfeld 1993; Porterfield and Ceas 2012).
The Pugnose Shiner is a timid and secretive species that immediately drops into vegetation when threatened. Their diet likely consists of plants, including filamentous algae, but also possibly microcrustaceans. This species occupies shallow water during warm months and deeper waters the remainder of the year. This is a short-lived species with a maximum lifespan of 3-years. Based on a specimen collected from Middle Fork Crow River (Kandiyohi County), the Pugnose Shiner attains 5.3 cm (2.1 in.) total length (Hatch et al. in preparation).
Conservation / Management
The Pugnose Shiner is vulnerable to the removal of littoral vegetation from lakes, the invasion of Eurasian water milfoil (Myriophyllum spicatum), increases in eutrophication from nutrient enrichment, and increases in water turbidity. The destruction of habitat may have isolated populations of this species and caused the entire range to be discontinuous. Additional losses of Minnesota’s populations would significantly impact the global security of this species (Hatch et al. in preparation). Monitoring and maintaining riparian areas around lakes and streams to avoid siltation as well as avoiding the removal of in-lake vegetation should be encouraged.
Conservation Efforts in Minnesota
The DNR’s Minnesota Biological Survey and State Wildlife Grant Program surveys (Schmidt and Proulx 2009) recorded this species at numerous new and historical locations across the central portions of the state, indicating a far wider distribution than previously thought. For the period 1950-1989, there were only 29 records, but from 1990-2013 there were 226 records. However, due to very limited funding, these surveys were conducted on a presence/absence basis, and more thorough sampling is needed to obtain accurate population estimates (Hatch et al. in preparation).
The recent inception of Minnesota’s Clean Water Legacy Program will eventually yield benefits to Pugnose Shiner habitats through nutrient and sediment load reductions. Shoreline owners are encouraged to explore the DNR’s Restore your Shore web page, which offers step by step suggestions in creating buffer strips to protect their lake’s water quality and explains why maintaining both terrestrial and aquatic vegetation is vital to Pugnose Shiners and other aquatic species.
A volunteer effort of the North American Native Fishes Association successfully established the species in Lake Elmo (Washington County) via donor stock from Fish Lake (Le Sueur County). Monitoring surveys in 2014 and 2015 found it abundant at all sites sampled (Nelson 2013; Schmidt 2014). The Pugnose Shiner, and a suite of four additional sensitive species, will serve as environmental indicators to reflect the success of the restoration efforts in lakes where natural colonization is no longer possible.
A genetic study of the Pugnose Shiner conducted at the University of Toronto found an east-west division between Iowa and Minnesota populations and others in Wisconsin, Michigan, New York, and Ontario. The data suggests two discrete post-glacial colonization routes emerged from the Mississippian Refugium, one northward and one eastward (McCusker et al. 2014).