Lepomis peltastes Cope, 1870
Lepomis megalotis peltastes
Basis for Listing
Northern Sunfish (Lepomis peltastes) were not reported in Minnesota until 1974, when Steve Hirsch (DNR fish biologist) collected a specimen from Hustler Lake (St. Louis County) inside the Boundary Waters Canoe Area Wilderness (BWCAW). This lone population was initially assumed to be introduced to the state. However, additional occurrences were found upon the discovery that sunfish specimens in the James Ford Bell Museum of Natural History fish collection had been misidentified. State DNR fish surveys have since reported scattered occurrences in north central Minnesota, which dovetail with the species distribution in southwestern Ontario (Holm et al. 2009). Northern Sunfish are typically rare and represented by only a few specimens in the catch at any locality. The species inhabits lakes of exceptional water quality, a feature that also attracts lakeshore development. Since its known distribution in Minnesota was relatively recently expanded, there is no evidence of extirpations. However, there is an unconfirmed report (no extant specimen) from Keller Lake (Ramsey County) in 1978, when Steve Hirsch (pers. comm.) identified a single specimen in an angler’s creel survey. Since then, six lake surveys (through 2007) have not reported it. The species is threatened in Wisconsin (Lyons et al. 2000) and extirpated in Iowa, where it has not been reported since 1932 (Harlan and Speaker 1987). The species’ scattered distribution, low abundance, and potential loss of habitat and diminished water quality due to shoreline development prompted listing the Northern Sunfish a special concern species in 2013.
The Northern Sunfish is a small sunfish that is typically 5.0-12.5 cm (2.0-4.9 in.) total length but may attain a maximum size of 15 cm (5.9 in.). The flanks are dark bluish-olive; gill cover flap is greatly elongated, with a red margin in adults; and pectoral fins are short, with a rounded or blunted point. They have a very small mouth. Hybrids do occur with other sunfish (Lepomis spp.) species (Lyons et al. 2006).
Northern Sunfish inhabit clear lakes, with average water transparencies of at least 2.7 m (8.9 ft.). Shorelines are relatively unaltered, with emergent vegetation and extensive shallows less than 0.9 m (3 ft.). Substrates are firm, comprised of marl/sand/silt and covered with detritus and diverse submerged vegetation. Muskgrass (Chara spp.) is a prevalent component in the species habitat. Elsewhere, the species also occurs in clear, sluggish, and heavily vegetated streams; however, there has been only one locality reported in Minnesota from this habitat type (Porterfield and Ceas 2012).
Biology / Life History
Sexual maaturity is age-2 for both sexes. Larger older individuals (Age 4+) are the first to spawn in June. Smaller younger adults follow after the older individuals have left the spawning areas. Nests are constructed in vegetation beds at depths of 15-92 cm (5.9-36.2 in.). Reproductive strategies used in other sunfish species have not been observed in Minnesota Northern Sunfish, including cuckoldry, which is when smaller “sneaker males” slip into the nest while the resident male is spawning with a female. Juveniles less than 3.0 cm (1.2 in.) are found scattered along the shoreline, typically in dense beds of bulrush (Schoenoplectus spp.) or muskgrass (Porterfield and Ceas 2012).
Conservation / Management
Additional surveys are needed to fully understand the species distribution in Minnesota. Eleven populations have been ranked as most secure, uncertain, concern, and most at risk. Populations of concern include Eagle and Potato lakes in the Crow Wing River system; most at risk include the Whitefish Chain in the Pine River system and Woman Lake in the Boy River-Leech Lake system (Porterfield and Ceas 2008). Minnesota DNR Aquatic Plant Management (APM) staff should be updated regularly of species occurrences in their area lakes in order to consider mitigation measures when requests are received for either vegetation removal or deposition of sand for swimming areas.
Conservation Efforts in Minnesota
The Minnesota DNR has funded distribution, genetic, and life history studies on the species (Porterfield and Ceas 2012, 2008; Schmidt and Proulx 2009). Northern Sunfish habitats receive protection within the boundaries of Voyageurs National Park, Chippewa and Superior national forests and border lakes shared with Quetico Provincial Park in Ontario. The recent inception of Minnesota’s Clean Water Legacy Program will eventually yield benefits to the species' habitats through sediment and nutrient load reductions.