Cycleptus elongatus (Lesueur, 1817)
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Basis for Listing
Historically, the blue sucker was a highly sought commercial species that was locally known as the sweet sucker. Pollution, dams, and siltation of spawning and feeding areas virtually eliminated the blue sucker from the Mississippi River downstream of the Twin Cites for several decades. Following the Clean Water Act of 1972, which eventually resulted in large improvements of habitat and water quality, the blue sucker reappeared in the Mississippi River upstream to Minneapolis and in the Minnesota River upstream to Granite Falls. Its northernmost state record is from the St. Croix River in Pine County. Nevertheless, the blue sucker's abundance is far below that reported in historical accounts, and it is generally rare throughout its range. There is general consensus that its habitat has been reduced by the construction of dams and siltation. For these reasons, the blue sucker was listed as a special concern species in Minnesota in 1984.
The blue sucker is blue or bluish black in color, and has a small, slender head that tapers to a fleshy snout. Its mouth is protractile, surrounded by a distinct groove, and its lips are thick and directed downward. Its dorsal fin is long and has 30-32 rays. Adult blue suckers typically grow to 76 cm (30 in.) in total length, with a maximum total length of 102 cm (40 in.). They typically weigh 2-3 kg (4-6 lbs.) (Hatch et al. in preparation). The largest specimen taken from Minnesota waters was 77.2 cm (30.4 in.) in total length, 51.3 cm (20.2 in.) in girth, and weighed 6.4 kg (14 lbs. 3 oz.).
Blue suckers prefer deep, swift water in pools and channels of large rivers with sand, gravel, or rubble bottoms. They are often associated with wing dams in the Mississippi River and with woody snags in the St. Croix River. Blue suckers are tolerant of high turbidities if currents are swift enough to prevent siltation (Hatch et al. in preparation).
Biology / Life History
Little information exists about the life history of the blue sucker. Few young of the year are reported, but available information suggests that this species may use sheltered backwaters as rearing habitat. Its streamlined shape adapts it for life in strong river currents. Adults probably migrate upriver long distances in both spring and autumn. Breeding may occur from April to June in water temperatures of 10°C (50°F) and higher (Brown 1971). Breeding males darken and develop small tubercles (small, hardened breeding growths) sprinkled on the head, scales, and rays of all fins. Presumably a bottom feeder, the blue sucker's diet likely includes aquatic insects, insect larvae, crustaceans, plant material, and algae. Young blule suckers are likley preyed on by walleye (Stizostedion vitreum) and small mouth bass (Micropterus dolomieu), as well as by fish-eating birds.
Conservation / Management
The species is extremely sensitive to pollution, and its presence indicates a healthy environment. The decline of the blue sucker in the 20th century was probably caused by siltation, pollution, overfishing, physical changes in the environment (such as the partial filling of channels by floods), and dams, which slow the current, increase silting, and block migration. Restoring blue suckers to historic habitats in Minnesota will require dam removal or installation of fish passage features such as ladders or lifts on the St. Croix River at Taylors Falls, the Minnesota River from Granite Falls to Big Stone Lake, and the Mississippir River at Lock and Dam 1. Basic life history information is also severely lacking for this species, and a better understanding is needed for the proper management of critical spawning, rearing, and seasonally utilized habitats.
Conservation Efforts in Minnesota
Fish surveys of the Mississippi River have shown increasing numbers of blue suckers since the early 1990s. There have also been recent records from the St. Croix and Minnesota rivers. Additional research needs for the blue sucker in Minnesota include life history studies, identification of habitat guilds, and identification of limiting factors and opportunities for fish passage around dams on the Minnesota, Mississippi, and St. Croix rivers.
Brown, C. J. D. 1971. Fishes of Montana. Montana State University, Bozeman, Montana. 207 pp.
Hatch, J. T., G. L. Phillips, and K. P. Schmidt. In preparation. The fishes of Minnesota.
Hatch, J. T., K. P. Schmidt, D. P. Siems, J. C. Underhill, R. A. Bellig, and R. A. Baker. 2003. A new distributional checklist of Minnesota fishes, with comments on historical occurrence. Journal of the Minnesota Academy of Science 67:1-17.