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The Central Muldminnow is a robust-bodied, mottled fish with a short, blunt snout, a short dorsal fin located posteriorly, and large scales over the head and body. The upper part of the body is olive-brown in color, mottled throughout, with up to 14 indistinct dark brown vertical bars on the sides, and a prominent dark vertical bar located at the base of the tail. The belly is yellow to white, and the fins are brownish. The mouth is terminal with a slightly protruding lower jaw. Gill rakers are short and stout, numbering 13 to 15. The dorsal fin has 13 to 15 soft rays, pelvic fin rays number 6 to 7, pectoral fin rays 14 to 16, anal fin rays 7 to 9, and all of the fins are rounded on the edges. It reaches a maximum length of 5 to 6 inches, with an average length of about 2 inches or slightly larger. The Central Mudminnow can tolerate very low oxygen concentrations.
The Central Mudminnow is scattered throughout eastern and northcentral Iowa and has been documented at one location in northwest Iowa. This species occurs in moderate to densely vegetated streams, sloughs, ponds, lakes and marshes. It avoids fast-moving waters. They are a hardy fish and found in areas where the oxygen concentration often reaches very low levels. Drainage of Iowa wetlands has eliminated suitable habitats in much of its original range.
Food is collected mostly from the bottom, with aquatic and terrestrial arthropods, snails, fish, plants and algae making up their diet.
State Records are not documented for non-game species.
The Central Mudminnow is used extensively as a bait minnow where it is plentiful. Many Walleye anglers prefer it for bait because of its hardiness.
The Central Mudminnow is uncommon in Iowa and is found scattered throughout eastern and northcentral parts of the state. It has also been documented in the Little Sioux River watershed in northwest Iowa and in the Mississippi River. However, suitable habitat throughout its original range has been eliminated due to drainage of Iowa wetlands.
The Central Mudminnow inhabits cool creeks, ditches, sloughs and heavily vegetated swamps, ponds, bogs and marshes. In parts of Missouri, the Central Mudminnow is associated with heavily vegetated marshes of American lotus, watercress, pickerel weed, sedges and cattails, and substrates of deep mud, peat or organic debris overlying sand. The Central Mudminnow is quite tolerant of high acidity and low oxygen water, as it is able to use it is air bladder as a lung. However, it avoids fast-moving waters and is intolerant of high turbidity. Researchers have found that the central mudminnow is able to survive high water temperatures in isolated pools, others cite high temperatures and the advent of agriculture, “which has made the natural waters turbid, silted the bottoms of creeks and ponds and obliterated many habitats by drainage,” as reasons for sporadic occurrence in its southern range. It has been noted that the Central Mudminnow is difficult to collect because it burrows deep into mud substrates where it cannot be seined.
Spawning begins in April at water temperatures ranging from 55 to 60 degrees F. Shallow backwater areas subject to overflow provide excellent breeding grounds, with a rise in water temperature providing the stimuli for spawning. The female deposits the adhesive eggs singly and directly in aquatic vegetation. Egg production is from 200 to 2,200, depending upon body size. The eggs hatch in about seven days.
Scales of the mudminnow do not show growth annuli; age is determined by viewing otoliths or estimated from length-frequency distribution. Life span of the mudminnow is quite long; some fish up to 9 years of age have been taken. Food is collected mostly from the bottom, with aquatic and terrestrial arthropods, snails, fish, plants and algae making up their diet.
As mentioned previously, the Central Mudminnow can be difficult to sample because it flees into bottom sediments when a small seine approaches, but once the water is stirred up and turbid, it can be easily captured. The mudminnow has both gas-absorbing and secreting organs in the swim bladder. When oxygen levels are insufficient in the water, it simply gulps air from the surface.
The central mudminnow is used extensively as a bait minnow where it is plentiful. Many walleye anglers prefer it for bait because of its hardiness.
Recent stream sampling information is available from Iowa DNR's biological monitoring and assessment program.
Harlan, J.R., E.B. Speaker, and J. Mayhew. 1987. Iowa fish and fishing. Iowa Conservation Commission, Des Moines, Iowa. 323pp.
Loan-Wilsey, A. K., C. L. Pierce, K. L. Kane, P. D. Brown and R. L. McNeely. 2005. The Iowa Aquatic Gap Analysis Project Final Report. Iowa Cooperative Fish and Wildlife Research Unit, Iowa State University, Ames.
Photo credit: Photo courtesy of Ohio Department of Natural Resources