Central Mudminnow

Characteristics

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, mottled throughout, with up to 14 indistinct dark brown vertical bars on the sides, and a dark vertical bar 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, 6 to 7 pelvic fin rays, 14 to 16 pectoral fin rays, 7 to 9 anal fin rays, and all of the fins are rounded on the edges. It reaches a maximum of 5-to 6-inches long, with an average length of about 2 inches or slightly larger.

Distribution

Uncommon in Iowa; scattered throughout eastern and north central Iowa. It has also been documented in the Little Sioux River watershed in northwest Iowa and in the Mississippi River. They are a hardy fish found in areas where oxygen often reaches very low levels. Drainage of Iowa wetlands has eliminated suitable habitats in much of its original range.

Foods

Food is collected mostly from the bottom, with aquatic and terrestrial arthropods, snails, fish, plants and algae making up their diet.

State Record

State Records are not documented for non-game species.

Expert Tip

The Central Mudminnow is used as a bait minnow. Many Walleye anglers prefer it for bait because of its hardiness.

Details

The Central Mudminnow lives in cool creeks, ditches, sloughs and heavily vegetated swamps, ponds, bogs and marshes. It is  tolerant of high acidity and low oxygen water, as it can use its air bladder as a lung. It avoids fast-moving waters and is intolerant of high turbidity. Researchers have found that the Central Mudminnow can 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 destroyed many habitats by drainage,” as reasons for sporadic occurrence in its southern range. 

Spawning starts in April at water temperatures of 55 to 60 degrees. Shallow backwater areas subject to overflow provide excellent breeding grounds, with a rise in water temperature providing the incentive for spawning. The female deposits the adhesive eggs singly and directly in aquatic vegetation. Egg production is 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 long; some fish up to 9 years old have been taken. 

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 Central Mudminnow has both gas-absorbing and secreting organs in the swim bladder. When oxygen levels in the water are low, it simply gulps air from the surface.

Recent stream sampling information is available from Iowa DNR's biological monitoring and assessment program.

Sources:

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