Fathead Minnow

Characteristics

The Fathead Minnow has a stout body that is moderately compressed laterally with a broad flat area just before the dorsal fin. A typical Pimephales, they have a shortened and closely attached first ray in the dorsal fin and smaller, crowded scales in front of the dorsal fin. The small, terminal mouth is oblique and without a barbel. Slender, slightly hooked pharyngeal teeth are arranged in a 4-4 array. The body is dark olive above with a shade of copper or brass behind the head and along the sides. The sides are lighter with a silvery hue, and the belly is white. A dusky band or blotch appears in the front and rear rays of the dorsal fin, which helps distinguish them from the Bullhead Minnow and Bluntnose Minnow. The lateral band is faint in fish from turbid waters and prominent in fish from clear water. An incomplete lateral line, which does not reach to the caudal peduncle, has 42 to 48 scales. Intestine length is about twice the body length and the peritoneum is black. Dorsal and pelvic fins have 8 rays, while the anal fin has 7 rays, and the pectoral fins have 15 or 16 rays. Spawning males develop a swollen, black head with breeding tubercles in three rows on the snout. Typical males are light silvery behind the opercle to the pectoral fins; then a dark bar extends to the insertion of the dorsal fin followed by a light bar to about mid-way along the dorsal fin.

Distribution

Found in every watershed in Iowa; common in nearly all fish collections from streams, natural lakes and man-made impoundments and reservoirs. It is found throughout the Mississippi and Missouri Rivers.

Foods

Microscopic plants, small insects and larvae, and occasionally fish.

State Record

State Records are not documented for non-game species.

Expert Tip

Catch these at your bait shop - they are the most common baitfish sold in Iowa.

Details

The Fathead Minnow is considered the most widespread and abundant fish species in Iowa. It can be found in streams of various sizes, but is most abundant in sluggish, intermittent streams, ditches and ponds with soft, silty mud or firm clay substrates or backwaters and muck-bottomed pools of larger rivers. It is intolerant of competition and predation, but uniquely adapted to stagnant pools, acid bog-ponds, and alkaline streams where extremes in pH, low oxygen levels, high turbidity, and high temperatures decrease fish diversity. It seeks refuge in stagnant pools of small Plains streams during extended dry periods. It is usually abundant in areas where the Bluntnose Minnow is absent.

Fathead Minnows spawn from early May through August. The adhesive eggs are deposited on the under surface of floating objects, and the male guards them. The eggs hatch in 5 to 6 days. Adults reach a maximum of about 3-inches long. 

Iowa anglers owe a great deal to this unobtrusive minnow. Besides being an important forage fish in most waters, it is the best baitfish available, and millions are sold in bait shops each year. Aquarium enthusiasts also collect fatheads for display.

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

Illustration by Maynard Reece, from Iowa Fish and Fishing