Fathead Minnow



Pimephales promelas

  • Characteristics - dark olive above with coppery tinge behind head and along sides, sides silvery and belly white; back broad and flat in front of dorsal fin; dusky band or blotch in front and rear rays of dorsal fin; maximum length of about 3 inches
  • Distribution - statewide in streams, man-made lakes and natural lakes
  • Foods - microscopic plants, small insects and their larvae
Other names - blackhead minnow, tuffy minnow

The fathead minnow is found in every watershed and is considered the most abundant and widespread fish in Iowa. It is listed as common to abundant in nearly all fish collections from streams, man-made lakes and natural lakes. The continental range of this cyprinid is centered in the Midwest and Great Plains states, but it also extends through the Great Lakes basin to New York, south to Texas and New Mexico, and north into the Yukon Territories.
Fathead minnow has a stout body form 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 advance 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. Body color is dark olive above with a tinge 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 specimens from turbid waters and prominent in specimens from clear water. An incomplete lateral line, which does not reach to the caudal peduncle, contains from 42 to 48 scales. Intestine length is about twice the body length and the peritoneum is black. Dorsal and pelvic fins contain 8 rays, while the anal fin contains 7 rays, and the pectoral fins contain 15 or 16 rays. Spawning males develop a swollen, black head with breeding tubercles appearing 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.
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 length of about 3 inches. Food of the fathead consists mostly of microscopic plants, small insects and larvae, and occasionally fish.