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Bigmouth Shiner

Bigmouth shiner, photo courtesy of Konrad P. Schmidt, copyright Konrad P. Schmidt


Slender, flat-bellied, and hump backed body form; eyes appear to focus upward when viewd from above; olive-yellow on back and silvery on sides and belly.


Bigmouth shiner Distribution

One of the most widely distributed and abundant minnows in Iowa. They are common to abundant in nearly all rivers and streams, occasional in the man-made lakes and reservoirs, and rare in the natural lakes.


Aquatic insects, detritus and plant material.

State Record

State Records are not documented for non-game species.

Expert Tip

One of the most important forage fishes in streams and an important bait minnow.


The bigmouth shiner is one of the most abundant and widespread fish species in Iowa. It is found in nearly all rivers and streams throughout the state, occasional in man-made lakes and reservoirs, and rare in natural lakes. With Iowa in the center of its continental range, the distribution of the bigmouth shiner is expanding due to changes in prairie stream habitats.

Bigmouth shiners are common in small, low to moderate-gradient prairie streams with slight current and unstable sandy bottoms. They are most abundant in streams having permanent flow. They are able to adapt to fluctuating water levels, turbidity, and pollutants, but require a sand substrate not covered with silts. In Iowa, they are one of the few species able to inhabit the sterile sand flats common in Iowa creeks. Some researchers have found that bigmouth shiners occupy cool creeks, but in Ohio they were found to be uncommon or absent in cool streams.

This shiner has a distinctive body form, being slender, relatively flat-bellied and hump-backed. Their eyes appear to focus upward, when viewed from above, because the pupil is skewered dorsally. Body color is olive-yellow on the back and silvery on the sides and belly. A mid-dorsal stripe, running along the top of the body, is continuous around the base of the dorsal fin. There is no pigment around the vent or at the base of the anal fin. There is no lateral band but the lateral line that has about 35 scales and is complete with paired markings called "mouse tracks" at each pore. Scales in front of the dorsal fin are smaller, crowded, and exceed 16 in number. The sub-inferior mouth, found on the bottom of the head and overhung by the snout, is horizontal and does not have a barbel. Hooked pharyngeal teeth on slender arches are arranged in an array formula of 1, 4-4, 1. Dorsal, anal, and pelvic fins contain 8 rays, while the pectoral fins contain 14 or 15 rays.

Bigmouth shiners are bottom feeders, utilizing aquatic insects, bottom ooze and plant material. Spawning occurs in May through July. Adults reach about 3 inches in length. This minnow is one of the most important forage fishes in our streams and is an important bait minnow.

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 Konrad P. Schmidt, copyright Konrad P. Schmidt.


Present in these Iowa water bodies:

Lake/Stream County Location Acres/Length
Otter Creek Fayette Located 3 miles southeast of West Union. 2.50
Spring Branch Delaware 3 miles east-southeast of Manchester off 205th Avenue. Parking available near highway 20 overpass and Manchester Fish Hatchery 2.20
Burr Oak Creek Mitchell Stream located just north of Osage. T98N, R16W, S4, 5, 9, 10 2.00