Iowa DNR
River & Stream Biological Monitoring
Fish and Benthic Macroinvertebrate Surveys
Physical Habitat Assessments

Western Blacknose Dace Rhinichthys obtusus

Cyprinidae (Minnows)
Trophic Class
Is Exotic to Iowa?
Is Lithophilous Spawner?
Is Hybrid?
State Listing Status
Not Listed
Assessment Program Statistics

This species was found at 442 bioassessment sites, 103 rapid fish bioassessment sites, 75 fisheries assessment sites, and 28 fisheries presence-only assessment sites. In total, it was collected at 575 distinct sites, or 41.5% of the 1385 total sites monitored by the bioassessment program. It is the 11th most commonly collected species.

The Western Blacknose Dace was collected in 844 bioassessment sampling sessions and 205 fisheries assessment sessions. It was present in 103 rapid bioassessment sessions and 39 presence-only sessions.

The biological assessment program has collected a total of 56,831 individual Western Blacknose Dace specimens, ranking it the #8 most collected fish.

Species Characteristics

Brownish to black above, and speckled sides with dark scales giving the fish a mottled look. A dusky lateral band is outlined above by a row of light scales. Spawning males develop a pink to red-colored lateral band. The sub-terminal mouth is oblique with equal jaws, and a barbell is on the posterior tip of the lower jaw. The upper lip is attached to the snout without a groove (a feature know as a frenulum), which is characteristic of Rhinicthys. There are 62 to 71 scales in the complete lateral line. Hooked pharyngeal teeth are arranged in a formula of 2, 4-4, 2. The peritoneum is silvery-colored, and the air bladder is well developed. Dorsal and pelvic fins have 8 rays, while the anal fin has 7, and the pectoral fins have 13 to 16 rays.

Species Distribution Maps

HUC12 watersheds where this species has been found