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

Smallmouth Bass Micropterus dolomieu

Centrarchidae (Sunfish)
Trophic Class
Top Carnivore
Is Exotic to Iowa?
Is Lithophilous Spawner?
Is Hybrid?
State Listing Status
Not Listed
Assessment Program Statistics

This species was found at 247 bioassessment sites, 8 rapid fish bioassessment sites, 104 fisheries assessment sites, and 1 fisheries presence-only assessment site. In total, it was collected at 351 distinct sites, or 26% of the 1350 total sites monitored by the bioassessment program. It is the 20th most commonly collected species.

The Smallmouth Bass was collected in 549 bioassessment sampling sessions and 406 fisheries assessment sessions. It was present in 8 rapid bioassessment sessions and 1 presence-only session.

The biological assessment program has collected a total of 24,769 individual Smallmouth Bass specimens, ranking it the #17 most collected fish.

Species Characteristics

A slender, streamlined-shaped fish with a moderately large mouth, where the upper jaw reaches about to the rear margin of the eye in adults. Spiny and soft parts of the dorsal fin are broadly connected with only a shallow notch between the lobes. The body is golden green on the sides and back with faint wavy olive blotches evenly spaced along the sides. Five olive-green bars radiate backward from the eye, and one forward to the end of the snout. The tail fin in young smallmouth is tri-colored with a black vertical bar separating the yellowish fin base. Pyloric caeca are not forked in contrast to forked pyloric caeca in the closely related Largemouth Bass.

Species Distribution Maps

HUC12 watersheds where this species has been found