Smallmouth Bass
Micropterus dolomieui (Lecepede, 1802)

member of the Sunfish Family (Centrarchidae)

photos by Konrad P. Schmidt













What's In a Name?
Smallmouth bass: named for the size of the mouth compared to the largemouth bass.

Micropterus (my-crop´-ter-us) means "small or short fin" in Greek; a reference to the damaged fin on the original specimen.
dolomieui (doe-loe-mew´-ee) named after Dieudonne' de Dolomieu, a French geologist and friend of Lecepede, who named the species.


    Where Do They Live?
Smallmouth bass now occur in all of the major drainages of Minnesota, but they were introduced to the Red and Rainy river systems. This means that one of the most popular sportfish in the Boundary Waters Canoe Area is actually an exotic species. Smallmouth are especially abundant in the upper Mississippi and St. Croix rivers and their larger tributaries. Smallmouth bass prefer clear, strong-flowing streams and rivers and medium-sized clear lakes with gravel or boulder shores. In both lakes and streams smallmouth often are found near boulders or rock out-cropping. They prefer somewhat cooler waters than the largemouth bass, but still are considered a warm-water species.


How Big Do They Get?
How Long Do They Live?
In general smallmouth do not grow as fast or get as big as largemouth bass. Still, this species often reaches 300 mm (12 in) or more, in many Minnesota lakes and streams. Very rarely it reaches 500 mm (20 in). Many anglers catch smallmouth that weigh 0.9-1.8 kg (2-4 lbs) in Minnesota. The state record is 3.6 kg (8 lbs). This fish was caught in West Battle Lake in Otter Tail County. Smallmouth frequently reach 7-10 years old, and on rare occasions may reach the age of 15 years.

    What Do They Eat?
Smallmouth larvae eat copepods, waterfleas, and other small zooplankton (small floating animals). At about 35 mm (1.5 in) they begin to include aquatic insect larvae and some small fish. At about 80 mm (3 in), they add crayfish to the menu. From 1 year old on, smallmouth bass eat mostly fish (darters, minnows, yellow perch, sunfishes, and others) and crayfish.

What Eats Them?
Larval and young-of-the-year smallmouth bass are preyed upon by larger bass, yellow perch, sunfishes, and northern pike. Other animals that probably eat young smallmouth include herons, frogs, and some snakes. As adults, smallmouth bass are eaten only by larger bass, northern pike, and musky. Humans are the main predator of adults.


How Do They Reproduce?
In Minnesota, smallmouth bass spawn mostly from the middle of May through the end of June when water temperature exceeds 15.5° C (about 60° F). We have records of spawning as late as early August, however. The male selects the spawning site and sweeps out a nest up to 1 m (3 ft) in diameter with his tail. The nest normally ends up in a gravel bed, often next to a log, boulder, or other obstruction in 1-3m (about 3-10 ft) of water. Once the nest is built, the male defends it aggressively from both male and female smallmouth. A female that wants to spawn has to be persistent. She may be helped somewhat by her change in appearance. The dark mottling on her body becomes more noticeable as the background color fades, and this may help communicate to the male that the female is ready. Once in the nest, both fish lay beside each other and release their eggs and sperm. This spawning act can be repeated every 30 seconds or so for up to 2 hours. When the female is done laying the eggs, she leaves the nest and the male stays behind to protect the eggs from predators. Both males and females usually spawn with more than one partner. A single female may lay 2,000-14,000 eggs, depending on her size.

The eggs (embryos actually) hatch in about one week and the free-living embryos continue to develop in the nest for about one more week. After that, they swim up into the water column and begin to feed. In lakes, the male smallmouth may continue to protect the larvae for a short time even after they swim up.


Conservation and Management
One of the top three warm-water sportfish in Minnesota (largemouth and northern pike are the other two). This species has been planted in many lakes and streams over the years. The principal management strategy is to protect it during the early spawning season and limit its daily catch.




Permission is granted for the non-commercial educational or scientific use of the text and images on this Web document. Please credit the author or authors listed below.

Photographs by Konrad P. Schmidt
Text by Nicole Paulson & Jay T. Hatch in cooperation with
the Minnesota Department of Natural Resources' MinnAqua Aquatic Program

This page developed with funds from the
MinnAqua Program (Minnesota Department of Natural Resources, Division of Fisheries)
and the
Sport Fish Restoration Program (Fish and Wildlife Service, US Department of the Interior)

Maintained by Jay T. Hatch
General College and James Ford Bell Museum of Natural History
University of Minnesota, Minneapolis/St. Paul

Last updated 23 October 2002