Smallmouth Bass

The smallmouth bass (Micropterus dolomieu) is a freshwater fish native to the rivers and lakes of eastern and central North America. It has since spread to other regions and countries, where it often disrupts their ecosystems. Alternate names for this species include smallie, brownie, bronzeback, and bronze bass. It makes a popular sport fish as well as a tasty dish.

Smallmouth Bass Fish Facts

• Small mouths: Yes, smallmouth bass have small mouths. This is in comparison to largemouth bass, which have disproportionately big mouths that appear to gape.
• Mucus-covered scales: This species has scales covered in mucus, which helps them swim faster and prevents infection.
• Invasive species: Far from being endangered, this species has caused problems in ecosystems outside of its native habitats. This happens when humans introduce them to non-native regions either deliberately or by accident.
• Involved fathers: Unlike the males of the vast majority of species in the animal kingdom, male smallmouth bass take an active role in the protection of nests and eggs.

Classification and Scientific Name

The scientific name for smallmouth bass is Micropterus dolomieu. The word Micropterus comes from the Greek words mikros, meaning “small,” and pteron, meaning “wing” or “fin.” Dolomieu is the last name of a friend of the scientist who named the species, Bernard Germain de Lacépède.

Scientists classify members of this species as bony fish, which means their skeletons are made primarily of bone rather than cartilage. They belong to the class Actinopterygii, a taxon comprising ray-finned fishes. Within this classification, they fall into the order Perciformes, which comprises over 41% of all bony fishes. This makes it the world’s largest and most diverse group of vertebrates. They further belong to the family Centrarchidae (“sunfishes”) and the genus Micropterus (“black basses”). Centrarchidae contains eight genera and thirty-eight species, four of which are extinct. Micropterus contains 14 species, though some still dispute the 14^th, the Choctaw bass (Micropterus haiaka).

Smallmouth Bass Appearance

Smallmouth bass manifest a range of dorsal colors from dark brown to bronze to olive to light green. Ventrally, their color fades to yellowish-white. The clearer the water, the darker the dorsal color. Dark brown bars cover their bodies vertically and their heads horizontally. These colors and patterns help them blend into their surroundings, especially along river beds with sediments like sand, gravel, and rocky substrates.

This species sports an additional adaptation: ctenoid (spiny-edged) scales covered in mucus. These scales not only provide a protective layer against damage and infection, but they also reduce water resistance. Moreover, these fish have six different types of fins: a spiny dorsal fin, a soft dorsal fin, a symmetrical caudal fin, an anal fin, pectoral fins, and pelvic fins. Their mouths are small and proportional, unlike those of largemouth bass.

Smallmouth bass can reach a maximum length of about 27 inches, though a length of 10 to 20 inches is more common. Most members of this species weigh less than five pounds. However, the largest individual on record weighed 12 pounds.

Smallmouth Bass Distribution, Population, and Habitat

Smallmouth bass are native to the cool freshwater bodies of water in eastern and central North America, specifically parts of the United States and Canada. Populations originally inhabited Hudson Bay, the St. Lawrence – Great Lakes system, except for Lake Superior, and the Mississippi River basins. They occurred naturally in parts of the following states and provinces: southern Quebec, North Dakota, south to northern Alabama, eastern Oklahoma, Virginia, and central Texas. These fish prefer the shallow, rocky areas of lakes and rivers without dense vegetation, usually swimming at depths no greater than 23 feet.

This species has since spread to many other states in America as well as several provinces in Canada. In addition to this, humans have introduced this species to a range of other countries as a sport fish or by accident. It has caused ecosystem disruptions in some of these regions.

Due to its stable population, the IUCN lists this species as Least Concern (assessment date: 2012, confirmed as of 2025).

Smallmouth Bass Evolution and History

As a species, smallmouth bass are relatively young in terms of their evolutionary history. The molecular clock, a method of determining the age of a species, suggests the Micropterus genus originated 26 million years ago during the Paleogene Period. The earliest bass fossil on record, discovered in Texas, dates to 23 million years ago. Smallmouth bass share a common ancestor with other extant species of black bass that lived as far back as 11 million years ago during the Miocene Era.

At this point, a marine transgression isolated several species from one other. During this time, smallmouth bass and their close relatives, spotted bass, diverged from the other black bass species. However, they only diverged from each other approximately 1.7 million years ago during the Pleistocene.

The Great Lakes formed approximately 15,000 years ago, eventually becoming home to populations of smallmouth bass. The bodies of water closest to glacial outlets contained the most genetically diverse populations. Lake Huron and Lake Erie, for example, connected to various outlets and therefore contained diverse mitochondrial lineages. Lake Superior, Lake Michigan, and northern Lake Huron, on the other hand, contained bass of a single mitochondrial clade. Other populations, like those in Lake Ontario and the St. Lawrence River, had little to no genetic diversity.

Smallmouth Bass Predators and Prey

Smallmouth bass are not only carnivores but also top predators in their ecosystems. They are opportunistic feeders, eating whatever they can reasonably overpower. Available prey varies according to the individual fish’s size and age, the season, and water temperature. Because of their small mouths, they are limited in the size of fish they can eat, unlike their cousin the largemouth bass. Though they are generally diurnal, scientists have also observed activity during dawn, dusk, and at night in warmer seasons.

What Do Smallmouth Bass Eat?

Despite its small mouth, this species occasionally goes after fish like yellow perch, threadfin shad, bluegills, sculpins, minnows, and other small sunfish. They also enjoy vertebrates like frogs and lizards as well as invertebrates like crayfish, bivalves, gastropods, annelids, and various insects. Juveniles prey on crustaceans, zooplankton, and aquatic insects.

What Eats Smallmouth Bass?

Because this species is a top predator in its ecosystems, it faces few threats. Humans are their biggest predator, though overfishing is not currently a concern for most populations. Other fish that prey on adults of this species include northern pike, muskellunge, and larger bass. Herons, frogs, and snakes may also prey upon juveniles.

Smallmouth Bass Reproduction and Lifespan

Smallmouth bass are oviparous, meaning they lay eggs instead of giving birth to live young. These fish are generally monogamous, though larger individuals occasionally practice polygynandry (where both males and females have more than one mate). They usually mate from May to June, though some individuals begin as early as April or end as late as July.

The male of a given mating pair builds a nest among the sand, gravel, or rocks of shallow lakes and rivers. The nest is usually within about 150 yards of previous nests. The female approaches and they swim around the nest together while rubbing and nipping each other. They spawn for five seconds on the bottom, resume circling the nest for 25-45 seconds, and then spawn again, repeating this pattern for approximately two hours. Females may go from nest to nest mating with other males.

The number of eggs a female lays depends on her size. A 10-inch female lays approximately 2,000 eggs. An 18-inch female, however, may lay in excess of 10,000 eggs. Females lay eggs in batches of 20 to 50 over a period of about 10 seconds until they are finished; this process can take as long as two hours. The male releases his milt to fertilize the eggs as the female deposits them in the nest. The male remains with the nest to guard it and the eggs, which hatch in four to 11 days.

Aside from spawning, these fish are solitary by nature. Males reach sexual maturity between three and five years of age while females mature by six years of age. A typical lifespan is between six and 15 years of age, though in extraordinary cases individuals have lived as long as 26 years.

Smallmouth Bass in Fishing and Cooking

Smallmouth bass are great for recreational fishing, though they tend to interfere with other species targeted for commercial fishing. The best time of year to catch smallmouth bass is anytime between spring and fall, though they are most active in the warm summer months. The best time of day is during the early morning or late afternoon hours as they tend to bite more readily in low light. They tend to swim in shallow waters with sandy or rocky bottoms.

To catch these fish, anglers can either try artificial lures or live bait. The best artificial lures are crawfish imitators like jigs, tubes, and grubs or baitfish imitators like spinnerbaits and crankbaits. The most reliable live baits are crawfish, minnows, and leeches. This species tends to fight hard, making them an enticing sport fish.

This fish also makes good eating, whether baked, fried, pan-fried, roasted, or grilled. It tastes milder and sweeter than its largemouth cousin, sporting white meat with a firm texture. Check out this recipe for roasted bass with summer vegetables.