The smallmouth bass is generally brown (seldom yellow) with red eyes, and dark brown vertical bands, rather than a horizontal band along the side. There are 13–15 soft rays in the dorsal fin. The upper jaw of smallmouth bass extends to the middle of the eye.
Males are generally smaller than females. The males tend to range around two pounds while females can range from three to six pounds. Their average sizes can differ, depending on where they are found; those found in American waters tend to be larger due to the longer summers, which allow them to eat and grow for a longer period of time.
Their habitat plays a significant role in their color, weight, and shape. River water smallmouth that live among dark water tend to be rather torpedo shaped and very dark brown in order to be more efficient for feeding. Lakeside smallmouth bass however, that live for example in sandy areas, tend to be a light yellow brown to adapt to the environment in a defensive state and are more oval shaped.
In the United States, smallmouth bass first moved outside their native range upon construction of the Erie Canal in 1825, extending the fish's range into central New York state. During the mid-to-late 19th century, smallmouth were transplanted via the nation's rail system to lakes and rivers throughout the northern and western United States, as far as California. Shippers found that smallmouth bass were a hardy species that could be transported in buckets or barrels via the railroad, sometimes using the spigot from the railroad water tank to aerate the fingerlings. They were introduced east of the Appalachians just before the Civil War, and afterwards transplanted to the states of New England.
With increased industrialization and development, many of the nation's eastern trout rivers were dammed, polluted, or allowed to silt up, raising water temperatures and killing off the native brook trout. Smallmouth bass were often introduced to northern rivers now too warm for native trout, and slowly became a popular gamefish with many anglers. Equally adaptable to large, cool-water impoundments and reservoirs, the smallmouth also spread far beyond its original native range. Later, smallmouth populations also began to decline after years of damage caused by overdevelopment and pollution, as well as a loss of river habitat caused by damming many formerly wild rivers in order to form lakes or reservoirs. In recent years, a renewed emphasis on preserving water quality and riparian habitat in the nation's rivers and lakes, together with stricter management practices, eventually benefited smallmouth populations and has caused a resurgence in their popularity with anglers.
Today, smallmouth bass are very popular game fish, frequently sought by anglers using conventional spinning and bait casting gear, as well as fly fishing tackle. In addition to wild populations, the smallmouth bass is stocked in cool rivers and lakes throughout Canada and the United States. In shallow streams it is a wary fish, though usually not to the extent of most trout. The smallmouth is highly regarded for its topwater fighting ability when hooked – old fishing journals referred to the smallmouth bass as "ounce for ounce and pound for pound the gamest fish that swims" Smallmouth bass are taken for the table, with filets of white, firm flesh when cooked. Today, many fishermen practice catch-and-release fishing to improve fish populations.
The current world record was caught at Dale Hollow Reservoir in 1955. The fish weighed 11 lbs, 15 oz.
M. dolomieu is found in clearer water than the largemouth, especially streams, rivers, and the rocky areas and stumps and also sandy bottoms of lakes and reservoirs. The smallmouth prefers cooler water temperatures than its cousin the largemouth bass, and may be found in both still and moving water. Because it is intolerant of pollution, the smallmouth bass is a good natural indicator of a healthy environment, though it can better adjust to changes in water condition than most trout species. Carnivorous, its diet comprises crayfish, insects, and smaller fish, the young also feeding on zooplankton.
The smallmouth’s original range extended through Minnesota and southern Quebec, south to the Tennessee River in Alabama and west to eastern Oklahoma and southwestern Arkansas. Found through the U.S., though not typically in Texas or Louisiana.