The Ecology of the American Smallmouth Bass

Fishing - The Ecology of the American Smallmouth Bass

Redbud trees blooming and streamside sycamores displaying new green leaves mark Oklahoma’s favorite sport fish spawning season, the Neosho smallmouth bass. Researchers with the Oklahoma Department of Wildlife Conservation implanted many Neosho smallmouth bass with radio tags in 2015.

Tracking them has revealed that they converge at various parts of the system throughout winter, such as rock-filled waters that appear barren.

Population Distribution

Micropterus dolomieu, commonly known as smallmouth bass, is an iconic species throughout North America that plays an essential ecological role as top predator in aquatic systems. The species is especially common and widespread in eastern U.S. regions and every county in Iowa where it serves as a popular game fish. Unfortunately, despite their widespread appeal and ecological relevance, our knowledge about population structures and dynamics of Iowa interior rivers that host smallmouth bass populations remains limited.

In this study, tagged smallmouth bass were tracked through three river reaches of Iowa’s central interior highlands to establish their habitat and movement patterns. We analyzed stomach contents of smallmouth and rock bass tagged for this research in order to assess diets. Overall, watershed conditions immensely influenced smallmouth population potential with finer-scale factors like flow, temperature and sediment combining to alter populations further.

At one point during the study, one-fourth of tagged smallmouth bass moved upstream or downstream and failed to return home, most coming from Boat Rock, East Bradford Island and South Bradford Island zones as well as Goose Island; those that did return spent 86.3 percent of their time within their release zones.

The smallmouth bass’s native range extends from southern Quebec through Minnesota and Alabama’s Tennessee River to eastern Oklahoma and southwestern Arkansas, where it was introduced through angler catch and release and artificial propagation. Although these methods have contributed to diversifying populations within its native range, their numbers have unfortunately seen some decrease due to human-caused changes to river basins that provide habitat.


Smallmouth bass are active fish that require diverse habitat features to thrive, including rocky or gravel bottoms, woody cover, deep water foraging areas and riparian buffer zones or forests; as well as rivers and lakes of various sizes (including ephemeral streams).

Smallmouth bass fisheries during prespawn tend to move around frequently during this period, searching for staging areas to begin their spawning run. You might find these bass in areas with steep drops or hard points on main lake islands; additionally they scout for potential nesting spots where they will build their gravel nests.

Smallmouth bass are highly sensitive to sudden changes in water temperature and clarity, which can disrupt their spawning process and force their eggs to hatch too early, decreasing survival rates. Clarity also plays a vital role, as sunlight penetrates deeper, encouraging aquatic vegetation growth that provides cover for female spawners as they spawn.

Smallmouth bass Micropterus dolomieu were observed preferring substrate types and habitat features that offered low light intensity and slow current velocity in a laboratory stream tank experiment, such as sand, cobble, boulders with various amounts of surface material, clear/opaque covers, and three types of opaque covers (Livingstone and Rabeni 1991). Their preferred habitat provided protection from predators, food sources, and shelter for juvenile fish (Livingstone & Rabeni 1991).

Human activities have the ability to adversely alter spawning habits by altering natural landscape features and increasing sedimentation. Erosion from construction projects may smother natural spawning beds, restrict oxygen exchange, and harm developing embryos. Researchers studying land use effects on smallmouth bass density found that species abundance was highest in forested stream segments, decreasing dramatically when moving towards urban streams.


Smallmouth bass are voracious predators, feeding on everything from invertebrates such as crayfish and minnows to larger species like alewife and shad. Preferentially feeding in clear water environments, their diet varies with age and conditions: young smallmouths typically feed on plankton found floating along currents and tides, while later generations typically consume 60% – 90% of their diet as crayfish and minnows (research has demonstrated this fact).

As smallmouth bass fish evolve and expand in size, they rely less on plankton for sustenance and more on aquatic insects like beetles and flies which often reside near water’s surface where smallmouth bass are easier to spot them. Once larger still, bass will start eating larger freshwater fish as well as terrestrial insects found on land if necessary.

Great Lakes lakes boast plenty of smallmouth bass habitat in the form of rocky points, humps, sandy shoals and mouths of feeder streams that provide ideal smallmouth bass habitat. Furthermore, Canadian Shield lakes contain numerous minnows, leaches and crayfish making these sites prime locations for this fish species.

Smallmouth bass feed on alewife and other forms of shad, making them easy targets for anglers during summer lake fishing trips. Smallmouths often linger near current breaks created by rocks humps, points, or ledges as well as structures such as docks or bridge abutments; when targeting rivers smallmouths can be caught drifting with spinnerbait or casting jig in current flow or working a crankbait in a shad pattern; in fall and winter they often hold over deep ledges while searching for alewife.

Food Sources

Smallmouth bass feed on an array of organisms, with plankton being their main food source at younger ages. Plankton are easily caught as it drifts in water currents or tides – easy prey for young bass. As they mature further they tend to favor aquatic insects that live underwater that make for easier capture; otherwise they will consume terrestrial insects that drop into water bodies from land-dwellers.

Crayfish resemble lobsters in appearance and provide smallmouth bass with an excellent source of food in lakes with abundant populations of crayfish. Smallmouth bass also consume minnows and leaches for sustenance, occasionally even feeding on species like their own if necessary to gain sufficient nourishment from other sources.

Depending on climate and location, Smallmouth bass generally spawn from May through June. They create gravel or rock nests in clean river or stream water with plenty of vegetation for cover during spawning season and are protected from other fish, intruders and predatory birds by male bass who protects it during spawning time.

Lady Evelyn Lake, located in Canada’s Canadian Shield region, provides an ideal environment for smallmouth bass to thrive. They can be found gracing the waters’ points, shoals, islands, and waterfalls as well as feeding stream mouths, eating minnows, leeches and crayfish (which can often be found plentifully here), although other fish might supplement their diets more effectively than main courses.


Smallmouth bass are among North America’s most sought-after freshwater game fish, boasting incredible acrobatic abilities and strong fight when hooked with hook and line. Anglers target them across their state’s lakes, rivers, creeks, and gravelly areas in search of this sportfish.

Smallies are opportunistic predators that feed on prey, including crabs, insects, and crustaceans. Baitfish such as shad and herring also fall within their diets; though opportunistic smallmouth can be very hard to catch due to their agile fighting ability and muscular body structures, smallmouth have become prized trophies at many fishing tournaments.

An ideal habitat for smallmouth bass must provide water current, sufficient depth, desirable secondary forage sources like tree breaks or sand/mud flats for cover, and natural food sources like crayfish.

Anglers must practice catch-and-release to sustain a sustainable smallmouth bass population and other fish species. When fishing for these bass, avoid fishing in their spawning areas to safeguard this vital resource for fishery preservation.

As with most fish species, bass are most responsive to lures continuously touching the bottom. Forward-facing sonar technology can eliminate much of the guesswork involved with fishing for bass, helping ensure your bait lands within its strike zone.

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