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Smallmouth Range

Underwater Smallie

Biology of

Smallmouth Bass (Micropterus dolomieui)

The smallmouth bass (Micropterus dolomieu) is a species of freshwater fish in the sunfish family (Centrarchidae) of the order Perciformes. It is the type species of its genus. One of the black basses, it is a popular game fish sought by anglers throughout the temperate zones of North America, and has been spread by stock to many cool-water tributaries and lakes in the United States and Canada. The smallmouth bass is native to the upper and middle Mississippi River basin, the Saint Lawrence River–Great Lakes system, and up into the Hudson Bay basin. Its common names include Smallmouth, Bronzeback, Brown Bass, Brownie, Smallie, Bronze Bass, and Bare back Bass.

Length 15"-26"
Weight 1½ - 11 lbs the world record is 11 lbs 15 ounces
Coloration brown, golden-brown, through olive to green on back sides lighter, with faint, evenly spaced, wavy olive blotches cream or white underside broad lateral line 5 olive-green bars radiate back from the red eye and 1 radiates forward to the end of the snout.
Body spiny and soft portions of dorsal fin broadly connected, with only a shallow notch between lobes. The tail fin in young distinctly tri-colored, with a black vertical bar separating the yellowish fin base.
Head large mouth, where the upper jaw reaches to near the rear margin of the eye in adults Mouth is geared to feed downward
Identification Distinguished from the largemouth by the maxilla extends rearward only about even with the pupil. Notch between the spiny and soft parts of the dorsal less pronounced irregular vertical bars or a continuous shading of dark brown above to a gray or cream below.
Habitat Primarily an inhabitant of swift flowing, less turbid waters in rivers and smaller streams, usually near rocks. (Prefers gravel under 1" in diameter to build nests and spawn). Deep cool clear water impoundments with good rock habitat.
Water temperatures must reach the low 60 ºs for spawning
Smallmouth need a great amount of dissolved oxygen and, in streams, a dependable stream flow and modest current.
Retreats to pools, undercut banks, deep water, or hides under rocks to avoid bright daylight. Most active in early morning and evening. In winter, they gather near bottom and some even bury into the mud, feed little until spring and water temperatures rise to about 42 º F
Food Crayfish are favored prey, though they also feed heavily on fish. Crustaceans like hellgermites are in there diet. Mayflies, Locust and other large insects are major source of food at times.
    Newly hatched young consume copepods and cladocerans but begin to forage on insects when about ½" long. By the time fingerlings are 1½" in length, insects and small fish comprise bulk of diet. Shad and other bait fish are favorite prey during fall in open water along with smelt and any other open water prey.
Reproduction Spawns in spring, in gravelly shallows of lakes or large, gentle eddies and slack water in rivers and streams, when water temperatures reach 62º- 64º F.
    Male assembles a saucer-shaped nest, 14"-25" in diameter, on the gravel, coarse sand or rock bottom by sweeping its tail over the substrate. The female lays 2,000 to 10,000 eggs and then heads for deep water.
    Male protects the nest from predators of his own and other species and fans the eggs free of silt until the sac fry emerge in 3-5 days, depending on water temperature. Re-nesting is quite common, particularly when early nests are destroyed by flood or similar natural disaster.
    Newly hatched sac fry swim over the nest in a school for about 6-15 days, moving sluggishly until all the nourishment in the yolk sac is consumed. The young fry are about one-half inch long when the yolk sac is absorbed, and they leave the nest to feed on small crustaceans and copepods.
    There is no relationship between the number of spawning fish and the success of the spawn. The strength of the year class depends solely on water conditions - in particular, the absence of a sudden cold snap or muddy floodwaters that can kill eggs and fry.
    Sexually mature in the second or third year, but where food is scarce or water relatively cool in all seasons, may not occur until third or fourth year around 10.6 inches long