Micropterus salmoides
Largemouth Bass

Largemouth Bass

Flora, fauna, earth, and sky...
The natural history of the northwoods



  • Micropterus, from the Greek, "small fin"
  • salmoides, from the Latin, salmo, "trout"; hence "trout-like"
  • Common name from large mouth, the line of which extends back past the eye.
  • Other common names include: Bigmouth Bass, Bigmouth Trout, Black Bass, Bucketmouth Bass, Green Bass, Green Trout, Hawg, Hog, Lineside, Lake Bass, Openmouth Bass, Oswego Bass, Slough Bass, Welshman


  • Kingdom Animalia
    • Phylum Chordata, animals with a spinal chord
    • Subphylum Vertebrata, animals with a backbone
      • Superclass Osteichthyes, bony fishes
      • Class Actinopterygii, ray-finned and spiny rayed fishes
      • Subclass Neopterygii
      • Infraclass Teleostei
        • Superorder Acanthopterygii,
        • Order Perciformes, perch-like fishes
        • Suborder Percoidei
          • Family Centrarchidae, sunfish
            • Genus Micropterus, black bass, largemouth bass


  • A rather slender, streamlined sunfish, with a very large mouth and an appetite to match.
  • Length commonly to 16"
  • Weight
    • the northern strain of largemouth seldom exceeds 10lbs
    • the southern subspecies (M. salmoides floridanus) is much larger
  • Coloration
    • dark green on top
    • silvery green to yellow green flanks
    • belly white to yellowish
    • dark, irregular stripe along side
    • eye usually gold
  • Body
    • spiny and soft portions of the dorsal fin are separated by a deep notch.
  • Head
    • upper and lower jaws extend past the gold-colored eye
  • Lifespan to 13 years.


  • Largemouth bass can be recognized by the lower jaw which extends past the back edge of the eye.
  • Distinguished from its smallmouth cousin by:
    • its proportionately large mouth; upper jaw extends beyond the eye
    • spiny first dorsal fin nearly separate from soft-rayed second fin


  • Great Lakes south to the Carolina coast and Gulf of Mexico
  • Lakes and streams throughout Minnesota. Most abundant in small to medium-size hard-water lakes of central, south central, west central, and northwestern regions. Least common in the lakes of the Lake Superior drainage and the streams draining the southeastern hills.
  • The Boundary Waters are at, or beyond, the northern edge of its natural range. Most, if not all, may be introduced to these lakes.


  • Though tolerant of turbid water, it favors lakes with clear water, sandy shallows, and abundant rooted aquatic weeds; also slow moving rivers or streams with soft bottoms. Many species of pondweeds, water lilies, coontail, elodea, cattails, and bulrushes provide excellent cover.
  • A "warm-water" species, it flourishes in waters warmer than 80º F. and can survive temperatures into the mid-90's.
  • In still water, nearly always near vegetation or other underwater structure. As the water continues to warm after the spawn, spend much of their time in the shelter of thick cover or deeper water.


  • Minnows, Yellow Perch (Perca flavescens), sunfish, frogs, crayfish, aquatic insects, and any small living animal or bird hapless enough to fall in the water. (Sorta like a northern 'gator.)
  • Feeds largely by sight, but also uses smell and the ability to feel vibration through the lateral line, a sense organ that runs longitudinally down their sides. Experiments have demonstrated its ability to locate and capture minnows by vibration alone.
  • Small sac fry feed on microscopic crustaceans, supplemented with insects and insect larvae as fish grows. Usually start foraging on fish when 1"-2" long.
  • During summer, they typically feed near water plants in shallow waters at evening and early morning.


  • U.S. Record: 22 lbs, 4 oz, from Montgomery Lake, Georgia, 1932
  • Minnesota Record: 8lbs, 13oz, from Tetonka Lake (LeSueur County).


  • Extremely popular sport fish.


  • Spawns early May into June, in 2'-6' of water over firm sand, mud, or gravel, when the water temperature is 63 º to 68 º F.
  • Male usually fans out a 20"-30" diameter, saucer-shaped nest with its tail prior to spawning, but sometimes they will spawn with very little nest preparation.
  • Female lays 2,000 to 7,000 eggs per pound of body weight, deposited on roots of submerged plants or grass. Eggs hatch in 3 -6 days, depending upon water temperature.
  • After spawning, female moves off to deep water; male guards the nest until the eggs hatch and mature into a swarm of black fry. During this time, the male strikes savagely at intruding fish (or lures) but does not eat. When fry reach an inch in length, they leave the nest. Male resumes feeding and may eat any young bass he encounters.
  • Largely because of the male's care in building and guarding nest, many fry survive, and a few adult bass can quickly populate new waters. There appears no correlation between number of spawning bass and subsequent number of young. Success of the spawn depends entirely on good spawning areas and stable weather. (A severe cold front, for example, may cause the male to desert the nest. Then the eggs or fry can be eaten by other fish.)
  • Both sexes usually reach sexual maturity in third year; faster growing bass can mature in second year. Male builds guarding the nest and eggs from all intruders, until hatching.


  • Interestingly enough, the generic name for our freshwater bass, Micropterus, meaning "small fin", is a misnomer. The speciman from which the genus was named had a damaged fin which gave the appearance of a small fin behind the dorsal. This characteristic, needless to say, is not shared by the other members of the genus. Ah, taxonomy is such an exacting science...


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Last updated on 13 November 1999