Fathead Minnow

Key Characteristics:

  • More pre-anal myomeres than post.
  • Most have a lateral stripe. Single dorsal fin. Pigment on top of the head.
  • Dorsal fin begins after the start of pelvic fin in some species (emerald and golden shiners).
  • Very hard to key out to species except for a few unique species until about 20 mm.
  • Midventral stripe
  • 21-25 preanal myomeres
  • 12-15 postanal myomeres

Larval Fathead Minnow. 5 mm. United States Fish Wildlife Service. Green Bay, WI. Adam Dziewa. 2018.


Larval Fathead Minnow’s Head Pigmentation. 5 mm. United States Fish Wildlife Service. Green Bay, WI. Adam Dziewa. 2018.


Different Stages of Larval Fathead Minnows. United States Fish Wildlife Service. Marian Shaffer. 2017.

Dr. Auer’s Dichotomous Key

  • Body not elongated, eel-shaped, round in transverse section, uniformly pigmented (1B)
  • Chin barbels absent (3B)
  • Snout short, its length usually less than 10% TL; median fins otherwise (5B)
  • Median fins or finfolds showing distinct separation (7B)
  • No adipose fin, or demarcation of one, in finfold (10B)
  • Preanal myomeres greater than or equal to postanal myomeres (14A)
  • Preanal myomeres significantly greater than postanal myomeres (difference greater than five myomeres) (15B)
  • Postanal myomeres greater than 10 (26B)
  • Preanal myomeres usually less than 30 (28A)
    • Cyprinidae (Carps + Minnows)

Adult History 

  • Physical Description
    • Body coloration: white belly, yellow sides, green/brown back, rounded snout and fins, upturned mouth does not extend to the eye, dark lateral line across the body, spot at base of tail, 43-49 lateral scales, anal fin has 7 rays (no spine), and dark spot on dorsal fin
  • Spawning Habitat
    • Slow-moving sections of water
    • Ponds, streams or shallow, weedy lakes, turbid streams, ditches, etc
  • Spawning Substrate
    • Eggs are deposited in either gravel or sand (underneath objects)
  • Spawning Behavior
    • Male prepares nest under objects (rocks, logs, sticks)
      • Develops dark coloration and breeding tubercles
    • After the female lays her eggs, the male comes back to fertilize and guard his eggs
      • Fans the eggs with his fins
      • Massages them with a mucus-pad on his back (between head and dorsal fin)
        • Keeps them clean and oxygenated
      • Won’t leave until all the eggs are hatched
  • Time of Year
    • May-August in Great Lake Basin
    • Spawning typically takes place at water temperatures of 60 – 70°F
  • Diet
    • Herbivorous
    • Insects, copepods, plant matter, algae, and protozoa

Adult Fathead Minnow. UW – Sea Grant, UW – Madison, and NOAA. John Lyons. 2013.

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