Gizzard Shad

Key Characteristics:

  • Pre-anal myomeres far greater than post-anal.
  • Pointy mouth usually ends terminally (1).
  • Very little pigment, mostly found near face and head (2).
  • Digestive tract long and feathery, visible along the belly of fish (3)
  • Anal fin rays (4) can be counted to determine species.
  • Under 20 for alewife, 20+ for gizzard shad. Those are the two species in Lake Michigan. Total fin ray number don’t come in until the fish is at least 10 mm so under 20 might not mean an alewife if the fish is very small.

Larval Gizzard Shad. 15 mm. United States Fish Wildlife Service. Green Bay Harbor, WI. Marian Shaffer. 2018.

 

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Physical Characteristics of Larval Gizzard Shad. 21 mm. United States Fish Wildlife Service. Green Bay Harbor, WI. Marian Shaffer. 2017.

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Larval Gizzard Shad. 23 mm. United States Fish Wildlife Service. Green Bay Harbor, WI. Adam Dziewa. 2018.

 

0003B

Anal Fin Rays for Larval Gizzard Shad. 23 mm. United States Fish Wildlife Service. Green Bay Harbor, WI. Adam Dziewa. 2018.

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 usually less than or equal to 10 (26A)
  • Preanal length 77 – 89% TL, ratio of preanal to postanal myomeres greater than 5.0 (27A)
    • Clupeidae – Herrings

Adult History 

  • Physical Description 
    • Small/medium terminal mouth, blunt snout, rays of the anal fin from a long thread (between 27-34 rays), silver-blue on top, could have a dark spot by the gill flap, deep-bodied, and has white sides and belly
  • Spawning Habitat
    • Shallow areas that are usually between 30 – 150 cm deep.
    • Ponds, Rivers, and Sloughs
  • Spawning Substrate
    • Reproduction occurs in tributary streams and along lakeshores
  • Spawning Behavior
    • When eggs and milt are released in schools, their eggs attach to sand, gravel, boulders, and algae
    • No nesting or parenting behavior showed
  • Time of Year
    • May through early August in Wisconsin
    • Spawning typically takes place at water temperatures of 50-70°F
  • Diet
    • Herbivorous (Filter-Feeder) / Pelagic Feeders
    • Zooplankton & Phytoplankton (Algae)
    • Organic Matter (Detritus)
Sea Grant – University of Wisconsin/NOAA

Adult Gizzard Shad. UW – Sea Grant, UW – Madison, and NOAA. John Lyons. 2013.

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