Threadfin Shad

Threadfin shad grow quickly and do not get as large as Gizzard shad. Average size is 4 inches.

Threadfin shad live primarily on microscopic plant and animal life, phytoplankton and zooplankton, which is why they are often found around rock riprap, bridge and dock pilings, and areas with gentle current where algae grows or is washed into the system. They are more surface-oriented than gizzard shad, and frequently move in huge schools just under the surface, sometimes migrating for miles each day.

Schools of threadfin shad seek shoreline cover each night. This cover can take the form of grass, moss beds, logjams, standing timber or brushpiles.

Early in the morning, generally shortly after dawn, the threadfin leave this shallow water cover for deeper areas where they may disperse slightly for the balance of the midday period and early afternoon hours.

The threadfin then re-group and return to the shallow water cover late in the afternoon, frequently by reversing the same exit route they used that morning.

Threadfin Shad /  Dorosoma Petenense

• Coloration:

  • Back dark gray to bluish black; sides and abdomen silvery.
     

• Mouth:

  • Bottom lip protruding; bottom of mouth cavity with black spots
    Top jaw stops in front of eye margin
     

• Body:

  • Deep, strongly compressed laterally. Average length less than 4inches. Scales cycloid, deciduous. Lateral line lacking. Median lateral series of scales 40-48. Ridge of sawlike ventral scutes on abdomen. Dorsal Fin filament: long, reaches almost to caudal.
     

• Biology:

  • Usually congregating in large schools over deep water in daylight hours, moving to shallower water at night.

  • Sensitive to cool temperature, swimming ability decreases below 54 degrees. Death occurs at 41°.

  • Seldom live beyond 2-3 years.

  • Distinct spot smaller than eye behind gill. Always present

  • Yellowish, except the dorsal; caudal deeper yellow.
     

•  Spawning:

  • Threadfin shad spawn on the surface shortly after dawn along a weedy shoreline or in open water around rafts of driftwood and debris.

  • Adhesive eggs stick to leaves and branches of shoreline vegetation or floating debris until hatching occurs in 2-4 days.

  • Spawning begins when surface temperature at dawn exceeds 62 F and may continue until surface temperature exceeds 83 F.

  • Most spawning happens in May and June but a September spawn may occur when plankton forage conditions are ideal.

  • Females carry 900 to 21,000 eggs for spawning annually.