Activities The Great Outdoors Species Profile: the Threadfin Shad Share PINTEREST Email Print Wikimedia Commons The Great Outdoors Fishing Fish Species Freshwater Fishing Saltwater Fishing Gear Hiking Climbing Skiing Snowboarding Surfing Paddling Sailing Scuba Diving & Snorkeling Learn More By Ronnie Garrison Updated February 17, 2019 The threadfin shad (dorosoma petenense, shown in photo) is an important baitfish in many lakes. They are small and provide high protein food for bass, crappie, stripers, hybrids and other fish. Description of Threadfin Shad The elongated fin on the dorsal fins gives the threadfin its name. The mouth is terminal and the lower part of the upper jaw is not notched. The anal fin has 20 to 28 rays; the dorsal, 10 to 13 rays. Color is bluish gray on the back with a persistent black or purple spot just behind the head. The lower side is silver to creamy white. The fins have a yellow tint, which gives it the local name of “yellowtails”). Size: Adults may reach five to seven inches but most are one to two inches long. Many shad die off each winter due to cold water--they can not live in water colder than 35 F and start dying off at 45 F—so not many reach a big size.Distribution: Native to the U.S. west of the Appalachian Mountains, north to Kentucky, west to East Texas, south to the Rio Grande drainage, and east to Floridian rivers, the threadfin shad have been transplanted to waters all over the U.S. They do best in large rivers and lakesFeeding habits: Plankton is the main food source for threadfin shad. They run in schools of similar size fish and you often see them feeding right on the surface late in the day when photosensitive plankton rises to the top as the sun sets.Spawn: Threadfin shad spawn on hard surfaces near deep water but right on the surface. It occurs when water temperatures reach about 60 F, usually during a full moon. The shad spawn is a prime time to fish for bass. Attraction to light: Threadfin are attracted to light, and at night they can be found around lighted docks. Many fishermen put out lights to attract them and the game fish that follow.Life cycle: Females lay eggs on hard surfaces in shallow water and males fertilize them from first light to sunrise when the water temperature reaches the high 60° range. Eggs hatch and the tiny shad school up and eat plankton, gradually moving to deeper water. They stay in the open deep water until time to spawn the next spring. Problems With Threadfin Shad Since threadfin shad are so sensitive to cold and don't grow to large sizes, they are not much of a problem for other gamefish, although the young shad do compete with young fish of other species for food.