Threadfin Shad (Dorosoma petenense)

A well-known forage fish and a member of the Clupeidae family of herring and shad, the threadfin shad rarely grows larger than 5 inches long, remaining small enough to be one of the most important open-water forage species for prominent freshwater gamefish, especially bass and stripers.

Identification

The threadfin shad is silvery with a deeply compressed body and is most easily recognized by the elongated, thin last ray on its dorsal fin. It has a small, dark shoulder spot, and its upper jaw does not project past the lower jaw.

It is similar in appearance to other herring, including the similar-size but more northerly ranging alewives and the larger gizzard shad, with which it shares overlapping ranges and many of the same waters. It is distinguished from gizzard shad of similar size by its more pointed snout, terminal mouth, black dots on its chin and the bottom of the mouth, and yellow fins.

Size

This species is commonly found at 21⁄2 to 4 inches long and can attain a maximum length of 9 inches. Many threadfins do not live longer than 2 years, although they can live as long as 4 or more years.

Life history/Behavior

Threadfin shad spawn in the spring and the autumn near or over plants or other objects. They are prolific but short-lived and are highly susceptible to winter kill from extreme cold temperatures, which helps keep their numbers in check.

Food and feeding habits

Threadfins are filter feeders that primarily consume plankton and organic detritus in open water; they occasionally feed on fish larvae and on the organic material found on or over sandy or silty bottoms. In reservoirs and large lakes, these fish are constantly on the move, searching for and feeding on minute plankton, the location and the level of which will vary seasonally and according to various factors.

Other Names

shad, threadfin.

Distribution

Threadfin shad occur throughout the Mississippi River basin, from the Ohio River of Kentucky and southern Indiana southwest to Oklahoma and south to Texas and Florida, as well as in other Gulf of Mexico drainages and Atlantic drainages in Florida. They are also present in rivers in Guatemala and Honduras. They have been introduced as a forage species in Hawaii and the western United States and to other areas in the mainland United States.

Habitat

Occasionally found in the brackish waters of estuaries and bays, threadfin shad are mainly a freshwater fish occurring in large rivers, reservoirs, lakes, and backwaters, where they principally inhabit open-water environs.

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