Threadfin Shad Shows Promise as Forage Fish in Colorado Rivers and Lakes

UNITED STATES FISH AND WILDLIFE SERVICE
For Release APRIL 28, 1957

The threadfin shad, a small prolific forage fish of Tennessee and other south-eastern States, has moved west and fishing in Lakes Mead, Havasu, and Mojave and at other places along the Colorado River is getting better, according to reports reaching the Fish and Wildlife Service of the Department of the Interior. As a result, prospects are bright for the three States bordering these waters, Nevada, Arizona, and California --to develop a sport fishery of national popularity.

Fishery biologists of the three States are not yet definitely linking the improved fishing results with the establishment of the threadfin, but they report that anglers in Lake Havasu who fish in the proximity of shad schools catch the most bass. Other facts which are either coincidental with the establishment of threadfin in the Colorado River waters or directly attributable to it include:The average growth of bass has increased over two inches a year; there is a greater survival of bass spawn; bass are biting better and biting earlier in the season; crappie fishing in Lakes Mead and Havasu is improving and the individual fish are bigger. There are also indications that when threadfin shad are available for trout, the trout are using it as forage.

Nevada became interested in threadfin shad after investigating reports of consistently poor fishing in Lake Mead. As a result of a Federal aid project started in 1951. Nevada decided that because of the fluctuating level of Lake Mead shallow water vegetation, vital as cover for small bass, did not have a chance to develop. This had the effect of leaving the small bass exposed to the predations of the larger fish and the natural stocking of the lake virtually stopped. The threadfin seemed to offer a solution; it has a high reproductive rate, is the right size for predators, and does not compete with bass for food.

Nevada made its first effort to establish threadfin in its waters in 1954 when it secured nearly 2,500 young threadfins from Tennessee. Unseasonably cold winter weather killed the entire shipment. California had also obtained threadfins from Tennessee and had a good survival. California contributed 125 shad to Nevada's program. The shad spawned and re-spawned to become thousands and formed the basis for Nevada's shad program. In the meantime Arizona obtained a stock from the Fishand Wildlife Service hatchery in New Mexico and began its part of the planting program.

Nevada planted some of its threadfins in Lake Mead and some in Lake Mojave. The fish “took hold” at once and in a short time schools of thousands of these shad were noticed in Lake Mead, There was similar success in Lake Mojave. Plantings in Havasu and the Colorado River itself were equally successful. Now the threadfin, although of no value in itself as a food fish, is providing needed forage for trout, bass and crappies.

The threadfin shad is a small relative of both the American shad--the well known table delicacy and angler favorite --and the common gizzard shad. (The latter sometimes is a nuisance fish, becoming overly populous and growing so large that mature individuals cannot be eaten by bass and other game fishes.) Seldom does the threadfin exceed six inches in length and therefore is a food source for game fish throughout its life. Because it feeds in areas not frequented by small bass and feeds on items young bass ignore, there is no competition for food.

Credit: U. S. Fish and Wildlife Service