by Jason Moak, Research Scientist
Spring is here and so are the American shad! The American shad (Alosa sapidissima) is the largest species of fish in the Herring family (Clupeidae), and is found all along the Atlantic Coast of North America. Prior to the World War II, American shad were considered one of the most valuable food fish in the United States. In 2002, Pulitzer Prize-winning author John McPhee published an entire book chronicling the history of the American Shad: “The Founding Fish.”
Adults of American shad are typically 3-6 years old and are between 16 to 21 inches long. These fish are anadromous, meaning they spend most of their lives in the ocean, but migrate up freshwater rivers to spawn. Southern populations of American shad only spawn once, and die shortly afterwards. In the Savannah River, American shad can usually be found in between February and May, when water temperatures are between 14 and 21 degrees Celsius (57 to 70 degrees Fahrenheit).
North American commercial fisheries for American shad have existed since the 1800’s, but catches have declined sharply since the early 20th century. Numerous factors led to the decline of this species, including the construction of dams that blocked access to historical spawning grounds, habitat destruction, overfishing, and pollution. Efforts to recover populations of American shad include enhancement through stocking of hatchery-reared fish, construction of upstream fish passage structures at dams, reduction of pollution, and limits on commercial and recreational fishing.
One interesting method of helping shad recovery, similar to a fish elevator, is used at New Savannah Bluff Lock & Dam, the last dam on the Savannah River between Augusta and the Atlantic Ocean. The U.S. Army Corps of Engineers, based on recommendations from the South Carolina DNR, operates the locks to allow fish to pass upstream of the dam during spawning season. This has been accomplished by allowing water to flow into the lock chamber, which serves to attract the American shad. Then, the downstream lock doors are closed, the lock is filled with water until it is level with the upstream river, and the upstream lock doors are opened, allowing the fish to swim out and upstream into the Augusta Shoals where there is a large amount of ideal spawning habitat.
Despite large declines in Savannah River American shad populations, restoration is currently considered to be sustainable. A study in the early 2000’s documented that half of tagged shad were able to move upstream through the lock and estimated that the population of shad that reached the Lock and Dam may be higher than 200,000 fish.