Distribution: American shad spawn in Atlantic coastal rivers from Florida to Eastern Canada. Aside from a few residual populations in New Hampshire’s coastal rivers, the majority of American shad reach the state by migrating up the Merrimack and Connecticut Rivers. Fish passage has been provided at the first three dams on the Merrimack River, although shad have difficulty navigating the fish passage facility at the Pawtucket Dam in Lowell, MA. On the Connecticut River, fish passage for shad is available at the three mainstream dams up to the historic limit of upstream shad migration at Bellows Falls.
Description: The American shad is a silvery, laterally compressed fish with a bluish green back and large scales. There is a row of diminishing dark spots behind the gill plate. The lower jaw is straight and fits into a notch under the upper jaw. The lower jaw of the alewife and the blueback herring is bent into a shovel shape and angled upward. American shad have a single dorsal and anal fin and a deeply forked caudal fin. Adult females attain sizes of up to 30 inches. Females are sexually mature at 19 inches in length.
Species commonly confused with: Alewife, blueback herring
Habitat: American shad spend most of their lives in the ocean, but they migrate upstream in medium to large sized freshwater rivers to spawn in reaches with moderate current.
Life History: The American shad is the largest member of the herring family. There is a significant difference in size between the sexes, with males usually weighing between 1 and 3 pounds, while the females grow larger and can reach over 8 pounds. Like salmon, river herring, and sea lamprey, shad are anadromous, which means they live in the ocean, but they spawn in freshwater. Each spring, thousands of shad migrate up the rivers along the Atlantic coast. Shad tend to congregate below falls or other obstructions in the river. Before the construction of dams in the early 1800s, places like Amoskeag Falls on the Merrimack River and Bellows Falls on the Connecticut River bustled with the activity of fishermen during the spring shad spawning runs. American shad may produce up to 600,000 eggs, which are fertilized by the smaller males over a period of days. Spawning takes place over sandy gravel substrate with moderate current. Juvenile shad hatch in about one week and feed on zooplankton in the river until the late summer or fall, when they migrate downstream to the ocean.
In northern rivers, shad will spawn in multiple years after about five years at sea. In southern rivers, most shad die after spawning. Adult American shad that leave rivers after spawning will follow the younger, non-spawning shad on a counterclockwise loop through the Bay of Fundy and back into the Gulf of Maine. As filter feeders on zooplankton, shad are well adapted to feeding in the murky waters of the Bay of Fundy, where the fastest tides in the world stir up tons of sediment. By the end of the summer, shad make their way to wintering areas in relatively close proximity to their home rivers. There they continue to feed on zooplankton to store up fat reserves for their spring spawning run. Shad do not eat while they spawn, so they must rely on stored energy for their exhausting migration up river. It is interesting that, even though shad do not feed on their spawning run, they can still be caught with hook and line using “shad darts” during their migration.
Conservation/Management: American shad still run up the rivers of the east coast, but their numbers are only a fraction of what they were in early colonial times. While over fishing took its toll, it was dam construction that really wiped out the abundant runs of shad and other migratory fish. Prior to a dam constructed on the Connecticut River at Turners Falls in 1798, American shad reached Bellows Falls and the Ashuelot River in great numbers. The Essex dam, in Lawrence, Massachusetts, built on the Merrimack River in 1847, wiped out the Atlantic salmon population and crippled the American shad run.
Commercial Harvest: American shad are among the fish managed by the Atlantic States Marine Fisheries Commission (ASMFC). The ASMFC was formed by the 15 Atlantic coastal states in 1942, with the understanding that fish do not recognize state borders. The Fisheries Management Plan for Shad and River Herring states that by 1993, commercial landings of American shad were estimated at 1.5 million pounds, down from 50 million pounds landed in the early 1900’s. A coastwide American shad stock assessment, conducted in 2007, found that shad populations are currently at an all time low and do not appear to be recovering. All commercial fishing for American shad in the ocean was banned in 2005. The latest proposed amendment to the management plan calls for further restrictions on shad mortality and the adoption of new goals for restoration based on estimates of historical shad landings.
Fish Passage: Although fishing regulations are important, improving fish passage at dams still offers the greatest room for improvement for restoring American shad populations. Only about 10% of the fish that make it passed the Essex Dam, on the Merrimack River, make it above the Pawtucket Dam in Lowell. On the Connecticut River, only a small fraction of the American shad that pass the Holyoke Dam in Massachusetts make it to the Vernon dam in New Hampshire. The good news is that fish passage can always be improved. The bad news is that shad are notoriously finicky about navigating river flows. The slightest change in flow, undetectable to the eye, can prevent a shad from entering a fishway. However, when conditions are favorable, shad will move through fish passage facilities by the thousands.
Restoration: American shad restoration efforts are managed by partnerships between state and federal agencies and NGO’s. The Merrimack River Policy Committee and the Connecticut River Atlantic Salmon Commission have approved Restoration Plans for American shad in their respective watersheds. United States Fish and Wildlife fish hatcheries, including the Nashua National Fish Hatchery in New Hampshire and the North Attleboro National Fish Hatchery in Massachusetts, are used to raise juvenile shad, which are then released into rivers to try to restore defunct runs or bolster existing ones. The New Hampshire Fish and Game Department uses a “shad truck” to transport adult shad from below dams to spawning habitat up river. Dam ownershave been required to provide downstream passage in an attempt to prevent juvenile shad from passing through turbines on their migration to the ocean in late summer.