Also known as
Atlantic shad, common shad, Connecticut river shad, herring jack, north river shad, Potomac shad, shad, Susquehanna shad, white shadBack to Top
What they look like
Usually called just "shad" on the west coast, the correct common name for this introduced species is American shad. The scientific name is Alosa sapidissima, from the Saxon word allis (an old name for European shad) and the Latin word sapidissima (most delicious).
American shad are flat-sided fish with a green or greenish blue metallic luster on its back shading through white to silvery on the belly. It has a row of 3 to 23 dark spots along its silvery sides, decreasing in size toward a deeply forked tail. These spots are not always visible, but show up when the fish are scaled. A very distinctive characteristic is the saw-like serrated edge along the midline of the belly. The lower jaw does not extend further than upper jaw. Teeth are missing in specimens greater than 8 inches.Back to Top
Where they live
American shad are the only anadromous shad on the west coast and have the ability to return to spawn for several years. They live most of their life in marine waters where little is known of their life history on the Pacific coast. At sea, shad are schooling fish and thousands are often seen at the surface in spring, summer, and autumn. They are hard to find in the winter, as they tend to go deeper before spawning season. They have been pulled up in nets at deep as 65 fathoms. Shad are river-specific and each has a discrete spawning stock and adults return to their natal river to spawn.
They are very sensitive to water temperature and any dramatic changes in the temperature of its habitat can have a very negative impact on the fish. They will not tolerate water temperatures below 41 °F. The ideal habitats for juvenile shad are large reservoirs. Fish ladders and dam bypasses are necessary to assist in the migration of the American shad past dams.
Shad are native to the Atlantic coast and were introduced to the Pacific coast in the early 1870s. Records document commercial landings in the Columbia River in 1885. Shad have become abundant and well established in the Columbia River and tributaries, including the Snake River and the Willamette Rivers. Shad are now found from southern California to Kodiak Island, Alaska.
Extensive biological and ecological information exists about American shad in its native Atlantic coast habitat. Similar information is lacking about American shad in the Columbia River system. Shad migrate upstream with adult salmon through fishways in the Columbia River dam system. Competition between salmonids and American shad for passage through fishways has resulted in some dams being modified to allow for better shad access to upstream habitat . American shad have migrated past Bonneville, The Dalles, John Day, McNary, and Priest Rapids Dams and as far as the Lower Granite Dam on the Snake River.
American shad flourished on the West Coast and in the Columbia River after their introduction in the late 1800s. The reasons for shad abundance vary, but it is strongly believed that the freshwater habitat created by dam reservoirs is ideal for spawning and rearing. The Dalles Dam was built in 1956, the adult shad count at Bonneville Dam (downstream) increased from a 22–year average of 15,475 fish (1938–59) to 329,850 fish in the period 1960–64.
The American shad introduced into the Sacramento River came from a hatchery on New York’s Hudson River. In 1885, shad were introduced into the Columbia River from the Susquehanna River in Pennsylvania. However, shad had been observed in the Columbia River earlier. It is believed they were transported northward by the Davidson Current that flows from San Francisco to Vancouver Island. Shad have become very abundant in the Columbia River system, with as many as 4 million shad estimated in 1990.Back to Top
What they eat
Like other herrings, the American Shad is primarily a plankton feeders, filtering copepods and mysids through their gill rakers, but will eat small shrimp and fish eggs. Occasionally they eat small fish, but these are only a minor item in their general diet. While migrating upriver they do not feed. Once American shad have spawned, they begin feeding again on their return to salt water. Juveniles feed on zooplankton and terrestrial insects.Back to Top
The American shad is the largest member of the herring family. On the east coast, American shad reportedly grow to 30 inches and more than 10 pounds. In Washington, the maximum size for an American shad was in the Columbia River at 24 inches and weighing 8 pounds. Average size here is 17 to 19 inches and three to four pounds. Females run an inch or two longer than males, and are correspondingly heavier. Shad can live to be 11 years old. During an average life span of five years at sea, the American shad may migrate more than 12,000 miles. Little is known of the ocean stage of shad life on the Pacific coast.Back to Top
Like salmon and steelhead, shad are anadromous. They enter freshwater rivers in the spring to spawn. Unlike Pacific salmon, they do not necessarily die after spawning. Depending on their geographical location, shad may spawn once and die, or they may survive to make several spawning runs per lifetime. With increasing water temperatures in the spring, mature American shad will migrate back to their native rivers to complete their life cycle. Upon entering freshwater, the belly of the shad changes from white to a darker color. American shad may spawn immediately on entering fresh water or may migrate upstream several miles to spawn. Water temperature influences the timing of spawning runs. The peak movement of shad through the Bonneville Dam occurs during temperature ranging from 62 to 66 °F. In the Columbia River American shad spawn in June to August when water temperatures are 60 to 65 °F. American shad males spend between 3 to 5 years at sea before becoming sexually mature and females between 4 to 6 years.
American shad spawn in groups of one female and one to several males. One female may emit eggs over a period of several days before all eggs have been dispersed. The number of eggs depends on size of female. Estimates of egg production (fecundity) range from 116,000-616,000 per female. The eggs are shed in small numbers near the surface between sundown and midnight over sandy pebbly substrate. After fertilization, the eggs slowly sink as they drift downstream for 2 to 3 days, finally becoming lodged in crevices or on aquatic vegetation. Fertile American shad eggs are a little over 1/8 of an inch in diameter, pale pink to amber in color, semi-buoyant and non-adhesive. Eggs can be found at any depth during spawning season, but are most numerous near the bottom. Eggs develop quickly, hatching within 6 to 10 days at temperatures ranging from 57 to 63 °F. Colder water increases the length of time to hatching. Young gradually work their way downstream, usually spending their first summer of life in the river.
Newly-hatched shad are around 3/8 of an inch in length. The yolk sac is absorbed in 4 to 5 days. Within 10 to 12 days after hatching, shad larvae will begin feeding primarily on copepods and chironomid larvae and in 3 to 4 weeks will reach approximately 3/4 of an inch long, with fully developed fins. Juvenile shad stay in fresh water for several weeks before moving seaward in late fall or early winter. American shad will grow to a size of 2 to 4 inches and months old by the time they leave fresh water.Back to Top
3 lbs. 13.6 oz. caught in the Columbia River, Clark County by angler Tom Magnuson on June 21, 2005