The American shad or Atlantic shad, Alosa sapidissima[1], is a species of anadromous fish in family Clupeidae of order Clupeiformes. It is not closely related to the other North American shads. Rather, it seems to form a lineage that diverged from a common ancestor of the European taxa before these diversified (Faria et al. 2006).
Habits
The shad spends most of its life at sea, but swims up fresh rivers to spawn. Unlike salmon, the fish survive breeding and can return to the sea; they do not inhabit fresh water except to spawn. At sea, shad are schooling fish; 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 as deep as 65 fathoms (119 m).
Like other herrings, the American Shad is primarily a plankton feeder, but will eat small shrimp and fish eggs. Occasionally they eat small fish, but these are only a minor item in their general diet.
The sexually mature fish enter the streams in spring or early summer when the river water has warmed to 50 to 55 °F (10 to 13 °C). Cooler water appears to interrupt the spawn. Consequently the shad run correspondingly later in the year passing from south to north along the coast, commencing in Georgia in January; in March in the waters tributary to Pamlico and Albemarle Sounds; in April in the Potomac; and in May and June in northern streams generally from Delaware to Canada.
In large rivers they run far upstream especially in the open rivers of the southeast. The apparent longest distance is in the St. Johns River of Florida, an extremely slow (1" drop per mile, 0.5 m/km) river that widens into large lakes; shad have been found 375 miles (600 km) upriver.
The fish select sandy or pebbly shallows for spawning grounds, and deposit their eggs mostly between sundown and midnight. Females release eggs in batches and produce about 30,000 eggs per batch, though as many as 156,000 have been estimated in very large fish. Total annual egg production is 200,000–600,000 eggs per female with larger fish producing more. In rivers north of Cape Fear the spent fish, now very emaciated, begin their return journey to the sea immediately after spawning. In southern rivers, most shad die after spawning.
The eggs are transparent, pale pink or amber, and being semi-buoyant and not sticky like those of other river herrings, they roll about on the bottom with the current. The eggs hatch in 12 to 15 days at 52 °F (11 °C), in 6 to 8 days at 63 °F (17 °C), which covers the range characteristic of Maine and Bay of Fundy rivers during the season of incubation.
The larvae are about 9 to 10 mm long. The young shad remain in the rivers until fall, when they move down to salt water; they are now 1½ to 4½ inches (70 to 110 mm) long, resembling their parents in appearance.
Nutritional information
Like most herring, shad are very high in omega 3, and in particular contain nearly twice as much per unit weight as wild salmon. They are also very low in toxins like PCBs, dioxins, and mercury by EPA standards.
Shad population
There has been a problem with declines in the shad population as early as the turn of the century. Many of the rivers where it was common now suffer from pollution; however, in some cases, the short length of time spent by shad in fresh water may minimize contamination. Shad are taken from the Hudson River and eaten, as scientists have found that they are not in the river long enough to be affected by PCBs and other contaminants.[2]
Such pollution, however, may damage the spawn, and studies have been undertaken to determine whether fingerlings suffer DNA damage. Some of the rivers in which the shad spawns have dams on them, eliminating much of the spawning grounds; in recent years, several small dams have been destroyed for just this reason. Pollutants, even if not harmful per se, may encourage the growth of unfriendly water fauna. And finally, shad have simply been overfished.
Even more important to the decline of the shad is the damming of the rivers and streams in which they spawn, as pregnant doe shad are quite heavy and do not jump even when hooked. As noted above, the number of shad caught in the Merrimack River declined from almost 900,000 in 1789 to 0 in 1888, due to the fishes' inability to reach their spawning ground.
Shad serve a peculiar symbolic role in Virginia state politics. On the year of every gubernatorial election, would-be candidates, lobbyists, campaign workers, and reporters gather in the town of Wakefield, Virginia for Shad Planking.
American Shad were introduced into the San Francisco Bay/Sacramento River system in California in the 1800s. Shad have spread throughout many river systems on the West Coast of North America. There is currently a very large shad population in the Columbia River. In recent years shad counts at Bonneville and The Dalles Dams have ranged from over two million to over five million fish per year. Shad return to the Columbia in May and June. Shad migrate upstream as far as above Lower Granite Dam on the Snake River and above Priest Rapids Dam on the Upper Columbia. Unlike many exotic/introduced species, it has not been confirmed that American Shad have serious negative effects on the environment or other native fish species in the Columbia.
Shad fishing
Early 19th century shad fishing on the
Peedee (Greater Pee Dee) River, South Carolina.
Shad are also valued as a sport fish that exhibit complex and little-understood feeding behavior while spawning. Unlike salmon, shad retain the ability to digest and assimilate food during the anadromous migration. Like other fish, their feeding instinct can be triggered by a variety of factors such as turbidity and water temperature. Anglers use both spinning and fly fishing tackle to pursue shad. Spin fisherman use a shad dart or a flutter spoon. Typically a downrigger is used to place the artificial lure at the desired depth and location. This is usually in the channel, or deepest part of the river. Much of the shad's migration places them in the lower potion of the water column which makes this the typical depth of choice for fishing. In the north, April through June is when shad spawn in coastal rivers and estuaries once water temperatures have reached 58 degrees Fahrenheit (14 °C). Fishing conditions typically improve as water temperatures warm and flow decreases.
References
- ^ "Alose". TheFreeDictionary.com. Farlex, Inc.. http://www.thefreedictionary.com/Alose. Retrieved 2007-04-26.
- ^ Hudson River Maritime Museum Kingston Shad Festival
External links
