American Shad (alosa sapidissima)
Life as a shad
American shad are anadromous fish, meaning they spend
most of their lives in saltwater but spawn in freshwater. Shad are found
along the Atlantic seaboard from Labrador to Florida. Shad are an important
food source for other fish such as bluefish and striped bass.
Rising spring temperatures prompt shad to leave the ocean
and return to the waters in which they were hatched. American shad live in the mainstem of rivers rather than in shallow streams. They return to lay their eggs only in habitat with a certain amount of water flow, the type of flow found in large rivers. This point is crucial when people plan for fishways to get American shad through dams. The fishways must pass a certain flow of water, or shad will not use them. Biologists believe the
fish find their natal streams through their uncanny sense of smell. Males
arrive on the spawning grounds first, followed by egg-laden females. A
female releases 100,000 to 600,000 eggs into the water to be fertilized
by several males. Adult shad return to the ocean soon after spawning.
The transparent fertilized eggs are carried along by
the current. The larvae hatch in 4 to 12 days. Juvenile shad spend their
first summer in freshwater. By autumn, the young shad gather in schools
and swim to the ocean. They will live in the ocean from three to six years,
until sexually mature then return to freshwater to complete their life
cycle. This sustained a thriving shad population for centuries, but this
changed as America prospered.
As human population increased so did the demand for
shad. The Chesapeake Bay shad fishery was an important seasonal industry
by the 1800s. Shad became one of the most commercially valuable fish in
the District of Columbia, Maryland, Pennsylvania, and Virginia.
By the late 1800s, excessive harvesting took its toll
on shad. This exploitation coupled with pollution and loss of spawning
grounds began a downward spiral of shad populations. From an annual harvest
of 17.5 million pounds at the turn of the century, Chesapeake shad harvests
dwindled to less than 2 million pounds by the 1970s.
The Susquehanna was once the Bay's most important river
for spawning shad. The Pennsylvania canal system, built in the 1830s,
required feeder dams that restricted migration to the lower 45 miles of
the river. Later, four hydroelectric dams eliminated all shad runs in
Pennsylvania. Meanwhile people continued damming other rivers throughout
Early attempts at creating fish passage, or fishways,
around dams failed. Resource managers attempted to restore shad stocks
by releasing hatchery-reared shad into rivers. This attempt proved futile
since overfishing continued and spawning grounds remained blocked. Populations
continued to decline and restocking efforts ceased by the 1930s.
Growth brought pollutants from mills, factories, mines
and domestic sewage that degraded vital shad spawning grounds. Improper
timber harvest and farming practices led to excessive erosion, further
degrading rivers and streams.
Shad all but disappeared from the Potomac River by the
1950s. In 1980, Maryland shad harvests fell to a record low of 25,000
pounds and the state placed a moratorium on shad harvests in the Chesapeake
Bay. Shad was one of the most abundant fish in Virginia. In the 1980s,
catches ranged from two to three million pounds. In 1992, fishermen harvested
less than 500,000 pounds. Virginia banned shad fishing in rivers and the
Chesapeake Bay after the 1993 spring harvest.
Restoring American Shad
Shad restoration is underway in 15 river basins from Maine
to Virginia. Success will depend upon improving water quality, preventing
overfishing and reopening spawning grounds. The goal is to achieve self-sustaining
runs of shad and to reopen hundreds of miles of spawning habitat. Federal
and state agencies and private organizations, working together, developed
an American Shad Fishery Management Plan. The plan calls for actions to
restrict harvests, restore stocks, and provide fishways around dams and
other barriers to spawning grounds.
One successful fish passage facility is an elevator system
at Conowingo Dam near the mouth of the Susquehanna River. Two elevators,
or fish lifts, move migrating fish to the top of the dam. The shad are
sorted out and transported, by truck, 60 miles upstream, past 3 dams to
their spawning grounds. Fish lifts at three other dams in Pennsylvania
should be in place by the year 2000. Other fish passage efforts have focused
on the Patapsco River in Maryland, the James River in Virginia and Rock
Creek in the District of Columbia. More than 170 miles of spawning habitat
are now open to anadromous fish.
Throughout the watershed, barriers are being removed or
modified, opening spawning areas to shad and other migratory fish. Road
culverts and gauging stations are being redesigned to provide the gradient
and flow of water the fish need. Dams no longer in use can be breached.
Breaching removes all or part of a dam to allow fish to swim upstream.
Dams still in use may require a fish ladder. A fish ladder
is an inclined water channel structure with a series of baffles or weirs.
The baffles interrupt and slow the flow of water, simulating pools and
rapids. Fish swim up the ladder just as they would swim up natural rapids.
Larger dams require fish lifts.
Fishways alone will not restore shad populations. After
a stream blockage is removed, biologists must reintroduce shad into newly
opened spawning grounds. Fertilized eggs and juvenile shad can be released
into upriver areas. Another technique captures adults that are ready to
spawn and releases them into newly accessible spawning areas.
Fishways and stocking must be reinforced by protecting important fish
habitat. Larval fish are more susceptible to pollutants in the water
and require good water quality to survive. Establishing sustainable
harvests is also critical to restoration. Atlantic Coast states have
agreed upon coast-wide harvest limits but not all states have enforced
these limits through legislation. Coastal harvesting still intercepts
many shad before they can reach protected waters to spawn.
Cooperation between federal and state agencies, private businesses and
individuals is the key to successful restoration of shad and other living
resources. The steps taken today to conserve migratory fish will sustain
commercial and recreational fisheries now and for future generations.