by J. Kocik
Table
The American shad, Alosa sapidissima, is an anadromous
species which occurs along the Atlantic coast from southern Labrador to
northern Florida. It also has been introduced along the Pacific Coast.
American shad undergo extensive seasonal migrations, moving into rivers
for spawning beginning in January in southern rivers, and continuing until
July in the northernmost portion of their range. After spawning, shad migrate
north along the coast to Canada where they feed during the summer. A southward
migration occurs later along the continental shelf where the fish overwinter
prior to spring spawning migrations to their natal rivers.
American shad have a range of life history patterns depending on their
river of origin. In southern rivers, shad return to spawn at age 4 and
die after spawning. Fecundity ranges from 300,000 to 400,000 eggs. Progressing
northward, increasing numbers of spawners survive, the mean age at first
spawning increases to 5, and fecundity decreases to 125,000 to 250,000
eggs.
Almost every major river along the Atlantic seaboard historically supported
a spawning population of American shad. They have been exploited for their
flesh and roe since prior to Euro-American settlement. Atlantic coast landings
exceeded 22,000 mt in 1896. In contrast, commercial landings north of Cape
Hatteras, N.C. have averaged less than 1,100 mt annually since 1980. Since
1993, annual landings have exceeded 600 mt only once, in 1995. The principal
gear used is the gillnet. Recreational angling is popular and catches may
be significant, but no comprehensive estimates are available.
Excessive fishing has been blamed for historic declines in abundance
in the Hudson and Connecticut Rivers, as well as in rivers in Maryland,
North Carolina, and Florida. Throughout North America, dam construction
along many larger rivers led to an almost complete disappearance of shad
in many watersheds and the loss of associated fisheries. Pollution in the
lower Delaware has been cited as the primary cause for the decline of the
fishery in that system.
The Atlantic States Marine Fisheries Commission has implemented a coastwide
management plan for American shad and river herring to facilitate cooperative
management and restoration plans between states. Restoration efforts have
involved habitat improvement, fish passage, stocking, and transfer programs.
Despite improved returns in some major river systems such as the Susquehanna,
Delaware and Connecticut Rivers, the range-wide abundance of American shad
is well below historic levels.
A recent assessment characterized fishing mortality for 9 river stocks
and resource trends for 13 river stocks of American shad. Total fishing
mortality rates (river and coastal) were below the overfishing definition
(F30%) for the 9 stocks that were evaluated. These results suggest that
recent levels of exploitation in coastal intercept fisheries have not adversely
impacted these stocks. In addition, juvenile shad production indices for
7 of these stocks suggested recruitment failure only in Maine. However,
the total range of extant American shad populations includes additional
populations in small river systems and small populations in larger river
systems that are actively being restored. Also, much historical shad habitat
is vacant and may be targeted for restoration in the future. For these
stocks, individual states have developed fishing mortality targets to protect
small stocks and rebuild others. Asssessment studies have not quantitatively
addressed these systems because of limited biological data. Like all mixed
stock fisheries, small stocks can be at risk under conditions of uncertainty.
Overall, this resource is considered to be fully exploited and at low levels
of abundance.
For further information
Crecco. V.A. 1997. Stock assessment of American shad from selected Atlantic
coast rivers. Atlantic States Marine Fisheries Commission, Washington,
D.C. ASMFC Spec. Rpt.
Gibson, M.R., V.A. Crecco, and D.L. Stang. 1988. Stock assessment of
American shad from selected Atlantic coast rivers. Atlantic States Marine
Fisheries Commission, Washington, D.C. ASMFC Spec. Rpt. No. 15.
Richkus, W. A., and G. DiNardo. 1984. Current status and biological
characteristics of the anadromous alosid stocks of eastern United States:
American shad, hickory shad, alewife, and blueback herring. Martin Marietta
Environmental Center, Columbia, MD.
