by K. Friedland
Table
The Atlantic, Acipenser oxyrhynchus, and shortnose, Acipenser
brevirostrum, sturgeons have been utilized as a high-quality food fish
and as a source of caviar since colonial days. Both species are distributed
as far south as Florida, but the Atlantic sturgeon is found as far north
as Labrador, Canada whereas the shortnose sturgeon ranges only to New Brunswick,
Canada.
Sturgeon once supported a substantial commercial fishery, but like other
anadromous species, their populations were adversely affected by industrial
use of rivers beginning in the 1800s and by overfishing. Their decline
has left only remnant populations of both species and has resulted in the
enactment of state management measures to protect the Atlantic sturgeon
and an endangered species listing of the shortnose sturgeon under the federal
Endangered Species Act (ESA). Today, the lack of fish passage facilities
at dams and poor habitat conditions continue to stand as impediments to
the re-establishment of many sturgeon populations.
The basic life history patterns for the two species are very similar,
but there are important differences in distribution and migration that
serve to minimize habitat overlap. Juveniles and adults of both species
are benthic (or bottom) feeders, consuming a variety of crustaceans, bivalves,
and worms. Sturgeons are relatively slow growing fish. As adults, shortnose
sturgeon reach body lengths of approximately 100 cm (40 in.) whereas Atlantic
sturgeon can attain more than twice that length. Both species begin spawning
migrations to freshwater during late winter to early summer. The migrations
occur later in the year at higher latitudes, and where the species co-occur,
the shortnose sturgeon tends to begin its spawning migrations earlier than
the Atlantic sturgeon. Both species are long lived (>15-20 years), mature
late in life and are highly fecund, with their total egg production increasing
proportionally to body size. Juvenile sturgeon remain in freshwater for
their first summer of life and then migrate to deeper, more brackish water
in winter. The juveniles migrate to and from freshwater for a number of
years before becoming marine and joining the adult migration pattern. Migrations
out of freshwater are well known for the Atlantic sturgeon, but have only
been recently documented for the rarer shortnose sturgeon. Tagging studies
have demonstrated that Atlantic sturgeon can migrate extensively along
the coast both north and south of their natal river systems.
A large commercial fishery for sturgeon once existed, but in recent
years the fishery has been limited and directed specifically at Atlantic
sturgeon. Around the turn of the century, landings of sturgeon, believed
to be a mix of the two species, were in excess of 3,000 mt (7 million lb)
a year. As these populations became overexploited, catches declined dramatically,
and only incidental landings were reported during the period 1900 to 1950.
Some fishing activity began during the 1960s in the Carolinas, which sustained
annual landings of perhaps 100 tons through the 1980s. These fisheries
are now closed. Increases in landings in the early 1990s were due to increased
catches in ocean fisheries off New York and New Jersey. Landings have since
declined precipitously to only 3 mt in 1996. There is no significant sport
fishery for sturgeon.
The Atlantic sturgeon is managed under an Atlantic States Marine Fisheries
Commission (ASMFC) plan in coordination with state regulations. The ASMFC
plan seeks to restore the commercial fishery to levels of 10 percent of
1890 landings (700,000 lb), while at the same time protecting stressed
populations of Atlantic sturgeon. The plan proposes a minimum size limit
(7 ft.) or other equally effective conservation measures as deemed appropriate.
The plan also provides for a research program to evaluate stock status
of Atlantic sturgeon. Atlantic sturgeon populations have declined to precariously
low levels prompting a call for a voluntary fishing moratorium and consideration
of a plan amendment. The National Marine Fisheries Service and U.S. Fish
and Wildlife Service have received a petition to list Atlantic sturgeon
as endangered; a decision is pending.
Shortnose sturgeon management is guided by a recovery plan under the
Endangered Species Act. The recovery plan is being revised to reflect the
increased knowledge accumulated on shortnose sturgeon populations and ecology
in recent years. The endangered status of some shortnose sturgeon populations
has been reviewed; a number of populations may be large enough to allow
reclassification of their status.
For further information
Dadswell, M.J., B.D. Taubert, T.S. Squires. D. Marchette, J. Buckley.
1984. Synopsis of biological data on shortnose sturgeon, Acipenser brevirostrum
LeSueur 1818. NOAA/NMFS Tech. Rep. 14.
Gilbert, C.R. 1989. Species profiles: life histories and environmental
requirements of coastal fishes and invertebrates (Mid-Atlantic Bight) Atlantic
and shortnose sturgeons. U.S. Fish. Wildl. Serv., Biol. Rept. 82(11.122);
U.S. Army Corps of Engineers TR EL-82-4.
