|
Shortnose Sturgeon
Shortnose Sturgeon
(Acipenser brevirostrum) From St. John's River
in Florida to St. John River in New Brunswick, this globally rare fish has many
aliases - little sturgeon, salmon sturgeon, softshell, pinkster, roundnoser, bottlenose or mammose. Whatever you call it, the Shortnose Sturgeon is one of the oldest,
most primitive species of bony fish on earth. Maryland's largest freshwater
fish has likely been swimming around for millions of years; sturgeon cousins of
this species have left behind fossils dating to 150 million years ago.
Shortnose Sturgeons, along with their larger cousins
Atlantic Sturgeons, have been an important part of human history on the
Chesapeake for thousands of years. Native Americans utilized these fish for
meat. The skin may be worked into leather. The first "cash crop" sent back to
Europe from the Jamestown settlement was sturgeon meat and caviar.
 Shortnose Sturgeons are bony fishes, without scales. Their
body surface is covered with five rows of plates or scutes. They have blunt
noses when they are adults (brevirostrum = Latin for short snout)
although the snouts are more elongated in juveniles. This feature contributes
to misidentification of younger fish as Atlantic Sturgeon. The Shortnose is the
smaller of the two sturgeon species found in the Bay, attaining a maximum length
of "only" 4.5 feet and weighing in at 50 pounds. The Atlantic Sturgeon, by
comparison, can reach lengths of 15 feet and tip the scales at 800 pounds.
Interestingly, Shortnose Sturgeon will grow faster in the southern populations
(North Carolina and southward) but reach larger sizes in the northern
populations (Connecticut and points north). The Shortnose is considered a
long-lived fish; the males seldom live to 30 years but the oldest females can
survive into their 60s.
 The sturgeon mouth is on the bottom of the head which
helps, as they are bottom feeders. Four whicker-like barbels near the mouth act
as sensors. Juveniles dine on benthic, or aquatic bottom dwelling insects, and
crustaceans. Adults enjoy a diet of mollusks and crustaceans. Sturgeons have
no teeth; they suck their food in and digest it in a gizzard-like organ (similar
to one found in birds).
For at least 70 million years, Shortnose Sturgeon have been
found in the Bay. Sturgeons are anadromous fish, meaning they spend most of
their life in the Bay (or the slower waters of the lower river reaches) and
migrate upstream to fast moving cooler waters to spawn. Shortnose Sturgeon
rarely leave their own river system and don't inhabit open ocean areas, although
they may be found infrequently in nearshore marine habitats. There are 19
individual populations of Shortnose Sturgeons within their total range, each in
its own river system (the Chesapeake Bay population includes the Potomac
River). Populations are managed separately because it is unlikely that they
would ever intermix, due to geographic separation.
The Shortnose Sturgeon was first listed as Federally
Endangered in 1967, under the Endangered Species Preservation Act (the precursor
to the 1973 Endangered Species Act). (Its listing classmates include the
recently delisted Bald eagle.) The reasons for this species' endangered status
are many. All stem from its vulnerability to habitat changes during is its life
cycle. It breeds slowly, lives long, and has specific habitat requirements for
different parts of its life.
The decline started back in the 1800's. Sturgeon, as the
source of caviar, were highly valued by commercial fishermen. Although the
Shortnose was not the target species, it was caught incidentally in the fishing
of Atlantic sturgeon and in the gill nets used to catch alewife and shad. In
1890, the Chesapeake Bay was the second largest caviar fishery, at 700,000
pounds processed per year. To add insult to injury, many dams were built in the
1800's and early 1900's, effectively cutting off the sturgeon from some spawning
grounds and altering the conditions of others.
The habitat of the Bay continued to degrade as
developmental and industrial pressures on shorelines affected both the fish and
their prey species. Industrial discharge, agricultural run-off, dredging and
disposal of shipping channels resulted in the alteration and loss of marshes and
mudflats which are the primary habitat for non-breeding sturgeon and their
favored mollusks and crustaceans. These activities also affect levels of
dissolved oxygen in the water, which has detrimental effects on many aquatic
species, both plant and animal.
These animals reach breeding age slowly; Chesapeake females
first spawn around 11 years of age. They also don't spawn every year so the
population is not rapidly replaced. Thus, they take a long time to recover from
population declines. Because they live so long sturgeon can also suffer from
bio-accumulation of toxins and heavy metals found in the water and in the foods
they eat.
In 1998, a recovery plan was put in place to be
administered by the National Marine Fisheries Service (NMFS). The plan
identifies threats to this species and outlines actions that should be taken to
help the Shortnose Sturgeon return to healthy population levels. Conveniently,
these actions will also support additional species which are considered valuable
and necessary to the health of the Bay, species like rockfish, blue crabs,
oysters, shad and various species of waterfowl. Recovery actions address water
quality issues and habitat alteration, access to quality spawning streams,
incidental take from legal fishing and poaching, and methods to boost the
population with stocking.
Additionally, the US Fish and Wildlife Service (USFWS),
NMFS and MD Department of Natural Resources are asking for help from the fishing
community. If you catch a live sturgeon (Shortnose or Atlantic), please
contact USFWS at 1-800-448-8322. Researchers will
weigh, measure and tag live specimens before releasing them back into the Bay.
For more information, including how to keep the fish alive before you reach the
dock, check out the MD Fisheries page:
http://www.dnr.state.md.us/fisheries/commercial/sturg100.htm
The plight of the Shortnose Sturgeon in the Chesapeake Bay
in not unique, nor are the measures we can take to help it back to health.
Improving water quality, understanding the value of a wetlands and shorelines,
recognizing the need to maintain or restore natural systems has benefits for all
of us who depend upon the Bay for our livelihoods and our lives.
- Photographs courtesy of Noel Burkhead (juvenile);
USFWS, Ian Park and
Brian Richardson (adults) |
