The Chesapeake Bay and its great tidal riversjoin to form the largest and most productive estuarinecomplex in North America. They supply vast amount of nutrients into coastal
waters and
provide a huge spawning and nursery area for many
species of fish.
The warm waters of the Gulf Stream flow north along
the East Coast until they collide with the
cool, plankton-rich waters of the
Labrador Current flowing south. The intermixing of these
currents
occurs near Cape Hatteras, North Carolina, and in adjacent waters. This puts the
southern coast of Virginia in the dynamic area where the Mid-Atlantic Bight and South Atlantic
Bight are joined, and brings a huge mix of finfish species into local
waters. In fact, Virginia is the
southernmost range of real abundance for many
temperate species of fish and the northern range
of abundance
for many subtropical species. The large peninsula which forms the Eastern
Shore of Virginia is flanked by a chain of uninhabited and unspoiled barrier islands.
These islands protect a rich complex of marshes, bays and sounds which
provide a
haven for a variety of marine life. The main portion
of the Chesapeake Bay follows
the ancient bed of the Susquehanna River. Dramatic forces during the Ice Age, which helped
shape the Susquehanna
Valley, and the rising ocean waters caused by the melting ice cap as the
Ice Age ended, transformed the southern portion of this river valley into the vast estuarine
complex
that today is the Chesapeake Bay. The Chesapeake
Bay continues as the place
where several of the great rivers in the eastern United States meet the ocean. The Susquehanna
River has the greatest
impact on the Bay contributing, on average, almost 50% of the freshwater
flowing into the Bay. The Potomac and the James Rivers provide more than 15% each, leaving
under
20% for the combined inflows from more than a dozen
other rivers including the Rappahannock,
York, Chester, Choptank and Nanticoke.
Water also flows into the Chesapeake Bay from
the ocean.
A relatively constant inward flow of ocean water occurs along the bottom at the
mouth of the Chesapeake Bay. These ocean waters, laden with salts and minerals, are heavier
and more dense than the freshwaters flowing from the rivers into the
Bay and out its mouth in
the upper portions of the water column. This pattern
of water circulation, with heavier saltwaters
flowing into
the Bay along the bottom while lighter freshwaters flow out near the surface,
was documented in a scientific study by the Virginia Institute of Marine Science.
The mixing of ocean and rivers waters in the Chesapeake Bay produces
waters which
are variably salty and fresh, often changing based
upon short term weather phenomena,
long term weather or climatic patterns, tides,
depth and location. However, certain patterns remain constant. Bay waters
along the eastern
side of the Bay are saltier than waters along the western shore. This is due in large measure to
the large inflows of freshwater
from the western rivers and a phenomenon called the coriolis
effect
– a result of the rotation of the earth. Tides, which are caused by the rise and fall of
ocean waters due primarily to the gravitational forces of the moon and
the sun, cause variations
in salinity. During high or rising tides salinities
increase in the Bay and move further up the Bay,
while the
opposite occurs on low or falling tides. Since tidal movement originates at the mouth of
the Bay (tides are the rise and fall of ocean waters), the times of the
peak high and low tides
vary by location. The "wave" of tidal flow starts
at the mouth of the Bay and must physically move
to its
upper reaches and up its tributary rivers. This takes time and the difference between the
time of the high tide at places near the mouth of the Bay and others
farther up the Bay or in the
tidal portion of its tributary rivers can vary by
as much as 4 – 6 hours.
Forces with seemingly little
connection to the Chesapeake Bay can have major impacts on
salinity
levels. For example, heavy rains in western Virginia, Maryland and Pennsylvania mountains
may create flash floods which can send pulses of freshwater down major
rivers. These
pulses are called "freshets" as they reach the brackish waters of the rivers near the
Chesapeake Bay, and these sudden
changes in salinity can have pronounced impacts upon
marine
life. In fact, the torrential rains in Pennsylvania during Hurricane Agnes in 1972,
creating epic floods from the Susquehanna River, had catastrophic effects on the Chesapeake
Bay.
In fact, Agnes may have been the "trigger" mechanism for the disappearance of vast areas of
underwater sea grasses in the
Bay. Unfortunately, the sea grasses have not been able to recover,
probably due to the combination of pollution, excess nutrients and turbidity associated with
water quality problems. Changing salinty levels are not the only dynamic
forces impacting the Bay environment. Water temperatures vary dramatically
on an annual
basis. The water temperatures found in the Chesapeake
Bay probably have the highest average
annual variance of any location on the East
Coast. Winter often produces skim ice and even
harder freezes
on the lower Bay tributary rivers, and several times in this century portions of the
main stem of the Chesapeake Bay have been covered with ice. Summertime surface water
temperatures in shallow bays may approach, or exceed, 90 degrees. Sudden
changes in
temperature, which may occur during extended
cold snaps in the fall or early winter,
can cause water temperatures to drop dramatically resulting in severe stress to fish and
other marine life.
Even events outside of the Bay can impact its water temperature regimen.
Heavy snowfall early
in the fall in the Blue Ridge mountains can result in a drastic lowering of the water temperatures in
the tributary rivers
running to the Bay. As these rivers feed into the Bay, the water temperature
can be lowered rapidly with often severe impacts on marine life. For
these reasons, the marine life found in the
Chesapeake Bay is among the hardiest
and most adaptable found anywhere in the world.
While life
in these dynamic surroundings is not easy, estuarine environments are extraordinary in
their richness and diversity of life. Most of the commercially and recreationally
important finfish
species of Virgnia spend a portion of their lives in an estuarine environment.
Estuarine communities begin with intertidal
salt marshes. These low areas, characterized by
muddy tidal
flats, spartina grasses, and small creeks, are nature's "buffer" zones. They provide
filtering areas that trap nutrients and, in recent years,
pollutants, preventing them from overburdening
the tidal rivers and bays. The
tidal marshes are teeming with life from the everpresent
snails,
fiddler crabs and worms to shrimps, "fundulus" minnows, blue crabs
and juvenile fish. Unfortunately, intertidal salt marshes and
wetlands have been disappearing in modern times due to the increasing pressure to
develop waterfront properties caused by the desire of more people to
live near the coast.
While this trend continues, the rate at which marshes and wetlands have been declining is
slowing, as regulations have
focused efforts on environmentally "friendly" development which
provides protection for these critical and sensitive areas. Increased protection of tidal marshes
and wetlands is a key component in maintaining the water quality of the
Chesapeake Bay and preserving
much of its marine life. Sea
grasses, mainly eelgrass, thrives in shallow
waters, often growing best in waters
that are somewhat protected from excessive wave and
current
movements. They provide protection for many small fish and molting blue crabs, making
this habitat attractive for numerous game fish. In addition, sea grass beds serve a filtering
role, helping sediments to trickle to the bottom which produces better
water clarity. Sea grass
beds dissipate wave energy, which helps to reduce shoreline erosion and improves water
clarity. Ironically, many
scientists believe excessive runoffs, a form of non-point source pollution
which causes increased water turbidity, was responsible for killing many sea grass
beds in the Chesapeake Bay during the 1970’s, probably triggered
by the torrential
rains and massive floods associated with Hurricane
Agnes in 1972. Thus, while sea
grasses are important in preserving and improving
water quality, it may have been poor water
quality which
killed massive sea grass beds 30 years ago.
During the last
fifteen years, however, the Chesapeake Bay clean-up initiatives have focused
on controlling agricultural and urban runoff, and sea grass beds are starting to make comebacks.
In many ways the health of sea grass beds may be a good measure of the
health of the Bay, since
sea grasses require good water quality, low in suspended
sedimentary runoff, nutrients, pollutants
and phytoplankton,
to thrive. Oyster rocks and bars are the major types of
natural
"reef communities" in the Chesapeake Bay. A host of small invertebrates are attracted to
the oyster rocks and contribute to the food chain. In turn, these "live
bottom" areas attract a host of
small finfish, which are sought out by even
larger game fish.
Oysters are filter feeders, straining
small plankton and nutrients from the water column, which
is
an important component of maintaining the Chesapeake Bay's water quality. At the start of the
20th century oyster rocks rising ten feet off the bottom were not uncommon.
Oysters were so
numerous they were thought to be able to filter an amount of water equivalent in volume to the
entire Chesapeake Bay in
less than a week. Disease, pollution and overharvesting have
reduced
oyster populations to a fraction of that level, and today’s population of oysters would
take nearly a year to filter the water volume of the Chesapeake Bay.
Rebuilding the oyster population
is a major priority of fishery managers in Virginia.
Another concern in recent years has been a declining
trend in some of the prime forage fish,
especially menhaden and bay anchovies,
in the Chesapeake Bay. Menhaden are the other major
filter
feeder associated with the Bay, thus serving a dual role as forage for many important recreation
fish and a component in the Bay water quality equation. Observers are
unsure whether
this decline is a short term phenomenon or a longer
term problem, but efforts are being mobilized
to investigate this issue. The Chesapeake Bay offers a tremendous variety
of recreational fishing
opportunities, but no fish is more symbolic of the Bay than the striped bass.
The Chesapeake Bay is the largest spawning and nursery area for striped bass on the East
Coast. As much as 80% of the coastwide migratory population is thought
to be native to the
Bay. Striped bass, like shad and herring,
are
anadromous; this means they spend the majority of their
lives in saltwater but return
to freshwater rivers to spawn. They can be caught in virtually every portion of the
Chesapeake Bay and its tributary
rivers. In addition, stripers can be found at some place in the
Bay
every day of the year. The resurgence of striped bass populations in recent years from the
population collapse in the 1970’s, which nearly culminated in their
listing as a threatened
species, is one of the spectacular success stories of modern fisheries management.
Striped bass provide just one of several
opportunities for small boat fishermen to do battle with
adversaries
which may weigh 50 pounds or more. In addition, the Bay offers seasonal runs of cobia,
red drum and black drum. Red drum and black drum appear in Bay waters
in mid-April, while
cobia usually appear on the Memorial Day weekend. The reappearance of seagrass beds in several
locations in the Bay may
be the reason speckled trout populations have grown in recent years.
Since the late 1980’s, speckled trout populations have been increasing, and the favorite
haunts of
this popular game fish are shallow water flats with abundant
seagrass beds.
The Chesapeake Bay is a summertime home for
many species of "panfish". Summer flounder,
croaker, spot, and small
gray trout are the favorite targets for many anglers bouncing baits
along the bottom. Spanish mackerel and small bluefish can be taken by a variety of methods
using artificial lures and bait, and in recent years anglers have started
to learn the
methods which are productive for catching the visiting
populations of spadefish and
sheepshead. The reappearance of some larger gray trout is welcome news for recreational fishermen
approaching the
new millenium and is another example of the positive contributions of
serious fisheries management. Tautog can be found over wrecks and obstructions
in the lower Chesapeake Bay all year but are most active when the water
is cool. They remain
active throughout the winter, as long as water temperatures remain in the low 40’s, or higher.
Black sea bass
can be found in the same areas from late spring through the fall.
REF:
Virginia Saltwater Angler’s Guide, Prepaired for the VMRC