Spawning
Life for the striped bass begins in the estuary:
at one time the Chesapeake Bay was the spawning ground for nearly
90 percent of the Atlantic population.
In late winter and spring, mature
striped bass move from the ocean into tidal freshwater to spawn.
Spawning is triggered by an increase in water temperature and generally
occurs in April, May and early June when water temperatures reach
60 to 68 degrees.
Female striped bass may spawn as early as age 4, but a year class may not reach
complete sexual maturity until age 8 or older. By contrast, most male stripers
reach sexual maturity at age 2 or 3.
Shortly after spawning, mature fish return to the coast. Most spend summer
and early fall months in middle New England near-shore waters. In late fall
and early winter they migrate south off the North Carolina and Virginia capes.
Stripers are river spawners that broadcast millions of eggs in the water currents
without affording any protection or parental care. During spawning, seven or
eight smaller males surround a single, large, female and bump her to swifter
currents at the water surface. At ovulation, ripe eggs are discharged and scattered
in the water as males release sperm. Fertilized eggs must be carried by river
currents until hatching (about 48 hours) to avoid suffocation. Fry and fingerlings
spend most of their time in lower rivers and estuaries. Because striped bass
eggs must remain suspended in a current until hatching, impoundments are unsuitable
for natural reproduction. Freshwater populations have been maintained by stocking
fingerlings, and, despite initial difficulties in hatchery procedures for obtaining
females with freely flowing eggs, a modern technique of inducing ovulation
with the use of a hormone has been successful.
Incubation, Hatching and Larval Stages - Striped
bass eggs hatch from 29 to 80 hours after fertilization, depending
on the water temperature. Larvae at this point have an average
size of 3.1 mm. The mouth forms in two to four days, and the eyes
are unpigmented. The larvae are nourished by a large yolk mass.
Eggs produced by female stripers weighing 10 pounds or more contain
greater amounts of yolk and oil reserve and have a greater probability
of hatching.
The larvae's survival depends primarily upon events during the first three
weeks of life. Typically striped bass larvae begin feeding about five days
after hatching, depending on water temperature. Eggs and newly hatched larvae
require sufficient turbulence to remain suspended in the water column; otherwise,
they will settle to the bottom and be smothered. As the larvae grow, they can
be found at progressively deeper levels of the water column.
Young stripers tend to move downstream to areas of higher salinity. Some less
than 2 years old migrate along the Atlantic Coast, but many do not migrate
until age 3, and most remain in the river system in which they were spawned.
Morone saxatilis
Common Names - striper, rockfish, rock, linesides.
Description - The striper is the largest member of the temperate bass
family.. The stripes are often interrupted or broken and are usually
absent on young fish of less than six inches. The striper is longer
and sleeker and has a larger head than its close and similar looking
relative, the white bass, which rarely exceeds three pounds. Striped
bass may variously appear to be light green, olive, steel blue, brown
or black. They earn their name from the seven or eight continuous stripes
that mark their silvery sides, extending from the gills to the tail.
Their undersides are usually white or silver, with a brassy iridescence.
Mature stripers are known for their size (they've even been known to
reach 100 pounds and nearly five feet in length) and fighting ability
Range - The Striper has been one of the most
sought-after commercial and recreational finfish in the Bay since
colonial times. Its habitat reaches from the St. Lawrence River
in Canada to the St. Johns River in Florida, and from the Swannee
River in western Florida to Lake Pontchartrain, Louisiana, and
the open waters of the Atlantic.
Habitat:- Estuaries are critically important to the life cycle of
striped bass, which use them as spawning grounds and nurseries. Mature
stripers are found in and around a variety of inshore habitats as well,
including areas off sandy beaches and along rocky shorelines, in shallow
water or deep trenches, and in rivers and the open Bay. Any significant
alterations of these habitats has the potential to disrupt the life
cycle of the striped bass.
Striped bass larvae feed primarily on copepods (crustaceans) in both
larval and mature stages, and cladocerans (water fleas). Juvenile stripers
eat insect larvae, larval fish, mysids (shrimp-like crustaceans) and
amphipods (tiny scavenging crustaceans that lack a carapace and have
laterally flattened bodies). Adults are piscivorous, or fish-eaters.
In summer and fall, stripers consume Bay anchovy and Atlantic menhaden;
in winter they eat larval and juvenile spot and Atlantic croaker; and
in spring they feed on white perch, alewives and blueback herring.
All Florida populations of striped bass are river dwellers rather than
anadromous (normally living in salt or brackish waters, but entering
freshwater streams to spawn). The species has been widely introduced
in numerous lakes, rivers and impoundments throughout the world. Stripers
prefer relatively clear water with a good supply of open-water baitfish.
Their preferred water temperature range is 65 to 70 degrees.
The Fishery:
The reasons for the sharp decline in the striped bass harvest during
the 1970s and 1980s are complex. Scientists determined that overfishing
caused the striped bass population to become more susceptible to natural
stresses and pollution. (The principle gear used in the Chesapeake
Bay commercial striped bass fishery included pound nets, haul seines,
and drift, anchor and stake gillnets.) In particular, fluctuations
in water temperature in spawning grounds cause significant natural
stress. But this is not the only stressor.
Low dissolved oxygen (DO) in the deeper water of the upper Chesapeake
Bay and in other areas has eliminated much of the summer habitat of
adult and juvenile striped bass.
Acidity and contaminants in spawning habitats may have influenced the
mortality of striped bass larvae in the Choptank, Nanticoke and Potomac
rivers. Research indicates that highly acidic rain reacts with aluminum
in the soil, causing it to dissolve in the water, which is lethal to
newly hatched stripers.
Salinity, turbidity, light, temperature and pH also affect the survival
of striped bass in their habitat.
Larval striped bass are also susceptible to toxic pollutants such as
arsenic, copper, cadmium, aluminum and Malathion, a commonly used pesticide.
Other hypotheses for the decline of striped bass in the Bay include
starvation of larvae, unfavorable climatic events, changes in water
use practices, competition with other species for food and space, and
poor water quality due to agricultural runoff and sewage treatment
practices.
Despite these threats, the striped bass stocks continue gradually to
increase in the Bay. Because the Bay remains the main spawning and
nursery area for 70 percent to 90 percent of the Atlantic stock, restoration
efforts remain critically important to the future of the striped bass
in the Chesapeake Bay
Feeding Habits - Stripers are voracious feeders and consume any kind
of small fish and a variety of invertebrates. Preferred foods for adults
mainly consist of gizzard and threadfin shad, golden shiners and minnows.
Younger fish prefer to feed on amphipods and mayflies. Very small stripers
feed on zooplankton. Like other temperate bass, they move in schools,
and all members of the school tend to feed at the same time. Heaviest
feeding is in early morning and in evening, but they feed sporadically
throughout the day, especially when skies are overcast. Feeding slows
when water temperatures drop below 50 degrees but does not stop completely.
Subspecies - There are no recognized subspecies.
Age and Growth - Stripers are fast-growing and long-lived and have
reached weights of over 80 pounds. Sexual maturity occurs at about
two years of age for male stripers and at four years of age for females.
They can reach a size of 10 to 12 inches the first year.
Eating Quality - Stripers are excellent eating fish and may be prepared
in may ways. Smaller fish are usually fried and larger ones are baked.
Congress passed the Atlantic
Striped Bass Conservation Act in 1984. Maryland and Delaware imposed fishing moratoria from 1985 to 1989,
and Virginia imposed a one-year moratorium in 1989. Although the fishery
reopened in 1990 following three successful spawning years, it remains
tightly restricted.
STRIPED
BASS
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