Stripped Bass

The migratory behavior of coastal striped bass is more complex than that of most other anadromous fish, which spend most of their adult lives in the ocean but migrate up rivers and streams to spawn. Their seasonal movements depend on their age, sex, degree of maturity and the river in which they were born.

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.

Spawning

• 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 in the Chesapeake Bay.
• 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.

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.

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.

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.