Forcenturies, fishermen lined the banks of rivers and streams throughout the Bay watershed, dipnetting for alewife and blueback herring as the fish made their spring spawning runs. Once so abundant, the fish were often referred to as glut herring.
Commonly known as river herring, both species are anadromous, spending most of their lives in the ocean but migrating to fresh water to spawn. The blueback herring is silver-sided with a bluish back, while the alewife, also silver, has a bronze-green back. Their silvery scales are an adaption for living in well-lighted surface waters. The scales scatter light to reduce the herring's visibility to predators. Both share a single dark shoulder spot and vary in length from 12 to 15 inches when fully grown.
Blueback herring range from Nova Scotia to northeast Florida, while the alewife can be found from Newfoundland to South Carolina. Except for the spring months, adults inhabit near-shore Atlantic Ocean waters. Juvenile river herring migrate from estuaries to coastal waters in the early fall and remain at sea until reaching sexual maturity in 3 to 6 years.
When ready to spawn, adults usually return to the same water in which they were born, although some straying does occur. No one knows exactly how they find their natal streams. Many scientists believe that this homing instinct may be due to a special sensitivity to magnetic signals, polarized light, and unique characteristics of the natal stream.
The onset of spawning is related to water temperature and length of day. The spawning season for alewife usually runs from March through April; blueback’s spawn from mid-April through late May.
Blueback herring prefer to spawn in swift water, while alewife favor slow-moving sections of streams. Upon reaching the spawning ground, males circle a lone female. As this mass of fish swirls around, the females releases her eggs and the males release their sperm. After spawning, the adults return to the ocean.
A female herring can lay several hundred thousand eggs. The tiny eggs, about 1 millimeter in diameter, are sticky and adhere to rocks, gravel, and debris. The eggs hatch in three to seven days.
Swift-flowing streams carry the larvae downstream. In Chesapeake Bay tributaries, juveniles are distributed throughout tidal and freshwater areas during the spring but move upstream during summer with the encroachment of saltier water. During fall, the water begins to cool and the young move downstream, beginning their first seaward migration.
The herring’s feeding habits vary with their age and habitat. While in fresh water, alewife feed mainly on single-cell algae and microscopic invertebrates. When they move into saltier water, the diet shifts to small shrimp and fish. Blueback feed primarily on plankton, which are tiny floating organisms.
Herring are food for estuarine and coastal predators, including striped bass. Eggs, juveniles, and adults are all important forage for many freshwater and marine fishes, birds, amphibians, reptiles, and mammals. Historically, the ample supply of river herring supported a large fishery. Colonists stored salted herring for winter food and used the oily backbones of blueback herring as lamp wicks.
Today, herring are harvested using pound, gill, and fyke nets and haul seines. Some herring are sold for consumption, and can be eaten fresh, pickled, or smoked. Herring are also harvested for their roe (eggs). The majority of commercially harvested herring, though, usually ends up as crab and eel bait, fish meal, or pet food.
Commercial landings of herring in the Bay peaked in 1908 at nearly 66 million pounds. During 1931, herring was the second most harvested finfish of the Chesapeake. By the early 1970s, herring stocks dropped dramatically and commercial harvests plummeted. From 1965-1985, harvests of herring in Maryland and Virginia declined by at least 80 percent.
A variety of factors has contributed to this decline. Between 1967 and 1977, foreign offshore fishing caught huge quantities of herring as the fish tried to migrate to the Chesapeake. Foreign interests also threatened herring throughout the rest of the year. In 1972, tropical storm Agnes decimated many fish populations and altered spawning habitat.
The recent depletion of river herring has been attributed to overfishing, pollution, and loss of spawning habitat. Spawning river herring must also run a gantlet of fishermen equipped with gill nets, pound nets, dip nets, and fishing rods. Pollution such as sediment runoff or acid rain can kill sensitive larval fish. In addition, dams, road culverts, stream-gauging stations, and debris impede herring migration. These blockages have eliminated nearly 1,000 miles of potential spawning habitat in Chesapeake Bay tributaries.
The decline of river herring has had significant economic and ecological impacts on the Bay area. Thriving herring runs offer sport and commercial fishing opportunities. In addition, they are a valuable food source for fish, mammals, amphibians, and birds. Largemouth bass, white and yellow perch, and other resident fish feed on juvenile herring. Adult herring are consumed by a variety of bird and fish species.
Of all anadromous fish caught in the Chesapeake, herring have dropped most dramatically. Only a few rivers support healthy populations. Federal, state, and private organizations have developed a fishery management plan to protect and enhance river herring stocks in the Chesapeake Bay and along the Atlantic seaboard.
To restore herring and other anadromous fish, historic migration paths and spawning grounds must be improved and in some cases re-established. Where possible, barriers such as dams, culverts, and debris are removed. The construction of artificial passageways, like fish ladders and lifts, help fish get over or around larger dams. Since 1989, almost 200 miles of spawning habitat have been restored and more rivers are slated for opening. Additional restoration efforts include restocking depleted streams with herring transferred from other river systems. There are also fishing restrictions in place in rivers, the Bay, and the Atlantic Coast to protect herring and other anadromous species from overharvesting.
The water quality of spawning and nursery habitat must also improve. Eggs and larvae require healthy streams to hatch and develop. Juveniles need unpolluted bays and tidal streams to grow.
This is where citizens can help. Maintaining streamside forests or vegetative buffers, and reducing the amount of nutrients applied to farms and yards, are two ways to protect the water quality of spawning grounds. Ultimately, habitat must be restored and protected to ensure abundant spawning runs of river herring in the Chesapeake Bay watershed.