Atlantic sturgeon

The Atlantic sturgeon is a subtropical diadramous fish species (migrates between fresh and saltwater). The range of the oxyrinchus subspecies extends from eastern Canada in the north to the eastern coast of Florida in the south. Historically, Atlantic sturgeon were present in approximately 38 rivers in the US from St. Croix, Maine in the north to the Saint Johns River, Florida in the south. Today, they are present in 32 rivers, and spawning occurs in at least 23 of those (NMFS, unpublished). The subspecies desotoi can be found along the Gulf Coasts of Florida west to eastern Louisiana. Atlantic sturgeon also once occurred in the Baltic Sea in Europe, but are now extinct from that area most likely as a result of human activity.

The Atlantic sturgeon inhabits large freshwater rivers when spawning and primarily marine waters when not breeding. They prefer to stay close to shore when in marine waters and are typically captured in areas of gravel or sand substrate. They can also be found in bays, river mouths, and estuaries. Marine waters where Atlantic sturgeon occur in New Jersey include Delaware and Raritan bays, as well as the Atlantic Ocean. The major rivers in New Jersey where they are found are the Delaware and Hudson rivers.

Sturgeon feed by feeling the substrate with barbels (sensory organs that look like whiskers) and vacuuming the river bottom with a protractile mouth. Young Atlantic sturgeon eat bottom-dwelling crustaceans and insects. Adults have been known to feed on insects, snails, marine worms, crustaceans, small fish, and a variety of other organisms.

The Atlantic sturgeon, like other sturgeon, is a long-lived, late maturing species. The species is anadromous, spending the majority of its life cycle in marine waters but reproducing in freshwater rivers.

Adult Atlantic sturgeon migrate between fresh water spawning areas and salt water non-spawning areas. Spawning is believed to occur in flowing water between the salt front and fall line of major rivers. They may also spawn in brackish water. The age at which Atlantic sturgeon are mature varies throughout their range with individuals in the south (South Carolina) reaching sexual maturity at 5–19 years and those in the north (eastern Canada) reaching sexual maturity at 22-34 years. In New Jersey waters, female Atlantic sturgeon most likely first breed at an age of about 11-19 years. Atlantic sturgeon may not breed every year. Gaps between each spawning may be 1-5 years for males and 2-5 years for females.

Atlantic sturgeon typically spawn between April and May in the mid-Atlantic region. Female sturgeon will produce anywhere from 400,000 to 8 million eggs during a spawning event. The number of eggs laid is dependent on the age and size of the female. Eggs are demersal (found on or near the bottom) and adhesive, sticking to rocks and plant material underwater. Eggs hatch about 4 to 6 days after fertilization.

The hatching larvae look like tadpoles, are about 2.9-4.5 inches long, and have an attached yolk sac. Larvae are bottom-dwelling and move downstream, mainly at night, to nursery grounds. Juvenile sturgeon will continue to migrate downstream into brackish waters and then occupy estuarine waters for the next few months or years. Once they reach a size of approximately 30–36 inches, the subadults may move to coastal waters.

Spawning within the Delaware River is thought to occur as far upstream as Bordentown, NJ, while the stretch of river between the Marcus Hook Anchorage and the mouth of the Schuylkill River, PA is a critical concentration area for sturgeon less than 2 years old. Young and adult Atlantic sturgeon may also be found within the New Jersey portion of the Hudson River. Larvae and eggs however, will not be encountered in this area. The Hudson River population spawns upstream in upstate New York.

Atlantic sturgeon have been known to live as long as 60 years, but they may live even longer.

Historically, the Delaware River most likely supported the largest population of Atlantic sturgeon in the world. However, overfishing of the species for its eggs and meat caused that fishery to collapse by 1901. The Atlantic sturgeon fishery was closed by Atlantic States Marine Fisheries Commission in 1998. The current population estimate for the Hudson River population (the healthiest population which remains) is approximately 870 spawning adults. The Delaware River is thought to support less than 300 adults spawning each year.

The Atlantic sturgeon was federally listed as endangered under the Endangered Species Act on April 6, 2012, when it was also considered endangered in New Jersey. This species is afforded protection under both federal and state Endangered Species Acts, Clean Water Acts, and fishing regulations. The species’ numbers were drastically reduced primarily due to overfishing, both for its meat and for its eggs, which were sold as caviar between 1870 and the early 1900’s.

River dredging and estuarine and freshwater habitat degradation, including river pollution, may have also been a cause for the species’ decline and continue to be potential threats to Atlantic sturgeon. Although water quality in the Delaware River is generally improving, contaminants such as endocrine disrupting chemicals (EDC’s) may pose serious threats to sturgeon and other fish species. These contaminants include PCB’s, dioxins, mercury, and cadmium. EDC’s have been linked in fish to reduced egg viability, increased early life stage mortality, anatomical defects in larvae, and other reproductive problems. There is also a potential risk for young sturgeon to be caught and killed in water intake systems in rivers and estuaries and extending towards the sea. Other threats to Atlantic sturgeon include boat/ship strikes, and mortality from commercial and recreational fishing (bycatch).

Fisheries experts are currently conducting research on both Atlantic and shortnose sturgeon within NJ and DE waters in order to determine their distribution, habitat use, and population size. The exact spawning location for Atlantic sturgeon is unknown. In addition, not much is known about the locations and habits of juvenile sturgeon. This lack of information is a serious problem in determining the impacts of human activities such as river dredging and other instream projects on critical areas for the species. Additional research is needed on what role the New Jersey portion of the Hudson River plays in maintaining that river’s population of sturgeon. Lastly, habitat use and movements of Atlantic sturgeon within Atlantic Ocean waters is also poorly understood and requires further study.