Threatened Fishes of the World: Acipenser oxyrinchus Mitchill, 1815 (Acipenseridae)

Abstract

Common names:Atlantic sturgeon,common sturgeon,sea sturgeon (E),esturgeon noire (F).Conservationstatus: Currentlyreceives federal pro-tection with U.S.fishery closed for40 years. Listed asthreatened in Canada (Birstein et al. 1997).Identification: D 38–46, A 26–28 rays, dorsal scutes 7–16, lateral scutes 24–35 and ventral scutes 6–9. Body elongated and spindle shape in cross section. Rostrum long forAcipenseridae. Juveniles have distinct black contour band running along dorsal surface of rostrum which disappears with age. Juveniles lack the oval-shaped black rostral patchof adults on the ventral surface of the snout. Two pairs of barbels, usually originating closer to the tip of snout than mouth. Upper lip indented in the middle and lower lipinterrupted. Rows of rhombic plates present between rows of scutes on the laterodorsal and lateroventral surface. Scutes do not undergo absorption and hook-like appendagepresent on all except in very large individuals. Preanal and postdorsal plates paired. Rhombic plates on either side of the anal fin larger than those co vering rest of body. Atlanticsturgeon may reach a size of 4m and weigh 350kg but nowadays most adults are much smaller. Weight for migrating mature males is 30–45kg and for females 50–110kg.Color variable throughout life. Juveniles have dark brown dorsum with dark scutes. Central portion of all dorsal scutes lighter. Central portion on head plates also light. Ventralsurface white. Adults usually dark brown on dorsum but sometimes peanut brown or even coppery in appearance. Ventral surface white or slightly yellowish. Illustration of aHudson River 110cm long juvenile by Paul Vecsei. Distribution: Occurs along the eastern coast of North America, from southern Labrador to northern Florida. In Canadararely seen in Hamilton Inlet of Labrador but a large stock (consisting mostly of immature individuals) is present in the Gulf of St. Lawrence and lower St. Lawrence River(Caron & Tremblay 1999). Recently, a few migrating adults were reported as far upstream as Sorel, Quebec (Bergeron personal communication). Large population presentin the Bay of Fundy, heavily exploited during the upstream migration in the St. John River. Atlantic sturgeon occur sporadically along the United States coast from Maineto the St. Johns River of eastern Florida (Bain 1997). Only the Hudson River has significant numbers of juveniles in the estuary with a few dozen adults re turning to spawnin the reaches of Haverstraw (Bain personal communication). A subspecies referred to as Gulf sturgeon, A. desotoi, inhabits the Gulf of Mexico and spawns in rivers alongthe northern coast of the Gulf from the Mississippi Delta to the Suwannee River (Wirgin et al. 1997). Abundance: Severely depleted throughout most of its range. In UnitedStates waters, the once enormous Hudson River population is now reduced, with very few adult migrants returning to spawn. With the closure of the commercial fishery, thispopulation is thought likely to recover since juveniles are present in large numbers in the lower estuary. Canadian populations occur principally in the Gulf of St. Lawrence,comprising mostly of juveniles. The whereabouts of the adults of this population is still unknown (Caron & Tremblay 1999). The St. John River has a healthy annual run ofadult spawners but is under severe exploitation. Licenses are being retired and with no new ones being issued, the Bay of Fundy/Saint John population may return to almostpre-exploitation abundance.Habitat and ecology: Atlantic sturgeon are thought to occur in coastal waters where food items abound. Since they feed on various invertebrates(principally mollusks) and fish species such as capelin, Mallotus villosus, they presumably rarely venture into deep waters. Life at sea is little understood for this species butjuveniles are known to remain in their river of origin until the age of 7 before migrating to sea. Reproduction: Atlantic sturgeon are anadromous and begin entering rivers inspring and early summer depending on the distance required to travel to their spawning grounds. Spawning takes place over rock-gravel substrate at a water temperature of 18