Threatened Fishes of The World: Acipenser brevirostrum Lesueur, 1818 (Acipenseridae)

摘要: Common names:shortnose sturgeon,pinkster (E), esturgeona museau court (F).Conservation status:Listed under the Endan-gered Species Act bythe USFWS, listed asthreatened in Canada.Identification: D 38–42, A 19–22 rays, 8–13dorsal scutes, 22–33 lateral 7–11 ventral plates. Body elongated, rostrum usually short but very variable. Two pairs of barbels present,always originating closer to tip snout than mouth. Mouth wide, upper lip indented middle and lower interrupted. Small denticlespresent on laterodorsal lateroventral surface. Scutes lighter surrounding body undergo minimal absorption largeindividuals. Pre anal plates posterior rectum vary number (1–3) never paired. Post dorsal are small, 1–2 Shortnosesturgeon may reach a size 1.5m weigh 25kg most fish caught less half that size. Color varies from overall peanut-butterbrown or black dorsum turning side with pronounced change white off-white Juveniles coveredwith small spots, not saddle markings as juvenile lake sturgeon, A. fulvescens. Drawing Hudson River 60cm adult byP. Vecsei. Distribution: Present along east coast North America portions rivers. In Canada, it is known only SaintJohn River. United States, its range disjunct 400km gap separating northern southern populations. distributionoccurs New Jersey Carolina. Unlike Atlantic oxyrinchus, which commonly move coast, shortnosesturgeon restricted their rivers origin. Abundance: Severely depleted throughout all range. Northern populations arethought have always been much larger generate flow marine migrants who colonize new (Kynard 1997). such case, theHudson population 40 000 adults likely source emigrants. This phenomenon poorly understood. All southernpopulations consist 1000 individuals deemed be minimum sustain viable level for vertebrates (Thompson1991).The St-John River, Brunswick previously thought harbors largest shortnose sturgeonin world. Habitat ecology: From spring until early fall, sturgeon inhabit deeper channels freshwater brackishzones During this period growth feeding, these ingest insects crustaceans. With declining water temperatures,they concentrated wintering grounds (Bain On non-spawning concentrate brakish waters, inspring they upstream tidal zone (Geoghegan et al. 1992). Pre-spawning hold pools near spawning sites.Reproduction: Shortnose amphidromous. Length at maturity ranges 45 55cm FL age greatlybetween sexes latitude. Males spawn intervals 2 years while females 3 5 year (Kieffer & Kynard1996). Spawning takes place between late April May over gravel substrate greatly The eggs adhesive andstick bottom. Threats: Dredging large increases siltation reduces food availability during onsetof exogenous feeding larvae. Dams blocked access sites many As stock recovers, poaching maybecome problem. Conservation action: listing U.S. Endangered has met variable results.The increased now considered stable. Connecticut markedly andsouthern continue threatened extinction.