Aquatic Species at Risk - Shortnose Sturgeon
Species - Details
Fishes (marine & anadromous)
COSEWIC Status : Special Concern (May 2005)
Region: New Brunswick
The shortnose sturgeon (Acipenser brevirostrum) is an ancient and long lived species that occurs in only 1 river system in Canada - the Saint John River in New Brunswick. Its long cylindrical shape is said to be "armoured" with 5 rows of boney plates or "scutes". It has a thick leathery skin that is olive green to brown above and white below. A darker mottled chain pattern runs along the top of the head area. Shortnose sturgeon are very similar in appearance to the Atlantic sturgeon and since they inhabit the same areas, are often misidentified. Shortnose sturgeon have been recorded at lengths of over a meter and at ages in excess of 60 years.
Distribution and Population
There are 19 population segments of shortnose sturgeon along the east coast of North America from New Brunswick south to Florida. Its only known occurrence in Canada is in the Saint John River system, NB. The Saint John River shortnose sturgeon is the most northerly population of the species and evidence suggests that they may also be the most genetically distinct.
A population estimated at 18,000 adults was determined during 1973-1977 for the St. John River. Recent work in the Kennebecassis River (location of an overwintering ground), a tributary of the Saint John River, produced an estimate of 2,000 adults. However, there is no current estimate for the complete lower estuary of the Saint John River. Aboriginal knowledge suggests that there has been a decline since the Mactaquac Dam was constructed in 1967.
The shortnose sturgeon spawns in fast flowing water over a boulder and gravel bottom. They generally over winter in the lower reaches of the Saint John River and in the spring migrate upstream as far as the Mactaquac Dam to spawn. Little is known about the juveniles, but the mean size of juveniles decreases upriver suggesting younger fish utilize more upstream habitats.
Shortnose sturgeon appear to be a social fish, exhibiting schooling (or shoaling) behaviour particularly in areas where there are strong currents. Feeding along the bottom, their preferred diet is small crustaceans and insects in particular, soft shelled clams.
Shortnose sturgeon males reach maturity at roughly 11 years of age and spawn every second year. Females mature later at approximately 13 years of age and spawn every 3 to 5 years, laying up to 200,000 eggs. The eggs sink and attach themselves to the rocks and gravel on the bottom of the river. After hatching, the larvae drift downstream.
Juvenile sturgeon usually migrate upstream in the summer and as the temperature in the river drops in the fall, move back downstream. It is thought that survival at the juvenile stage is critical to population abundance. Evidence suggests that shortnose sturgeon and Atlantic sturgeon compete for food and habitat.
This is an anadromous species restricted to a single river system in Canada where spawning fish require unhindered access to freshwater spawning sites; but the population may have been divided since 1967 by the Mactaquac Dam. These large, slow growing, late maturing fish are conservation dependent. There is thought to be some risk to the species through mortality from hydroelectric facilities, by-catch in commercial fisheries, and poaching. However, there is no immediate threat that would lead to elimination of the population in a very short period of time.
Saint John River shortnose sturgeon are susceptible to bycatch in commercial gaspereau and shad fisheries, and reportedly in the recreational angling fishery for smallmouth bass. Although they are required to be released unharmed in these fisheries, shortnose sturgeon are particularly vulnerable during their spawning run. Since a gaspereau fishery happens at the same time as the sturgeon are running, any catch and release from this fishery may interrupt or curtail shortnose sturgeon spawning.
Pollution from pulp mills, as well as farming and forestry activities along the Saint John River could also have negative consequences for this population.
Shortnose sturgeon currently receive protection through the federal Fisheries Act which prohibits the killing of fish by any means other than fishing and which provides protection against fish habitat alteration, disruption or destruction and pollution. Minimum size limits and gear restrictions in recreational sturgeon fisheries reduce the likelihood of this species being captured. The commercial fishery is managed through The Maritime Provinces Fishery Regulations (SOR /2001-452 s.28) made pursuant to the Fisheries Act. These regulations provide for gear and minimum fish size restrictions as well as seasonal closures. The recreational fishery is regulated under the New Brunswick Fish and Wildlife Act.
Shortnose sturgeon has been listed as Endangered by the Endangered Species Act in the United States since March 1967. It has had International Union for Conservation of Nature (IUCN) Red Book Status since 1996, when it was assessed as Vulnerable, and is listed on Appendix 1 of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).
COSEWIC 2005. COSEWIC assessment and update status report on the shortnose sturgeon Acipenser brevirostrum in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vi + 27 pp. (www.sararegistry.gc.ca).
Species at Risk Act - Legal Listing Consultation Workbook, Shortnose Sturgeon, 2005.
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