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Shortnose sturgeon

The shortnose sturgeon (Acipenser brevirostrum) formerly occupied rivers and estuaries along the Atlantic seaboard from New Brunswick to northern Florida [1]. It was driven to near extinction by overfishing, by-catch in the shad fishery, damming of rivers, habitat destruction, and deterioration of water quality. Scientists and fishermen in the 19th and early 20th centuries did not distinguish between Atlantic and shortnose sturgeon, so there are no historical population estimates. Clearly, however, by the early 20th century populations were declining and by the 1950s or earlier had become endangered. The sturgeon was placed on the endangered species list of 1967.

Shortnose sturgeon populations are divided into 19 management units based on presumed reproductive isolation [1]. Recent genetic analysis generally supports the management units, but suggests that the Delaware River be combined with Chesapeake Bay and the Ogeechee River be combined with the Altamaha River [2]. The 1987 draft and 1988 final federal recovery plans recommended that each of the units be treated as a distinct population segment that can be recovered and delisted separately. The 1987 draft recommended downlisting the Connecticut, Delaware, and Hudson River populations to "threatened" and delisting the Kennebec System population as recovered.

- Seven large populations (>=1,000 fish): Saint John River (NB), Kennebec System (ME), Connecticut River (CT, MA), Hudson River (NY), Delaware River (DE, NJ, PA), Savannah River (SC), and Altamaha River (GA).
- Two small populations (<1,000 fish): Winyah Bay (SC, NC) and Ogeechee River (GA).
- Ten very small populations (<100 fish): Penobscot (ME), Merrimack River (MA), Chesapeake Bay (MD, VA), Cape Fear River (NC), Santee River (SC), Cooper River (SC), "ACE" Basin (SC), Satilla River (GA), St. Marys River (FL), St. Johns River (FL).

- Five improved populations: Kennebec System (ME), Connecticut River (CT, MA), Hudson River (NY), Savannah River (SC), and Altamaha River (GA).
- One stable population: Delaware River (DE, NJ, PA).
- No declining populations
- Thirteen unknown populations: Saint John River (NB), Penobscot (ME), Merrimack River (MA), Chesapeake Bay (MD, VA), Winyah Bay (SC, NC), Cape Fear River (NC), Santee River (SC), Cooper River (SC), "ACE" Basin (SC), Satilla River (GA), Ogeechee River (GA), St. Marys River (FL), and St. Johns River (FL).

Five of the seven large populations, and four of the six improved/stable population are north of Chesapeake Bay. The southern populations are generally smaller and less well known. Six of the seven large populations are improved/stable. All of the unknown populations are small/very small with the exception of the St. John River (NB). The latter trend likely indicates that the small populations consist of numbers too small support robust trend estimates. The species overall trend has improved since being placed on the endangered species list in 1967.

* Kennebec System (Kennebec, Sheepscot, Androscoggin Rivers, ME). This population increased from an estimated 7,222 adults (95% CI 5,046-10,765) in 1977-1981 [1] to 9,488 in 1998-2000 [5]. The 1993 capture rate in the Adrosscoggin River was the highest ever recorded [1]. Since the 1998 removal of Kennebec Dam, the upstream range has increased [5].

* Connecticut River (CT, MA): Sturgeon in the upper and lower Connecticut River have been largely separated by the Holyoke Dam for 157 years. The Upper Connecticut River was estimated to support 297-515 total fish 1976-1978 and 47 and 98 spawning fish in 1992 and 1993 respectively [1]. The Lower Connecticut supported approximately 875 adults in 1988-1993 [1, 8] and 1,800 in 2003 [8].

* Hudson River (NY). The shortnose sturgeon occupies a 246-km section of the Hudson River from New York City to Troy Dam upstream of Albany [4]. This population is larger than the other 19 management populations combined. From late spring through early fall adults use deep, channel habitats of the freshwater and brackish reaches of the estuary. In the late fall, most or all adults concentrate at a single overwintering site in the river channel near Kingston while juveniles remain in the estuary. In the spring, adults spawn at a single location slightly downstream of the Troy Dam. The larvae gradually disperse downstream with juvenile sturgeon that inhabit much of the estuary during the summer, but occupy a more limited range in the southern portion of the estuary during winter.

Due to fishing prohibitions and habitat protection efforts (the population has not been augmented with hatchery fish or translocations), numbers in the Hudson River increased dramatically between 1979 (12,669 spawning fish (95% CI = 9,080-17,735)), 1980 (13,844 (95% CI = 10,014-19,224)), and 1994-1996 (56,708 (95% CI = 50,862-64,072)) [4]. The size and age of individual fish and the demographic structure of the population as a whole indicate a healthy condition typical of non-endangered, long-lived species.

The 1998 federal recovery plan specifies that a sturgeon population is to be considered viable if it has at least 10,000 members, is on a stable or improving population trajectory, and is protected from degradation of its key habitat areas [2]. As the demographic parameters have been exceeded and the spawning and overwintering habitats appear stable, some biologists have recommended that the Hudson River population be designated as a distinct population segment and removed from the endangered species list as recovered species [4]. Delisting, however, would require the establishment of management agreements to guarantee long-term protection from unsustainable fishing, by-catch, pollution, and habitat degradation.

* Savannah River (SC): Between 1984 and 1992, approximately 97,000 shortnose sturgeon were stocked in the Savannah River [1]. The 1999-2000 population had many more adults than in 1992, primarily due to presence of stocked fish, but there was little evidence of reproduction [3]. The 1999 population was estimated at 3,000 fish [5].

* Altamaha River (GA): Population estimates on the Altamaha River were 2,862 total fish in 1988 (95% CI=1,069-4,226) [1], 798 in 1990 (95% CI=645-1,045) [1], 468 in 1993 (95% CI=316-903) [1], and 5,910 (95% C.I. 4,740-7,848) in 2003-2005 [7].

* Delaware River (DE, NJ, PA): The Delaware River population was 6,408-14,080 in 1981-1984 [1], 10,000 in 2002 [6], and 8,445 in 2004 [5].

* Saint John River (NB): The only Canadian population occurs in the Saint John River system, New Brunswick, including its tributary, the Kennebecasis River [11]. Construction of the Mactaquac Dam in 1967 closed off much the former spawning grounds while logging, development and pollution from agricultural and industrial sources degraded habitat and water quality. A fish lift was built into the dam, but there is no record of sturgeon using it, probably because the intake is only 1.8 m down in water 12.8 m deep. It is not known whether sturgeon persist above the dam. In the lower Saint John River below the dam, the 1973-1977 population was estimated at 18,000 adults (+/-30%) [11]. Surveys conducted in recent years were not sufficient to estimate a total population and were not comparable to prior surveys due to differences in methodology [11, 12]. Aboriginal people familiar with the river, however, tend to believe the population has declined since the construction of the Mactaquac Dam [11].

* Merrimack River (MA): unknown trend. The 1989-1990 population was estimated at 33 total fish [1].

* Penobscot (ME) Dennys, Machias, East Machias, Ducktrap: the last report is of a single fish in 1978 [2].

* Chesapeake Bay (MD, VA): unknown trend, very small population [1, 5].

* Winyah Bay (Waccama, Pee Dee, Black Rivers; SC, NC): unknown trend [1].

* Cape Fear River (NC): unknown trend, likely less than 50 individuals [1, 5].

* Santee River (SC): unknown trend [1].

* Cooper River (SC): unknown trend [1], 100-300 fish in recent years [5].

* "ACE" Basin (Ashepoo, Combahee, and Edisto Rivers; SC): unknown trend [1].

* Satilla River (GA): unknown trend

* Ogeechee River (GA): unknown trend. The 1993 population was estimated to have 266 adults [9] and 361 total fish [1]. The 1999 population was estimated at 195 adults, which was not statistically different from the 1993 estimate [9].

* St. Marys River (FL): unknown trend.

[1] National Marine Fisheries Service. 1998. Recovery Plan for the Shortnose Sturgeon (Acipenser brevirostrum). Silver Springs, Maryland. 104 pages.
[2] Wirgin, I., C. Grunwald, E. Carlson, J. Stabile, D.L. Peterson, and J. Waldman. 2005. Range-wide population structure of shortnose sturgeon Acipenser brevirostrum based on sequence analysis of the mitochondrial DNA control region. Estuaries 28(3):406-421.
[3] Smith, T. I. J., M. C. Collins, W. C. Post, and J. W. McCord. 2002. Stock enhancement of shortnose sturgeon: a case study. Pages 31–44 in W. VanWinkle, P. Anders, D. H. Secor, and D. Dixon, editors. Biology, management, and protection of North American sturgeon. American Fisheries Society, Symposium 28, Bethesda, Maryland.
[4] Bain, M.B, N. Haley, D.L. Peterson, K.K. Arend, K. Mills, and P. Sullivan, 2000. Shortnose sturgeon of the Hudson River: an endangered species success story. EPRI-AFS Symposium: Biology, Management and Protection of Sturgeon, 2000 Annual Meeting of the American Fisheries Society, St Louis, MO, August 23-24, 2000.
[5] National Marine Fisheries Service. 2004. Biennial Report to Congress on the Recovery Program for Threatened and Endangered Species, October 1, 2002–September 30, 2004.Washington (DC): Department of Commerce.
[6] National Marine Fisheries Service. 2002. Biennial Report to Congress on the Recovery Program for Threatened and Endangered Species, October 1, 2000–September 30, 2002.Washington (DC): Department of Commerce.
[7] DeVries, R.J and D.L. Peterson. 2006. Population dynamics and spawning habitat of shortnose sturgeon in the Altamaha River, Georiga. Georgia Chapter of the American Fisheries Society, 2006 Annual Meeting, Gainesville, GA, January, 2006.
[8] Connecticut Department of Environmental Protection. 2003. Working with Nature: Shortnose Sturgeon. Webpage (http://dep.state.ct.us/whatshap/press/2003/mf0730.htm) Accessed January 31, 2006.
[9] Bryce, T.D., Bryce, J.E. Fleming and J.P. Kirk. 2002. Fort Stewart Assesses Status of Shortnose Sturgeon: A 2001 Update. Environmental Update, A Quarterly Publication of Army Environmental News 14 (1). Available at (http://aec.army.mil/usaec/publicaffairs/update/win02/win0220.html).
[10] Crossman, J.A., A. Giberson, R. Hardy, R.M. Browne, and M.K. Litvak. 2003. Estimating population size and wild growth rates of the shortnose sturgeon (Acipenser brevirostrum) in the St. John River, NB. Canadian Conference for Fisheries Research and the Canadian Society of Limnologists, January 2-5, 2003, Ottowa, ON.
[11] 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.
[12] Litvak, M.K. 2006. Personal communication with Matthew K. Litvak, Department of Biology, University of New Brunswick, St. John, NB, February 1, 2006.

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