|Scientific Name:||Elliptio spinosa|
|Species Authority:||(Lea, 1836)|
|Taxonomic Notes:||A list of synonyms for this species can be found on The MUSSEL project web site (Graf and Cummings 2011).|
|Red List Category & Criteria:||Endangered A2ac; B2ab(i,ii,iii,iv) ver 3.1|
|Assessor/s:||Cummings, K. & Cordeiro, J.|
|Reviewer/s:||Bohm, M., Seddon, M. & Collen, B.|
|Contributor/s:||Richman, N., Dyer, E., Whitton, F., Soulsby, A.-M., Kasthala, G., McGuinness, S., Milligan, HT, De Silva, R., Herdson, R., Thorley, J., McMillan, K., Collins, A., Duncan, C. & Offord, S.|
Elliptio spinosa has been assessed as Endangered under criteria A2ac and B2(i,ii,iii,iv), as it is restricted to no more than five locations in a single river system of limited extent and its range within this system is declining. Recent survey efforts have failed to find many living individuals of this species and it may actually be Critically Endangered, following more targeted surveys. In addition to this, population declines have been estimated as between 50-70% (NatureServe 2009) over the past 15-25 years, based on observed range contractions, population declines in known sites and declines in occupancy rates. This falls within the timespan of three generations, with a generation length being estimated as approximately ten years.
For example, in the Altamaha basin in Georgia and based on 241 sites sampled prior to 2000 and 120 sites sampled after 2000, pre-2000 site occupancy is estimated at 10% (24 sites) and post-2000 site occupancy at 6% (7 sites) (Wisniewsky et al. 2005). Failure to detect specimens downstream of Doctortown during the early 1990s suggests contraction of historical range. Recent surveys of the Ohoopee River (see Wisniewski et al. 2005) suggest the species may still be declining. Finally low numbers collected during recent surveys compared to historical surveys suggests the species has declined from historical levels (USFWS 2005). The reproductive success appears to be drastically reduced because very few juveniles or even small individuals are found. The water quality may not be very good in all regions of the river which may be why this species is declining in areas where there are few disturbances and the water quality does not appear to be poor overall. This indicates that it is likely that little recruitment is occurring within the populations.
Overall, the Altamaha Spinymussel can no longer be found in most of its historic collection sites on the Ocmulgee and Altamaha Rivers and the historical locations that had extant populations have significantly reduced numbers (USFWS 2002).
|Range Description:||The historical range of the Altamaha Spinymussel was restricted to the Coastal Plain portion of the Altamaha River and the lower portions of its three major tributaries, the Ohoopee, Ocmulgee, and Oconee rivers. The Altamaha River is formed by the confluence of the Ocmulgee and Oconee rivers and lies entirely within the State of Georgia. This species is now restricted to the middle and upper (coastal plain portion) Altamaha River, the lower Ocmulgee River, lower Oconee River and the lower Ohoopee River (USFWS 2002, 2003, 2005), which given the threats and their severity is likely to equate to no more than five locations.
The species is probably extirpated from the Ohoopee River, and most of the historical sites on the Ocmulgee and Altamaha Rivers no longer have this species (USFWS 2002). The decline over the last 10-25 years is based on habitat loss/degradation.
Overall, the extent of occurrence is estimated as less than 20,000 km2 (size of the drainage), although within this drainage, the true extent of occurrence for this species is more likely to be between 1,000-5,000 km2 (NatureServe 2009). Its area of occupancy is estimated as less than 500 km2 (NatureServe 2009), thus falling within the threshold for Endangered under criterion B2.
Native:United States (Georgia)
|Range Map:||Click here to open the map viewer and explore range.|
In the Ohoopee River, Keferl (1981) historically found the species in thinly scattered beds in the lower five miles of the river with live specimens in seven of eight sites. By the early 1990s, only two live specimens were found at the same sites in the lower Ohoopee (Keferl 1993) and it was only in 13.2 % of the 273 stations sampled from 1993 through 1997. Resurveys in 2001 found no specimens and so the species may be extirpated from this system with the decline occuring over the last 15 years.
In recent sampling done on the Altamaha River covering 12 miles and sampling 23 stations, only one living Altamaha Spinymussel was found and no shells (Law Engineering and Environmental Services, Inc. 1998). The species is probably extirpated from the Ohoopee River system (Stringfellow and Gagnon 2001, USFWS 2002) and Oconee River system (E. Keferl, pers. comm. 2001, USFWS 2002) or present in such low numbers that it is undetectable. Severe declines are also evident in the Ocmulgee River and Altamaha River (Stringfellow and Gagnon 2001, USFWS 2002).
The species is also known from the coastal plain portions of the Ocmulgee River from its confluence with the Oconee River upstream to Wilcox Co. Surveys in the 1960s, 1990s, 2000-2001, 2004 of over 90 sites revealed live specimens at ten sites distributed from Jacksonville downstream to the Oconee River confluence. Former large populations at Red Bluff and near Jacksonville are now reduced to only three live specimens in that area found in 2002. Historical populations from the Ocmulgee River near Lumbar City (H.D. Athearn Collection) are now reduced to only 19 live individuals since 1993. A new survey conducted by the Nature Conservancy in the lower Ocmulgee in 2004 revealed no specimens. In a survey of 131 stations (93 Altamaha River, 19 Ocmulgee River, 5 Oconee River, 4 Ohoopee River, 10 Little Ocmulgee River), 94 specimens were found at 27 stations (Anonymous 1995).
(1) no Altamaha Spinymussels were found in the Ohoopee River;
(2) most of the historical collection sites on the Ocmulgee and Altamaha rivers no longer have mussels;
(3) the historical locations that had extant populations had significantly reduced numbers (fewer than 25 live mussels found in over 250 person hours searched); (4) although juvenile mussels are generally difficult to find, historic surveys were successful at finding some juveniles (USFWS 2003, 2005).
This indicates that it is likely that little recruitment is occurring within the populations. Overall, most sites are clustered geographically within short reaches of the lower Ocmulgee River and the Altamaha River upstream of Route 301, and there are long reaches with no specimens separating occurrences. Failure to detect specimens downstream of Doctortown during the early 1990s suggests contraction of historical range. Recent surveys of the Ohoopee River (see Wisniewski et al. 2005) suggest the species may still be declining. Finally, low numbers collected during recent surveys compared to historical surveys suggests the species has declined from historical levels (USFWS 2005). Based on 241 sites sampled prior to 2000 and 120 sites sampled after 2000, pre-2000 site occupancy in the Altamaha basin in Georgia is estimated at 10% (24 sites) and post-2000 site occupancy at 6% (7 sites) (Wisniewski et al. 2005). This indicates a decline of approximately 40% in the Altamaha basin.
Overall the Altamaha Spinymussels can no longer be found in most of its historic collection sites on the Ocmulgee and Altamaha Rivers and the historical locations that had extant populations have significantly reduced numbers (USFWS 2002). This reduction is believed to have occurred over the last 15-25 years which is less than 3 generation lengths (generation length is approximately 10 years; J. Cordeiro pers. comm.), and has been estimated as between 50-70% (NatureServe 2009).
|Habitat and Ecology:||
The spines of the Altamaha Spinymussel presumably help anchor individuals in the shifting sand bottom which is its preferred habitat. Sickel (1980) found the species only in sandbars of coarse to fine sand in the main stem of the Altamaha. Keferl (1981) collected individuals in stable portions of sand banks in the Ohoopie. USFWS (2005) includes the following habitat description: associated with stable, coarse to fine sandy sediments of sandbars, sloughs, and mid-channel islands and appears to be restricted to swiftly flowing water.
The generation length of this species is approximately 10 years (J. Cordeiro pers. comm. 2012).
The greatest threat to this species is destruction, modification, or curtailment of its habitat or range. This can be attributed to the following (from USFWS 2002, 2003, 2005):
(1) Sedimentation including siltation from surface runoff causing reduced feeding and respiratory efficiency, disrupted metabolic processes, reduced growth rates, increased substrata instability, physical smothering, and reduced recruitment of juveniles.
(2) Industrial forest management practices using timber harvest methods resulting in ground disturbances as well as creation of unpaved roads to extract timber cause sediment loading throughout the Altamaha River basin.
(3) Operation of the Edwin I. Hatch Nuclear Power Plant on the Altamaha River in Appling County could pose a threat to habitat. Concerns were expressed in 2001 in a letter for relicencing of the plant about potential adverse impacts through entrainment of potential host fishes and thermal discharges causing heat stress, algal blooms, and oxygen depletion in the river. Expansion of the operation of the plant was proposed in late 2001, doubling the size of the intake basin and dredging 44,000 cubic yards of material annually from the basin; channelization is also part of the expansion. The plant intake basin could disrupt the natural morphology of the point bars that provide mussel habitat and prevent a portion of the coarse sand essential for habitat formation from travelling downstream.
(4) Contaminants including heavy metals and municipal wastewater discharge effluent may cause decreased oxygen, increased acidity, and other water chemistry changes lethal to mussels. Effects depend upon length of exposure and mussel life stage. Heavy metal contaminants and wastewater treatment effluent are among other contaminants that could negatively impact this species. Discharges of these contaminants (including some illegal discharges recently) should be controlled if effects to the mussels are to be eliminated. Recreational usage such as mooring of large houseboats also releases contaminants.
(5) Agricultural contaminants include nutrient enrichment from poultry farms and livestock feedlots, pesticides and fertilizers form row crop agriculture.
The Oconee, Ocmulgee, and Ohoopee River systems contain significant acreage in cotton and onion farming and malathion is utilized as a pesticide in cotton farming. Recently (March 23, 2005), a Senate Bill was passed to direct the Georgia DNR to create provisions for submerged timber salvage in the mainstem Altamaha River and Flint River and this salvage logging ("deadhead logging") seeks to recover commercial timber that sank to the river bottom. The removal of such logs may negatively impact this species and further effects need to be researched before logging is undertaken.
Additional threats to the species include the following (from USFWS 2003, 2005):
(1) Over-collection (this is an attractive species as far as freshwater mussels go) may have been a localized factor in the decline of this species, particularly in the Ohoopee River (E. Keferl, pers. comm. in USFWS 2002, 2003).
(2) Disease and predation, although poorly known, is a normal aspect of the population dynamics of a healthy mussel population; however, predation may amplify declines in small populations of this species.
(3) The inadequacy of existing regulatory mechanisms is a factor in some populations. Point source discharges within the range of the Altamaha Spinymussel have been reduced since the inception of the Clean Water Act, but this may not provide adequate protection for filter feeding organisms that can be impacted by extremely low levels of contaminants. Several wood processing mills located in the Altamaha River basin discharge effluent directly into the basin's streams. There are currently no requirements within the scope of Federal environmental laws to specifically consider the Altamaha Spinymussel during Federal activities, or to ensure that Federal projects will not jeopardize its continued existence.
(4) Invasive species (Flathead Catfish Pylodictis olivaris and Asian Clam Corbicula fluminea) have been introduced into Altamaha River basin. Asian Clams compete for space, minerals, and food (Williams et al. 1993).
(5) Drought conditions persisted in Georgia since 1998 and opened stream beds to all-terrain and four-wheel drive vehicles (Stringfellow and Gagnon 2001) and created low flow rates resulting in diluted water volume increasing concentrations of stream contaminants.
Loss of historical populations, decreased numbers of individuals at sites, and increased threats all contribute to this species' vulnerability.
This species is a USFWS candidate species (USFWS 2005). STEWARDSHIP NEEDS: 1) Maintain high quality habitat, consisting of flowing water sandbar sites in the Altamaha and lower portions of tributaries; 2) Determine the ecological requirements, including its fish host; 3) Monitor and regulate land use in the watersheds, to minimize non-point pollution.
The species is endemic to Georgia and is protected by Georgia's Endangered Wildlife Act of 1973 (USFWS 2005), which would protect the species from direct take and increase awareness of species conservation. Williams et al. (2010) lists this species as endangered according to the AFS assessment. Further research regarding taxonomy, population trends, ecology and threats impacting this species is required. Monitoring of population trends will help elicit necessary conservation strategies in response to population status. National legislation and site protection is required to help protect this species.
|Citation:||Cummings, K. & Cordeiro, J. 2012. Elliptio spinosa. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 22 May 2013.|
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