Elliptio chipolaensis

The classification of the Atlantic Slope species of Elliptio is currently in a state of confusion. Johnson (1970) lumped many named taxa under a single name. Current research is finding many of these synonomized taxa to be valid species. This research is in progress and will result in the recognition of numerous additional taxa in this genus. Possibly large genetic differences exist between populations in the same habitats but different drainages (Davis, 1981; Kat et. al., 1984). This species resembles Elliptio nigella, its counterpart in the Flint and Chattahoochee rivers (both species are endemic to Apalachicola River system); but needs genetic validation.

This species has declined significantly, with a loss of more than 75% of historic sites, and is confined to only a few remaining sites in a single drainage of limited extent (about 100 km); only one site hasg good viability. Populations are steadily declining and face continued threats. Critical habitat has been designated along the single remaining watershed where the species occurs.

This species was once thought to be endemic to the Chipola River system (van der Schalie, 1940) until Brim Box and Williams (2000) located a single museum specimen from a Chattahoochee River tributary (Howards Mill Creek) in southeastern Alabama and southwestern Georgia; however, that population is believed to have been extirpated. The historic range is centered throughout much of the Chipola River mainstem and several of its headwater tributaries at 17 historic sites. Populations in Dead Lake and Cowarts and Spring creeks (Chipola River) may also be extirpated (USFWS, 2003; Mirarchi et al., 2004), leaving only about 100 km of occupied habitat left in the Chipola River drainage.

Occupied range includes only about 60 miles (100 km) of the Chipola River system and hence represents one occurrence. A status survey conducted between 1991-1993, that covered at least 75% of all historic sites, found it at five sites (USFWS, 1998). Currently, six sites are known from Marshall and Dry creeks and the upper two-thirds of the Chipola River main stem (USFWS, 2003). The only remaining extant populations in the Chipola River headwaters are at Big and Cowarts Creeks (Williams et al., 2008). The Howards Mill Creek (Chattahoochee River, Alabama) population discovered through a museum specimen by Brim Box and Williams (2000) is now extirpated.

This species is highly restricted in distribution, occurs in generally small subpopulations, and shows little evidence of recovering from historical habitat losses without significant positive human intervention. Principal causes of decline include impoundments, channelization, pollution, and sedimentation that have altered or eliminated habitats that are essential to the long-term viability of many riverine mussel populations. Detailed information on these threats can be found in USFWS (2003) and include: (1) exploitation by native Americans and for pearls and pearl buttons plus overcollection for scientific purposes (very localized, low impact, historical only); (2) habitat alteration- impoundment causing loss of habitat, loss of shoal habitat, thermal alterations, daily discharge fluctuations, bank sloughing, seasonal oxygen deficiencies, coldwater releases, turbulence, high silt loads, and altered host fish distribution (widespread, high impact, ongoing); (3) impoundment- channelization for navigation and maintenance causing sedimentation and contamination (moderate scope, high impact, historical and ongoing); (4) habitat alteration- gravel mining causing riparian forest clearing, channel modification, disrupted flow, water quality modification, impacts on host fish populations, substrate disturbance/siltation, pollution (moderate scope, high impact, historical and ongoing); (5) contaminants- heavy metals, arsenic and ammonia from poultry and animal feedlots, industrial/municipal effluent, agricultural nutrient enrichment from poultry farms and livestock feedlots, herbicides/pesticides, nutrients from aquaculture ponds, urban stormwater runoff, municipal waste discharge (high-moderate scope, high impact, historical and ongoing); (6) sedimentation- from agricultural, silvicultural, and roadway activities, clearing of riparian vegetation, and flood control activities, gravel mining, livestock grazing (high-moderate scope, high impact, historical and ongoing); (7) urbanization- highways, infrastructure, recreational activities (low scope, moderate-low impact, historical and ongoing); (8) "deadhead logging"- disruption of habitat, increased sediment (localized in Florida only, moderate impact, potential future threat); (9) water withdrawal- mostly for irrigation (moderate impact, moderate scope, ongoing); and (10) introduced species- Asiatic clam, zebra mussel, black carp (moderate-low scope, moderate impact, ongoing). Many of the impacts discussed in USFWS (2003) occurred in the past in conjunction with human development of the Apalachicolan Region. However, the species and its habitats continue to be impacted by excessive sediment bed loads of smaller sediment particles, changes in turbidity, increased suspended solids (primarily resulting from nonpoint-source loading from poor land-use practices, lack of BMPs, and maintenance of existing BMPs), and pesticides.