Degree of Threat: High
Comments: Siltation from poorly conducted agricultural and silvicultural activities, agricultural and silvicultural runoff; chicken farm litter nutrients; gravel/sand mining and oil/gas exploration; localized industrial (pulp mill in Escambia in Alabama near Florida border), municipal pollution; watershed development (bridge, highway construction, etc.). Silvicultural activities and chicken farms are expanding in southern Alabama. Twenty-five different impoumdments have been proposed for the Choctawhatchee River system alone (Blalock et al., 1998). Bank sloughing has impacted habitat in the Escambia mainstem in Florida. The stream and river habitats are vulnerable to habitat modification, sedimentation, and water quality degradation from a number of activities. Highway and reservoir construction, improper logging practices, agricultural runoff, housing developments, pipeline crossings, and livestock grazing often result in physical disturbance of stream substrates or the riparian zone, and/or changes in water quality, temperature, or flow. Sedimentation can cause direct mortality of mussels by deposition and suffocation (Ellis, 1936; Brim Box and Mossa, 1999) and can eliminate or reduce the recruitment of juvenile mussels (Negus, 1966; Brim Box and Mossa, 1999). Suspended sediment can also interfere with feeding activity of mussels (Dennis, 1984). Many of the confirmed extant populations of this species are in the vicinity of highway and unpaved road crossings due to ease of access for surveyors. Highway and bridge construction and widening could affect populations of these species unless appropriate precautions are implemented during construction to reduce erosion and sedimentation, and maintain water quality standards. The construction of reservoirs and the associated habitat changes (e.g., changes of sediments, flow, water temperature, dissolved oxygen) can directly impact mussel populations (Neves et al., 1997). Nutrients, usually phosphorus and nitrogen, may emanate from agricultural fields, residential lawns, livestock feedlots, poultry houses, and leaking septic tanks in levels that result in eutrophication and reduced oxygen levels in small streams. Other factors include (1) over-utilization for commercial, recreational, scientific, or educational purposes (note: species is not commercially valuable nor are the streams and rivers it inhabits subject to harvesting activities for commercial mussel species), (2) disease or predation (poorly known but may contribute to the further decline of these species due to their restricted distributions and low numbers associated with extant populations), (3) the inadequacy of existing regulatory mechanisms (note: less success in dealing with non-point source pollution impacts, particularly sediments, to small stream drainages), (4) catastrophic events (populations are generally small and geographically isolated), (5) host fish loss or decline (note host not known), (6) populations below effective population size to maintain long term viability (some populations below required population size to maintain long-term genetic viability), (7) invasive species (Asiatic clam, zebra mussel, black carp) (see USFWS, 2003).
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