Title: American malacological bulletin
Identifier: americanmal4519861987amer (find matches)
Year: 1983 (1980s)
Authors: American Malacological Union
Subjects: Mollusks; Mollusks
Publisher: (Hattiesburg, Miss. ?) : (American Malacological Union)
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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22 AMER. MALAC. BULL. 4(1) (1986) Creek is very shallow although potholes do occur around sandstone outcroppings, logs and bridges. Potholes are re- peatedly filled and scoured by seasonal floods. There is little sign of channel degredation although there is some evidence of lateral erosion from the middle stretches of Cole's Creek to its mouth. Bridges on the stream are 40-50 years old and show little evidence of having supporting understruc- ture degraded by stream movement.
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Fig. 1. Streams of southwest Mississippi. Open circles represent localities searched. Numbers represent the number of species col- lected at specific localities. The Homochitto River is the largest stream in the study area and drains 3108 sq. km with a mean annual flow of 42 cms (Lower Miss. Region Coor. Comm., 1974). Headwaters and tributaries are generally canopy-covered with seasonal potholes and eddies around sandstone outcrops, logs and debris. The main channel is known for its quicksand and ever- changing channel, although most of this reputation has been earned in the last 40 years. In 1938-1940, channel modifica- tion by the U.S. Army Corps of Engineers in the lower reach of the river reduced the length by 24 km. Wilson (1979) found that the resulting increase in the slope of the water surface, resistance reduction and corresponding increase in stream velocity has caused vertical degredation of up to 5.7 meters and lateral channel movement of up to one kilometer. Tribu- taries in the lower reach have been similarly affected. The Buffalo River is the smallest and the southern- most stream in the area. It drains 1087 sq. km and has a mean annual flow of 15 cms (Lower Miss. Region Coor. Comm., 1974). The middle reach and headwaters are shallow and lie within a wide sand-filled flood channel. Potholes and eddies are occasionally found along outside bends and around logs and other obstructions. In the Delta the lower reach is deep and bayou-like with little or no perceptible current. RESULTS AND DISCUSSION Sixteen species of unionid mussels and the Asiatic clam were collected from the study area (Table 1). All species are common Mississippi Region fauna. Live mussels were found at only 11 of the 60 sites surveyed (Fig. 1). Most of the other 49 sites provided little or no evidence of mussel fauna. Only a few weathered shells were collected in the lower half of Bayou Pierre. Live individuals were commonly taken in the upper one third of the drainage. The largest commun- ity encountered was along a 200 m length of stream near the headwaters where eleven species were collected around sunken logs, logjams and protected eddies. At other upstream locations mussels were also found in greatest abundance around stabilized substrata protected by submerged timber. Fusconaia flava and Ouadrula pustulosa (Lea, 1831) were the only species commonly collected in unprotected sand. The record of Lampsilis straminea claibornensis from Bayou Pierre by Hartfield and Cooper (1983) was a misidentification of Lampsilis radiata luteola. Habitats in Bayou Pierre with relatively high concen- trations of bivalves consisted of stable and protected sand or silty substratum in a narrow, low-flow channel defined by vegetated banks and with few sand or gravel bars. Unfortun- ately this type of habitat appears to be gradually disappear- ing from the system. Rich (1968) noted that agricultural activities and canopy removal were responsible for the gradual filling of the main channel of Bayou Pierre and that the average depth of potholes had gradually diminished from two to one meter. In his 1976 survey of the Bayou Darter, Teels stated that the eroded and non-eroded portions of Bayou Pierre met approximately 3 km downstream from the Smyrna crossing. In 1983 erosion extended to the Smyrna bridge, and it was observed during a recent visit in 1985 that the erosion extended over 1.5 km upstream from the bridge and had claimed the most diverse mussel community encoun- tered during our survey. No mussels were found in the main channel of Cole's Creek, but two species, Toxolasma texasensis and Uniomerus tetralasmus (Say, 1831) were collected in Shanktown Creek, a small tributary. Pools between logjams and sandstone out- crops in this narrow stream appear to maintain the mussels during low flow when there is little current. The Homochitto is the largest stream in the study area, but only seven species have been collected from it. During 1980-1981 we were unable to find either live mussels or shells in the main channel of the Homochitto or its tributaries. However in 1982 a bivalve community consisting of Lamp- silis radiata luteola, Villosa lienosa, Toxolasma texasensis, Anodonta imbecillis, Fusconaia flava, Elliptio crassidens (Lamark, 1819) and Uniomerus declivus was found in a 200 m reach between a U.S. Forest Service dam on Clear Springs Creek and Richardson Creek. Clear Springs Dam is the oldest tributary dam in the Homochitto drainage and was dedicated the year after chan- nelization of the lower Homochitto was completed. Sub- stratum below the dam is sand and gravel stabilized by

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