Status of Rare and Endangered Freshwater Mussels in Southeastern Oklahoma

We reviewed the conservation status of rare and endangered species of mussels in southeastern Oklahoma by completing surveys of 10 long-term monitoring sites on the Kiamichi River and five sites in the Little River. We found extant populations of the Ouachita rock pocketbook, Arkansia wheeleri, scaleshell, Leptodea leptodon, winged mapleleaf, Quadrula fragosa, and rabbitsfoot, Quadrula cylindrica cylindrica. This is the first reported documentation of Q. fragosa in the Little River. When our data are compared to historic records, populations, particularly of A. wheeleri and Q. cylindrica, appear to be declining. RESUMEN—Revisamos el estado de conservación de las especies raras de mejillones y en peligro de extinción en 10 sitios de muestreo a largo plazo en el rı́o Kiamichi y 5 sitios en el rı́o Little en el sureste de Oklahoma. Encontramos poblaciones existentes de Arkansia wheeleri, Leptodea leptodon, Quadrula fragosa y Quadrula cylindrica cylindrica. Reportamos por primera vez a Q. fragosa en el rı́o Little. Cuando los resultados son comparados con registros históricos, las poblaciones, particularmente de A. wheeleri y Q. cylindrica, parecen estar disminuyendo. One of the most critically imperiled freshwater groups in the United States is freshwater mussels (Family Unionidae; Strayer et al., 2004). The United States Fish and Wildlife Service recognizes 12% of native freshwater mussels to be extinct and 23% as threatened or endangered, while the Nature Conservancy considers 68% of native mussels to be at risk (Biggins and Butler, 2000). Mussels are long-lived, iteroparous, and spend a portion of their lives as obligate ectoparasites on a fish host (McMahon and Bogan, 2001). These life-history characteristics have made them particularly susceptible to anthropogenic impacts. The highest diversity of freshwater mussels occurs in the southeastern United States, which provides habitat for almost 270 of the about 300 North American species (Williams et al., 1993; Neves et al., 1997). Oklahoma, on the periphery of the highest species richness for mussels, is still home to a diverse and speciose assemblage of freshwater mussels with about 55 species in the state. One river basin, the Kiamichi-Little River Basin, supports about 80% of all species of mussels that can be found in Oklahoma (Table 1; D. E. Spooner et al., in litt.). Historically, both of these rivers also have been home to a number of rare and endangered species of mussels including the Ouachita rock pocketbook, Arkansia wheeleri, scaleshell, Leptodea leptodon, winged mapleleaf, Quadrula fragosa, and rabbitsfoot, Quadrula cylindrica. Arkansia wheeleri (syn. Arcidens wheeleri) is a federally listed, endangered species whose historical distribution includes the Kiamichi River and Jackfork Creek (a tributary to the Kiamichi River), the Little River, the Ouachita River in Arkansas, and Pine Creek and Sanders Creek in Texas (Martinez, 2004). As of the early 1990s, the most substantial remaining population occurred in the Kiamichi River within a 123-km stretch upstream of Hugo Reservoir (Vaughn and Pyron, 1995; Martinez, 2004; C. C. Vaughn et al., in litt.). Other smaller populations were known to occur in the Little River in Oklahoma and the Ouachita River in Arkansas (Martinez, 2004; C. C. Vaughn, in litt.; C. C. Vaughn et al., in litt.). Leptodea leptodon, also a federally listed, endangered species, was known historically from 55 rivers across the United States in Alabama, Arkansas, Illinois, Indiana, Iowa, Kentucky, Minnesota, Missouri, Ohio, Oklahoma, South Dakota, Tennessee, and Wisconsin (Syzmanski, THE SOUTHWESTERN NATURALIST 53(1):45–50 MARCH 2008