Effects of Protective Limestone Treatment on Water Chemistry and Fisheries Management in Laurel Bed Lake, Virginia

Abstract

Dolomitic limestone additions to the acidic water of Laurel Bed Lake in southwestern Virginia have resulted in significant improvements in both the water quality and fishery. Pretreatment water quality showed the lake and its tributary to have high acidity with pH near or <5.0; negative acid neutralizing capacity (ANC) values; aluminum concentrations (AlT) > 150 μg/L; and low calcium to hydronium (Ca/H) ratios. The acidity is the result of atmospheric acid deposition, natural acidity from wetland origins and lack of carbonate-bearing minerals in the watershed. Limestone treatments have achieved target pH >6.5, ANC >100 μeq/L, AlT <60 μg/L and Ca/H >600. Iron and trace element concentrations have decreased. The dose-mass and frequency of limestone treatment to maintain circumneutral conditions has been found to be 150 tons introduced at two year intervals. Prior to implementation of this project, rock bass (Ambloplites rupestris) were overabundant and stunted (mean Total Length (TL) = 155 mm). The lake was drained, and the rock bass were removed. Stocked fingerling brook trout (Salvelinus fontinalis) survived and grew well following lake liming. Smallmouth bass (Micropterus dolomieu), stocked in response to the recurrence of rock bass, also performed well. An angler survey suggested that both species were important to the lake's fishery. The lake is now managed as a catch-and-release fishery for smallmouth bass and a put-and-grow fishery for brook trout.