Hepatic Copper Concentrations and Condition Factors of Largemouth Bass (Micropterus salmoides) and Common Carp (Cyprinus carpio) from Copper Sulfate-Treated and Untreated Reservoirs

Abstract

ABSTRACT The application of copper sulfate to surface waters for nuisance algae control has been practiced for decades. Despite its long history of use, questions persist about the fate and bioavailability of copper (Cu) in water bodies receiving copper sulfate applications. This study compares the hepatic Cu content of largemouth bass (Micropterus salmoides) and common carp (Cyprinus carpio) sampled from two reservoirs in southern California with contrasting copper sulfate treatment histories. Lake Mathews is the terminal reservoir for the Colorado River Aqueduct and has received over 2000 tons of CuSO4·5H2O over the past ~20 years. As a result of repeated copper sulfate treatment, Lake Mathews has an average Cu sediment content of 290 μg·g−1 dry weight. Copper Basin Reservoir, also part of the Colorado River Aqueduct system, has not previously received any CuSO4 applications and thus has a much lower sediment Cu content (8 μg·g−1). The mean hepatic Cu content of small bass (mean length ~24 cm) was significantly higher for individuals sampled from Lake Mathews than from Copper Basin Reservoir (22.9±20.5 vs. 4.3±4.4 μg·g−1, respectively), although no statistically significant difference (at p≤0.05) was found for large bass (mean length ~41 cm) from the two reservoirs. The mean hepatic Cu concentration of carp from Lake Mathews was significantly higher (at p≤0.05) than that of carp from Copper Basin Reservoir (76.8±42.3 vs. 51.3±22.4 μg·g−1, respectively). No apparent negative effects associated with copper sulfate application or copper accumulation within fish were found, however, as condition factors (K) for fish from Lake Mathews were either comparable to or higher than those from Copper Basin Reservoir (e.g., for small bass, K was 1.78±0.11 vs. 1.46±0.10, respectively).