Changes in the Black Bass Community and Fishery with Oligotrophication in West Point Reservoir, Georgia

Abstract

We examined the fishing tournament and population responses of largemouth bass Micropterus salmoides and spotted bass M. punctulatus to the oligotrophication of West Point Reservoir (10,467 ha), Georgia. State-mandated reductions in point- and non-point-source phosphorus loadings, primarily from the Atlanta metropolitan area, resulted in a decline of nearly an order of magnitude in total phosphorus concentrations (TP) entering the reservoir from the late 1980s to 1999. Concurrent with this decline in TP, chlorophyll-a concentrations at a midreservoir station declined from more than 40 μg/L in 1987–1988 to 9–17 μg/L by 1997–1999, which was lower than the goal of 27 μg/L. Chlorophyll-a concentrations near the dam forebay were less than at the midreservoir station and also declined over time. Largemouth bass recruitment decreased and spotted bass recruitment increased. Growth rates of age-4 and older largemouth bass and the relative weight of preferred–memorable (38–51 cm) fish declined. Slower growth combined with lower recruitment resulted in a more than twofold decline in electrofishing catch rates of largemouth bass longer than 406 mm (legal minimum length). The infusion of slower-growing spotted bass (304 mm minimum length for tournaments) into the black bass fishery was associated with a decrease in the average weight of fish caught by tournament anglers but increased the percent of anglers catching at least one fish in a tournament with no long-term change in catch per effort. The amount of tournament angling effort to catch a black bass weighing more than 2.27 kg increased from about 100–200 h in the late 1980s to over 500 h by the late 1990s. Oligotrophication of West Point Reservoir has resulted in the restructuring of the black bass population with fewer, smaller, and less robust largemouth bass and more abundant, but smaller, spotted bass in the fishery. When establishing water quality standards that result in reduced nutrient loading, fishery and water quality managers should collaborate with the public to achieve compromises between esthetics and fisheries.