A comparison of methods for calculating condition index in eastern oysters Crassostrea virginica (Gmelin, 1791)

A number of techniques have been reported to estimate condition index in oysters and other bivalve molluscs. We report and compare condition index, estimated by three different methods, for oysters collected from a single reef in the James River, Virginia over a four week period in the summer of 1987. Two indices express condition as a ratio of dry meat weight to shell cavity volume, but differ in methods of estimating shell cavity volume. A third method expresses condition as a ratio of dry meat weight to dry shell weight. Within the size range 36-96 mm length there is no effect of size on index values. We suggest that indices based on both shell cavity vqlume and shell weight have utility in reflecting biochemical or nutritive status; however, intercalibration is difficult and comparisons of data from different authors and locations limited in scop