Daily variability in abundance and population characteristics of tidal salt-marsh fauna

Nekton and macrocrustacean population levels and characteristics were studied in two similar tidal marsh creeks. Absolute and area-adjusted data were analyzed to determine variability resulting from daily population fluctuations. Two sampling schemes—intensive 3-d seasonal and periodic 1-d—were examined by constructing probability matrices to compare the accuracy of data comparisons resulting from each scheme. The probability of inaccuracies in comparisons of abundance using nonreplicated sampling schemes ranged from 0% to 100%. Significant differences between consecutive day data were observed for population characteristics such as blue crab (Callinectes sapidus) sex ratios, spot (Leiostomus xanthurus) length-weights, killifish: sciaenid ratios, and killifish: blue crab ratios. These data support the need to account for short-term variability when assessing mobile aquatic fauna abundance in estuarine wetlands.