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 popul
ation fluctuations. Two sampling schemes-intensive 3-d seasonal and pe
riodic 1-d-were examined by constructing probability matrices to compa
re the accuracy of data comparisons resulting from each scheme. The pr
obability of inaccuracies in comparisons of abundance using nonreplica
ted sampling schemes ranged from 0% to 100%. Significant differences b
etween consecutive day data were observed for population characteristi
cs such as blue crab (Callinectes sapidus) sex ratios, spot (Leiostomu
s xanthurus) length-weights, killifish: sciaenid ratios, and killifish
:blue crab ratios. These data support the need to account for short-te
rm variability when assessing mobile aquatic fauna abundance in estuar
ine wetlands.