Prey pulses are short and infrequent events of peak prey availability and provide ample feeding opportunities for higher trophic level predators. Zooplankton are a basal component of estuarine food webs, that frequently experience substantial changes in availability. Studying the extent of zooplankton pulses and their effects on estuarine fish communities is important for understanding resource flow and trophic processes in these essential habitats. The aim of my PhD is to determine the timing and frequency of zooplankton pulses in estuaries and how these pulses affect fish community composition and diet. First, I look at zooplankton abundance over time in Ross River estuary, Townsville, and identify pulsing and non-pulsing taxa. Second, I compare the fish community composition during zooplankton pulses and periods with low zooplankton abundance. Lastly, I analyze the stomach content of estuarine fish to determine if opportunistic diet shifts occur during zooplankton pulses. From these data I will construct a model of zooplankton pulses and fish responses in tropical estuaries.