The long.term goal of the project is to identify and describe key processes which govern the abundance, composition and distribution of zooplankton in the ocean. Recent results on the relationship of copepod perception to clearance rate pointed to the significance of perception, and led to the main hypothesis, underlying the research proposed for the next three years. Both, signal perception performance, and the ability to respond to it, determines whether prey organisms avoid, escape from, or are captured by predators. This project will examine the behavior of various abundant prey (ciliates, copepod nauplii) and predators (nauplii, copepodites and adult copepods) found off the southeastern continental shelf of the U.S.A. The results will be used to taxonomically classify behaviors, and to calculate mortality rates for early juveniles of abundant species of copepods. Estimates of in situ mortality rates for early juveniles even of the most abundant copepod species are scarce and very difficult to obtain. The approach of quantifying species.specific, and stage.specific behaviors of motion, feeding, etc., in relation to sensor performance and morphology, will ultimately lead to an understanding of copepod existence and co.existence in the ocean. In combination with ecologically oriented efforts and parallel studies on the physiology of mechanosensors and chemosensors the proposed studies will aid in an understanding of what governs zooplankton behavior in the ocean.