The annual hydrological cycle of floodplains supports fishes that are uniquely adapted to optimize resources throughout the year. Such adaptations to changing environments include air-breathing for seasonally hypoxic waters and directed movements to best utilize habitats as they become available. This study examined the environmental, temporal and body-size influences on air-breathing behavior and movement ecology of Arapaima sp., one of the most economically and ecologically significant species in the Amazon. Acoustic (n=15) and radio (n=12) telemetry was used to study the influences on air-breathing and movement ecology of arapaima in the Central Amazon. Generalized additive mixed models showed that temperature was the most influential predictor of air-breathing intervals, followed by body size. The shortest breathing intervals were associated with consecutive "aggressive" breaths while the longest breathing intervals had consecutive "calm" breaths. Generalized linear mixed models showed that flood stage was the most important predictor of residency time, directional movement, and rate of movement. Fish moved faster in the flood and dry stages than the rising and falling stages, and spent longer in one place in the rising and falling stages than the flood and dry stages. Findings of this study may be used to inform management decisions for arapaima conservation, such as protected habitat and population counts, with applications to fishes across river-floodplain ecosystems globally. / Master of Science / The annual hydrological cycle of floodplains supports fishes that are uniquely adapted to optimize resources throughout the year as their environment changes. Such adaptations include air-breathing for seasons with low oxygen levels and directed movements (i.e. upstream, downstream) to best utilize habitats as they become available during the year. This study examined the environmental, temporal and body-size influences on air-breathing behavior and movement ecology of <i>Arapaima</i> sp., one of the most economically and ecologically significant species in the Amazon. Acoustic and radio telemetry was used to study the influences on airbreathing and movement ecology of arapaima in the Central Amazon. Model results showed that temperature was the most influential predictor of air-breathing intervals, followed by body size. The shortest breathing intervals were associated with consecutive “aggressive” breaths while the longest breathing intervals had consecutive “calm” breaths. Generalized linear mixed models showed that flood stage was the most important predictor of how long a fish spent in a given area, the direction in which it travels and the rate at which it moved. Fish moved faster in the flood and dry stages, and spent longer without moving in the rising and falling stages. Findings of this study may be used to inform management decisions for arapaima conservation, such as protected habitat and population counts, with applications to fishes across river-floodplain ecosystems globally.