Fish with perennial life histories that inhabit ecosystems where water availability fluctuates seasonally must have movement behavior that accommodates this environmental change. Landscape structure is expected to influence magnitude and direction of these movements by affecting the distribution of water in space and time. Predicting the effects of climate change and restoring historical hydrology in the Florida Everglades, a large wetland that undergoes regular contraction in ecosystem size during seasonal droughts, requires information on how fish movement is affected by spatiotemporal patterns of water availability. We used radio telemetry to quantify spatial scale and direction of displacement of Florida Gar (Lepisosteus platyrhinchus) from focal areas of the Everglades that differ in their seasonal hydrology and position relative to drought refuges. Displacement distances increased during both rising and dropping water levels compared to periods of stable water depth, but increased more and in more directed fashion when ecosystem size was contracting. The initial position of fish relative to natural (i.e., creeks and sloughs) and artificial (i.e., canals) refuge habitats directed dry-season movement and influenced displacement distances by attracting individuals from long distances and reducing inclination of nearby fish to disperse. During rising water, displacement distances overlapped between locations near and far from dry-season refuges because of increased displacement from crowded refuge habitats and decreased movement distances at short-hydroperiod marshes. Florida Gar display flexible movement strategies that accommodate the influence of landscape context on hydrology and distance to drought refuges. Modification of the canal-levee network, managed water releases, and climate change in the Florida Everglades will interact with seasonal displacement of this abundant predator in shaping its population dynamics and food web impacts during and after drought disturbances.
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Vol. 2015 • No. 1