Ecological influences on the local movement dynamics of the blackspotted topminnow, Fundulus olivaceus

Movement of individuals throughout a landscape is fundamental to a wide array of ecological processes; however, the interacting spatiotemporal effects of environmental influences on movement remain poorly understood. Using a series of mesocosm trials, we examined relationships between local abiotic and biotic variables and movement patterns of the blackspotted topminnow, Fundulus olivaceus, using passive integrated transponder (PIT) tags. In one series of trials, we assessed the influence of local population factors (density, sex ratio) and phenotypic variables (growth, condition) on movement rates across seasons (spawning, nonspawning). Movement was strongly influenced by different factors seasonally, and movement rates were approximately 7.5 times higher in the spawning season compared to nonspawning periods. Males moved more than females and movement was greater in low-density treatments; however, these patterns persisted only during the spawning period. In a second series of trials, we examined abiotic (habitat complexity) and biotic (predator; Micropterus punctulatus) influences on the movement dynamics and habitat usage of F. olivaceus. Predators were found to suppress movement; however, this response was ameliorated by the presence of habitat structure. Movement rates of F. olivaceus were negatively related to predator movement and individuals showed a higher propensity to group in the presence of the predator. The predator induced shifts in habitat usage, as individuals utilized the shallower habitat at a greater frequency and for longer durations compared to trials without a predator. Taken together, our results suggest local environmental variables may strongly influence spatiotemporal movement behaviors of F. olivaceus.