Collaborative Research: A Multidisciplinary Study of Selective Tidal-Stream Transport: Bio-Physical Coupling and Behavioral Mechanisms

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Many invertebrates and fishes use selective tidal-stream transport (STST) for horizontal movement. STST is based on a vertical migration pattern, in which animals leave the bottom and enter the water column during one phase of the tide and remain on or near the bottom during the other phase. One remarkable but unstudied aspect of STST within a species is the reversal in the direction of migration at different life history stages. Migration of the blue crab Callinectes sapidus, involving a reversal in STST direction following spawning, is the focus of this multidisciplinary research. During spawning migration, ovigerous females use ebb-tide transport to move seaward from estuaries. After releasing larvae, they reverse direction and undergo flood -tide transport to re-enter the estuary. The specific goals of this research are to: use biotelemetry to observe and characterize the pattern of movement and physical conditions during the spawning migration; simulate observed physical conditions and migratory pathways and extrapolate these results in time and space using a coupled bio-physical model; determine whether the behavior underlying STST is mediated by an endogenous rhythm in activity or by behavioral responses to exogenous cues; and determine the cues mediating the onset of ebb-tide transport by females with mature eggs and flood-tide transport of post--spawn females. The study integrates the fields of biological and physical oceanography and will expand our understanding of the cues, behaviors, and physical mechanisms underlying STST, a common life history trait among many marine and estuarine species that is essential for continuation of populations. Specifically, combining results from field observations and laboratory experiments with a circulation model will allow researchers to predict hydrologic and meteorologic conditions that promote or impede female blue crab migration to and from spawning sites and estimate the relative contribution of larvae released from different areas of an estuary to the supply of developing larvae in coastal waters.