Swimming is a key factor in energy acquisition, energy expenditure, and survival of fishes. The ability to efficiently obtain food while avoiding becoming food for predators is strongly affected by the presence of structures such as rocks, weeds, windfall trees, corals, artifical reefs etc. These structures are especially important in streams, oceanic currents, and tidal flows. The ability of fish to use structures depends on morphology and behavior which vary among species. Consequently interactions with habitat structure affect population dynamics, community compostition and the evolutionary biology. In spite of the importance of structure to so many apsects of the lives of fishes, there has been little research on mechanisms employed. Our research will be the first attempt to provide a common mechanistic understanding and predictive model for fish interactions with the complex structures they prefer. We examine behavior and swimming performance as fish use complex structure, determining imposed current velocity and fish morphology. We expect our results will help explain habitat preferences in relatively stable or predictable situations such as lower river reaches, many inland lakes, and offshore marine habitats. We also believe our results will help explain how fish survive in or are excluded from more naturally stressful habitats, such a temperate streams and intertidal zones. We believe our research will have impact on fisheries management. Addition of structure is a common habitat improvement practice and field experience show that various stuctures can be used to attract different fish species. Our results should provide a predictive basis for such habitat improvement practices.
