The shifting balance of littoral predator-prey interaction in regimes of hydrodynamic stress.

Above lowshore levels of wave-beaten rocky shores, desiccation from tidal exposure and hydrodynamics stresses from wave action are thought to create refuges from predation, allowing concentrations of sedentary prey such as mussel beds. Underwater time-lapse photography on rocky shores in Southern California revealed that dense aggregations of spiny lobsters prey on mussels during nocturnal high tides. In contradiction of the refuge hypothesis, the densest aggregations occurred on midshore levels of the most wave-exposed site, a semi-protected site showed intermediate densities, and a protected site showed only sparse numbers of lobsters.