Schematic of possible behaviors of larvae retained nearshore during upwelling and downwelling. Larvae may be retained near coast during downwelling (convergent flow against coast) if they try to maintain preferred depth in face of converging and downwelling flow. Conversely, larvae may be retained during upwelling (divergent flow at the coast) if they try to maintain a preferred depth in face of upwelling flow. For this to work, larvae must respond to pressure changes, swimming up on pressure drop and down on pressure rise, and must swim as fast or faster than vertical current speeds