Modelling the swimming response of late stage larval reef fish to different stimuli

This paper examines the importance of directed motion towards reefs by late stage larval reef fish for determining recruitment rates to substrate-associated adult populations. The significance of reliance on different sensory faculties for orientation, and of different larval swimming and sensory capabilities, is explored with mathematical models. A 4-way classification is examined, separating weak and strong swimming larvae, and larvae relying on current-dependent and -independent cues for orientation. The relative importance of factors determining supply rates varies among these 4 cases, but, in general, purely hydrodynamically based considerations of incidental recruitment, or passive entrainment in re-circulatory features around reefs, appear less important than considerations of larval swimming, and the interaction of swimming with these physical transport processes. The extent of sensory capabilities of larvae proves to be a critical parameter, and the rate of larval supply depends sensitively upon it, for species relying on both current-dependent and -independent cues. The consequences of these findings are discussed, with particular reference to the potential for active behaviour to influence settlement patterns of different species.