Abstract
We evaluate the hypothesis that the vertical migration of Periphylla periphylla is governed by its sensitivity to light intensity. By applying an individual-based model where random walk is combined with assumed individual responses to light, we compare the predicted vertical distributions with acoustical observations. Important features of the observed P. periphylla distributions can be explained by a simple proximate light response where individual P. periphylla avoids light above a certain threshold but also has a preference for very low light intensities. In addition to accounting for the observed synchronous diel vertical migration phenomenon in P. periphylla, this simple mechanism also accounts for simultaneous asynchronous vertical migrations observed for part of the population.