Conspecific alarm cues are a potential effective barrier to regulate foraging behavior of the sea urchin Mesocentrotus nudus.

A cost-effective approach to controlling foraging and feeding behaviors of sea urchins is essential for the management of kelp beds. Laboratory experiments were designed to investigate whether alarm cues from crushed conspecific urchins can effectively prevent the foraging and feeding behaviors of the sea urchin Mesocentrotus nudus under the static seawater condition. The present study found that the number of M. nudus that foraged successfully was significantly lower when alarm cues were placed between the kelp and the sea urchins. This result indicates that alarm cues could play an important role in critical kelp-bed areas. It probably prevents sea urchins from foraging by acting as a barrier. Further, we found that alarm cues around the kelp significantly affected foraging behavior of M. nudus, indicating that the alarm cues around the kelp are a potential effective way to prevent sea urchins from foraging for the kelp. In addition, the number of sea urchins that stopped feeding was significantly higher in the group in the presence of alarm cues than that in the control group. This indicates that alarm cues may have an application in stopping sea urchins from feeding. However, there was no significant difference of Aristotle's lantern reflex between the groups with and without alarm cues. These results indicate that alarm cues greatly affect foraging behavior, but not Aristotle's lantern reflex of M. nudus. All together, the present study suggests that alarm cues have an application potential in the management of the kelp beds as green engineering. Future studies are essential to further investigate the chemical basis of the alarm cues of sea urchins for the application in large-scale.