Artificial reefs reduce the adverse effects of mud and transport stress on behaviors of the sea cucumber Apostichopus japonicus

Abstract

Poor survival of seeds reduces the production efficiency of the sea cucumber Apostichopus japonicus in pond culture. We investigated the effects of sea mud on the movement-related behaviors of A. japonicus with different body sizes. Mud significantly decreased crawling behavior and wall-reaching behavior in small seeds (~ 1 g of body weight), but not in the large ones (~ 2.5 g of body weight). These behaviors were significantly greater in the large seeds of A. japonicus than those in the small individuals when they were both on the mud. This clearly suggests that mud has negative effects on the movement-related behaviors of small seeds, but not on large individuals. We further assessed the effects of inevitable transport stress on the movement-related behaviors of A. japonicus on mud. Significantly poorer performances in crawling behavior, wall-reaching behavior and struggling behavior were observed in stressed A. japonicus (both sizes) than those in unstressed groups. These new findings indicate that transport stress further increases the adverse effects on the movement-related behaviors of A. japonicus on mud. Moreover, we investigated whether adverse effects can be reduced when individuals are directly seeded onto artificial reefs. Crawling behavior, wall-reaching behavior and struggling behavior in stressed A. japonicus (both sizes) seeded onto artificial reefs were significantly greater than those on mud, whereas artificial reefs did not significantly improve the crawling and struggling behaviors of unstressed small seeds. These results collectively indicate that mud and transport stress show negative impacts on the movement-related behaviors of sea cucumbers. Artificial reefs greatly reduce these adverse effects and probably contribute to improving the production efficiency of sea cucumbers in pond culture.