Effects of artificial reefs on selectivity and behaviors of the sea cucumber Apostichopus japonicas: New insights into the pond culture

Cost-effective reefs improve the yield of sea cucumber Apostichopus japonicas cultured in ponds. The reaction to reef models was studied in laboratory experiments regarding selectivity and fitness-related behaviors (crawling, feeding and defecation) in different roughness (rough and smooth), angles (30°, 60° and 90°) and heights (3.5, 7, 10.5 and 14 cm). The present study found that significantly more sea cucumbers selected the rough model, with significantly better crawling frequency, tentacles activity frequency and defecation behavior compared with those on the smooth model. This indicates that rough materials in artificial reefs are appropriate for the fitness-related behaviors of sea cucumbers. Regarding the angles, the 30° model attracted significantly more sea cucumbers than those of 60° and 90°. Among the three angles, sea cucumbers in the 30° model showed significantly better defecation behavior, while showed higher frequencies of crawling and tentacles activity in comparison with the 90° model. In other words, the models of 30° and 60° serve as the "toilet" and the "kitchen" of sea cucumbers better in defecation and food intake. No significant difference was found in the number of sea cucumbers selecting any model of three heights. The 7-cm model sees significantly higher frequencies of crawling and tentacles activity than the ones of 3.5 and 14 cm. These results indicate that the higher reef may not necessarily be valuable in the pond culture and a shorter one may help boost the feeding efficiency of sea cucumbers.