Influences of Substrate Grain Size on the Burrowing Behavior of Juvenile Meretrix meretrix

SIMPLE SUMMARY: Meretrix meretrix lives in substrates at a depth of 1–20 cm; the substrate has an influence on its growth, survival, living habits, and behavioral characteristics. In this study, we investigated the effects of different grain size substrates on substrate preference, burrowing ability, and behavior during the substrate selection process of M. meretrix. These results indicated that juvenile M. meretrix had a significant preference for and a stronger burrowing ability in fine sand. As the substrate grain size increased, the burrowing ability and preference of M. meretrix decreased, and these bivalves showed behavioral characteristics such as a prolonged selection time and an increased percentage of movement. In addition, by observing the substrate selection behavior of M. meretrix, we divided the selection process of the substrate by juvenile M. meretrix into four stages: preparation, selection, burrowing, and end stages. ABSTRACT: The substrate is the key environmental factor that affects the growth, survival, population and distribution of dwelling mollusks in mudflat settings. To clarify the effect of the substrate grain size on soft substrate preference, burrowing ability and behavior during the selection process of juvenile Meretrix meretrix, four different grain size substrates (coarse sand, medium sand, fine sand, and natural substrate) were set up for comparison. The results indicated that: (1) the burrowing ability of juvenile specimens in fine sand was the strongest; (2) the degree (from high to low) of the juvenile’s preference for the four substrates was in the order of fine sand > natural substrate > medium sand > coarse sand; and (3) the selection process of the substrate by the juveniles could be divided into four stages: preparation, selection, burrowing and end stages. These stages showed the behavioral characteristics of a longer selection time and higher percentage of movement in coarse sand. Therefore, our results demonstrated that sea areas or ponds with fine sand as the main component are more suitable for stock enhancement with M. meretrix. These results provide basic data for habitat selection and suitability evaluations for the aquaculture of M. meretrix.