Some Factors Influencing Reburrowing Activity of Soft-Shell Clam, Mya arenaria

Three size-groups of soft-shell clams,Mya arenaria, averaging 45, 60, and 74 mm in shell length were placed in aquaria and their rate of reburrowing measured. The substrate in each aquarium consisted of sand particles: (I) less than 0.5 mm, (II) 0.5 to 1 mm, (III) 1 to 2 mm, (IV) 2 to 4 mm, and (V) an equal combination of the previous 4 sizes. New specimens were tested at every 5 C rise or fall in ambient water temperature and observations were made periodically for 48 hours. The three variables, water temperature, clam size, and sediment particle size were highly significant (1% level), in influencing clam reburial activities by the end of the second hour through the termination of the experiment 48 hours later. Optimum water temperatures for reburrowing were between 8.8 and 21 C. After 48 hours, 62% of the small, 39% of the medium, and 21% of the large clams had reburrowed in all experimental tests combined. The aquarium with less than 0.5 mm substrate particle size had the greatest percentage of reburrowed clams of each size. As the particle size increased, progressively less reburrowing took place. Most reburrowing took place between 4 and 8 hours after the start of the experiment.