Effect of Grain Size on the Burrowing Force of Pacific Sand Lance

Abstract

Pacific sand lances, Ammodytes personatus, are nutrient dense forage fish important to salmon recovery and orca conservation in the San Juan archipelago. Sand lances burrow into sandy sediments during quiescence and in response to threats. Ammodytes spp. choose habitats with specific sizes of sediment particles, but the biological reasons for their preferences are poorly understood. Burrowing force in different sediments is measured using resin models of sand lance and a materials testing system. The final testing methods are validated by first varying the volume of sediment, mixing procedure, and speed. Laboratory limitations do not preclude comparison with in-vivo activity. There is a non-linear relationship between force and grain size. In general, coarser sediments are more difficult to penetrate. When the scales were removed, models more easily penetrated the sediment, but produced a similar non-linear trend. Burrowing forces are correlated with observed habitat preferences, and may be useful in habitat predictions.