Scaling of Burial Mechanics in Parophrys vetulus, the English Sole

Abstract

Flatfishes (Pleuronectiformes) rapidly bury themselves under sediments using body undulations and fin movements. During burial, a fish must fluidize a volume of the substrate to displace it into the water column and distribute it over the surface of the body. Thus the burial behavior forces the fish to interact with the fluid environment and a granular medium and is affected by size of the organism and grain size. We used the English Sole, Parophrys vetulus, as a model to explore the effects of scaling on burial. We recorded burial events from 15 fish across a size range (5 to 30 cm in total length), keeping sand grain size consistent, using high speed video at 250 fps and determined undulation frequency, time to burial, and percent body coverage. We found larger fishes took longer to bury and moved with a lower undulation frequency, but were able to cover themselves as effectively as smaller fish (91.6%). Undulation frequency decreased with body length to the -0.53 power; time to burial increased to the 0.67 power. We also used 5 individual fish of similar size (5.7 – 8.1 cm) and changed the size of the particle provided as substrate (125 – 710 microns). We found grain size does not affect the undulation frequency or time to burial of small fish, but as particle size increases, the percentage of the body covered decreases. It is possible that fish cannot fluidize particles of larger grain sizes as effectively as they can smaller grain sizes. Taken together, these results reveal that the timing of flatfish burial is a function of fish size and the success of the behavior is affected by the relative grain size of the sediment.