Comparison of the flux of broken barnacle plates from a caged living barnacle community (0.8 g m (super -2) day (super -1) ) with a similar but uncaged barnacle community nearby (30 g m (super -2) day (super -1) ) suggests that feeding activity by the sheepshead, a predatory sparid fish, is the chief fragmenter of barnacle plates caught in 2 x 2.2 m traps. Sediment recovered from an uncaged trap suspended under a floating dock contained four components. The individual fluxes of these components for the period June 1979-January 1980 was barnacle plates 4-46 g m (super -2) day (super -1) , fragments of the encrusting barnacle community 0-3, quartz sand 1-4, and mud in the form of barnacle fecal pellets 0.3-7. Summed up, these materials yield a layer of sediment 8-16 mm thick each year. The flux of broken plates varied from a peak in late September to a low in December January, probably due to migration of sheepshead out of the study area during spawning. Quartz sand found in the traps was shown to be transported by mullet.