Physical and biological factors influencing mussel (Mytilus trossulus, M. edulis) settlement on a wave-exposed rocky shore

Settlement rates of mussels Mytilus trossulus and M. edulis onartificial collectors (aquarium filter wool) and natural substrata weremeasured in tidepools and on emergent rock in recently ice-scoured and non-scoured regions of a rocky shore near Halifax, Nova Scotia, Canada. Patternsof abundance and size distribution of mussel settlers differed markedlybetween artificial collectors and natural substrata. Settlement rate onartificial collectors was directly related to water flux, and was highest onice-scoured emergent rock and lowest in non-scoured tidepools. Settlementrate on natural substrata was related to a suite of biological(macroalgal/barnacle cover) and physical factors (water flux, tidal height,flushing time), and was highest in ice-scoured tidepools and lowest on ice-scoured emergent rock. Large postlarval mussels (>5 min shell length) werecommon on natural substrata but rare on artificial collectors. Recruitmentpatterns of mussels on natural substrata reflected the distribution ofsettlers, suggesting that settlement patterns are important in determiningthe distribution and abundance of mussels in this population.