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 on artificial collectors (aquarium filter wool) and natural substrata were measured in tidepools and on emergent rock: in recently ice-scoured and non-scoured regions of a rocky shore near Halifax, Nova Scotia, Canada. patterns of abundance and size distribution of mussel settlers differed markedly between artificial collectors and natural substrata. Settlement rate on artificial collectors was directly related to water flux, and was highest on ice-scoured emergent rock and lowest in non-scoured tidepools. Settlement rate 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 mm shell length) were common on natural substrata but rare on artificial collectors. Recruitment patterns of mussels on natural substrata reflected the distribution of settlers, suggesting that settlement patterns are important in determining the distribution and abundance of mussels in this population.