Patterns of distribution and abundance of the temperate sea cucumber Australostichopus mollis on a rocky subtidal reef

Abstract

Temperate species of sea cucumber found on rocky subtidal reefs often have a patchy distribution. If rocky reef complexity is important to the temperate sea cucumber Australostichopus mollis then this should be correlated with relative differences in their abundance along the coast. These temperate subtidal rocky reefs present a variety of possible habitat types that can be patchy in their distribution along the coast. Subtidal surveys were conducted along a 2.5-km stretch of coast and counts of A. mollis recorded along with changes in the composition of a number of physical features of reef structure. Abundance of A. mollis decreased from 1 individual/2 m 2 in headland outcrops to 1 individual/20 m 2 and 1 individual/ 100 m 2 for coastal areas and inner bays respectively. This was associated with a decrease in percentage composition of large boulders, which were between 0.5 and 1 m along their longest diameter and were part of a predominantly rock and boulder substrate. Where sea cucumber abundance decreased for identified location types there was also a corresponding decrease in kelp cover and an increase in open rock faces of a ridged or corrugated structure. Physical features of temperate reef structure, their contribution to overall reef complexity, and location along the coast, are determining factors mediating the distribution and abundance of A. mollis. © 2011 The Royal Society of New Zealand.