Typically abalone are found clustered into aggregations of many individuals along gutters and ledges that dissect the surfaces of the reefs they inhabit. Commercial abalone divers take advantage of this clustering behaviour and specifically target aggregations to minimise the time spent searching for abalone and maximise their catch rates. This approach to abalone harvesting would be expected to progressively reduce the number and size of the aggregations to produce a less clustered pattern of distribution. Most methods used to detect changes in abalone abundance that result from fishing assume that abalone movement will have minimal effect on post-fishing patterns of distribution.

Abalone are generally viewed as relatively inactive organisms that occupy specific homesites from which they seldom move. Evidence for this lack of movement includes the oval shaped 'scars' of bare rock, free of algae and other immobile invertebrates, that remain after abalone are harvested. However there are many anecdotes describing the tendency for abalone to reform aggregations after fishing and during spawning periods. Presumably the latter promotes fertilisation success by increasing the quantities of sperm and eggs that mix in the water. It is unclear why abalone may aggregate into clusters outside spawning periods. If re-aggregation does occur after fishing, it is also unclear where these 'replacement' abalone come from. There is some speculation that small abalone may emerge from crevices and cryptic habitat. Other hypotheses include small-scale movements within aggregations or migration from unfished areas. An understanding of how re-aggregation occurs after fishing and to what extent it occurs, is essential to determine its effect on estimates of abalone abundance and to estimate important population characteristics such as rates of natural mortality.

Keywords: Haliotis rubra, abalone, dispersal, movement, aggregation, natural mortality, tag-loss, tag-recapture, stunted, growth.