Recruitment dynamics and growth of the barnacle Tetraclita serrata on the east coast of southern Africa

Abstract

Recruitment of Tetraclita serrata was determined from archival photographs of permanent 0·25 m2 quadrats at several sites along the Transkei coast. Periodogram analyses revealed regular annual recruitment although both spatial and interannual variation in recruitment intensity was high. Differences in long-term abundance between sites showed no geographic pattern nor were they related to human disturbance. Recruitment intensity, however, was found to be related to mean abundance indicating limited larval dispersal. Barnacles increased in basal diameter by 7·6 mm in the first year, declining to 4 mm by the third year. Individual growth was variable with bursts of rapid growth interspersed with periods of little or no growth. Barnacles larger than 20 mm comprised only 6% of the population and an analysis of individual longevity indicated a mean lifespan of 2·7 ± 1 year (SD). The important role of this species in structuring intertidal communities is discussed in relation to the effects of human exploitation.