Aspects of the population dynamics ofChthamalus dentatus(Crustacea: Cirripedia) on the Transkei coast of southern Africa

Abstract

Long-term fluctuations (3–9 years) in the abundance of the barnacle Chthamalus dentatus were determined from archival photographs of permanent 0,25 m2 quadrats in the mid-littoral at 11 sites along the Transkei coast. These data were combined with a more detailed analysis of growth and recruitment over one year. Recruitment occurred in spring and autumn, but periodogram analyses revealed additional cycles with frequencies of 24–36 months. There was no geographic pattern in long-term differences in abundance between sites nor were these related to human disturbance. Recruitment intensity was significantly related to mean abundance of adults, which may indicate limited larval dispersal or gregarious settlement. Maximum aperture length increased by 3,0 mm in the first year but increased by only 1 mm·year−1 in the third year. Individual growth was variable, with small individuals often overtaking larger ones. There were few large individuals, those of 7,0 mm or more constituting only 3% of the population. An analysis of longevity indicated a mean lifespan of 1,5 + 0,5 years.