Population dynamics and overgrowth of the sea fan Eunicella cavolini (Coelenterata: Octocorallia)

The population dynamics of Eunicella cavolini Koch was investigated from 1989-91 at three study sites in the Bay of Calvi (Corsica, France). Population density was highest in the channel (149-180 colonies m(-2)), intermediate at the wall (54-66 colonies m(-2)) and lowest at the boulders (15-19 colonies m(-2)). Mortality, expressed as percentage of colonies that died within 1 year of investigation, did not differ between the study sites and showed large variability (8.3-26.7%). Expressed as percentage of new colonies on total colony numbers, recruitment was highest in the channel (11.7-20.1%), intermediate at the wall (7.4-12.0%) and lowest at the boulders (0-8.3%). A growth formula for E. cavolini developed in an earlier study (Velimirov, 1975) was shown to be suitable for the investigated study sites. The estimated maximum age was 21 years. Age frequency distribution did not vary strongly between subsequent years during the 3-year investigation. However, the age structure differed strongly between study sites. Overgrowth of colonies was highest at the boulders, intermediate at the wall and lowest in the channel. Overgrowth increased with colony age until the age of 4 years. Mortality of E. cavolini is mainly due to detachment and overgrowth. (C) 1996 Academic Press Limited