IMIS

Density and size of Chromis fumea (Pisces: Pomacentridae) were regularly monitored during 13 months (from August 1996 to August 1997), on two artificial reefs in New Caledonia (south-west Pacific ocean): a ship-wreck (CT2) just after scuttling, and an assemblage of iron boxes (Caissons) sunk more than 50 years ago. The settlement of C. fumea was first observed 20 August 1996 and lasted 20 days. At the beginning the recruits were 1 cm size-class fish and at the end 2 cm size-class. This major settlement phase was again observed one year later (September 1997). A second minor settlement phase occurred in December 1996 on CT2. Significant immigration of adults was also observed between November 1996 (6 cm) and April 1997 (7 cm), indicating that this species is capable of medium range migration (>50 m). Population size decreased by 87·8% between the settlement of juveniles and the first immigration phase of adults. The final density of the 1996 cohort was 10·5% of the initial input of recruits on CT2 and 19·3% on Caissons. Initial density of recruits was 3·4 times higher on CT2 than on Caissons, whereas density of juveniles was similar at the end of the survey, indicating that post-settlement mortality was greater on CT2. Chromis fumea von Bertalanffy growth models were similar on CT2 and Caissons. This short-lived species is characterized by an initial rapid growth phase (K>3·36 y−1), with the fish reaching 68·5% of L∞ in three months, and a second slower growth phase (1 cm in ten months).