LOCAL-SCALE PATTERNS OF LARVAL SETTLEMENT IN A PLANKTIVOROUS DAMSELFISH - DO THEY PREDICT RECRUITMENT

The degree to which local-scale spatial variation in larval supply pre dicted subsequent patterns in juvenile densities was examined for a pl anktivorous damselfish (Dascyllus trimaculatus) at Moorea, French Poly nesia. D. trimaculatus young settle from the plankton to sea anemones, where they remain until becoming free-ranging adults. Daily settlemen t onto anemones without fish was estimated at several sites in a lagoo n for one 14-day period and compared with patterns in the density of j uveniles that had accrued after 10 successive settlement periods. Spat ial variation attributable to larval supply occurred mostly among indi vidual anemones, between the halves of each study site, and among diff erent locations in the lagoon. In contrast, there was relatively littl e variation at any spatial scale in the density of young after 10 sett lement pulses. Several mechanisms were examined that could account for the observed reduction in spatial variance through time, and three in volving interactions with young already present were implicated. First , settlement was not independent of residents (the density of young al ready on an anemone); compared with the absence of fish, settlement wa s facilitated at low and inhibited at high densities of residents. Sec ond, older juveniles moved among local anemones, and the immigration a nd emigration rates per capita varied with density on an anemone. Fina lly, per capita mortality during the first few days after settlement w as density-dependent. These findings emphasize the critical need to di stinguish among effects that arise from the delivery of larvae, the av ailability of appropriate habitat, and interactions that affect fish a t settlement and immediately thereafter.