Developmental delays, recruitment storage and adult attrition rates in local populations of a tropical damselfish
Proceedings of the 10th International Coral Reef Symposium
Storage of recruitment variation in the adult life stage and developmental time lags are important to the dynamical and persistence properties of populations. We explored these aspects for the three-spot dascyllus (Dascyllus trimaculatus), a tropical reef planktivore that has a three-stage life history. After a planktonic dispersal phase, larvae of D. trimaculatus settle to sea anemones where they shelter as juveniles until they become free-living at maturity. In this system, adult dynamics could be influenced by fluctuations both in larval settlement per unit of suitable habitat and in the abundance of sea anemones, the essential habitat for the immature stages. Here we estimated (1) the time lag in settlement after suitable habitat becomes available, (2) the developmental delay between initial larval settlement and maturity (juvenile stage duration), and (3) the rate of attrition of the local adult population following cessation of recruitment from the juvenile stage (adult ‘storage’). Initial larval colonization occurred within a few days of anemones becoming available. The lag between initial larval settlement and first appearance of adult-stage fish was ~ one year. When juvenile habitat (sea anemones) was extirpated, local abundance of adult D. trimaculatus began tracking downward within a few weeks of anemone loss and the local population functionally became extinct after ~ two years (range 14 to 36 months). The attrition rate of adult fish over the first year, a time equivalent to the juvenile developmental period, was ~ 60%. That there was relatively little ‘storage’ of juvenile recruitment in the adult population indicates that the throughput of juveniles will have a dominant influence on the dynamics of adult stage D. trimaculatus.