Estimates of adult and juvenile mortality for labrid fishes at One Tree Reef,Great Barrier Reef

Few estimates of natural mortality have been reported for coral reef fishes, yet this information is essential for predicting the effects of recruitment fluctuations on adult populations. In this study, mortality of adult (10 species) and juvenile (11 species) labrid fishes resident on ten isolated patch reefs in One Tree Lagoon, southern Great Barrier Reef, was estimated by visual censuses covering 30 mo, from November 1981 to April 1984. Numbers of adults of all species declined linearly over this period. Mortality rates differed significantly among species, ranging from 4.9 to 69.5% per annum. Average life-span for fishes that had survived the first year of life varied from 1.6 to 11.5 yr, depending on species. Average juvenile mortality varied among species from 25 to 91.8% per annum and was highest for abundant schooling species. Different cohorts of the same species also experienced significantly different rates of mortality. No clear relationship emerged between the number of new recruits and the number of fishes surviving to one year of age. The influence of recruitment fluctuations on adult populations of labrid fishes may be difficult to predict.