Age, growth and retrospective stock assessment of an economically extinct sparid fish, Polysteganus undulosus, from South Africa

Age and growth of the endemic, reef-dwelling sparid, Polysteganus undulosus were determined by using archived otoliths collected in 1962 and 1963, bef ore the fishery collapsed. Estimates of age ranged up to 20 years, but repr oducibility of the age estimates was low because of stacking on the otolith margins in older fish. Validation of annual deposition of the opaque band indicated that active deposition occurred during late winter and spring. No difference in growth rate between the sexes was observed and the growth ra te for the combined sexes was described by the following logistic equation: L-t = 942 mm TL/(1 + exp(-0.277 year(-1)(t - 5.178 years))). The age-at-50 % maturity was 8.8 years. A retrospective stock assessment revealed that, a lthough in the early 1960s, the yield-per-recruit, was optimal, the spawnin g biomass of P. undulosus was already at 25% of its unfished level. This st udy thus suggests that management strategies for slow-growing, long-lived, aggregating reef fishes should go beyond optimising yield alone and pay par ticular attention to the status of the spawning stock. (C) 2001 Elsevier Sc ience B.V. All rights reserved.