The effect of territorial adult pomacentrid fishes on the recruitment and survival of juveniles on patches of coral rubble

Abstract

Pomacentrus wardi Whitley is one species of a guild of territorial herbivorous pomacentrid fishes which compete for space within patches of rubble substrata on reefs of the Great Barrier. An experiment has been made on a series of adjacent patches of rubble to assess the importance of the presence of adult residents on the recruitment and survival of juvenile P. wardi, and on the use of the rubble patch by non-territorial benthic-feeding fishes. Recruitment of juvenile P. wardi, and survival of experimentally added juvenile P. wardi were both greater in patches from which all adult pomacentrids had been removed than in patches with undisturbed adult populations. Patches in which the removal of adults was only partially successful did not show these effects. Experimentally added juveniles survived only poorly, whether in undisturbed patches or in patches first denuded of adults. Denuded patches were visited by greater numbers of roving benthic-feeding fishes than were undisturbed patches. Numbers of adult pomacentrids varied little over a year in undisturbed patches, and recovered within six months in denuded patches. The results are discussed with reference to the coexistence of P. wardi and other members of its guild.