The ecological significance of the combtoothed blenny in a coral reef ecosystem

At Heron Island reef, Great Barrier Reef Australia, biomass densities and mean wet mass of Ward's damselfish Pomacentrus wardi and the jewelled blenny Salarias fasciatus were not significantly different at 2·37 v . 2·95 g m⁻² and 8·7 v . 7·9 g, respectively. Whereas S. fasciatus significantly exceeded P. wardi in (1) total number of bites per day (3427 v . 1155), (2) the mass of epilithic algal community consumed per bite (2·19 v . 0·14 mg) and (3) total organic carbon consumed per day (487·31 v . 35·46 mg C m⁻² day⁻¹). Territorial behaviour differed also between the two species. Pomacentrus wardi chased from their territories a smaller proportion of blennies than roving grazers ( i.e . scarids, acanthurids, siganids and pomacentrids) relative to S. fasciatus . Salarias fasciatus chased c . 90% of other blennies from their territories, while chasing only c . 20% of all damsels that entered. Both P. wardi and S. fasciatus rarely chased non‐grazers. The chasing behaviour of S. fasciatus was size dependent, with resident fish chasing only individuals of its own family ( i.e . Blenniidae) that were the same or smaller size. Pomacentrus wardi may have tolerated S. fasciatus grazing within its territory, as it contributes to territory defence from other blennies. The possibility that the interaction between the two species is facilitative, rather than competitive, is discussed. It was concluded that salariine blennies play an important, and previously underestimated role in coral reef trophodynamics.