Live coral trade impacts on the mushroom coral Heliofungia actiniformis in Indonesia : potential future management approaches

Abstract

The poorly regulated aquarium trade in live corals poses yet another threat to fragile coral reef ecosystems. The Indonesian authorities routinely allocate some of the highest trade quotas in South Sulawesi to Heliofungia actiniformis despite a lack of data on the impacts of current collection practices on this species. Semi-structured interviews with fishermen and in situ surveys revealed a size-selective fishery towards small polyps. This resulted in a shift of size-frequency distributions, and reduced overall abundances at harvested sites. Total mortality rates calculated using a catch curve approach at harvested sites were significantly higher compared to those known from unharvested sites for polyps sized 0–11 cm. Recorded exploitation rates were 0.1 and 0.7 for polyps sized 0–4 cm and 4–11 cm respectively. The application of a utility per recruit approach, calculated with a Thompson and Bell model, revealed maximum potential economic yield to occur at a size of 5 cm, corresponding to an age of 5 years. This is 5 years before the attainment of reproductive maturity, and 15 years before the attainment of maximum biomass yield per recruit. A predictive model indicated the need for a 5 cm size limit to curb economic overfishing, and protect attached anthocauli stalks capable of maintaining the trade through continued asexual reproduction. In addition, a reduction of exploitation rates for polyps in the 4–11 cm size bracket to 0.5 is urgently needed. Calculations reveal that this would in fact be possible without lowering current profits. Achieving long term sustainability will in addition to a reduction of harvest quotas necessitate an effective protection of spawning stocks through stricter enforcement of existing marine protected areas.