Hydnophora exesa is widespread and relatively common throughout its range (1) (4), but is under threat from many of the factors affecting coral species worldwide (1). It is estimated that 20 percent of the world’s coral reefs have already been effectively destroyed and show no immediate prospect of recovery, and 24 percent of the world’s reefs are under imminent risk of collapse due to human pressures. These human impacts include poor land management practices that are releasing more sediment, nutrients and pollutants into the oceans and stressing the fragile reef ecosystem. Over fishing has ‘knock-on’ effects that results in the increase of macro-algae
[ ] that can out-compete and smother corals, and fishing using destructive methods physically devastates the reef (7).
The major threat to corals is global climate change, with the expected rise in ocean temperatures increasing the risk of coral ‘bleaching’, in which the stressed coral expels its zooxanthellae, often resulting in the death of the coral. Climate change may also lead to more frequent, severe storms, which can damage reefs, and rising carbon dioxide levels may make the ocean increasingly acidic, reducing the ability of coral to create its hard skeleton. Such stresses can also make corals more susceptible to disease, parasites and predators, such as the crown of thorns sea star (Acanthaster planci) (1) (7) (8) (9) (10).
These global threats are compounded by localised human impacts, such as coral harvesting, disturbance by fisheries, irresponsible tourism, invasive species, pollution and sedimentation (1) (7) (8) (9) (11). Hydnophora exesa is popular in the live aquarium trade. In 2005 Fiji had a quota of 662 live pieces, but Indonesia is the main exporter, with a quota of 10,900 pieces exported in 2005 (1).