Among the coelenterates, which are all aquatic animals, over 95% of the species are marine. Coelenterates have covered large areas of shallow sea bottom in the tropics mainly as reef-dwelling corals. Coelenterates on reefs, predominantly stony corals, soft corals, gorgonians, black corals, and sea anemones, form the basis of the richest shallow-water ecosystem of the world. To provide shelter and food to many other organisms, like trees in tropical rain forests.
It is ironic that the coral reefs of SE Asia, which are the richest in coelenterate species, also are the most critically threatened. Due to their biodiversity and productivity these reefs support the presence of large human populations, which, however, do not exploit their habitat in a sustainable way.
Exploitation and protection of reef corals.
Like other organisms, corals have various biological enemies. They are subject to predation, parasitic infestations, diseases, and to inter-specific competition. Present-day species that have succeeded to cope with these biological threats and interactions are now in danger. Species that are threatened with extinction are placed on lists to improve public awareness and to regulate their trade (Table 2 , Table 3 ). All the listed coelenterates are benthic. The criteria for their inclusion in the lists or exclusion from the lists are not always clear. For practical reasons, like the inability to identify the animals at species or genus level, the lists are of general nature. It would perhaps be more effective to exclude species that are only locally threatened, and to focus on species that are threatened with global extinction.
Coelenterates that are used in the jewel, aquarium and souvenir trade are in serious danger because of their systematic exploitation. Precious red and pink corals (Corallium spp.) and black corals (Antipatharia), which are listed by the IUCN (Table 2), are traditionally known as valuable merchandise for which special fishing gear has been developed in the Pacific and the Mediterranean. The awareness of over-fishing has stimulated the development of fisheries management and the cultivation of some Corallium spp. The absence of Corallium in CITES (Table 2) is due to strong lobbying by the precious coral industry.
Many species of stony corals represented in Table 3 are collected in SE Asia for the international aquarium and souvenir trade. Among dead corals traded, there are many belonging to branching species of Acropora, Pocillopora, and Seriatopora, mushroom corals, such as Fungia spp., and the blue octocoral Heliopora. The live corals selected for the aquarium trade are usually species with much soft tissue, preferably able to survive detached from a hard substratum, such as those belonging to the scleractinian genera Goniopora, Heliofungia, Polyphyllia, Trachyphyllia, Cynarina, Euphyllia, Catalaphyllia, Plerogyra, Physogyra, and Nemenzophyllia.
Export permits are still issued based on quota and therefore the regulation through CITES does not necessarily affect international trade. To coral taxonomists the annual quota for the export scleractinains seem to be unrealistically high. Exploitation of live corals should be made more sustainable by selective collecting and trade. Critaria proposed for consideration are:
(1) a minimum and maximum coral size per species,
(2) preference given to cultivated corals over those collected from the reef,
(3) control and guarantee of the least destructive way of collecting and transportation,
(4) temporary moratoriums in international trade, except for public aquaria and other institutions that try to cultivate them.