In general, the numbers of individuals of different species are limited. To a degree, this is very obvious, as no species can ever grow to unlimited numbers, which if not kept in check by something, all species could. The actual regulatory mechanism is often thought to be either by competition for species capable of exhausting their resources (or having them exhausted by other, competing species) or by predators keeping prey numbers so low that the prey never experience any lack of the limiting resource. Do note that this means that animals either starve on a regular basis, or live in more or less constant fear of being killed!. The cuddly-feely-touchy-nature-is-so-wonderful scenario is probably more or less always wrong. But, I digress from the subject of this post, which is why so many species of scorpion fish coexist in Lembeh, given that they all are predators, and given that they all eat fish.
In general, coexistence for species limited by resources requires that the species in question differ somewhat in their resource use. In scorpion fish this probably happens through two mechanisms.
The first would be for different species to use different parts of the strait. This clearly happens, which is why no one would look for Ambon scorpion fish in coral patches, no one would look for bearded scorpion fish on sand flats and the only place you would expect to find blotchfin scorpion fish would be in rubble, where you would also find the paddle flap rhinopias. Even within a specific habitat, scorpion fish can limit competition by choosing different hunting grounds. In coral covered areas, leaf fish often hunt perched on exposed coral heads, while bearded scorpion fish lie in ambush at coral bases. As there are so many habitats in Lembeh, many different scorpion fish can coexist without competing with each other.
Species specific habitat choice probably takes care of most of the potential competition among scorpion fish. Remaining interspecific competition is to a high degree reduced by size differences, and thus differences in prey sizes, among coexisting scorpion fish. Thus demon stingers who often coexist with Ambon scorpion fish will take much larger prey than the Ambons take, and bearded scorpion fish and coral scorpion fish, coexisting on coral patches, will have no overlap in diet choice.
In this way, by a primary difference in habitat choice and a secondary difference in sizes when coexisting in the same habitat, many species of scorpion fish can coexist in the same general area. That, being a diver that likes scorpion fish, is a great thing!
