The Bloodfish (Sanguichthys rufus, meaning Red Bloodfish) was a cyprinid which inhabited Skull island's backwater canals and freshwater estuaries. Its bright red coloring was thought to provide it camouflage against the murky tannin stained water that was its preferred.
The ancestor of blood fish was thought to have been a barb in the puntius genus. It was theorized that the ancestral blood fish was introduced to skull island around eight thousand years ago by proto-Malayan's who sought to settle the island. The barb was likely imported as a domestic food fish. Exactly how the islanders transported the fish to the island is an enigma, however the success of their efforts hint at an extremely high level of technological sophistication. Following their arrival(as with all alien species) the barbs escaped into wild waterways. Skull island's native class of fish Dipterus, were an extremely diverse cast of lungfish, relics of the Permian period. Because of their isolation, evolution left them woefully unprepared for the barbs. Soon intense competition for food and attrition from foreign disease drove most of the lungfish to extinction. The two remaining species included the infamous piranhadon and the grotesque skull island panderichthys malus (which only superficially resembled the Devonian age panderichthys). Having wiped out most of the indigenous fish species the barbs diversified into the myriad of fish germane to skull island. Soon vacated niches were filled by an eccentric freak show, from the clumsy stink fish to the vicious needle mouth and the rosy red blood fish.
The barbs essentially replaced the lungfish. In skull island's freshwater ecosystem blood fish were omnivorous opportunists which kept the local insect populace in check. During the breeding season of death wasps and needle gnats vast schools of blood fish congregated near the surface feasting on larvae and unwary adults. During seasons when the insects migrated away from water the blood fish reverted to their barb like habits and scavenged detritus from the water beds. Blood fish was the most popular prey for medium sized skull island aquatic predators. A few neopedes subsisted entirely on them. Despite dedicated efforts blood fish did not survive skull island's destruction. Their remote domain made them impossible to capture and conserve.