Three pretty colors of ribbon eels can be observed in sandy or rubble areas close to reefs. Most scuba divers will only see their heads sticking out while a free swimming ribbon eel is an exciting and rare sight. These eels can grow up to a size of 130 cm.
It was long believed that the black, blue and yellow ribbon eel are separate species. However, they are all the same at different stages of age and gender. Ribbon eels start their life as male black eels, change to male blue when adult and at a last stage they become yellow females.
Therefore ribbon eels are called protandrous hermaphrodite as all females derived from males.
There is different theories when they change to female. The females are larger so they might change gender when reaching a certain size. Another theory says that if two ribbon eels are in the same area one can change into female if it is essential for the survival of the species. Most probably both theories are correct.
While the ribbon eels can live for up to 20 years it is very unusual to see a yellow female ribbon eel as they die shortly after mating and laying eggs. In the male phase the eels might stay in the same hole for years.
One threat is the aquarium trade as the ribbon eels mostly don’t survive long in captivity and can’t be bred in tanks.