This month’s fish is the Ringscale Triplefin, Enneapterygius atrogulare. Triplefins are a family of small substrate-living fishes, probably related to the blennies and gobies. They derive their name – surprise – from the fact that they have their dorsal fin split in three. It’s nice to have common names that are descriptive, even though such fish as the old wifes and the stinkfish are always good for a laugh.
The interesting thing about the triplefins is that they are sexually dimorphic. No, that’s not something you will see at the upcoming Mardi Gras parade in Sydney, but it means that the male and female fish look differently. The males are striking red with a black head, while the females are drab brown. While the reason for this is not certain, it often has to do with male territorial behavior. The male fish owns a small patch of rock, and uses his striking colors to fend off other males, whereas, naturally, he does not take an aggressive stance against females in his vicinity.
While they are somewhat tricky to find, these fish are not that hard to photograph, since they like to stick to their piece of rock. Even once they get spooked, they usually come back within a minute or so.