Almost every reef fish gets out of the way of breaking waves. This one lives in them.
The whitebar damselfish holds the surge zone: the top few meters over the reef crest, where the water runs one way, stops, and runs back, and the visibility is half foam. It grazes algae off the rock between sets and jams itself into a hole when the next one arrives. Divers rarely go there because there is nothing to do in a meter of moving water and a lot of rock to be pushed onto, so a fish that is genuinely common goes largely unrecorded. Snorkelers along a rocky shoreline meet it constantly.
One mark does most of the identification: a single broad pale bar across the middle of a dark olive-brown body, with the rear end paler than the front. Below the back of the dorsal fin there is a dark spot, ringed and eye-like in young fish and fading as the fish grows. Nothing else in that habitat looks like it.
Like the other algal-turf damsels it defends a patch of rock and treats everything that swims over it as a thief. The size limit is 12 cm, which in surge is enough fish to hold a position against animals that could swallow it in calm water.
Eggs are laid on cleaned rock, stick where they are put, and are guarded and fanned by the male until they hatch, which is the only way demersal eggs survive in that much water movement. The species runs from the 🌊 Red Sea across the Indo-Pacific to Pitcairn, a very large range for a fish tied to one narrow band of habitat.
The genus. Plectroglyphidodon Fowler & Ball 1924 - plectro- (plaited). ETYFish
- dark olive-brown body crossed by one broad pale bar at mid-body
- dark spot below the rear of the dorsal fin, eye-like in young fish and fading with age
- pale tail and pale rear body behind the bar
- in the top few meters, in the whitewater, wedged among rocks
- up to 12 cm
Why it's threatened
There are no known major threats.
Threat classification from the IUCN Red List.
