Bluestreak Cleaner Wrasse

This is a young wrasse, averaging 10 cm (3.9 in) long, at most 14 cm (5.5 in). It can be recognized due to a wide, longitudinal, black stripe running along the side and eye; the back and the stomach are white (sometimes slightly yellowish). This white part changes to a bright blue on the front of the animal, while the black band widens at the tail. The young are black with an electric-blue line.

The bluestreak cleaner wrasse is found on coral reefs in the tropics from the Red Sea and Indian Ocean to the western Pacific (including Papua New Guinea, Japan, Fiji, and French Polynesia). It was first recorded from the Kermadec Islands Marine Reserve north of New Zealand in 2015, after researchers examined hundreds of hours of unused documentary film footage.

Cleaner wrasse males defend specific living territories from other males in which they are able to have control over the females in those territories. When the dominant male no longer exists in that territory, one of the larger females is able to change sexes to take control over that territory.