Description:

Dorsal spines: 3 (last very small under skin); Dorsal rays: 26-28; Anal spines: 0; Anal rays: 23–25.

Reddish brown upper body and pale grey below, colours divided by a narrow blue stripe from the pectoral fin to the tail. Skin between scales on lower body dark. Small mouth 
that opens a little above centre line of body, lower jaw projecting. Distinct groove before eye and below nostril. 5-6 blue, scaleless oblique grooves on cheek. An orange 
bar edged in blue runs from behind the eye to the base of the pectoral fin. Tail strongly concave, blue grey, with dark posterior margin and bright red side margins.

Maturity: Lm unknown. Range unknown. Max Length: 35cm TL.

Usually occurs in deep seaward reefs (depth 15-200m, usually 50-200m). Planktivore feeding on zooplankton and fish larvae. Taken occasionally by bottom fishing. 
The main population is believed to live below 75m.
 

This species is not protected or subject to fishery regulations. It is caught in the hand line fishery, but is a very rare component of the catch.

Discover Life. Xanthichthys caeruleolineatus Randall, Matsuura &. Zama, 1978 BLUELINE TRIGGERFISH https://www.discoverlife.org/20/q?search=Xanthichthys+caeruleolineatus (06/11/18).
Encyclopedia of Life. Xanthichthys caeruleolineatus Outrigger Triggerfish.  http://eol.org/pages/212552/overview (06/11/18).
Froese, R. & D. Pauly. Eds. (2018). Fishbase. https://www.fishbase.de/summary/Xanthichthys-caeruleolineatus (06/11/18).
Hoover, J.P. (2005). Blueline Triggerfish Xanthichthys caeruleolineatus hawaiisfishes.com. http://www.hawaiisfishes.com/fish_of_month/past_fom/fom_09_05.htm (06/11/18). 

Nevill, J.E.G. (2019). Xanthichthys caeruleolineatus, Outrigger triggerfish. Seychelles Seatizens. www.seatizens.sc. https://seatizens.sc/species/xanthichthys-caeruleolineatus-randall-matsuura-zama-1978/ (edited 19/06/22).