Acanthuridae (surgeonfishes) are another great group of fish which comprises two sub-groups: the Naso and the doctorfishes.

Doctorfishes

The doctorfishes are named thus because a kind of scalpel arms their tail. These fish have a round form and generally rather drab colours (black, brown, gray dark). They often form significant shoals in the passes or on their proximity. The majority of the species are herbivorous, but some feeds primarily on plankton. Many doctorfishes are required for their flesh, although they can sometimes be toxic. Most common, the maito, is however so often toxic that it is forbidden for sale. The doctorfishes also have a rather long life, their initial growth being very fast, reaching rather quickly sexual maturity. When maturity, the growth slows down considerably. These fish are less vulnerable than the loaches because they reproduce younger but also recruitment is in general significant, thus compensating for the strong mortality which some of these species (predation and fishing) undergo.

Naso spp.

Naso spp., or unicorn fishes, are characterized by an excrescence on the face. The Polynesians particularly appreciate their flesh and in some islands certain species (ume) were reserved to the chiefs. Naso spp. are divided into herbivorous species (Naso unicornis and N.lituratus), planctophages species (N.annulatus, N.hexacanthus, N.caesius) and mixed species which are initially herbivorous (when young) then planctophages (N.brevirostris, N.vlamingi). Naso spp. live in general in shoals. Their biology is rather badly known, but they would have a fast growth and a relatively early reproduction what makes them less vulnerable to fishing. These fish can be seen especially in the large atolls, most of the time around the pinnacles and to a lesser extent near the passes.