The selachians are fish whose skeleton consists of cartilage.  In the lagoons they are the sharks and the stingrays. In the atolls the diversity of Selachians is relatively low.

Sharks 

Among the frequent sharks one counts 4 species:  the black tip shark, the white tip shark, the gray shark and the lemon shark.

• The black tip shark (Carcharinus melanopterus) ou mao mauri,

• the white tip shark (Trianodon obesus) ou mao mamaru, 

• the grey shark (Carcharninus amblyrhinchos) ou raira, which can form relatively significant concentrations, particularly in the passes and around the pinnacles,

• the lemon shark (Negaprion acutidens) ou mao arava. 

The other sharks are generally solitary, like the tigersharks (Galeocerdo cuvieri ; mao tore tore) and the nurseshark (Nebrius ferrugineus ; mao rohoi)

On the biotope of the external slopes of the atolls,  there are also Carcharinus albimarginatus.

In pelagic water around the atolls There are other sharks which seldom enter inside the atolls: hammerhead, open sea white fin, "mako" and whaleshark.

The stingrays 

The stingrays are the other selachians present in the lagoons. There are only very few species of stingrays in Polynesia and their density is always low (except for occasional concentrations on shallow waters of some atolls). In the atolls one observes especially Himantura fai, a stingray which lives in the mud-bottoms of the lagoons, where it feed on molluscs and shellfishes.  

The "manta" stingrays, very great species which reaches more than 2 m,  can mostly be seen in the large atolls, generally near the passes. This species is pelagic, swimming constantly in full water and mainly feeding on plankton.