Size: Male P. sp. 'steveni taiwan' can attain a maximum total length of about 17 cm, while females usually stay several centimeters smaller with a maximum total length of about 13 cm.
Habitat: P. sp. ‘steveni taiwan’ inhabits the pure rocky habitats which mainly consists of huge boulders. Territorial males defend territories on top of rocks at rather deep levels—most males are found at a depth of more than 15 meters. Most of the year there is a heavy current around the reef, sometimes so strong that it is difficult for a diver to swim against, even with fins! The only species that braves such a current is P. saulosi. P. sp. ‘steveni taiwan’ may have been forced by the current, which is strongest at the top of the reef, to settle in deeper regions. Females can sometimes be seen in shallower water, usually in loose groups of less than 25 members.
Breeding: Territorial males defend a large section on the upper side of a large boulder. They feed from within their territories but not from the spawning site which often shows a lush growth of algae since all other herbivores are prevented from feeding there as well. Ripe females can thus at once see the spawning site within the male’s territory and judge the safety of its position. Mouthbrooding females are normally found by themselves and do not gather in nursery schools.
Comments: In contrast to P. sp. ‘steveni imperial’, which is often sympatric with other Stevenis, P. sp. ‘steveni taiwan’ is the only Steveni found in its area of distribution. Given the distribution and habitat preference of P. sp. ‘steveni taiwan’ I believe that it is old enough to have been present at low lake levels thousands of years ago. Their current discontinuous distribution possibly represents relict populations from such a period. It may share a common ancestor with P. taeniolatus and P. sp. ‘steveni taiwan’, but due to the complete isolation from all other populations it may have developed into a different species, adapted to their specific environment. The relatively large eye of P. sp. ‘steveni taiwan’ could therefore be an adaptation to the depth at which it lives.