Rock Wrasse, Halichoeres semicinctus
The Rock Wrasse, Halichoeres semicinctus, whose common Spanish name is Señorita Piedrera, is a member of the Wrasse or Labridae Family, known collectively as “doncellas”, “señoritas” and “viejas” in Mexico.
The Rock Wrasse has an elongated compressed body with a width that is 29-34% of standard length with the body becoming wider with maturity. The females and males of the initial phase (IP) are pale green to pale yellow orange with scattered black dots on the upper back. The fins are of similar color to the body. The terminal phase (TP) males (normally longer than 30 cm) are similar to the IP individuals except they have a prominent pale-edged black bar mid-body just behind the gill openings. The fins are of similar color to the body except pectoral fins are yellow. Juveniles have a white mid-lateral stripe and a black ocellated spot in the middle of the dorsal fin. The head has a small terminal mouth equipped with two pairs of enlarged canine teeth at the front of both jaws and a prominent large canine at the rear of the top jaw. The caudal fin is straight or slightly rounded and the dorsal fin has nine spines and twelve rays. The body is covered with large scales.
The Rock Wrasse is found over sandy or rubble bottoms adjacent to rocky reefs from within tidal pools to depths up to 260 feet. They reach a maximum length of 38 cm (15 inches). At night they sleep half buried in sand with their head protruding and have been found stranded on some occasions in the early morning by overnight very low tides. During the day they forage for small invertebrates. In Mexican waters the Rock Wrasse is found along the entire west coast of Baja and throughout the Sea of Cortez; they are absent from along the coast of the mainland south to Guatemala. They are a small, rare, poorly studied species and very limited information is available about their behavioral patterns.
The Rock Wrasse is most likely confused with the Chameleon Wrasse, Halichoeres dispilus (black blue-ringed blotch just below the third and fourth dorsal spines) and the Red Shouldered Wrasse, Stethojulis bandanensis (small teeth; thin blue stripes on head and upper back).
The Rock Wrasse is too rare and too small to be of interest to most.