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. Globally, there are seventy species in the genus Halichoeres, of which nineteen are found in Mexican waters, ten in the Atlantic and nine in the Pacific.
The Rock Wrasses have elongated compressed bodies with a depth that is 29 to 34% of standard length; more mature fish have wider bodies. Females and males of the Initial Phase (IP) are pale green to pale yellow-orange with scattered black dots on their upper back. Their fins are similar in color to the body. Terminal Phase (TP) Males are normally longer than 30 cm and similar to IP individuals except that they have a prominent pale-edged black bar mid-body just behind their gill openings. Their fins are similar in color to the body except for the pectoral fins, which are yellow. Juveniles have a white mid-lateral stripe and a black ocellated spot in the middle of their dorsal fin. They have a small terminal mouth equipped with two pairs of enlarged canine teeth at the front of both jaws and a prominent large canine tooth at the rear of their top jaw. Their caudal fin is straight or slightly rounded and their dorsal fin has nine spines and twelve rays. Their body is covered with large scales.
The Rock Wrasses are found over sandy or rubble bottoms adjacent to rocky reefs within tidal pools at depths up to 260 feet. They reach a maximum length of 38 cm (15 inches). They sleep half-buried in sand at night with their head protruding and are occasionally found stranded by overnight very low tides in the early morning. During the day they forage for small invertebrates. In Mexican waters they are found along the entire west coast of Baja and throughout the Sea of Cortez and are absent from along the coast of the mainland south to Guatemala. They are a rare and poorly studied species and very little is known about their behavioral patterns.
The Rock Wrasse is most likely confused with the Chameleon Wrasse, Halichoeres dispilus (black-blue ringed blotch just below third and fourth dorsal spines) and the Red-Shoulder Wrasse, Stethojulis bandanensis (small teeth; thin blue stripes on head and upper back).
The Rock Wrasses are too rare and too small to be of interest to most.