Emerald Wrasse, Thalassoma virens

The Emerald Wrasse, Thalassoma virens, is a member of the Wrasse or Labridae Family, and is known in Mexico as señorita esmeralda. Globally, there are twenty-eight species in the genus Thalassoma, of which four are found in Mexican waters, one in the Atlantic and three in the Pacific Ocean.

The Emerald Wrasse has an elongated compressed bodies with a depth that is 33% to 36% of standard length. Females and males in the Initial Phase (IP) have a dull green coloration with red-brown spots that afford a vertical pattern of wide broken stripes. Their head is covered with small red spots and vertical broken stripes. Their fins are darker than the body. Terminal phase (TP) males have a uniform greenish-blue coloration which extends to the fins. They have a small terminal mouth equipped with enlarged canine teeth at the front of both jaws (one pair above and one pair below). Their anal fin has 3 spines and 10 to 12 rays; their caudal fin is slightly concave in females and has long pointed lobes in males; their first dorsal fin has 8 spines; their second dorsal fin has 12 or 13 rays; and, their pectoral fins have 15 or 16 rays. They are covered with large scales.

The Emerald Wrasses are coastal residents found within rocky shores exposed to surges from the intertidal zone at depths up to 9 m (30 feet). They reach a maximum of 36.6 cm (14.4 inches) in length established by the fish I caught and pictured above. They feed diurnally on small crustaceans, sea urchins, mollusks, and brittle stars. The Emerald Wrasse is poorly studied with very limited information available about their lifestyle and behavioral patterns including specific details on age, growth, longevity, movement patterns, diet, habitat use, and reproduction.

The Emerald Wrasse is a resident of Mexican waters of the Pacific Ocean but has a very limited distribution being found from the tip of the Baja, Baja California Sur, as established by fish that I have caught, northwards to La Paz within the Sea of Cortez, and around the Revillagigedo Islands.

The Emerald Wrasse is a fairly easy identification and cannot be confused with any other species due to its unique colorations with one possible exception being the Banded Wrasse, Halichoeres notospilus (dark bars on the sides that extend into the dorsal fin).

Note: several productive discussions with Dr. Benjamin Victor (www.coralreeffish.com) related to the lifestyle of this species are acknowledged. Dr. Victor believes that the Emerald Wrasse “settled out” in the Los Cabos area during periods of El Niño and these are mostly similar to 1998–1999 fish. He also indicated that they are elusive, secretive, and exceedingly fast swimmers that spend a significant amount of time in the high surge zones very close to shore. The Emerald Wrasses are small and of limited interest to most but they are a gorgeous fish! They are retained by subsistence fishermen.