Bluehead

Bluehead, Thalassoma bifasciatum

The Bluehead, Thalassoma bifasciatum, whose common Spanish name is cara de cotorra, is a member of the Wrasse or Labridae Family, known collectively as doncellas, señoritas, and viejas in Mexico. This fish is also known as the Bluehead Wrasse. The Bluehead is truly a gorgeous fish. Globally, there are 28 species in the genus Thalassoma, of which four are found in Mexican waters, this one in the Atlantic and three in the Pacific.

The Blueheads have elongated, compressed, and fusiform bodies with a depth that is 22% to 26% of standard length. Juveniles have a black mid-lateral stripe that changes into broken blotches with maturity; those found in coral reefs are yellow above and white below this stripe while inshore fish are all white. Females and males of the Initial Phase (IP) can have yellow heads and yellow upper bodies that abruptly transition to white ventrally with two square spots behind their eyes or they can have their mid-lateral stripe broken into a series of blotches and be yellowish to greenish on their back. They have the ability to quickly change colors as needed. Terminal Phase (TP) males, which make up only 4% of the population, have a blue head, black and white bars behind their head, and a green to blue-green body. Their caudal fin has black lobes and their pectoral fins have black margins. Their head has a blunt snout and mid-sized eyes. They have a small protrusible terminal mouth with thick lips, one pair of canine teeth at the front of both jaws, and a single row of conical teeth on the margin of both jaws. Their caudal fin changes with maturity being truncate or slightly rounded in juveniles and lunate in adults. Their anal fin has three spines and 10 or 11 rays and their dorsal fin has eight spines and 12 or 13 rays. Their lateral line is unbroken and bends down abruptly at the rear of the dorsal fin. They are covered with large scales.

The Blueheads are very common and found in large schools in and around coral reefs, inshore bays, and seagrasses at depths up to 140 feet in water temperatures between 23oC (73oF) and 26oC (79oF). Some of the larger reefs can contain up to 10,000 individuals. They reach a maximum length of 25.0 cm (9.8 inches). They have relatively small home ranges and adults do not leave the reefs where they have settled. They utilize their pectoral fins for swimming, thus appearing to drag their tail. They feed primarily on zooplankton and small benthic crustaceans including echinoderms (sea stars, brittle stars), mollusks, and polychaetes, as well as ectoparasites found on other fish. Reproduction is via protogynous sequential hermaphroditism with individuals beginning life as either male or female; females can change sex later in life and become males. Large terminal males collect in spawning aggregations in known breeding sites which are visited by females on a daily basis. Each male may spawn with up to 100 females a day. Fertilization is external and the eggs hatch within 24 hours; eggs and larvae are pelagic. They are known to be preyed upon by Graysby, Greater Soapfish, Red Hind, Roughtail Stingray, Spotted Moray, and Trumpetfish. They have a lifespan of up to three years. They are of current scientific interest as an important model for understanding the physiological and neurobiology basis of sex change.

The Blueheads are found in all Mexican waters of the Atlantic.

The Bluehead is most likely confused with the Clown Wrasse, Halichoeres maculipinna (three bars across face) and the Wrasse Blenny, Hemiemblemaria simula (spot behind third dorsal ray does not extend to caudal fin base).

From a conservation perspective, the Blueheads are considered of Least Concern being very common and found over a wide range. They are prone to coral reef destruction and local endangerment. Due to their beautiful coloration and hardiness, they are used extensively in the aquarium trade. They are not valued as food fish due to their small size. They are bold and will approach divers and snorkelers making them popular with underwater explorers. They are considered an important component of the reef environment providing services as cleaner fish by removing ectoparasites and dead tissues from the fins and gills of other fish.

Bluehead, Thalassoma bifasciatum, Juvenile. Fish caught from coastal waters off Key West, Florida, April 2017. Length: 10.1 cm (4.0 inches). Catch, photo, and identification courtesy of Dean Kimberly, Atlanta, GA.

Bluehead, Thalassoma bifasciatum, Initial Phase (IP) Female. Fish caught from coastal waters off Key West, Florida, April 2017. Length: 12.5 cm (4.9 inches). Catch, photo, and identification courtesy of Dean Kimberly, Atlanta, GA.

Bluehead, Thalassoma bifasciatum, Terminal Phase (TP) Male. Fish caught from coastal waters off Key West, Florida, April 2017. Length: 14 cm (5.5 inches). Catch, photo, and identification courtesy of Dean Kimberly, Atlanta, GA.