Red-shoulder Wrasse, Stethojulis bandanensis
Red-shoulder Wrasse, Stethojulis bandanensis. Fish caught from coastal waters off Taipei, Taiwan, October 2018. Length: 13 cm (5.1 inches). Catch, photograph and identification courtesy of Eli (obsessiveangling.word-press.com).
The Red-shoulder Wrasse, Stethojulis bandanensis, is a member of the Wrasse or Labridae Family, and is known in Mexico as vieja manga roja. Globally, there are ten species in the genus Stethojulis, with only this species found in Mexican waters, and it in the Pacific Ocean.
The Red-shoulder Wrasse has an elongated fusiform body with a depth that is 22% to 26% of standard length. Their coloration varies significantly by sex. Females In the Initial Phase (IP) are gray-brown with a thin white stripe along the head and below the eye that continues to the rear of the body. They have a yellow patch behind the mouth and below the eyes, a red blotch immediately above the pectoral fin base, numerous small white spots on the upper half of the sides. The ventral portions are whitish with the front half of the scales gray and a pair of small, black and white ocelli on the center of the caudal fin base. Terminal Phase (TP) males are blue green to yellow brown dorsally and bluish to whitish ventrally. They have a bright red patch above the pectoral fin base, four thin blue stripes on the head that continue onto the body with the upper and lower stripes extending to the caudal fin and the two middle stripes ending behind the pectoral fin base. They have a small terminal mouth equipped with conical teeth of uniform size. Their anal fin has 3 spines and 11 rays; their caudal fin is rounded; their dorsal fin has 9 spines and 11 rays; and, their pectoral fins have 14 or 15 rays. They are covered with large scales. Their lateral line is abruptly bent down behind the dorsal fins.
The Red-shoulder Wrasse are found in as solitary individuals or in small groups in and around coral and rocky reefs at depths up to 30 m (100 feet). They are sexually dimorphic with females reaching a maximum of 8 cm (3.2 inches) and males 15 cm (5.9 inches) in length. They feed on brittle stars, crabs, mollusks, and sea urchins. They have the ability to quickly bury themselves in the sand substrate as a defense mechanism and for sleeping. Reproduction is oviparous with distinct pairing. The Red-shoulder 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 Red-shoulder Wrasse is a resident of all Mexican waters of the Pacific Ocean but has a very limited distribution, being found in small isolated populations in coastal waters of the greater La Paz area, Baja California Sur, north of Puerto Vallarta, Jalisco. They are well known in the Indo-Pacific.
The Red-shoulder Wrasse is most likely confused with the Chameleon Wrasse, Halichoeres dispilus (similar markings but lack the red blotch immediately above the pectoral fin base).
From a conservation perspective the Red-shoulder Wrasse is currently considered to be of Least Concern with stable, widely distributed populations. They are too small in stature to be of interest to most. However, they are utilized by the aquarium trade at a small level but require high maintenance and are difficult to maintain.