Swallow Damselfish, Azurina hirundo
Swallow Damselfish, Azurina hirundo. Fish caught from coastal waters off Santa Catalina Island, May 2018. Length: 13 cm (5.1 inches). Catch, photograph and identification courtesy of Eli (obsessiveangling.wordpress.com).
The Swallow Damselfish, Azurina hirundo, is a member of the Damselfish or Pomacentridae Family, and is known in Mexico as castañuela golondrina. Globally, there are two species in the genus Azuina, of which this species in the only species found in Mexican waters of the Pacific Ocean.
The Swallow Damselfish has an elongated, slender, fusiform, compressed body with a depth that is 25% to 33% of standard length. They are a steel blue color being darker dorsally with an orange hue on throat. They have a prominent black spot at the base of their pectoral fins and the margin of their caudal fin is white and the outer half of their pectoral fins are yellow. Their head is pointed with similar upper and lower profiles with a small terminal protrusible slightly oblique mouth that opens in the front that is equipped with two rows of teeth. Their anal fin has 2 spines and 12 or 13 rays and is low; their caudal fin is strongly forked; their dorsal fin has 12 spines and 10 to 12 rays and is low; and they have 20 or 21 pectoral rays. They have 25 to 27 gill rakers on their lower arch. Their body is covered with large rough scales. Their lateral line is incomplete and runs along the top of the caudal peduncle.
The Swallow Damselfish is a tropical non-migratory demersal fish that are found in small schools around shallow rocky reefs in shallow waters at depths up to 30 m (100 feet). They reach a maximum of 17 cm (6.7 inches) in length. Reproduction is oviparous with pairing of individuals. The males will fertilize and then guard the nest providing fanning to oxygenate the eggs. The eggs are demersal and adhere to the substrate. The Swallow Damselfish 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 Swallow Damselfish is a resident of Mexican waters of the Pacific Ocean but has a very limited distribution being found only in the coastal waters adjacent to Alijos Rocks and the Coronado and Revillagigedo Islands.
The Swallow Damselfish is a straight forward identification that might be confused with the Silverstripe Chromis, Chromis atrilobata (deeper body, white spot at the rear of its dorsal fin, caudal fin with dark outer rays).
From a conservation perspective the Swallow Damselfish is currently considered to be Near Threatened due to their limited distribution and recent warm water events that have adversely affected their populations. They are exceedingly rare, found in remote locations and seldom seen by humans.