FIRST RECORD OF CAPTIVE SPAWNING AND LARVAL REARING OF THE MELANURUS WRASSE Halichoeres melanurus  

The Labridae family is the most threatened family of coral reef fishes in the world, as defined by number of threatened species, with 23 species listed as critically endangered, endangered or vulnerable by the International Union for Conservation of Nature (IUCN Red List, 2015). Among these 23 species, 7 belong to the Halichoeres genus. Wrasses are also popular in the aquarium trade and the second most imported family of marine ornamental fishes in the United States, with over 200 different species of wrasses imported each year. The development of captive spawning and larval rearing protocols is a critical tool for the protection of natural ecosystems and the growth and sustainability of the aquarium trade.

A spawning population of melanurus wrasses, Halichoeres melanurus, was acquired and composed of one terminal phase male with three females. The species is a protogynous hermaphrodite and females can be positively identified by the presence of an anterior dorsal ocelli, which becomes absent at the beginning of the transition to male. At sunset the male rose to the highest point of structure in the tank and began a vibrant display followed by continuous chasing.  After the identification of an accepting female, the pair spawned hundreds up to several thousand pelagic eggs into the water column.  Eggs measured 660 µm in diameter. Despite this small size, larvae hatch out relatively large (~2.5mm) but with a very small mouth gape (~125µm).  Larvae were reared in a static 18 L aquarium and were ready to feed at 3 days post hatch (dph). The rearing water was darkened with microalgae and larvae were fed Parvocalanus crassirostris nauplii at 2 nauplii/mL.  Lights were on continuously until larvae were 12 dph and over the next 8 days gradually reduced to a 14 hour light: 10 hour dark photoperiod.  Varying size fractions of copepod nauplii were maintained in the tank throughout the rearing process and at 14 dph (Fig. 1), Otohime-A micro diet (75-250µm size) began being broadcast fed to larvae.  Larvae reached flexion by 15 dph and sand was then added to the bottom of the tank. By 22 dph, larvae settled into the sand and emerged 24 hours later as juveniles (Fig. 2). A second rearing trial demonstrated the importance of substrate, with delayed settlement at 35 dph, 48 hours after sand was added to the tank. The melanurus wrasse appears to be a good candidate for aquaculture production and a good model for the development of rearing protocols for other wrasse species.