Dragonets are small to medium (2 – 30 cm), slender, scaleless, slow-moving, benthic reef fishes, comprising 18 genera/186 species. They are found in oceans worldwide but most species inhabit tropical and subtropical seas of the Indo-Pacific up to 200 m living on sand, rubble or mud and feeding on small benthic invertebrates. Most dragonets are well camouflaged and have little economic value but brightly colored species (Synchiropus splendens, S. picturatus and S. ocellatus) are popular aquarium fishes. These species are heavily collected and sporadically available through aquaculture.
Redbarred dragonet – Synchiropus rubrovinctus (May of 2011)
The Redbarred Dragonet or Tiny Hawaiian Dragonet, Synchiropus rubrovinctus, is a rare, cryptic dragonet species that has only been found around Japan, New Caledonia and Hawaii at depths of 3 to 260 feet (1 to 80 m). It reaches a maximum size of just 5 cm (1.9”) (personal observation).
S. rubrovinctus juveniles were raised in the spring of 2011-2015 from eggs collected in coastal waters off Oahu. The larvae measure just 1.1 mm TL at hatching. They are able to feed on small copepod nauplii (Parvocalanus sp.) at first feeding (3 dph), despite their small size (1.9 mm TL). Preflexion larvae develop deep red pigmentation on the body with dense melanophores on the tail and mid trunk section. Flexion occurs near 10 dph at 3.1 mm TL. Metamorphosing larvae are bright red in color. They complete settlement by 20 dph (6 mm TL).
S. rubrovinctus larvae are very easy to raise on copepods (Parvocalanus sp.). Juveniles can be effectively grown out on newly hatched artemia and shredded frozen seafoods. Spawning behavior was observed after 6 months between a large male (50 mm TL) and multiple slightly smaller females. This attractive species is easy to grow out to market size in a relatively short time and would make an excellent nano reef fish. All cultured S. rubrovinctus were donated to growers or released into the ocean.
Longtail Dragonet – Callionymus decoratus (October of 2012)
The endemic longtail dragonet (Callionymus decoratus) is believed to be the most common dragonet species in Hawaii waters.
The eggs of this species were regularly collected in egg net tows off the west side of Oahu and juveniles were reared on several occasions. C. decoratus eggs are pelagic, spherical and about 0.6 mm in diameter. Features of the larvae include small size at hatching (1.1-1.2 mm); sharp spinous processes on the fin folds; dense melanophores; heavy reddish pigmentation; rapid development; and their small size (about 6 mm) at settlement.
C. decoratus prove easy to raise on copepods with very high survival rate through settlement. The larvae have a relatively large mouth at first feeding and despite their small size (1.9 mm) are able to feed on small copepod nauplii. The larval period of C. decoratus in culture is about 16 days.