The Hawaii Larval Fish Project
Larval rearing of the orange butterflyfish, Chaetodon kleinii
October 01, 2015
Family: Chaetodontidae > Genus: Chaetodon > Species: C. kleinii
Butterflyfishes are mostly small, conspicuously colorful reef fishes with deep, laterally compressed bodies and small mouths. The family comprises 130 species in 11 genera. The striking chromatic patterns make butterflyfishes very popular among marine aquarists; however, many species have specialized diets, such as stony coral polyps, and fare poorly in captivity, refusing to feed.
The Chaetodon genus is by far the largest among the Chaetodontidae, with about 90 described species. Chaetodon members reportedly have never been cultured. The larvae have complicated rearing requirements during the later stages, including a specialized diet that consists primarily of chaetognaths (Sampey et al., 2007). The supply of wild Chaetodon eggs collected for this project has not been sufficient to resolve these problems. Adult butterflyfish fish pairs were brought into the RCT hatchery in 2015 to provide a proximate and consistent egg source for extensive larval culture research.
Butterflyfishes rarely reproduce in captivity. The Black-lipped Butterflyfish (Chaetodon kleinii) appeared to be a good candidate for captive breeding because it is an exceptionally hardy, relatively small butterflyfish species that is common on shallow reefs here in Hawaii and spawns in pairs as opposed to aggregations. This species occurs throughout much of the tropical and sub-tropical Indo-Pacific, at depths from 13 feet to 400 feet.
Two C. kleinii adults were collected as a mated pair off Oahu and conditioned in a 100-gallon tank on a mixed seafood diet. The pair spawned immediately after being introduced to the broodstock tank and then periodically following a 3-month period of photoperiod and temperature manipulation. Spawns of up to 2,500 eggs with 30% fertility were recorded.
C. kleinii juveniles were raised from hatchery-spawned eggs in the spring of 2015. The eggs were spherical, clear, contain a single oil globule and measure 0.7 mm in diameter. The larvae hatched at 2.1 mm TL with yellow pigment dots running along the notochord. They began to feed three days after hatching (dph) at 2.6 mm TL. Bony plates, called tholichthys, formed on the head during the late pre-flexion stage. Flexion began near 18 dph at 5.6 mm TL and was completed near about 25 dph (6 mm TL). The larvae had moderate to heavy yellow and dark pigment spots on the body through day 30 at 6.6 mm TL. The body of post-flexion larvae gradually took on a silvery appearance and the tholichthys plates became larger, extending from the head onto the body. The transformation period was long in captivity. The black bar through the eye and the white posterior margin on the dorsal first appeared near 65 dph (12 mm TL), full bottom orientation and juvenile behavior took place by 84 dph (24 mm TL), and complete juvenile coloration and meristic characters were present by 94 dph (27 mm TL).
C. kleinii larvae generally suffered minimal mortality up to flexion, with a spike of high mortality during flexion, and gradual mortality during the post-flexion stage up to juvenile transformation. The larvae were raised in multiple tanks on various live food mixes of rotifers, cultured copepods and wild plankton. Only larvae fed predominantly wild plankton survived through settlement. The cultured C. kleinii's 60-day post larval duration is similar to that of other wild subtropical Chaetodon larvae (Booth and Parkinson, 2011) but the more than 30-day metamorphosis/transformation period appears to be unnaturally delayed. The experimental rearing of C. kleinii sheds light on various biological bottlenecks, which are likely to considerably impede the commercial culture of this species and probably other Chaetodon members.
Booth D., Parkinson K. Pelagic larval duration is similar across 23 of latitude for two species of butterflyfish (Chaetodontidae) in eastern Australia. Coral reefs 30, 1071-1075 (2011).
Sampey, A, McKinnon, AD, Meekan, MG and McCormick, MI (2007). Glimpse into guts: overview of the feeding of larvae of tropical shorefishes. Marine Ecology Progress Series 339: 243-257.