Damselfishes are mostly small (2” to 4” long), brightly colored and highly territorial coral reef fishes comprising 19 genera/200 species. They occupy a variety of important ecological roles as territorial “algae farmers”, detritivores, grazers, schooling planktivores, prey for reef piscivores, and even facultative parasite pickers. Damselfishes are the most heavily traded marine fish in the aquarium trade due to their bright colors, small size and low price. However, only the clownfishes are available consistently through aquaculture due to their short and uncomplicated larval stage. Other heavily traded damselfish species (Chromis, Chrysiptera and Dascyllus sp.) are more difficult and costly to raise and very abundant in the wild, making them less desirable farming candidates.
Hawaiian Sergeant – Abudefduf abdominalis (September 2012)
The Hawaiian Sergeant (Abudefduf abdominalis) is a large, colorful damselfish, endemic to the Islands of Hawaii. A. abdominalis was reared from collected eggs removed from nests in waters off the west side of Oahu in August, 2012.
A. abdominalis eggs are elliptical, adhesive, contain bright red yolk and measure 1.2 x 0.6 mm in size. The eggs hatch after 5-9 days, depending on water temperature. Features of A. abdominalis larvae include the early forming dorsal spines and pelvic rays; enlarged pelvic fins; yellowish body covered with small, black spots; and sudden changes in form and pigmentation with little growth. A. abdominalis larvae are easy to rear on copepods but, during the postflexion stage, they are somewhat sensitive to light and water circulation changes. The A. abdominalis larval period in culture was about 20 days.
Sergeant damselfish (Abudefduf species) are inexpensive and potentially aggressive aquarium fish with limited value to the aquarium trade. However, the beauty, interesting behavior and short rearing phase of the larvae makes experimental breeding very worthwhile.
Hawaiian Dascyllus – Dascyllus albisella (August 2013)
The Dascyllus genus comprises ten, deep bodied and mostly pale colored (D. auripinnis is colorful) damselfish species limited in distribution to the Indo-Pacific. Members of this genus generally form schools of up to a few dozen individuals over coral heads and feed on zooplankton in the water column. All species are believed to be protogynous hermaphrodites. The eggs are laid on hard substrate and defended by the male until they hatch. Juvenile dascyllus are attractive and hardy but will often grow into aggressive adults that dominate community fish tanks so novice aquarists usually purchase them. Several members of this genus have been captive-bred but not for commercial purposes.
Hawaiian dascyllus (Dascyllus albisella) juveniles were reared on two occasions in July and August of 2013 from collected, wild eggs. D. albisella is endemic to the Hawaiian Islands and Johnston atoll. It spawns year round and increases reproduction when water temperatures rise during the spring and summer months.
D. albisella eggs (0.5 x 0.7 mm) are oval; clear; and contain a large, single oil globule. D. albisella larvae hatch after 4 days (2.4 mm TL) at 78°F. They are capable of feeding on 60-70 micron nauplii less then 24 hours after hatching. Flexion occurs 10-13 dph (4.0-5.1 mm TL). During this period the body noticeably widens and develops reddish pigmentation around the mid-section. D. albisella larvae start to settle near 20 dph (5.5 mm TL) when the body pigmentation becomes darker and more disperse. They aggregate along the tank sides and can start to feed on artemia. By 25 dph the larval body is almost completely black with white patches under the pectoral fin and the dorsal fin. At this time the larvae can safely be transferred to juvenile grow-out. Full characteristic juvenile color and behavior is present by about 30 dph (7-9 mm TL). D. albisella juveniles have the tendency to gorge themselves on artemia without suffering from digestive disorders. This species is easy to raise on copepods and undergoes no obvious bottlenecks or critical periods of high mortality.
In the ocean, Hawaiian Dascyllus settle out among branches of the hard coral, Pocillipora meandrina, and the tentacles of sea anemone, Heteractis malu, when available. For a related study, University of Hawaii scientists “seeded” the juveniles cultured for this project on P. meandrina coral heads to test their survivorship and growth. Eight months later most of the restocked juveniles were still alive, which indicates that successful artificial settlement of this species is possible.
Bret Danilowicz first raised D. albisella and D. aruanus for fish PHD thesis research at University of Hawaii way back in September 1992.
Oval Chromis – Chromis ovalis (April 2014)
Oval chromis (Chromis ovalis) were cultured once for this project in March 2014. This Hawaiian endemic damselfish forms large schools, sometimes high in the water column, where it feeds on plankton. Though juveniles are colorful, oval chromis are not popular aquarium fish because adults are large (up to 7”) and relatively unattractive.
C. ovalis spawn from February through May. Reproductive behavior begins with males forming temporary territories and clearing nest sites on rocks, spaced at least 3 feet apart. Males take on courtship colors and repeatedly swim up into the water column to entice females to spawn.
Female C. ovalis will typically lay thousands of eggs that hatch in 3-4 days. C. ovalis eggs are oval and very small, measuring just 450x500um and are usually attached to macro algae on the nest site. A small portion of the nest was removed and incubated in a 5-gallon bucket until just before hatching. About 100 larvae hatched in the larval tank when the eggs were exposed to light.
C. ovalis larvae measure 2.2 mm TL (total length) at hatching and lack pigmented eyes and a mouth. They feed on very small copepod nauplii 2 days after hatching at 2.4 mm TL. The critical flexion period occurs between 13 and 18 dph (days post hatch) at 3.9-4.3 mm TL. The larvae begin to settle (associate with tank sides) near 33 dph at close to 8 mm TL. Juvenile transition is rapid and completed in 2-3 days.
C. ovalis larvae were raised on wild and cultured copepods and the juveniles were grown out on artemia, cultured copepods and frozen foods. The small food size requirements of the first feeding larvae, sporadic mortality events during first feeding and flexion and the relatively long larval stage makes C. ovalis one of the more difficult damselfish species to culture. This is the first documented larval rearing of C. ovalis.
Twelve cultured 1” juvenile C. ovalis were released onto a coral head to assess their survival instinct on the reef. Most of the fish failed to seek shelter and lacked predator recognition and an escape response. It was surprising to see how quickly the surrounding predatious reef fish (Parupeneus insularis, Iniistius baldwini) detected this behavior and preyed on the released fish. The result highlights the importance of training hatchery-raised fish destined for restocking.