Synopsis
- Orangeband or orangebar surgeonfish larvae (Acanthurus olivaceus) were raised from wild-spawned eggs at 77–79F on cultured copepods, Artemia, and micropellets.
- The larval duration was 130 days.
- First record of Orangeband surgeonfish culture.
Background
A. olivaceus is an attractive surgeonfish. Adults have an orange, blue-framed band on the shoulder, an ornate lyre-shaped tale, and a body color that can change from dark to light two-tone olive. A. olivaceus is also unusual in that juveniles have a distinct yellowish coloration. Adult A. olivaceus are moderately common on shallow tropical and subtropical Indo-Pacific reefs from Hawaii to Western Australia. They live singly or in small schools and feed on detritus, diatoms, and fine filamentous algae. A. olivaceus is a hardy and mostly docile aquarium fish, but because of its large size (averaging 12”) it requires large tanks (150+ gallons) with lots of swimming room.
Culture
A. olivaceus juveniles were raised from eggs collected above reef bottom in 40–60 feet of water along Oahu’s south shore in September, 2018. Initially, the larvae were grown in a static 20-gallon tank system (77–79F, 16:8 photoperiod) together with a mix of species, predominantly redlip parrotfish (Scarus rubroviolaceus) and Hawaiian flagtails (Kuhlia xenura). The tank was flushed through a filtration system periodically, starting on day 17. The fish were offered Parvocalanus sp. from day 3–40, Artemia sp. from day 37–104, Otohime pellets from day 35–157, and nori and grated shrimp/scallops from day 104–157. They were moved to a 55-gallon-barrel juvenile grow-out system on day 103. Juveniles were donated to the Waikiki Aquarium on day 157.
Development of Eggs and Larvae
A. olivaceus eggs are spherical, clear, average 0.75 mm in diameter, and contain a single oil globule. The larvae began to feed 3 dph (days post hatch) at 2.5 mm TL (total length). Flexion occurred from 22–31 dph at 4.3–6.1 mm TL. Flexion larvae developed a long first dorsal and anal spine and a deep, triangular-shaped body. The distinctive acronurus stage (late postflexion stage) began near 55 dph at 15 mm TL. At this stage, the larval body becomes silver, oblong, and extremely laterally compressed. Juvenile behavior was first observed on 90 dph at 31 mm TL and first color on 115 dph at 39 mm TL. All fish were fully colored juveniles by day 140.
Conclusion
A. olivaceus is the third surgeonfish species raised for the Hawaii Larval Fish Project, after A. triostegas and A. xanthopterus. The three species appear to have two main rearing challenges throughout the early stages (up to acronurus stage). First, they are sensitive to microbial infections and second, they have a small mouth size. To meet these challenges, UV filtration, high flush rates through the larval tank, and frequent feedings of copepod nauplii, enriched SS-rotifers and micropellets (Callan et al. 2018) were used to culture A. triostegas and A. xanthopterus. A. olivaceus larvae were raised similar to A. triostegas and A. xanthopterus larvae but without rotifers.
Settlement (juvenile behavior) was first observed by day 62 for A. xanthopterus, by day 93 for A. triostegas and by day 90 for A. olivaceus. Juvenile transformation then took about 7 days, 15 days and 40 days to complete, respectively, for each species. Despite the long metamorphosis, A. olivaceous larvae are very robust and can essentially be treated like juveniles once they settle. No fish were lost after 85 dph. This species is more docile and easier to grow out than A. triostegus. The long A. olivaceus larval phase in culture was a surprise. Like A. triostegas, this species has a much shorter natural larval duration (50-60 days) and would probably settle sooner under more ideal rearing conditions (more space, more frequent feedings).
References
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