Captive spawning, early development and larviculture of the dwarf hawkfish, Cirrhitichthys falco ( Randall, 1963) with experimental evaluation of the effects of temperature, salinity and initial prey on hatching success and first feeding

摘要

The dwarf hawkfish, Cirrhitichthys falco is one of the popular species in the aquarium trade. However, the limited breeding resources nowadays available represent a clear limitation towards the rearing of this species. The aim of this study was to report the successful results on natural spawning of C. falco, a description of embryonic and larval development stages and appropriate rearing condition (temperature, salinity and initial prey) for the larviculture. Natural spawning of C. falco in captivity from 31 July 2014 to 31 July 2015 was described. A single male dominated a harem of eight females, spawning with each at dusk 30 min after sunset. Over a 365-d period, the females produced 357 spawns, 76.6 ± 0.9% of which resulted in fertilized eggs. The average fecundity per spawn was 1348 ± 712 eggs. Newly hatched larvae were 1.99 ± 0.09 mm in total length (L_T) and had an oil globule in the ventroanterior area of the yolk sac. At 2 days post hatch (dph), the larvae measured 3.04 ± 0.03 mm L_T, with the yolk sac and oil globule being completely absorbed. First feeding took places at 2 dph which is marked by the widening of the gut. On the scanning electron microscope observations, the fertilized egg membrane was smooth and lack surface sculpturing. The distribution density of pores was 2.8 pores μm~(-2). The micropyle was circular, and the diameter was 5.60-5.62 μm. At 2 dph, several neuromasts were found on the head, body surface and caudal fin membrane. At 18 dph, the larvae measured 5.22 ± 0.02 mm LT, dorsal and anal fin rays were formed. Consider the hatch, survival, deformity, and survival activity indices, the water temperature 26 °C and salinity 27-30 psu may be a suitable rearing condition for the larvae. In the first feeding experiment, the survival was not significantly in feeding treatment B (Eu-plotes sp. 20 ciliates mL~(-1)), C (Euplotes sp. 10 ciliates mL~(-1) + Brachionus ibericus 10 rotifers mL~(-1)) and D (Euplotes sp. 10 ciliates mL~(-1) + B. ibericus 5 rotifers mL~(-1) + Microsetella sp. 5 nauplii mL~(-1)), but all higher than treatment A (starved control) in 3-4 dph of C. falco larvae. The results indicate that Euplotes sp. may be an important initial prey for the first feeding larvae. These findings provide a basis for further studies to determine the successful captive breeding of C. falco and other valuable ornamental hawkfishes.