The importance of copepods as live feed for larval rearing of the green mandarin fish Synchiropus splendidus

The green mandarin fish, Synchiropus splendidus, is a popular marine aquarium species, but currently sourced largely from the wild. To establish a reliable feeding regime for its larvae in captivity, a series of experiments were conducted. In the 1st experiment, newly hatched larvae were fed either unenriched rotifers (ss-type), rotifers enriched with Algamac 3000 or a mixture of commercial enrichments. An unfed control was also set up, which suffered a total mortality by 5 day post-hatching (DPH). All feeding treatments had similar low survival (<3.3%) by 11 DPH, suggesting rotifer enrichment bore little benefits. In the 2nd experiment, larvae were fed enriched and unenriched rotifers at 10 mL−1 and a mixed diet of 2 copepods (nauplii and copepodites of Parvocalanus crassirostris) + 8 rotifers mL−1. The copepods co-feeding with rotifers treatment showed dramatically improved survival (50%) as compared to rotifer feeding only treatments (≤5.6%) by 12 DPH (p < 0.01). The copepods + rotifers diet also generated significantly larger larvae (p < 0.01). The 3rd experiment aimed at determining the minimum quantity of copepods required for co-feeding with rotifers. Five treatments of copepods provided at 0, 0.1, 0.5, 1.0 and 2.0 mL−1 with rotifers making up the rest of a total of 10 prey mL−1 were set up. Larval survival to 11 DPH were significantly higher in the 2 copepods + 8 rotifers mL−1 and 1 copepods + 9 rotifers mL−1 treatments (52% and 48%) than other treatments (<19%) while no significant difference was detected between the two treatments. Larval growth was not significantly different among all copepod feeding treatments, even copepods were provided at only 0.1 mL−1, and they were all significantly higher than the rotifer feeding only treatment (p < 0.05). Our results demonstrated the importance of copepods as prey for rearing early larval S. splendidus and suggested that they should be co-fed at least 1.0 mL−1 to ensure good survival.