RECENT IMPROVEMENTS IN ADVANCING THE CULTURE OF YELLOW TANG Zebrasoma flavescens; AN UPDATE ON PROGRESS AT OCEANIC INSTITUTE

Yellow Tang (Zebrasoma flavescens) are the most heavily exported reef fish from Hawaii, with nearly 400,000 individuals collected annually. Recent legislation in Hawaii has suspended the collection of this iconic marine aquarium fish, despite significant data supporting the sustainability of this fishery. While the culture of this species has recently been successful, significant challenges remain in the rearing process that need to be overcome before cultured animals could become widely available in the market. In particular, the prolonged use of copepods in the rearing process needs to be addressed, as this represents one of the single largest impediments to commercialization. This study compared two feeding regimens, an "original" diet treatment which was initially used to successfully rear this species and a "revised" diet treatment, which differed only in the timing of the introduction of the live feed items and weaning periods to frozen and formulated feeds.  The objective of this effort was to significantly reduce the amount of copepods and rotifers utilized in the rearing process.

This study consisted of two parts, a replicated small-scale trial which test the effects of feeding regimen and a subsequent, larger "pilot scale" demonstration of this "revised" diet regimen. . Both diet regimens consisted of Parvocalanus crassirostris nauplii, enriched  Brachionus rotundiformis rotifers, and Artemia nauplii, followed by a transition to dry and frozen feed items. Eggs were stocked at 40 L^-1 into replicate (n=3) 200 L tanks for the feeding regime trial. Eggs were stocked at 19 L^-1 in a single 1,000 L tank, which tested the "revised" feeding method at pilot-scale. Fish reared on the revised feeding regime were observed to grow faster in body length and body depth after two weeks in culture, and also transitioned more quickly to juveniles as 41% had completed their transition to juvenile coloration by 70 days post hatch (dph). Fish reared under the "original" feeding regimen did not attain full juvenile coloration during the study period.  Survival to 70 dph was not significantly different between treatments and was 0.13% ± 0.13 and 0.29% ± 0.17 in the "original" and "revised" feeding regimens, respectively. In the pilot-scale portion, growth was comparable to that of both treatments in the 200 L scale trial, but survival to the same time point was much better at 1.9%. Although not specifically compared under this period, this improved survival rate in larger tanks is routinely observed and something that warrants further research.  The results of this research shortened the copepod and rotifer feeding periods for Yellow Tang, while not limiting growth or survival. This outcome significantly enhances the commercialization potential for this, and likely other Acanthuridae, species.