Although the majority of the marine ornamental fish market is satisfied through the sale of wild caught individuals, ornamental aquarium consumer's preference is shifting to include more aquacultured fish due to the knowledge of declining ecosystems, the need for sustainable products and concerns related to capture methods. Melanurus Wrasse (Halichoeres melanurus) and Pacific Blue Tang (Paracanthurus hepatus) are of great interest to aquaculture due to their popularity in the marine aquarium trade and lack of established commercial rearing methods. Pelagic spawning species produce underdeveloped larvae that rely on a diet of copepod nauplii and other small, easily digestible zooplankton. Environmental parameters, such as light intensity, can influence survival and feeding success in a culture setting. Challenges associated with these characteristics need to be addressed for production of pelagic species to become commercially viable.
Here, we experimentally evaluated different larval rearing protocols from 0 to 3 dph. Algal and prey densities were evaluated to determine a suitable rearing environment that resulted in increased survival and feeding incidence during the transition from endogenous nutrition to exogenous feeding. Pelagic eggs were collected, enumerated and stocked into 15 L static tanks. For evaluation of algal density, a control treatment was included with no algae present and three treatments containing Tisochrysis lutea were examined at 100,000, 300,000, or 500,000 cells/ml. To investigate live feed density requirements, Parvocalanus crassirostris nauplii were stocked at densities of 2.5, 5, or 10 nauplii/ml. Potential feed attractants were also evaluated, comparing a control treatment with no feed attractant to the addition of taurine, tryptophan, or betaine at 10-5 mg/L in the rearing environment. For each experiment, P. crassirostris nauplii (< 75 µm) were provided at 3 dph and the larvae were able to feed for five hours. The larvae were then harvested, enumerated and visually inspected for ingestion of nauplii using a dissecting microscope with digital camera attachment. Results suggest a T. lutea density of 300,000 cells/ml is optimal for both survival (P < 0.0001) and feeding incidence (P = 0.02) for Melanurus Wrasse and for survival of the Pacific Blue Tang (P < 0.0001). Prey density experiments resulted in no difference in feeding incidence across treatments for both species. Inclusion of feed attractants decreased survival (P < 0.0001) and had no effect on feeding incidence for Melanurus Wrasse. These results will help to shape commercial production protocols and inform decisions about feasibility of production for these valuable ornamental species.