GREENWATER CULTURE AND LARVAL DEVELOPMENT OF THE MELANURUS WRASSE Halichoeres melanurus

The Labridae family is one of the most popular families of fishes in the marine aquarium trade. Wrasses encompass over 500 species, however, less than ten have been successfully cultured in captivity with no current commercial production of ornamental species. Wrasse species within the genus Halichoeres are prime candidates for commercial production primarily due to their short larval duration compared to other wrasse genera.

A preliminary study was conducted to describe larval development and culture requirements of the Melanurus wrasse (Halichoeres melanurus). Fertilized eggs measuring 0.627 ± 0.013 mm in diameter were stocked in a 125 L tank at a density of 25.2 eggs/L. Larvae (8 ± 3) were sampled and measured throughout development and post metamorphosis (Figure 1). Newly hatched larvae measured 1.590 ± 0.140 mm (notochord length) and lacked a functional mouth and gastrointestinal tract. Initiation of exogenous feeding, swim bladder inflation, and flexion were observed at 3, 10, and 15 days post hatch (DPH), respectively. Completion of metamorphosis was first observed at 37 DPH with a mean standard length of 11.851 ± 0.230 mm. Larval growth appeared linear over the 45-day period. Survival through metamorphosis was 0.54% yielding 17 juvenile wrasses.

To further refine culture methods, a study was conducted to evaluate the effect of algal density on survival and growth of Melanurus wrasse larvae (0-3 DPH). The study consisted of five temporal replicates per Tetraselmis chuii algal density treatment (0 cells/mL, 50k cells/mL, 100k cells/mL, and 200k cells/mL). Fertilized eggs were stocked in 13L larval tanks at 10 eggs/L. Larvae were harvested and measured at 3 DPH. Larval survival was significantly (P > 0.05) higher in 50k cells/mL and 200k cells/mL treatments compared to the 0 cells/mL treatment, indicating that early microalgae introduction plays a significant role in larval survival before initiation of exogenous feeding. Larval growth did not vary significantly among treatments.

Information gathered from these trials will help to advance commercial aquaculture protocols for the Melanurus wrasse and guide future aquaculture research with additional Labrid species.