Egg Hatching, Stocking, Larval Feeding, and Handling Mortality of Guinean FingerfishMonodactylus sebae

Abstract

Experiments were conducted on Guinean Fingerfish Monodactylus sebae to evaluate egg and larval stocking densities, stocking methods, water quality effects on egg hatching success, and the effects of different live food organisms on larval growth and survival. Egg hatching percentage was determined for four egg stocking densities (10, 20, 30, and 40 eggs/L). The lowest stocking density, 10 eggs/L, had a significantly higher mean hatching percentage (65.0 ± 18.54%) than the 30- and 40-eggs/L treatments but did not vary significantly from the 20-eggs/L treatment. Eggs were incubated in salinities of 0, 5, 10, 15, 20, 30, 40, 45, and 50 g/L to evaluate the effect on hatching success. The hatching success was over 70% for salinities of 0–30 g/L. The highest hatching success (98%) occurred in the 5-g/L treatment, and the 40- and 50-g/L treatments had significantly lower hatching success than all other treatments. Three live food organisms were fed to larvae to determine effects on growth and survival over a 9-d period. Diets were enriched rotifers Brachionus plicatilis, nauplii of the copepod Parvocalanus crassirostris, and nauplii of the copepod Pseudodiaptomus pelagicus fed at equal densities of 10 organisms/mL once daily. Larvae were stocked at 20 fish/L. At 9 d posthatch (dph), survival was not significantly different among treatments and larvae fed P. pelagicus had a significantly longer SL (mean ± SD = 4.28 ± 0.42 mm). Larvae were netted and exposed to air as a stressor at 6, 14, 22, 30, 38, and 46 dph for durations of 30, 60, 120, and 240 s. The 30-dph treatment had the lowest survival among all treatments regardless of experimental duration, followed by the 38-dph treatment. Results suggest that to avoid high handling mortality, Guinean Fingerfish should not be handled during metamorphosis (30–38 dph).