LIGHT INTENSITY AND SALINITY EFFECTS ON EGGS AND YOLK SAC LARVAE OF THE SUMMER FLOUNDER

Abstract The effects of light intensity and salinity on eggs and yolk sac larvae of summer flounder Paralichthys dentatus were examined under controlled laboratory conditions. Fertilized eggs (early gastrula stage), obtained by induced spawning of captive broodstock, were stocked (53 eggs/L) into forty-eight 5-L translucent containers under light intensities of 0 (constant dark), 500, 1,000, and 2,000 lx and at salinities of 26, 31, and 36 g/L. Temperature was 19°C and photoperiod was 12 h light:12 h dark. Light intensity and salinity produced significant (P < 0.05) additive effects on larval growth. At the stage when 97% of the yolk sac was absorbed (114–131 h postfertilization, hpf), at the first-feeding stage (129.5–135 hpf), and at yolk exhaustion (153.5–159 hpf), notochord lengths were generally maximal at low light intensity (500 lx) and high salinity (36 g/L) and minimal at high intensity (2,000 lx) and low salinity (26 g/L). Yolk utilization efficiency declined significantly (P < 0.01) with increa...