Diet and light intensity effects on survival, growth and pigmentation of southern flounder Paralichthys lethostigma

Interest in the culture of flatfishes has increased globally due to high consumer demand and decreased commercial landings. The Southern flounder Paralichthys lethostigma inhabit South Atlantic and Gulf of Mexico waters and support important commercial and recreational fisheries. In spring, 1996, a two-part larval rearing study was performed with Southern flounder to examine the effects of three larval diets and two light intensities on survival, growth, and pigmentation. The first part of the study consisted of feeding 6 d post-hatch (dph) (3.0 +/- 0.1 mm TL) larvae three diets: 1) rotifers Brachionus plicatilis at a rate of 10/mL from day 1-9 and Artemia nauplii (3/mL) from day 7 through metamorphosis; 2) rotifers fed day 1 through metamorphosis and Artemia fed day 7 through metamorphosis; or 3) same diet as treatment 1 plus a commercial larval diet added day 13 through metamorphosis. The second part of the study examined the effects of two light levels: low-light (mean 457 lux) and high-light (mean 1362 lux). At 24 C, metamorphosis began on day 23 (mean fish size 8.2 +/- 0.6 mm TL) in all treatments and was completed by day 30, Analysis of survival, size, and pigmentation data indicated there were no significant differences among feed treatments or between light treatments. Overall survival was 33.4% (+/- 15.9) and mean length was 11.5 mm TL +/- 1.3. Only 35% of the larvae, were normally pigmented. Reexamination of the pigmentation on day 37 indicated fish reared at the low light intensity through metamorphosis (day 30) but exposed to high light intensity for 1 wk pot-metamorphosis had become significantly more pigmented.