Improving live feeds: effect of a mixed diet of copepod nauplii (Acartia tonsa) and rotifers on the survival and growth of first-feeding larvae of the southern flounder, Paralichthys lethostigma.

摘要

The objective of this study is to compare the survival and growth of flounder larvae fed exclusively S-type or SS-type rotifers, two strains of Brachionus rotundiformis, to those fed a 50/50 diet of copepod nauplii and S-type rotifers. For 14 d, starting at the onset of first feeding, survival and growth of larval southern flounder were determined using 3 diets. Nine containers were divided into 3 treatment groups based on prey composition. Prey organisms were introduced to all larval rearing containers approximately 18 h before the anticipated beginning of first feeding. Thereafter, all treatments received prey twice daily (0900 and 1500 h) at a density of six organisms/mL. Treatment A received SS-type rotifers, Treatment B S-type rotifers and Treatment C a combination of S-type rotifers (3/ml). all rotifers were enrich prior to introduction into the treatment replicates. At stocking means for initial TL, TH, and weight of larvae were 2.88+or-0.134 mm, 0.56+or-0.024 mm, and 0.23 mg, respectively. S-type rotifers had a mean lorica length of 0.219+or-0.033 mm and a mean width of 0.177+or-0.025 mm. SS-type rotifers had a mean lotica length of 0.161+or-0.027 mm and mean width of 0.130+or--0.021 mm. Copepod nauplii had a mean length of 0.124+or-0.016 mm and a width of 0.070+or-0.016 mm. It was also observed that survival of larvae in the mixed copepod/rotifer feed treatment was significantly greater (71+or-7%) than that of the S-type rotifer only treatment (23+or-8%) and of the SS-type rotifer only treatment (31+or-12%)..