1Hokkaido Mariculture Fisheries Experiment Station, Muroran, Hokkaido 051-0013, 2Graduate School of Marine Science and Technology, Tokyo University of Marine Science and Technology, Minato, Tokyo 108-8477, Japan
We examined the effect of dietary docosahexaenoic acid (DHA) on larval development, growth rate, survival rate, and starvation resistance of brown sole Pleuronectes herzensteini larvae fed live foods (rotifer or Artemia nauplius) enriched with different levels of DHA. In Expt. I, one-day-old larvae were fed rotifers Brachionus rotundiformis enriched with four levels of DHA for 15 days at 15°C. In Expt. II, 20-day-old larvae were fed Artemia nauplii enriched with four levels of DHA for 27 days at 15°C. The fatty acid profile of the larvae reflected the fatty acid composition of their diet in both experiments. In Expt. I, larval survival rate increased with the DHA level in rotifers increasing from 0 to 0.6% on a dry matter basis, but decreased with the DHA level from 0.6 to 3.3%. This suggested that the DHA requirement of brown sole larvae during the rotifer feeding period might be 0.6% on a dry matter basis of rotifers. Meanwhile, in Expt II，larval survival rate improved markedly in response to the increase of DHA content in Artemia, and reached a plateau from 1.4 to 2.8% of DHA level in Artemia on a dry matter basis. This characteristic is exceptional and unique in larvae of marine species. It was also demonstrated that DHA in live foods promoted larval development but survival was clearly depressed in larvae fed rotifer with high percentages of DHA (3.3%).