Enhanced biological performance of intensive sea bream (Sparus aurata) larviculture in the presence of phytoplankton with long photophase

Sea bream larvae were reared under intensive conditions either with (pseudo-green water technique) or without (clear water technique) the addition of phytoplankton in the rearing tanks, under 24- or 18-h photophases. Phytoplankton presence in the rearing medium resulted in 44 17% survival and individuals of 2.0 +/- 0.2 mg wet weight after 20 days of rearing. With the clear water method, both survival and growth decreased to 16 +/- 6% and 1.1 +/- 0.2 mg, respectively. The daily consumption rate (as milligram of carbon consumed per milligram body carbon) at the beginning of exogenous feeding was 0.5 day(-1) for all experimental conditions. At later stages, individuals reared with phytoplankton present had a daily consumption rate of about 0.7 day(-1), while those reared with the clear water technique presented consumption rates from 1.0 (for 24-h photophase) to 1.9 day(-1) (for 18-h photophase). The mean food assimilation efficiency of the larvae, expressed as a Food Conversion Index (FCI), was between 6.3 +/- 1.4 (for 18-h photophase) and 8.2 +/- 1.2 (for 24-h photophase) for the individuals reared in the presence of phytoplankton. For larvae reared using the clear water technique, FCl was between 12.8 +/- 2.4 (for 24-h photophase) and 20.1 +/- 5.3 (for 18-h photophase). (C) 2002 Elsevier Science B.V. All rights reserved.