Survival, growth and food conversion of cultured larvae of Pangasianodon hypophthalmus, depending on feeding level, prey density and fish density

In young fish larvae feeding efficiency is generally proportional to prey density, so feeding in excess is needed to maximise growth and survival. Increasing fish density might contribute to improve food conversion, but it can also impact negatively on fish growth or survival. Larvae of Pangasianodon hypophthalmus were raised until 192 h after hatching (hah) in 30-L tanks in a recirculating system (light regime: 12L:12D, 29.6 +/- 1.2 degrees C) at three stocking densities (10, 30 and 90 fish L-1), and fed every 3 h with Artemia nauplii at 1, 3 or 9 times a reference feeding level (RFL; 50% increase per day), thereby producing five different prey densities (from 10 to 810 RFL L-1). Except for the highest prey density, survival (20-60%) was dependent on feeding level, whereas fish growth (12.5-17.6 mm TL at 192 h AH) was more influenced by prey density than by feeding level. Both variables were negatively affected by fish density, but to a much lesser extent than by food availability. At all fish densities, the gross conversion efficiency (CCE, 0.13-0.42) was highest at 1 RFL and decreased for higher feeding levels, but not between I and 3 RFL at 90 fish L-1, which provided the best compromise between survival, growth and GCE in this study. Temporal variations in the effects of food availability and fish density are interpreted in respect to the developmental pattern of P. hypophthalmus. (C) 2009 Elsevier B.V. All rights reserved.