Effect of microalgae concentration on larval survival, development and growth of an Australian strain of giant freshwater prawn Macrobrachium rosenbergii

The present study investigated the effects of microalgae Nannochloropsis sp. addition and concentration on larval survival, development and growth of an Australian strain of M. rosenbergii (lineage 11). Newly hatched larvae were reared to postlarval (PL) stage under the condition of no algae addition ('clear water') and four Nannochloropsis concentrations of 2.5, 6.25, 12.5 and 25 x 10(5) cells/ml. All treatments were in quadruplicate and each replicate had 30 larvae stocked in a 5L vessel. Larvae were fed 3 Artemia/ml throughout with 100% water exchange daily. The results showed that larval survival to PL at the two higher algae concentrations of 12.5 and 25x10(5) cells/ml (70.8 and 63.3%, respectively) were significantly higher (P<0.05) than those of lower algae concentrations of 2.5 and 6.25x10(5) cells/ml and the 'clear water' treatments (26.7, 35.0 and 30.0%, respectively). Meanwhile, the fastest mean development to PL (30.6 days) registered at the highest algal density was 14 days shorter than that of the 'clear water' treatment (44.3 days). Larval development at the two higher algal densities were significantly shorter than that of the 'clear water' treatment and larval development of the highest algal density was further significantly faster than those of the two lower algal densities (40.1 and 40.0 days) (P<0.05). The mean dry weights of newly settled PL of the two high algal density treatments were also significantly heavier (P<0.05) than those of the lowest algal density and the 'clear water' treatments. The results have shown that the addition of Nannochloropsis sp. at appropriate levels substantially improved performance of larval culture of the Australian strain of M. rosenbergii, suggesting that the Australian native strain has a promising potential for aquacultural development. (C) 2009 Elsevier B.V. All rights reserved.