The effect of reduced Artemia and rotifer use facilitated by a new microdiet in the rearing of barramundi Lates calcarifer (BLOCH) larvae

Abstract Since live feeds are costly and variable in nutrition, early weaning onto artificial microdiet is advantageous. Thus, we tested a new commercial microdiet using several rearing protocols aimed at reducing live feed inputs. Barramundi Lates calcarifer (BLOCH) larvae were reared from 2 days post hatch (dph) to 28 dph and their survival, growth and stress tolerance were examined. Six protocols with 4 replicates were set combining different protocols that progressively excluded live feeds (rotifers and Artemia ). Rearing protocols using no rotifers (protocol-G) and feeding rotifers for 3 (G3), 7 (G7) and 12 (G12) days were conducted with a 3 day weaning period onto Gemma Micro (Skretting) microdiet followed by feeding microdiet solely. According to a common rearing protocol, 2 protocols received rotifers for 12 days, Artemia for 9 days and either Proton (INVE) as control (P12A) or Gemma Micro (G12A) co-fed from 6 dph. Protocols G12 and G12A were reared until 36 dph in order to compare growth post weaning. Barramundi larvae development was affected by rearing protocols, with co-feeding rotifers and Gemma Micro allowing complete replacement of Artemia . Significantly better growth and similar larvae survival and health was achieved compared to co-feeding rotifers, Artemia and Proton. By including Artemia in the protocol with Gemma Micro survival was significantly improved, but growth was inhibited to 28 dph. Due to compensatory growth in protocols G12 and G12A, whereby accelerated growth occurs in response to previous poor nutrition caused by the weaning process, larvae grew equally well to 36 dph in these protocols. Larval growth and survival positively correlated with the number of days that rotifers were fed in those protocols that did not receive Artemia . High lipid levels and relatively higher amino acid leaching rates were considered contributing factors to achieving better larvae growth and survival. We found that the best protocol for rearing barramundi larvae involves feeding enriched rotifers from initial exogenous feeding to 3 days after the initiation of stomach differentiation at 5 mm standard length (SL), and including supplemental levels of enriched Artemia from 5 mm, to post metamorphosis at 12 mm. Co-feeding barramundi larvae on microdiet (i.e. Gemma Micro) should start when the larvae reach 5 mm, in order to establish microdiet early and allow a more efficient weaning process.