Abstract
In this study, a flow‐cytometric cell cycle analysis method to assess instantaneous growth rate of whole larvae of the Australian barramundi Lates calcarifer was developed and validated. High‐resolution DNA measurements of either fresh, frozen or RNA later ‐preserved larvae (gap0–gap1, G 0 –G 1 , coefficient of variation ( c.v. ) 0 –G 1 , S (DNA synthesis) and G 2 –M (Gap2–Mitosis). This technique can be also used for individual fish tissues such as brain, liver, fin and muscle. For the first time, the combined proportion of replicating nuclei (into S and G 2 –M phases) of whole fish larvae and absolute growth rate in length (mm day −1 ) has been correlated in commercial aquaculture conditions. Fast growing L. calcarifer larvae had an overall hyperplasia advantage as indicated by a greater proportion of cells in the S+G 2 –M phase compared with slow growing larvae, which might explain the increasing differences in size during culture. In a fasting trial, larvae ceased growth while maintaining the constant initial rates of cell division throughout a 6 day period. For a highly fed fast growing control group, cell division rates significantly increased after day 4. Flow‐cytometric cell cycle analysis of whole fish larvae may provide fish biologists and aquaculturists with a better understanding of how cell division rates influence early growth in natural and artificial environments.