Phenotypic correlation of growth traits between different developmental stages in <I>Artemia sinica</I>

For analyzing phenotypic correlation level of growth traits at different developmental stages,three different strains of Artemia sinica were collected from different provinces in China. Fifty larvae per strain were selected randomly and reared separately for 30 days. In this growth period,the total length (TL) of A.sinica was measured every 5 days. The body length (BL),body width (BDW) and body weight (BW) were also measured at the last two stages. Then phenotypic correlation coefficients of growth traits among the different stages were estimated at individual level. The results indicated that the smaller the correlation coefficients were,the longer the intervals between two stages were. For example,the correlation coefficients between 5 d and 25 d were only 0.073,0.091 and 0.026 for SIN,YIM and ALXZ respectively. Moreover,the correlation coefficients among the stages before and after 15 d were even negative. It was implied that the early stage selection method was not applied to improve growth traits in A.sinica,especially when selecting at the stages before 15 d. Although significant positive correlation were found among four growth traits at 25 d and 30 d stage,the correlation coefficients were smaller than expected. It was implied that BL and BDW could not substitute for BW as breeding object traits when breeding fast-growing new strain with large body shape. The multi-traits aggregated selection method based on selection index theory will be needed for the above breeding object.