The Marking Characteristics of Otoliths of Larval Grass Carp (Ctenopharyngodon idellus) by Immersion in Alizarin Complexone

Abstract:

The grass carp Ctenopharyngodon idellus is one of the main economic fish species for release and resource enhancement in China. In this study, the otoliths of larval grass carps were marked for 1 d by alizarin complexone (ALC) to confirm the feasibility and appropriate conditions for the method. The results showed that lapillus, sagitta, and asteriscus could be successfully marked. The marking rings were observed under both visible light and fluorescence, the latter of which was most obviously observed using blue excitation light. Overall, lapillus had the best marking effect, followed by sagitta. ALC immersion had no significant effect on fish survival and growth. The appearance and disappearance of fluorescent signals on the otolith, the beginning and end of immersion of the fish had a time lag of about 12 h. At 60 d of recovery of the culture after immersion, the ALC mark ring was still visible, indicating that the ALC-marked effect was evident and could exist for quite a long time. This method has a strong feasibility for marking and effect assessment of the larval grass carp for future resource enhancement and release.