A Pilot Study Assessing a Concentration of 100 mg/L Alizarin Complexone (ALC) to Mark Calcified Structures in Hypophthalmichthys molitrix

Abstract

The effectiveness of chemical compounds for marking hard tissues in juvenile silver carp (Hypophthalmichthys molitrix) is not well known. We analyzed the use of alizarin complexone (ALC) as a fluorescent marker to mark the various hard structures of juvenile silver carp. Experimental fish (~2 months old) were randomly assigned to either control or marking groups, which were immersed in 0 or 100 mg/L ALC solutions, respectively, for 2 days. The otoliths, fin rays, and scales of the fish were then sampled, visualized using fluorescence microscopy, and evaluated after 10 days. The ALC treatment was effective for marking certain hard structures and the marking color was affected by the light source. There were no obvious differences in the marking efficiency of rays from pectoral, dorsal, ventral, anal, and caudal fins, but the lapilli and lateral line scales were marked most effectively from the sampled otolith and scale types, respectively. Our findings indicate that ALC immersion and fin ray and scale sampling can be used for the effective marking and non-lethal evaluation of hard structures in juvenile silver carp.