Otolith marking for eggs, larvae and juveniles of ocellate puffer Takifugu rubripes by alizarin complexone and tetracycline

Abstract

  Effective conditions for alizarin complexone (ALC) and tetracycline (TC) staining for the otoliths were examined in ocellate puffer eggs, larvae and juveniles to establish optimal methods by immersing in ALC or TC solution or by TC oral administration. To determine the optimum ALC or TC immersion conditions, eggs, larvae and juveniles were immersed in various combinations of ALC (5-100 mg/L) and TC (50-1000 mg/L) concentrations and treatment durations (6-24 h). To determine the optimum conditions for oral administration, juveniles were reared using artificial diets with various concentrations of TC (2.5-50 mg/g) and treatment periods (1-9 days). For both methods, optimum conditions were judged by the presence of fluorescent marks on otoliths under B-excited UV light and high survival rates (>90%) during the treatment. As a result, 9-19 combinations of concentration and duration of ALC and 2-11 combinations (TC) were found to be effective for immersion, and 5-11 combinations for oral administration depending on the fish stage. Fluorescent marks of ALC and TC were detected after more than 5 years and the treatments had no effect on the post-treatment survival and growth. These results suggest that these methods can be applied to surveys of stocking effectiveness by mark-recapture studies.