Mass-Marking Method for Fish Eggs and Larvae

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This project was planned to establish a method of mass-marking fish eggs and larvae. Based on thd preliminary works on the ayu, Plecoglossus altivelis, otolith-tagging by immersion eggs and larvae in solution of fluorescent sudstances was nesly developed as follows.(1) Screening of marking agents and optimum treatment condition Alizarin complexone (ALC), tetracycline (TC) and calsein (CAL) presented a distinct scarlet-pink, yellow and yellowish hreen fluorescent ring, respectively. Optimum conditions for ALC and TC teatment was 50-200 mg/l and 200-300 mg/l for about 1 day. CAL was less successful.(2) Mark retention and effect of marking treatment TC and ALC treatment had no unfavourable effect on survival and growth of the ayu and the red sea bream Pagrus major reared for 5 months to 2 years after treatment, and clear fluorescent marks were confirmed in every fish treated.(3) Availability of otolith-tagging This technique was confirmed to be available for about 25 species including both marine and freshwater species. Mark-recapture experiment of ALC-treated red sea bream was conducted in a small cove Oita prefecture in 1987 and 1988. Experinents were successful and we confirmed the availability of this method in a field survey.