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<br />Muth <br />and the mean was used as a subjective comparison of mark quality among experimental <br />groups (Muth and Nesler, 1989; Muth and Bestgen, 1991). <br />The double-mark experiment started 1 day after eggs not used in the single-mark <br />experiment had hatched. A total of 2,200 larvae was divided into 110 experimental groups <br />(two maintained as controls), each with 20 specimens. Marking and rearing were <br />conducted in 1-1 glass beakers placed in a covered water bath at 170C. Larvae were first <br />immersed in buffered solutions of 12.5, 25, 50, or 100 mg ALC/I distilled water for 6, 12, and <br />18 h. Larvae were removed from test solutions immediately after ALC treatment, and <br />numbers of dead larvae were recorded. Surviving larvae were reared in well water for 24 h. . <br />After the 24-h rearing period, larvae were next immersed in buffered solutions of 150, 250, <br />or 350 mg TC/I distilled water for 6, 12, and 18 h. All possible combinations of ALC: TC <br />concentrations and immersion durations were tested (total of 108 combinations). Larvae <br />were removed from test solutions immediately after TC treatment and reared in well water <br />for 3 days. Larvae surviving to the end of rearing were counted and fixed and preserved in <br />100% ethanol. Procedures for mark examination were the same as those described in the <br />single-mark experiment; intensity of ALC and TC marks in otoliths was evaluated separately <br />for each mark type. <br />In the single-mark experiment, hatching success decreased and mark quality <br />increased as immersion duration increased at ALC or TC concentrations of ~ 150 mg/l. <br />Lowest percent egg hatch ranged from 30 to 45% in treatments of 250 and 350 mg ALC/I <br />for 36 h, 450 mg ALC/I for 24-36 h, 150-350 mg TC/I for 36 h, and 450 mg TC/I for 30 and <br />36 h. Hatching success was 90-100% in the remaining ALC or TC treatments and in the <br /> <br />4 <br />