Theme D: Developing optimal release strategies
40. THE USE OF PLASTIC OVAL TAGS FOR MARK-RECAPTURE STUDIES OF JUVENILE JAPANESE FLOUNDER Paralichthys olivaceus ON THE NORTH-EAST COAST OF SHANDONG PROVINCE, CHINA
Hongjian Lv, Xiumei Zhang, Peidong Zhang, Wentao Li
College of Fisheries, Ocean University of China
Lvhongjian1986@yahoo.cn
As part of a stock enhancement research project in Shandong Province, China, plastic oval tags (POTs) were used to mark juvenile Japanese flounder, Paralichthys olivaceus (70-133mm total length). Optimal tag placement locations, retention, tagging rates and mortality were evaluated. Plastic oval tags were attached in an anterior direction of the caudal peduncle near the middle of dorsal fin and vertebra (location a) and near the middle of anal fin and vertebra (location b). Three days after tagging, both tag locations tested showed tag retention over 99%, and one-way ANOVA test showed no significant difference in POT retention between location a and b. Maximum tagging rates for tagging operations were 200-250 fish h-1 operator-1 in 2009 and 300-350 fish h-1 operator-1 in 2010, respectively. Moreover, tagging mortality ranged from 0.2% to 0.7% and there was no significant difference between the two years (P > 0.05). To study their migratory movements, recapture has been carried out in the coastal waters of Weihai City: 21,202 individuals in July 2009 at Beihai and 18,350 individuals in July 2010 at Lidao. The number of recaptured individuals from four recapture methods were 434 (2.05%) in 2009 and 619 (3.37%) in 2010. The predominantly northward dispersal of P. olivaceus from release site in 2010 was probably influenced by environmental conditions and food availability. However, a radiative moving from release site was observed in 2009. The longest mark-recapture duration was 496 days, with a distance up to 215 Km from release site in 2009. Mean speed of released fish was calculated as 0.46 Km day-1 in 2009 and 1.05 Km day-1 in 2010. Furthermore, depth profiles suggested all juveniles were captured in depths of 2-60m, and the tagged juveniles spent most of the first 3 months between 3-17 m on the edge of land (=17 Km from the release site), which was followed by movements into 20-60 m depths. Patterns of movement showed a seasonal shift to deeper waters over time towards winter in both 2009 and 2010. These results indicated that the POTs for P. olivaceus were successfully developed and can be applied for stock enhancement research project, especially for long-term (>6 months) movement and behavioral studies.
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