The implement of plastic oval tags for mark-recapture in juvenile Japanese flounder ( Paralichthys olivaceus ) on the northeast coast of Shandong Province, China

Abstract

As part of the stock enhancement research project of Shandong Province, China, plastic oval tags (POTs) were used to mark juvenile Japanese flounder for release, Paralichthys olivaceus (70 to 133 mm total length, TL), in 2009 and 2010. Optimal tag placement locations, retention, tagging rates, and mortality were initially evaluated. Mark–recapture experiments were carried out in the coastal waters of Weihai City to study their migratory movements: 21,202 individuals in July 2009 at Beihai and 18,350 individuals in July 2010 at Lidao. The number of recaptured individuals were 434 (2.05% recapture rate) in 2009 and 620 (3.38% recapture rate) in 2010. A radiative movement from the release site was observed in the 2009 experiment; however, the tagging experiment showed a predominantly northward dispersal of tagged flounder from the release site in 2010. The mean movement speed of the released fish was calculated as 0.46 km day -1 in 2009 and 1.05 km day -1 in 2010. Furthermore, in 2009, the average TL and wet mass increments were 36.3 ± 8.4 mm month -1 and 27.13 ± 16.09 g month -1 , respectively 1 to 6 months after releasing; however, the increments were 14.7 ± 8.8 mm month -1 and 5.65 ± 4.17 g month -1 , respectively in 2010. Key words : Paralichthys olivaceus, plastic oval tag, mark–recapture, movement, growth.