OTOLITH MARKING OF PERCOCYPRIS PINGI AT EARLY LIFE STAGES

Percocypris pingi is an endemic fish to the upper reaches of the Yangtze River. However, the wild resources and distribution areas of this fish have dramatically declined because of anthropogenic influences including cascade dam construction and overfishing. Artificial propagation and releasing juveniles into its distribution areas is one of important approaches to restore wild populations of P. pingi, and has been implemented for several years. Developing responsible methods to tag or mark released individuals is helpful in discriminating them from wild-born populations, which is very important to assess the stocking enhancement programs. Otolith marking is an important, cost-effective approach to massively mark larval and juvenile fish in many stocking programs. However, there is still a lack of robust research on otolith marking of P. pingi. In order to assess the feasibility of otolith marking methods for P. pingi at early life stages, heated water of (20.8±0.3)℃ and chilled water of (10.8±1.2)℃ were used to thermally mark 20-day-old P. pingi, and 50—200 mg/L solutions of Alizarin complex one (AC) and Alizarin red S (ARS) were respectively used to mark 35 and 45-day-old P. pingi that had been thermally marked. The results showed that: (1) the otolith increments were distinct to be recognized, and the regressed equation between lapillus Increment width (IW) and the duration in heated water (T) was IW=0.16462+0.24762T; (2) The red-orange fluorescent marks on otoliths were clearly identified under green laser; (3) the quality of AC mark was significantly affected by concentration (P<0.05), not significantly affected by total length (P>0.05), and the mark quality among lapillus, sagitta and asteriscus had significant differences (P<0.05); (4) the quality of ARS mark was not significantly affected by concentration and total length (P>0.05), and the mark quality among lapillus, sagitta and asteriscus had significant differences (P<0.05). The results of this study suggested that the methods of otolith fluorescent, thermal and their combinational marking could be used for marking P. pingi at early life stages.