**2. Material and Methods**

#### *2.1. Sample Collection*

A total of 51 parrotfish were collected from Hainan and Sansha in China (collection information available in Table 1). All samples in this experiment were obtained with the assistance of local fishermen and buyers on 5 October 2018. Back muscles were collected from each sample and preserved in 95% ethanol prior to DNA extraction. All samples were preserved at the South China Sea Fisheries Research Institute, Chinese Academy of Fisheries Sciences, China.

**Table 1.** Voucher and sequence information for the 51 specimens. Process IDs are sequence numbers of voucher specimens in GenBank, and Voucher IDs are voucher numbers in the South China Sea Fisheries Research Institute. BOLD is a summary of identification based on the barcode sequence of each species obtained using the BOLD.


### *2.2. DNA Extraction*

DNA was extracted from the muscle samples using a HiPure Mollusc DNA Kit (Axygen Biosciences, San Francisco, CA, USA) according to the manufacturer's instructions. All DNA samples were stored at −20 ◦C, followed by polymerase chain reaction (PCR) amplification.

#### *2.3. PCR and DNA Sequencing*

Fragments of the mitochondrial *CO*I gene were amplified using the following universal fish barcoding primers: forward fish-F 5 -TCRACYAAYCAYAAAGAYATYGGCAC-3 and reverse fish-R 5 -ACTTCAGGGTGACCGAAGAATCAGAA-3 . The total volume and thermal cycle sequences of the PCR were performed as described previously [35]. The amplified PCR products were checked for optimal fragment sizes on 1.5% agarose gels. The PCR products with a single bright band were sent to Beijing RuiBiotec (Beijing, China) for sequencing in both directions. All sequences were loaded onto BOLD in the project.
