2.2 Morphological identification
The body length, weight and other measurable traits of the specimen were measured. The morphological taxonomic characteristic of Tetraodontiformes is mainly base on the body shape, fin number, stripes, spots, body color and mouth shape, etc described by Chen & Zhang (2015) and Su & Li (2002).

2.3 DNA extraction and quality inspection

DNA was extracted from the muscle of fish by using TIANamp Marine Animals DNA Kit (TIANGEN BIOTECH (BEIJING) CO.,LTD.). For detailed steps of DNA extraction, refer to the kit manual. DNA samples were stored at -20 ℃.
Nano-300 micro-spectrophotometer (Allsheng) was used to detect the concentration and purity of DNA samples, and the quality of the DNA samples was detected by 1% agarose gel.

2.4 PCR amplification and DNA sequencing

The published universal primers for fish DNA barcodes (Ward et al., 2005) were used for PCR amplification and sequencing, and the length of the amplification product was 707bp. The primers were as follows:
COIF: 5’-TCAACCAACCACAAAGACATTGGCAC-3’
COIR: 5’-TAGACTTCTGGGTGGCCAAAGAATCA-3’
PCR amplification was in total volume of 25 μL, containing 12.5 μL Taq Mixture (2ⅹ), 2 μL DNA template, 1 μL of each primer (10 μM) and 8.5 μL ddH2O. Thermo cycling were carried out as follows: 94 ℃ for 5 minutes, 94 ℃ for 30 seconds, 53~56 ℃ for 30 seconds, 72 ℃ for 1 minute, cycle 35 times from step 2 to step 4, finally 72 ℃ for 10 minutes. PCR products were detected by 1% agarose gel, and the qualified samples were sent to BGI in Qingdao for direct bidirectional sequencing.

2.5 Data analysis

The raw sequences were assembled by seqman of Lasergene software package (Swindell & Plasterer, 1997; Burland, 1999) and aligned by Cluster W in BioEdit version 7.0.9 (Hall, 1999). After correction and alignment, the effective sequence length was 687 bp. The haplotypes were analyzed by DNASP version 5.10.01 (Librado & Rozas, 2009). Each haplotype sequence was compared for similarity in NCBI (https://www.ncbi.nlm.nih.gov/) and BOLD (http://www.barcodinglife.org/). The top matches showing ≥ 98% similarity were used as the preliminary identification results. Then based on Kimura- 2- parameter (K2P) mode (Kimura, 1980), the genetic distance of different taxonomic levels of Tetraodontiformes was calculated.
Bothus myriaster and Glyptocephalus stelleri were selected as the outgroups, based on the haplotypes of COI gene of Tetraodontiformes, the Neighbor-joining tree (NJ tree) of Tetraodontiformes was constructed in Mega 7.0 (Kumar, 2015).