Species Identification Of Fish Maw In China Trade Markets Using DNA Barcoding(COI)

Fish maw("Huajiao" in Chinese)is a common name of dried sea food made of fish swimming bladder,also known as "Yudu","Yupao" and "Yubai".Fish maw is one of the "eight sea food treasures" in China,is well-known because of its richness in collagen content and medical function.The utilization of fish maw can be traced back to 2000 years ago in Han Dynasty.Fish maw are traditionally made of species from Sciaenidae(Perciformes).With the increase of fish maw consumption,the decline of inshore fishery resources,the promotion of long-distance fishery in China and the globalization of trade market,fish maw from all over the world has been imported to China.Species for making fish maw have expanded from sciaenids to other marine and freshwater fishes.In this study,totally 405 fish maw specimens were collected from dried seafood markets in 9 cities of China,including Beijing,Wenling of Zhejiang Province,Xiamen of Fujian Province,Shantou,Shenzhen,Dongguang,Guangzhou and Zhanjiang of Guangdong Province,and Hong Kong in 2015-2018.First of all,every fish maw specimen was assigned into a morphological type,and its trade name was noted.DNA barcoding sequences(COI)from maw specimens were obtained and analyzed from each individual specimen,and were identified to species level or genus level based on COI comparison from databases and molecular phylogeny analysis.Finally,the fish maw identification guideline was developed for the first time based on fish maw morphology and molecular results.The main results of this study are as follow:(1)Twenty-three morphological types are classified from 340 completed fish maw specimens.Eight types belong to single-layered maw,including carrot-shaped,carrot-shaped with lateral appendiges,carrot-shaped with two upright ears,carrot-shaped with two long attached tubes,funnel type,"Y" type,piece of paper type and olive type.Fifteen types are double-layered maw,including carrot-shaped,round carrot-shaped,carrot-shaped with vein lines,carrot-shaped with lateral appendages,carrot-shaped with two upright ears,carrot-shaped with two long attached tubes,cylinder type,flat bag type,heart-shaped type,kongmin light type,Pipa type,"T" type,"U" type,"Y" type,crescent-shaped type and enlongated conical type.Additionally,39 specimens of fried fish maw and 26 specimens from maw debris were collected.(2)Eleven local trade names were noted from the 340 completed fish maw specimens,including "Imported Mian Maw","Local Mian Maw","Mian Maw","Huang-Hua-Yu Maw","Jin-Qian-Du","Spide Maw","San-Ya-Yu Maw","Bai-Hua Maw","Grouper Maw","Eel Maw" and "Cod Maw".(3)The DNA barcoding COI gene sequences of 210 maw specimens were successfully obtained,including 197 completed maw,4 fried maw and 9 maw debris,and the success rates were 57.94%,10.26%and 34.61%,respectively.All COI gene sequences were BLAST(basic local alignment search tool)within GenBank and FISH-BOL,and further confirmed to species or genus level using NJ phylogenetic tree.Totally 37 fish species from 5 orders(Anguilliformes,Cypriniformes,Siluriformes,Ophidiiformes and Perciformes),9 families and 27 genera were identified;among these,26 were confirmed to species level and 11 to genus level.(4)Fish maw trade in China shows the globalizaition trend.Among the 26 fish species identified,only 8 occur in Chinese waters.The rest 19 fishes distribute in Africa,America and Indo-West Pacific beyond China.(5)Two fish species,listed as "Critically Endangered"(CR)in IUCN Red List were found,both from Sciaenidae.One is Totoaba macdonaldi,a large sciaenid listed in CITES Appendix I since 1977,and the another is Bahaba taipingensis,an endemiclarge species in China,listed as Grade II of National Protected Animals.Based on international and national regulation and law,the commercial capture and trade of the two species are banned.Our research revealed the illegal trade of threatened fish species in China.(6)Base on molecular data and morphology of fish maw,the first fish maw identification guideline is made,which will provide baseline for further study on fish maw identification and international trade monitoring.