| Cephalopods are referred to all species of Cephalopoda in the mollusc phylum, with a short life cycle, fast growth speed and fast variation of biomass and have important ecological value and economic value.In recent years, the Cephalopods resource research mainly concentrated in the East China Sea and the South China Sea, less research on the resource of the Bohai Sea and the Yellow Sea. In order to provide theoretical basis for the conservation and sustainable utilization of Cephalopods, this research based on the survey data of biological resources in Yellow sea and Laizhou Bay, combined with the Literature data of Cephalopods in the East China Sea and South China Sea, comprehensive analys is of the Cephalopods resource status in offshore water of China. In addition, try using DNA barcoding of squids to make sure the evolutionary status of them.According to 214 stations of 2004-2012 years trawl survey data in the Laizhou Bay, the species composition, quantity distr ibution, spatial distribution, and correlation between the catch rate and environmental factors were analyzed with the catch rate. The results showed that there were five species of Cephalopods in the Laizhou Bay, inc luding Loligo spp., Octopus variabilis, Octopus ocellatus, Sepioda birostrata and Euprymna morsei, belonging to 4 genera 3 families 3 orders.The dominant species were squids and Octopus ocellatu. Squids occupied dominant status in different seasons, while the Octopus ocellatu only in autumn showed dominant status. The species composition and quantity distribution had changed in inter annual and seasonal. The seasonal regularity of resources is autumn > summer > spring.Spatially, the resources of Cephalopods were uniform distribution in the entire bay in the spring, the amount of resources was greater than the outside in the summer, the amount of resources outside was greater than the inner in the autumn.According to 352 stations of 2006-2013 years trawl survey data in the Yellow Sea, to study the Cephalopods resources status in this area. The results showed that there were 14 species of Cephalopods in the Yellow Sea, belonging to 8 genera 6 families 3 orders. The dominant species were Todarodes pacificus, Loligo japonica, Loligo edulis, Loligo beka, Sepia andreana and Sepioda birostrata. Ommastrephids and Loliginids were dominant groups. In the spring, the dominant species were Loligo japonica and Sepioda birostrata; in the summer, the dominant species were Todarodes pacificus and Loligo edulis; in the autumn, the dominant species were Todarodes pacificus and Loligo beka; in the winter, the dominant species were Loligo beka and Loligo japonica. The species composition and quantity distribution had changed in inter annual and seasonal. The seasonal regularity of resources is summer > autumn > spring > winter. Spatially, the resource of Cephalopods was increasing from north to south.According to published literature on the East China Sea and the South China Sea, the resources of Cephalopods to summarize and sort out. The results showed that there were 14 dominant species in the East China Sea, and there were changes in inter annual and seasonal. Octopus ocellatus, Abralia multihamata, Sepia esculenta, Sepia kobiensis and Euprymna morsei play important roles in the East China Sea. There were changes in the resources of Cephalopods, and the amount of resources in winter and spring was less than that in summer and autumn. Squids occupied an important position of Cephalopod resources in the South China Sea. There were 5 dominant species, Loligo chinensis has been the dominant species in all time. Compared with the condition in the 1980 s, Sepia lycidas and Loligo beka dominance decreased, and Loligo duvaucelii and Loligo edulis dominance increased. There were changes in the resources of Cephalopods, and the amount of resources in winter and spring was less than that in summer and autumn.According to COI gene sequence, using DNA barcoding of nine economic squids for molecular identification and molecular sys tem evolution relationship reconstruction.The results showed thatthe A+T content of the genomes was greater than the G+ C content, so the base composition have obvious A+T bias. Average genetic distance between squid species was 16.23%, average intraspecif ic genetic distance was 0.51%, interspecific genetic distance is 32 times as much as intraspecific genetic distance. Phylogenetic analysis showed that each squid respectively clustered to one branch in the phylogenetic tree and separated apart from other species, forming different evolutionary branches. These represented the COI as a DNA barcode for squid species and genus identification is feasible. Found that Loligo beka have already appeared differentiation and formed two groups. The average genetic distance of the two groups was 0.22% and 0.60%, the genetic distance between the two groups was 5.93%, and the genetic distance ratio was 27 and 10. This provided molecular evidence for identifying subspecies of Loligo beka. In addition, resorted the squids evolutionary position, provided molecular evidence for genus level division of squids. |
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