Study On The Resources And Plylogenetic Evolution Of Cartilagious Fishes In Fujian Coastal Waters

In this paper, the present situation of cartilaginous fishes resources based on the data from bottom trawl surveys in Fujian coastal waters during 2006 and 2007 were analyzed. Some mitochondrial cytochrome c oxidase subunit I (COI) gene of cartilaginous fish were amplified, sequenced and analyzed, and phylogenetic tree was constructed. AFLP technology was used as the preliminary studies of phylogeny evolution in the cartilaginous fishes too. The main results were as follows:1. Based on the data from bottom trawl surveys in Fujian coastal waters during 2006 and 2007, the species composition,quantity,resource density,habitat density and its seasonal variation of cartilaginous fishes were analyzed. The results showed that there were 17 species of cartilaginous fishes belonging to 5 orders, 9 families and 9 genus in four voyages, and Myliobatiformes was the dominant order, which accounted for 9 species. Spring, summer, autumn and winter voyages caught 8, 13, 15 and 9 species of cartilaginous fishes respectively; Chiloscyllium plagiosum, Raja hollandi, Dasyatis laevigatus, Dasyatis navarrae, Narke japonica and Dasyatis microphthalmus were caught in four voyages. The percentage of weight in cartilaginous fishes caught in four voyages accounted for 15.99% of total fishes; the average resource density and habitat density accounted for 99.38 kg/km2 and 295.81 ind/km2 respectively; the average resource density were highest in summer, which was 170.28 kg/km2,and the average habitat density were highest in autumn,which was 504.73 ind/km2. The average resource density in eastern Fujian coastal waters was highest, which was 200.77 kg/km2. The average resource density in Xiamen coastal waters was highest in spring and winter, while eastern Fujian coastal waters were highest in summer and autumn. In 17 species of cartilaginous fishes the appearing frequency of Dasyatis zugei was highest, which was 27.08%. The resource density of Dasyatis navarrae was highest, which was 21.52 kg/km2;While the habitat density of Chiloscyllium plagiosum was highest, which was 86.25 ind/km2. The IRI of Chiloscyllium plagiosum was highest, which was 756.52. Chiloscyllium plagiosum and Dasyatis zugei were dominant cartilaginous species in Fujian coastal waters.2. 618 bp mitochondrial COI gene of 15 species of cartilaginous fishes counted for 74 individuals were obtained by PCR technique, belonging to 35 haplotypes. Within 618bp mitochondrial COI gene there were 267 variable sites which contained 253 parsim informative sites and 14 singleton sites,without any insertion or deletion site. The average base compositions of 35 haplotypes were 31.8%,26.2%,25.4% and 16.6% for T, C, A and G, respectively. Average G concentration of all cartilaginous fishes was lower (from 14.7% to 18.3%). The average A+T content was 57.2%, higher than the G+C content (42.8%). A+T average content in 1st, 2nd, 3rd codon sites were 45.5%, 57.2% and 68.7% respectively. Average ratio of conversion and transversion for all the sites was 1.4, and the first codon site had the highest ratio (5.0). The conversion value (52) and transversion value(43) in the third codon site were significantly higher than the first and second codon sites. Based on Kimura 2 parameter model, the genetic distances of 15 species of cartilaginous fishes counted for 74 individuals were calculated. The average genetic distance within all rays and skates individuals was 0.1626, while within shark individuals was 0.0851. The genetic distance between shark and rays–skates was 0.2664. Within 74 individuals the average genetic distance was 0.1936. Took the homology sequences of 35 haplotyes and Hydrolagus lemures as cluster analysis and constructed NJ cluster tree. Clustering tree showed that the same species individual were clustered as one branch, and all the same genus species were clustered as one branch too. The clustering tree according traditional classification system. The studies showed that mitochondrial COI gene can be used as species and classcification identify of these cartilaginous fishes.3. AFLP technology was used to study the systematic evolution of 14 species of cartilaginous fishes in Fujian coastal waters. For 71 cartilaginous individual, six pairs of selective primers (E-AAG/M-CTA, E-AGG/M-CCG, E-ACG/M-CCG, E-AGG/M-CAG, E-ACC/M-CTA,E-ACC/M-CCG) amplified 241 AFLP locis,including 236 polymorphic locis. The analysis results of Popgene software showed that the genetic distances within 14 species were 0.1308～0.5720. The genetic distance between Dasyatis navarrae and Dasyatis akajei was lowest(0.1308), while between Scoliodon sorrakowah and Narke japonica was highest(0.5720). UPGMA clustering tree showed that the same species were clustered together, but for family and upgrade taxa, clustering result were different to traditional classification system. Results showed that AFLP technology was an effective way in the study of cartilaginous fish phylogenetic evolution below genus taxa.