The mottled skate, Raja pulchra, is an economically valuable fish. However, due to a severe population decline, it is listed as a vulnerable species by the International Union for Conservation of Nature. To analyze its genetic structure and diversity, microsatellite markers were developed using 454 pyrosequencing. A total of 17,033 reads containing dinucleotide microsatellite repeat units (mean, 487 base pairs) were identified from 453,549 reads. Among 32 loci containing more than nine repeat units, 20 primer sets (62%) produced strong PCR products, of which 14 were polymorphic. In an analysis of 60 individuals from two R. pulchra populations, the number of alleles per locus ranged from 1–10, and the mean allelic richness was 4.7. No linkage disequilibrium was found between any pair of loci, indicating that the markers were independent. The Hardy–Weinberg equilibrium test showed significant deviation in two of the 28 single-loci after sequential Bonferroni’s correction. Using 11 primer sets, cross-species amplification was demonstrated in nine related species from four families within two classes. Among the 11 loci amplified from three other Rajidae family species; three loci were polymorphic. A monomorphic locus was amplified in all three Rajidae family species and the Dasyatidae family. Two Rajidae polymorphic loci amplified monomorphic target DNAs in four species belonging to the Carcharhiniformes class, and another was polymorphic in two Carcharhiniformes species.

In order to prove the fisheries-related hypothesis of the presence of two local populations of the mottled skate, Beringraja pulchra in the Yellow Sea (Sensu Jo et al., 2011), the geographic variations of 90 individuals (in molecule) and 129 individuals (in morphology) were investigated. The skates were collected from the middle Yellow Sea (Daechungdo), southern Yellow Sea (Heuksando), and the middle East Sea (Ulleungdo) using gill nets, bottom trawls and longlines. Comparing 471 base pairs of mitochondrial DNA cytochrome c oxidase subunit I (mtDNA COI) sequences, only three haplotypes (BR1-BR3) were found. The Daechungdo and Heuksando individuals displayed all three haplotypes, whereas the Ulleungdo individuals displayed a single haplotype (BR3). Pairwise fixation indices (FST) showed that the Daechungdo and Heuksando individuals were not genetically distinguishable (with a value of −0.0344), whereas the Ulleungdo individuals were clearly distinct from both the Daechungdo and Heuksando individuals (with values of 0.6875 and 0.6871, respectively). Similar to the molecular result, a canonical discriminant analysis based on seven morphometric characters showed that the Ulleungdo individuals had positive values on the first axis, whereas those from the other two locations had negative values, slightly differentiating the two populations (East Sea population vs Yellow Sea population). This study is the first to identify two populations of mottled skate in the northwest Pacific.

This study investigated the food quality characteristics of mottled skate Raja pulchra including the proximate composition, taste, color, flavor and texture as affected by area caught (Heuksando and Daecheongdo), sex and fish weight (heavy, intermediate and light grades). Based on viable cell counts, all of the mottled skates studied remained fresh. The moisture and protein contents of the mottled skate did not differ by the area caught and fish weight, but differed by fish sex. The taste of mottled skate was affected only by fish weight. The texture of the mottled skate differed according to fish sex and fish weight. The odor intensity did not differ for the three parameters.

Catches, CPUE, fishing season, disc width composition and fishing ground were studied to rebuild skate ray, Raja pulchra resource by the offshore longline fishery in Heuksan-do, Korea. Annual catches and CPUE of skate ray were increased from 2003 to 2010 (CPUE: from 2007 to 2010) continuously. The main fishing season of the skate ray was from December to next May. Disc width at 50% maturity for Raja pulchra by sex were estimated to be 65.83cm, 57.01cm by female and male respectively. The range of disc width was 22.3-112.0cm and the average disc width was 66.9cm, 60.0cm by female and male of Raja pulchra respectively during 2007-2010. Annual average of disc width of female skate ray was decreased from 2007 to 2010. The fishing grounds were formed from the coastal water off Hong-do to the coastal water off Gyeogyeolbiyeol-do, Korea. The center of fishing ground in October was formed in the northwestern coastal water off Gyeogyeolbiyeol-do and separated from that of the other months.

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