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Skates and rays are commercially important fish in South Korea, and among them, Beringraja pulchra has the highest economic value. However, the similar morphological traits among skates and rays are often exploited for seafood fraud. Here, we designed both Beringraja pulchra-specific and skate-universal primer sets, capable of detecting short sequences in the cytochrome oxidase subunit I gene, and developed highly sensitive and reliable quantitative real-time PCR (qPCR) assays to differentiate between Beringraja pulchra and other skate and ray species. AΔCq method based on differences in the amplification efficiency was developed, validated, and then used to confirm the presence of Beringraja pulchra in twenty-six commercial skate products. The averageΔCq value obtained for other skate species (18.94 ± 3.46) was significantly higher than that of Beringraja pulchra (1.18 ± 0.15). For on-site applications, we developed an ultra-fast qPCR assay, allowing for completion of the entire analytical procedure within 30 min.

Summary 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.

The by-products of the skate processing industry have bioactive properties but are mostly discarded. In the present study, the properties of skate cartilage, a major by-product of skate processing that is rich in chondroitin sulfate (CS) and type II collagen were investigated. Enzymatically-hydrolyzed type II collagen peptides (CP) and thermally hydrolyzed CS oligosaccharides (CSo) from skate cartilage were prepared and their antioxidant activities were studied. High free radical scavenging activity was observed in the

The mottled skate, Beringraja pulchra is one of the commercially important fishes in the market today. However, B. pulchra identification methods have not been well developed. The current study reports a novel real-time PCR method based on TaqMan technology developed for the genetic identification of B. pulchra . The mitochondrial cytochrome oxidase subunit 1 (COI) nucleotide sequences of 29 B. pulchra , 157 skates and rays reported in GenBank DNA database were comparatively analyzed and the COI sequences specific to B. pulchra was identified. Based on this information, a system of specific primers and Minor Groove Binding (MGB) TaqMan probe were designed. The assay successfully discriminated in 29 specimens of B. pulchra and 27 commercial samples with unknown species identity. For B. pulchra DNA, an average Threshold Cycle (Ct) value of 19.1±0.1 was obtained. Among 27 commercial samples, two samples showed average Ct values 19.1±0.0 and 26.7±0.1, respectively and were confirmed to be B. pulchra based on sequencing. The other samples tested showed undetectable or extremely weak signals for the target fragment, which was also consistent with the sequencing results. These results reveal that the method developed is a rapid and efficient tool to identify B. pulchra and might prevent fraud or mislabeling during the distribution of B. pulchra products.

참홍어는 홍어목 가오리과에 속하는 연골 및 저서성 어류의 하나로서, 대표적인 판새류 중의 하나이다(Jo et al., 2013). 참홍 어의 형태는 최대 전장이 1.5 m에 달하는 대형어류로, 전체 모 양의 경우 마름모로서 가오리와 비슷하나, 더 둥글고 가로로 퍼 져 있고, 색의 경우 등이 갈색이면서 연한 색의 크고 작은 둥근 무늬가 있고, 배는 흰색이다. 또한, 참홍어의 형태는 꼬리의 경 우 수컷은 1줄, 암컷은 3줄로, 이들에는 날카로운 가시가 줄지 어 있고, 배지느러미 뒤쪽의 경우 대롱모양의 생식기 2개가 몸 밖으로 튀어 나와 있으며 가시가 나와 있다(Hwang, 2009). 참 홍어의 생태는 30-200 m의 깊이와 5-15°C 범위에 서식하는 냉 수성 어종이고, 주로 새우류와 소형 어류 등을 먹이로 하는 생태 적 특성을 가지고 있으며, 깊은 바다에서 삼투압 조절을 위하여 생체 내 질소화합물의 최종 대사산물인 요소를 사용하는 대표 적인 어종 중의 하나이다(Ishihara, 1990; Jeong, 1999). 이와 같 은 생태적 특성으로 인하여 참홍어는 우리나라 연안의 경우 흑 산도 연안과 대청도 연안과 같은 서해안 등에서 주로 서식되고, 어획되어 이들 지역의 주 소득원이 되고 있다(Chyung, 1977; Jo et al., 2012a). 참홍어는 어획 후 빙온 이상의 온도에 저장 하 는 경우 요소(urea)가 암모니아(ammonia)로 전환되어 코를 자 극하는 향, 톡 쏘는 맛과 같은 특유의 풍미를 나타낸다. 따라서 호남지방에서는 예로부터 서해안에서 어획된 참홍어의 고유 특 울릉도산 참홍어(Beringraja pulchra)의 관능 및 영양 특성 임양재·조현수·정경숙·황보규·강상인·허민수·김진수*

To obtain geographical range and growth-kinetics parameters of mottled sake (Beringraja pulchra) populations in the Yellow Sea, three mark-recapture experiments were carried out. Overall, 991 tagged individuals were released, and 4.1% of them were recaptured with the mean release period of 339 d (range, 8-1,420 d) and the mean growth rate of (female, ; male ). In the first experiment, 667 individuals were released at Heuksan Island from April to June, 2007-2009, and 30 individuals were recaptured mainly at the north and the north-east coasts of the island, indicating absence of migration to the south of the island. In the second experiment, 323 individuals were released at several fishing grounds scattered in the Yellow Sea in 2010-2013, and 11 individuals were recaptured at points deviated to all directions from the releasing points. As the last, one individual was released with pop-up satellite archival tag at a costal point (`N, `E) off Hong Island on May 21, 2010. The tagged individual migrated to a north-east location (`N, `E) of Eocheong Island by Aug. 25, 2010. The data archived for the three months in the tag indicated that the migration path had depths of 48-80 m and temperature of . The results indicated that mottled sake populations had a localized habitat ranges at the north of Heuksan Island and the west of Hong Island while growing at the rate of .

Catch of the mottled skate Raja pulchra in waters of Primorye in the spring period was recorded. Until this time, in Russian waters of the Sea of Japan, its habitation only off Western Sakhalin was reliably known. The length of the caught specimen was TL 115 cm, which exceeds the length known from published sources. Possible ways of penetration of the mottled skate along the continental coast from the southern part of the Sea of Japan and from the north from Western Sakhalin are discussed.

The gonadsomatic index (GSI) of mottled skate was the highest in April, GSI and HSI showed a reverse phase for its reproductive cycle. The fish had one pair of egg capsules, having 1 to 7 fertilized eggs, and spawned all the year round. When surveying the reproductive characteristics of females over 63 ㎝ in disc width, we found the spawning peak was between April to June, and the appearance ratio of egg capsules was the highest in May (32.1%). The eggs were hatched at 8°C, 13°C, 18°C, water temperature (12.8 to 24.2°C), and the best hatching temperature was 18°C. The number of fish hatched was 4 to 5 fish/egg capsules, and the hatching rate was 100%. The sex ratios of hatching larvae were 45.5% female and 54.5% male. Therefore this study will provide fundamental data and information for artificial reproduction of the mottled skate.

This study was conducted to compare quality characteristics of imported skate rays. The moisture content was higher in imported skate rays than in domestic mottled skate, while the protein content displayed a contrasting pattern. From measurements of the volatile basic nitrogen content, pH, viable cell counts, and urea and ammonia contents, the freshness of skate rays imported from Chile, Canada and Uruguay was considered to be inferior to domestic mottled skate, while the freshness of skate rays imported from the USA was similar. The measurement of physicochemical properties revealed that four kinds of imported skate rays were of inferior quality, as compared to domestic mottled skate.

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.