Korean Rockfish Research Articles

Effect of Yellow Clay on the Oxygen Consumption Rate of Korean rockfish, Sebastes schlegelii

Yellow clay dispersion has been applied to minimize fisheries impact by the red tide Cochlodinium polykrikoides blooms in Korean coasts since 1995. The present preliminary study documents the effect of yellow clay on Korean rockfish, Sebastes schlegelii, in terms of oxygen consumption rate (OCR). The OCR in the low clay suspension (0.05 and 0.23 %, w/w) showed normal level compared to the control. In contrast, the OCR for each one of three replicates in the high clay suspension (1.16 and 5.58 %, w/w) was not returned to the previous level that clay was not treated, indicating that high clay suspension ( 1.16%, w/w) might give negative effect on Korean rockfish. Overall, this result suggests that field application of clay to control Harmful Algal Blooms (HABs) may not give impact on Korean rockfish once the clay is dispersed in a low concentration ( 0.23 %). In order to understand the changes of OCR in the repeated exposure to clay, it is required to do further studies on the changes of OCR when the fish is exposed to clay repeatedly after recovery in the normal seawater.

해상가두리 양식장에서 배합사료 및 생사료 공급에 따른 조피볼락(Sebastes schlegeli)의 성장 및 육질 비교

This study was conducted to compare extruded pellets (EP) and soft extruded pellets (SEP) with a raw fish-based moist pellet (MP) diet on the growth and flesh quality of Korean rockfish Sebastes schlegeli. Three groups of 20,000 fish (initial mean weight 133 g) per net-cage (<TEX>$6{\times}12{\times}7m$</TEX>) were fed commercial EP, SEP or MP for 16 months. The survival of fish fed SEP was higher than those of fish fed EP or MP. The highest growth performances were observed in the mean weight gain, total weight gain, and feed efficiency of fish fed MP, followed by those fed EP and SEP. Among the fish fed on extruded pellets, the total weight gain of fish fed SEP was higher than that of those fed EP, while fish fed EP grew faster than those fed SEP. No notable differences in body composition, sensory scores or textural properties of the dorsal muscle were observed in fish fed on EP, SEP or MP. Thus, it is suggested that extruded pellets, rather than raw fish-based moist pellets, could be fed to Korean rockfish without compromising flesh quality.

Low-value fish used as feed in aquaculture were a source of furunculosis caused by atypical Aeromonas salmonicida

Many Korean rockfish farms (Sebastes schlegeli) have suffered from a disease causing high mortalities, since outbreaks of furunculosis first occurred in 2008. The aims of this study were to investigate the causal agent of the disease as well as the epidemiological aspects of its occurrence. Rockfish and low-value fish which are used as feed in rockfish farms were sampled and examined for isolation of the causal agent of the disease. All isolates derived from the rockfish were non pigmented, relatively slow-growing bacteria, which were characterized as atypical Aeromonas salmonicida. In particular, vapA gene sequences of the isolated bacteria were most closely related to A. salmonicida. Some of the sampled low-value fish, including big head croaker, Japanese anchovy, and Konoshiro gizzard shad, were infected with atypical A. salmonicida as well. In this study, a total of 22 isolates of A. salmonicida were each determined to be partially resistant to amoxicillin and to oxytetracycline and trimethoprim/sulfamethoxazole. The mean value generated by normalized resistance interpretive (NRI) analysis for florfenicol was 36.6mm, with a standard deviation (SD) of 2.2mm. Using a 2.0 SD limit, the wild type cut off value was ≥32mm, indicating that our isolates were all classified as wild type strains for florfenicol. This study indicates that low-value fish used as feed in the sea-cage rockfish farms are a key source of furunculosis, which may cause continuous disease incidence since the first outbreaks.

Evaluation of citrus by-product on growth performance, innate immunity and disease resistance against Edwardsiella tarda of Korean rockfish Sebastes schelgeli

Evaluation of citrus by-product on growth performance, innate immunity and disease resistance against Edwardsiella tarda of Korean rockfish Sebastes schelgeli

Molecular cloning and expression analysis of estrogen receptor betas (ERβ1 and ERβ2) during gonad development in the Korean rockfish, Sebastes schlegeli

Estrogen receptors (ER) play a crucial role in mediation of estrogen activities. Here we report the isolation and expression analysis of ERβ1 and ERβ2 from ovary Korean rockfish (Sebastes schlegeli). were isolated using reverse transcription-polymerase chain reaction (PCR) and rapid amplification of cDNA ends procedures. The cDNA of this study, ERβ1 (588 amino acids) and ERβ2 (659 amino acids) were identified using reverse-transcriptase PCR (RT-PCR) and rapid amplification of cDNA ends procedures. Structural analysis showed both ERβs contain six typical nuclear receptor-characteristic domains. Phylogenetic analysis indicated that Korean rockfish ERβs were highly conserved among teleost. RT-PCR confirmed that the ERβs were widely distributed in both gonads and extra gonadal tissues. Further, we analyzed the expression patterns of male and female S. schlegeli during the reproductive cycle using quantitative real-time PCR (qRT-PCR). The results showed that the highest expression levels were observed in testis at immature sperm stage for both of KrERβ1 and KrERβ2. For female, the expressions of KrERβ1 and KrERβ2 were significantly higher in the ovary at the early-oocyte stage. Cloning these two ERβ subtypes in the Korean rockfish, together with the information on expression levels in adult fish has given us the foundation to investigate their possible role in brain-pituitary-gonad neuroendocrine axis in future studies.

Cloning and expression analysis of Foxl2 during the reproductive cycle in Korean rockfish, Sebastes schlegeli

Foxl2 is a member of the winged helix/forkhead family of transcription factors and is known to regulate ovarian aromatase, which plays a crucial role in ovarian differentiation. To address the role of Foxl2 in gonads and brain during gonadal development, we isolated the full-length cDNA of Foxl2 and analyzed its spatiotemporal expression patterns in the viviparous teleost Korean rockfish, Sebastes schlegeli. Tissue distribution pattern revealed that the Foxl2 was detected in the liver, fat, gill, brain, and ovary, but could hardly be found in the testis. Reverse transcriptase PCR suggested that Foxl2 in Korean rockfish may involve in ovary development in the study of expression level during gonads development. It also revealed that the stage of highest expression level for Foxl2 was almost much earlier than cyp19a1a and cyp19a1b during the gonadal development stage in gonads and brain except for cyp19a1a in brain. Furthermore, the expression pattern of Foxl2 as well as aromatases may imply the role of Foxl2 in the up-regulation of aromatases not only in the female fish but also in male.

The caligid life cycle: new evidence fromLepeophtheirus elegansreconciles the cycles ofCaligusandLepeophtheirus(Copepoda: Caligidae)

The developmental stages of the sea louse Lepeophtheirus elegans (Copepoda: Caligidae) are described from material collected from marine ranched Korean rockfish, Sebastes schlegelii. In L. elegans, setal number on the proximal segment of the antennule increases from 3 in the copepodid to 27 in the adult. Using the number of setae as a stage marker supports the inference that the post-naupliar phase of the life cycle comprises six stages: copepodid, chalimus I, chalimus II, pre-adult I, pre-adult II, and the adult. We observed variation in body length in both of the chalimus stages which we consider represents an early expression of sexual size dimorphism. We interpret the larger specimens of chalimus I as putative females, and the smaller as putative males; similarly with chalimus II, larger specimens are putative females and the smaller are males. Two patterns of life cycle are currently recognized within the Caligidae but the evidence presented here reconciles the two. We conclude that the typical caligid life cycle comprises only eight stages: two naupliar, one copepodid, and four chalimus stages preceding the adult in Caligus, but with the four chalimus stages represented by two chalimus and two pre-adult stages in Lepeophtheirus. This is a profound change with significant implications for the aquaculture industry, given that lice monitoring protocols include counts of chalimus stages and use temperature to predict when they will moult into the more pathogenic, mobile pre-adults. Lice management strategies must be tailored to the precise life cycle of the parasite.

부산 연근해의 해양오염퇴적물과 식용 어류 체내의 PCBs와 유기염소계 농약의 분포 및 잠재적인 인체 위해성평가

Polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) contents in marine sediment and edible fish (4 species) from the estuary near the Yongho wharf in Busan were determined to assess their presence and their potential health risk to the local population through fish consumption was also assessed. Levels of ΣPCBs and ΣDDTs in marine sediment were 3.22~ 197.65 and 1.77~20.27 ng/g dw, respectively. HCHs and endosulfan sulfate concentrations in bottom sediment were 1.42~6.08, 0.56~ 13.89 ng/g dw, respectively. The bottom sediment in the offshore of the Yongho wharf may be characterized as semi-polluted status with potential adverse marine biological effects in terms of sediment quality guidelines of US NOAA. The mean concentrations of ΣPCBs in the tissues of olive flounder (Paralichthys olivaceus), Korean rockfish (Sebastes schlegelii), file fish (Stephanolepis cirrhifer) and abbysal searobin (Lepidotrigla abyssalis) were 67.37, 10.20, 48.26, 22.81 ng/g lw, respectively. DDTs and HCHs were also detected in all fish samples. Lifetime cancer risk and target hazard quotient to local residents due to those fish consumption were found to pose negligible cancer and non-cancer risk.

Redescription of two Pennellids (Copepoda, Siphonostomatoida) from Korea with a key to species of Peniculus von Nordmann, 1832

Redescriptions of two pennellid copepods, Peniculus minuticaudae Shiino, 1956 and Peniculus truncatus Shiino, 1956, are provided, based on postmetamorphic adult females collected from marine ranched fishes captured at Tongyeong marine living resources research & conservation center, Korea. Peniculus minuticaudae was collected from the soft fin rays of black scraper Thamnaconus modestus. It can be distinguished from the other two closely related congeners Peniculus ostraciontis Yamaguti, 1939 and Peniculus truncatus by having a well developed triangular-shaped abdomen; the abdomen is rudimentary in other two species. This is thefirst report of the occurrence of Peniculus minuticaudae in Korea. Peniculus truncatus was collected from the dorsal fin of Korean rockfish Sebastes schlegelii. It can be distinguished from Peniculus minuticaudae by the combination of a rudimentary abdomen, long neck and setae on leg 1 and from Peniculus ostraciontis by the long neck, slender trunk, and setae on leg 1. It is also shown that Peniculus truncatus captured from the same host in Korea was misidentified as Peniculus ostraciontis and hence, this is thesecond record of the occurrence of Peniculus truncatus in Korea. A key is provided for the 14 nominal species of Peniculus.

Cloning and expression analysis of vasa during the reproductive cycle of Korean rockfish, Sebastes schlegeli

Vasa, which is a conserved member of the DEAD-box protein family, plays an indispensable role in primordial germ cell proliferation. However, the expression of vasa gene during the reproductive cycle in ovoviviparous fish has not been documented. In this study, the full-length sequence of vasa was obtained from the ovary of Korean rockfish (Sebastes schlegeli) using reverse transcription-PCR and rapid amplification of cDNA ends. The Vasa with a mature protein of 650 amino acids showed greatest homology (84%) with giant gourami (Osphronemus goramy) and Pacific bluefin tuna (Thunnus orientalis). The expression of vasa mRNA in Korean rockfish was detected in gonads only, suggesting its specific role in gonadal development. In addition, seasonal changes in the vasa expression levels were examined in gonads by quantitative real-time PCR. The vasa transcript levels in adult testis were found higher during spermatogenesis than during spermiation. The vasa transcript levels remained relatively high at the early ovary stage but declined during ovary maturation in adult female fish. These results suggest that the vasa gene play an important role in spermatogenesis and early oogenesis during the reproductive cycle of Korean rockfish.

Cloning and expression analysis of the cytochrome P450c17s enzymes during the reproductive cycle in ovoviviparous Korean rockfish (Sebastes schlegeli)

Cytochrome P450c17 (CYP17, 17α-hydroxylase/17, 20-lyase) plays a critical role in the production of androgens and estrogens in vertebrates. We isolated the full length cDNAs of P450c17-I and P450c17-II from Sebastes schlegeli. The cDNA sequences of P450c17-I and P450c17-II encoded 515 and 533 amino acid residues respectively. The putative P450c17-I and P450c17-II enzymes of Korean rockfish share high sequence identity with that of Japanese flounder (92% and 81%) respectively. Our current study describes that P450c17s of Korean rockfish are mainly expressed in gonads, head kidney and kidney by RT-PCR. Quantitative real-time PCR showed that the expression patterns of Korean rockfish P450c17s were developmental stage-dependency. In addition, the testosterone (T) and gonadosomatic index (GSI) levels further support the important role of P450c17-I during shift in steroidogenesis. Taken together, this study provides information about the Korean rockfish P450c17s characterization and mRNA expression as such helps in further understanding of its function in gonadal development.

Cloning and expression analysis of follicle-stimulating hormone and luteinizing hormone receptor during the reproductive cycle in Korean rockfish (Sebastes schlegeli)

Full-length cDNA sequences encoding the receptors for follicle-stimulating hormone (FSHR) and luteinizing hormone (LHR) were isolated from ovary of Korean rockfish (Sebastes schlegeli) using reverse transcription-polymerase chain reaction (PCR) and rapid amplification of cDNA ends procedures. The cDNA of the KrFSHR encodes a predicted protein of 703 amino acids that showed the greatest homology with European seabass (Dicentrarchus labrax) (78 %) and gilthead seabream (Sparus aurata) (73 %). The cDNA of the KrLHR encodes a predicted protein of 703 amino acids and exhibited the highest homology with European seabass (Dicentrarchus labrax) (79 %) and gilthead seabream (Sparus aurata) (76 %). Besides the gonads, expressions of GTHRs mRNA were also obtained in extra gonadal tissues. Seasonal changes in the gonads expression profiles of KrGTHRs mRNA were examined by quantitative real-time PCR, and the present results suggest that levels for KrFSHR mRNA increase during gonadal growth, whereas KrLHR shows high levels during the late gamete generation period. Our study provides molecular characterization of the GTHRs and expressions profile during reproductive cycles, reinforcing previous knowledge of GTHRs important role in the reproductive endocrine regulation of Korean rockfish.

Draft Genome Sequence of Staphylococcus saprophyticus subsp. saprophyticus M1-1, Isolated from the Gills of a Korean Rockfish, Sebastes schlegeli Hilgendorf, after High Hydrostatic Pressure Processing

A bacterium designated M1-1 was isolated from the gills of a Korean rockfish, Sebastes schlegeli Hilgendorf, after high hydrostatic pressure processing. Studies of 16S rRNA phylogeny and comparative genomics demonstrated that the isolate belongs to Staphylococcus saprophyticus subsp. saprophyticus. Here, we report the draft genome sequence of S. saprophyticus subsp. saprophyticus M1-1 (KACC 16562).

Genetic Diversity and Population Structure in the Heavily Exploited Korean Rockfish, Sebastes schlegeli, in Korea

The Korean rockfish, Sebastes schlegeli, is a valuable and intensively exploited species in Korea. We discuss the genetic diversity and genetic structure of four Korean rockfish populations using eight microsatellite loci. In total, 161 different alleles from 138 individuals were observed. Average allele number per locus ranged from 2.5 to 23 and allelic richness varied from 13.38 to 14.63 within a population. Despite a long history of stocking practices, we found very high levels of polymorphism (mean heterozygosity = 0.810), which is comparable to other congeneric species. No significant difference in genetic diversity and molecular genetic variance (FST and RST) was observed among four local samples (P &gt; 0.1). Little indication of contemporary inbreeding (FIS= 0.051) or population structure (K = 1) was detected. This absence of differentiation may reflect high levels of gene flow along the coast of Korea. Our study demonstrates that rockfish in Korea should be managed as a single unit. Currently, the species does not appear to be genetically threatened, but the potential for a rapid loss of genetic diversity remains. This information on the genetic characteristics of Korean rockfish populations has important implications for fisheries management and conservation efforts, and will aid in the sustainable exploitation of the fishing resources and the preservation of biodiversity.

Fractionation and Characterization of Fractions with High Antioxidative Activity from the Gelatin Hydrolysates of Korean Rockfish Sebastes schlegelii Skin

The purpose of this study was to obtain a fraction with high antioxidative activity from second rockfish gelatin hydrolysates (SRSGHs), which were hydrolyzed with Alcalase and Flavourzyme through ultrafiltration membranes with serial digestions for 1 and 2 h, respectively, and to investigate the feasibility of this fraction as a potential functional food ingredient. Among various fractions that were ultrafiltered from the SRSGH with four types of membrane (1, 5, 10, and 30 kDa), the SRSGH-III fraction, which permeated the 10 kDa membrane but not the 5 kDa membrane, showed the highest antioxidant activity (protection factor=5.13) and angiotensin-I-converting enzyme-inhibiting activity (<TEX>$IC_{50}$</TEX>=0.82 mg/mL). These results suggest that the SRSGH-III fraction from the SRSGH can be used as a functional food ingredient. However, further studies examining its antioxidant activity in vivo as well as the different antioxidant mechanisms are needed.

Short Communication Isolation and characterization of microsatellite markers for the Korean rockfish, Sebastes schlegeli

The Korean rockfish (Sebastes schlegeli) is an important commercial fish that is widely used in aquaculture. We isolated and characterized 18 polymorphic microsatellite loci from the Korean rockfish using a (GT)(13)-enriched genomic library. Polymorphism was assessed in 48 individuals from a single population collected from the northern coastal waters of the Yellow Sea. The observed and expected heterozygosities ranged from 0.0244 to 0.7660 (mean 0.4194) and 0.0244 to 0.8758 (mean 0.5002), respectively. Polymorphism at these loci indicated from two to 15 alleles (mean 5.7); 14 of 18 loci conformed to Hardy-Weinberg equilibrium. These markers should be useful for management and conservation studies of this species.

치어기 조피볼락 사료내 β-1,3 글루칸의 첨가가 성장 혈액 및 전어체 조성에 미치는 영향

This study was conducted to investigate the effects of dietary supplementation of β-1,3 glucan on growth, hematological and body composition in juvenile korean rockfish, Sebastes schlegeli fed the white fish meal based diets for 6 weeks. Four experimental diets were formulated to contain control (without supplementation of glucan), 0.05%, 0.1% and 0.5% (this diet was fed to fish daily, bi-weekly as three different dietary treatments) β-1,3 glucan per kg diet (Control, D

치어기 조피볼락 사료내 구기자 첨가효과

A 8-week feeding trial was conducted to investigate the effects of dietary supplementation of Kugija (Lycium chinense) on the growth and immunological response in juvenile Korean rockfish (Sebastes schlegeli). Six experimental diets were supplemented with Kugija at 0, 0.1, 0.5 1.0, 3.0 and 5.0% () on a dry-matter basis. After 2 weeks, triplicate groups of 30 fish initially averaging 3.360.2 g (meanSD) were randomly distributed into the aquarium and were fed one of the experimental diets for 8 weeks. By the end of the 8-week feeding trial, fish fed the and diets exhibited a higher weight gain and specific growth rate than fish fed and diets (P diet showed significant higher value than that of fish fed the , and diets (P diet was significantly higher than that of fish fed the and diets (P and diets was significantly higher than that of fish fed the diet (P and diets was significantly lower than in fish fed the other diets (P diet was significantly lower than those of fish fed the and diets (P and diets. Lysozyme activity of fish fed the and diets was significantly higher than that in fish fed the and diets (P diet was significantly higher than those of fish fed the and diets (P and diets. Fish fed Kugija showed lower early mortality than fish fed a Kugija-free diet upon challenge with Vibrio ordalii. The results suggest that feeding of Kugija (Lycium chinense) enhances growth, non-specific immunity and disease resistance in juvenile Korean rockfish.

Effects of Dietary Recombinant Bovine Somatotropin Levels on Growth, Plasma Recombinant Bovine Somatotropin Concentrations, and Body Composition of Juvenile Korean Rockfish, Sebastes schlegeli

Abstract This experiment was conducted to study the effects of the graded recombinant bovine somatotropin (rBST) levels on growth, plasma rBST concentrations, and body composition of Korean rockfish, Sebastes schlegeli, and to estimate the optimum oral dosage of rBST. Seven experimental diets were formulated to be isonitrogenous and isocaloric and to contain 49.0% crude protein and 16.7 kJ available energy/g, with 0, 5, 10, 15, 20, 25, or 50 mg rBST/kg body weight (BW)/wk (rBST0, rBST5, rBST10, rBST15, rBST20, rBST25, and rBST50, respectively). After the feeding trial, fish fed all the diets supplemented with rBST showed higher weight gain (WG), feed efficiency (FE), specific growth rate (SGR), and protein efficiency ratio (PER) than those fed the rBST0 diet (P &lt; 0.05). WG of fish fed rBST15, rBST20, rBST25, and rBST50 diets was significantly higher than that of fish fed rBST0 and rBST5 diets (P &lt; 0.05); however, there were no significant differences among fish fed rBST10, rBST15, rBST20, rBST25, and rBST50 diets. FE of fish fed rBST15 and rBST20 diets was significantly higher than that of fish fed rBST0, rBST5, rBST10, and rBST50 diets, and fish fed rBST10, rBST25, and rBST50 diets had significantly higher FE than those fed rBST0 and rBST5 diets (P &lt; 0.05). SGR of fish fed all the diets supplemented with rBST was significantly higher than that of fish fed rBST0 diet (P &lt; 0.05); however, there were no significant differences among fish fed all the diets supplemented with rBST. PER of fish fed rBST15 and rBST20 diets was significantly higher than that of fish fed rBST0, rBST5, and rBST50 diets, and fish fed rBST10, rBST25, and rBST50 diets had significantly higher PER than those fed rBST0 and rBST5 diets (P &lt; 0.05). Whole‐body protein of fish fed rBST15 diet was significantly higher than that of fish fed rBST0, rBST5, and rBST10 diets (P &lt; 0.05); however, there were no significant differences among fish fed rBST15, rBST20, rBST25, and rBST50 diets. Plasma rBST concentrations of fish fed all the diets began to rise at 3 h after oral administration of rBST; the maximum plasma rBST concentration peaked at 12 h and returned to the basal level at 24 h. Broken‐line model analyses of WG and FE were 12.8 and 13.2 mg rBST/kg BW/wk, respectively. These results indicated that the optimum oral dosage could be greater than 12.8 mg rBST/kg BW/wk but less than 13.2 mg rBST/kg BW/wk in juvenile Korean rockfish.

Effects of 7,12-dimethylbenz(a)anthracene on growth and haematological parameters in Korean rockfish, Sebastes schlegeli (Hilgendorf)

The objectives of the present experiment were to determine the effects on growth factors and some haematological parameters in Korean rockfish, Sebastes schlegeil, after dietary 7,12-dimethylbenz(a)anthracene (DMBA) exposure at 0.6, 1.2, 2.4 and 4.8 mg kg[superscript [-]1] diet for 8 weeks. The specific growth rate of the fish exposed to DMBA ([>/=]1.2 mg kg[superscript [-]1]) showed significantly lower performance than the control. Following 8 weeks of exposure, the DMBA-exposed groups (2.4 and 4.8 mg kg[superscript [-]1]) had a significantly higher mean hepatosomatic index. Condition factor of the fish exposed to DMBA did not show any statistically significant deviation from the control (P>0.05), although the mean values were somewhat lower than those of the control group. Observations on haematological parameters indicated DMBA treatment induced a severe anaemia. Total protein, albumin and total cholesterol concentrations decreased following exposure to DMBA at 2.4 and 4.8 mg kg[superscript [-]1]. In contrast, serum bilirubin and blood urea nitrogen in fish exposed to DMBA increased. Significant decreases in serum electrolytes, chloride, phosphorus, magnesium and calcium, and osmolality were observed in all DMBA-treatment groups. All DMBA-treatment groups showed a significantly higher activity of lactate dehydrogenase and alkaline phosphatase. Serum transaminase activity after the highest level of 4.8 mg kg[superscript [-]1] DMBA was significantly increased. The key finding from this study is that rockfish exposed to dietary DMBA at concentrations of 1.2 and 2.4 mg kg[superscript [-]1] diet are likely to experience adverse impacts in growth and haematological property respectively.