Black Rockfish Sebastes Schlegeli Research Articles

Isolation and Identification of Pathogenic Vibrio Species in Black Rockfish Sebastes schlegeli

Four pathogenic Vibrio species were isolated from three diseased black rockfish Sebastes schlegeli in Yantai, Shandong Province, China. The strains were identified based on physiological and biochemical characteristics and 16S rDNA sequencing and named SF-2, SF-3, SF-5, and SF-6, respectively. SF-2 was Vibrio scophthalmi, SF-3 was V. harveyi, SF-5 was V. alginolyticus, and SF-6 was V. parahaemolyticus. This is the first time that V. scophthalmi was isolated from black rockfish. The present research shows that V. scophthalmi is a potential pathogen. Detection of virulence genes using polymerase chain reaction showed that SF-3, SF-5, and SF-6 carried FlaB; SF-5 and SF-6 carried TcpA; and SF-2, SF-5, and SF-6 carried ToxS. Tdh, Trh, Tlh, ToxR, and Zot were not detected. SF-3, SF-5, and SF-6 all had protease, gelatinase, lipase, and lecithinase. They were all intermediately sensitive to erythromycin, whereas SF-2, SF-5, and SF-6 were sensitive to spectinomycin, and SF-3 was sensitive to cotrimoxazole and chloramphenicol. They were resistant to most antibiotics and multidrug resistance was obvious.

실험사료 중 크릴 첨가가 조피볼락 Sebastes schlegeli 치어의 성장 및 체성분에 미치는 영향

실험사료 중 크릴 첨가가 조피볼락 Sebastes schlegeli 치어의 성장 및 체성분에 미치는 영향

Optimal Conditions for Long-distance Transportation of Live Black Rockfish (Sebastes schlegeli) and Changes in their Characteristics during Transport

ABSTRACTOptimal transport conditions for the live black rockfish and changes in their characteristics during long-distance transport were investigated. Oxygen consumption by black rockfish was lowest at 4°C and increased as the water temperature increased up to a maximum at 10°C. At a water temperature of 8°C and 10°C, the plasma glucose concentration of the fish was 36.2 and 38.2 mg/dL, respectively. The mean weight of the fish reduced to approximately 2.8% of initial weight after 16 days of storage at 8°C. The fish did not feed, and the survival rate of fish stored for 16 days at 8°C was 98.4%. The longer the live fish were stored in the container, the quicker the onset of rigor mortis after the slaughter was reached. Compared with fillets from control fish, the chewiness of fillets was somewhat lower (17.3%) after storage of fish for 16 days, but the softness of the fillets was slightly higher (21.6%). From these results, it was suggested that the optimum temperature for long-distance transport of the live fish was 8°C and that the long transport period of live fishes decreased their fillet quality more rapidly after fish death.

Antihelminthic potential of quinacrine and oxyclozanide against gill parasite Microcotyle sebastis in black rockfish Sebastes schlegeli.

The aim of this study was to assess the treatment potential of quinacrine and oxyclozanide against Microcotyle sebastis (Monogenea: Polyopisthocotylea) infection in cultured black rockfish Sebastes schlegeli. The oral administration of quinacrine led to a reduction in the mean abundance of M. sebastis infection in all quinacrine-treated groups, and the groups of fish administered quinacrine at 50, 100, and 200 mg kg(-1) for 3 consecutive days showed a parasite mean abundance that was 50 to 30% lower compared to that of the control group, suggesting that quinacrine has a therapeutic potential against M. sebastis. Although oxyclozanide showed a very high in vitro killing activity, in oral administration experiments, only the groups of fish administered 200 mg kg(-1) showed less than 50% mean abundance of M. sebastis compared to the control groups, suggesting that the absorption efficiency of orally administered oxyclozanide might be low in black rockfish and/or that M. sebastis might be less sensitive to orally ingested oxyclozanide. As praziquantel has been the sole therapeutic against M. sebastis infection in Korea for a long time, a broadening of available control measures is advisable in order to reduce the possible emergence of praziquantel-resistant M. sebastis. In our study, although quinacrine and oxyclozanide showed a therapeutic potential against M. sebastis, the treatment efficacy was not high enough to replace praziquantel. Thus, after investigations on the pathological effects and pharmacodynamics, use of quinacrine or oxyclozanide in combination with praziquantel may be considered as a way to prevent praziquantel resistance in M. sebastis.

A microsatellite genetic linkage map of black rockfish (Sebastes schlegeli)

Ovoviviparous black rockfish (Sebastes schlegeli) is an important marine fish species for aquaculture and fisheries in China. Genetic information of this species is scarce because of the lack of microsatellite markers. In this study, a large number of microsatellite markers of black rockfish were isolated by constructing microsatellite-enriched libraries. Female- and male-specific genetic linkage maps were constructed using 435 microsatellite markers genotyped in a full-sib family of the fish species. The female linkage map contained 140 microsatellite markers, in which 23 linkage groups had a total genetic length of 1334.1 cM and average inter-marker space of 13.3 cM. The male linkage map contained 156 microsatellite markers, in which 25 linkage groups had a total genetic length of 1359.6 cM and average inter-marker distance of 12.4 cM. The genome coverage of the female and male linkage maps was 68.6% and 69.3%, respectively. The female-to-male ratio of the recombination rate was approximately 1.07:1 in adjacent microsatellite markers. This paper presents the first genetic linkage map of microsatellites in black rockfish. The collection of polymorphic markers and sex-specific linkage maps of black rockfish could be useful for further investigations on parental assignment, population genetics, quantitative trait loci mapping, and marker-assisted selection in related breeding programs.

Combined Effects of Copper and Temperature on Antioxidant Enzymes in the Black Rockfish Sebastes schlegeli

Copper has been widely used to control algae and pathogens in fish culture ponds. However, its toxic effects on fish depend not only on its concentration in the water but also on the water quality. A laboratory experiment was conducted to assess copper toxicity in the black rockfish Sebastes schlegeli using a panel of antioxidant enzymes, including glutathione (GSH), glutathione S-transferase (GST), glutathione peroxidase (GPx), glutathione reductase (GR) and superoxide dismutase (SOD), at different levels of copper at three water temperatures (WT, 18, 23, <TEX>$28^{\circ}C$</TEX>) for 4 days. After exposure to two copper concentrations (100 and <TEX>$200{\mu}g/L$</TEX>), GSH levels and GST activities increased significantly, depending on WT (P < 0.05) in the liver, gill, and kidney of the black rockfish. GPx and SOD activities decreased significantly with both increasing WT and copper treatment in the organs of black rockfish (P < 0.05). These changes can be seen as initial responses to temperature stress and as a sustained response to copper exposure. This also indicates that GSH and related enzymes activities were sensitive indexes to stress by toxicants such as copper. The present findings suggest that simultaneous stress due to temperature change and copper exposure can accelerate changes in enzymes activities in the black rockfish. This provides another example of synergism between environmental temperature and pollutants, which may have important implications for the survival of fish in polluted environments during seasonal warming and/or global climate change.

Characterization of the Dmrt1 gene in the black rockfish Sebastes schlegeli revealed a remarkable sex-dimorphic expression

The Dmrt genes encode a large family of transcription factors with a conserved zinc finger-like DNA-binding DM domain. The function of Dmrt1, one of the family members, in sexual development has been well studied in invertebrates and vertebrates. In the present study, the full-length cDNA of Dmrt1 was isolated from the testis of Sebastes schlegeli. The full-length cDNA of S. schlegeli Dmrt1 (SsDmrt1) was 1,587bp and contained a 189-bp 5' UTR, a 489-bp 3' UTR and a 909-bp open reading frame, which encoded 302 amino acids with a conserved DM domain and an male-specific motif domain. Phylogenetic analysis showed the evolutionary relationships of SsDmrt1 with other known Dmrt genes in fish and tetrapods. Several transcriptional factor-binding sites in the 5' promoter were identified that might regulate SsDmrt1 expression. Quantitative real-time PCR analysis indicated that SsDmrt1 was expressed in all of the inspected larval developmental stages from 1 to 35days after birth and that the level of expression gradually decreased. The expression of SsDmrt1 in adult gonads was sexually dimorphic with extremely high expression in the testis, but very low expression in the ovary. No expression was detected in other tissues. Using in situ hybridization, we demonstrated that SsDmrt1 was specifically expressed in the germ cells of both the testis and the ovary. Thus, our results suggest that SsDmrt1 may have an important role in the differentiation of both the testis and the ovary of S. schlegeli.

Nutritional Characteristics of Black Rockfish (Sebastes schlegeli) Fed a Diet of Fish Skin

This study investigated the effects of diets substituted with different levels (0, 5, 10, and 20%) of flounder skin meal (FSM) on the nutritional composition of black rockfish Sebastes schlegeli. Fish (10.05 ± 0.44 g) were fed to apparent satiation twice daily for 8 weeks. Adding FSM decreased crude lipid levels and increased crude protein and ash. The abundant fatty acids in the FSM-added group were C16:0, C18:1-cis (n9), and C22:6n-3. The major amino acids in the samples were glutamic acid, aspartic acid, glycine, leucine, alanine, lysine, and arginine. The abundant free amino acids in the FSM-added group were taurine, glutamic acid, alanine, leucine, and arginine. Six free sugars were found in all groups. Glucose was predominant, followed by mannose, rhamnose, fucose, fructose, and ribose. Among the three organic acids in the whole body of black rockfish, lactic acid was predominant, followed by citric acid and oxalic acid. Total organic acid content in the control was significantly higher than those of FSM substitution groups.

울금(Curcuma longa L.) 첨가 사료 공급이 조피볼락(Sebastes schlegeli) 체성분에 미치는 영향

This study investigated the effect of diets supplemented with different levels (0, 1, 3, and 5 %) of turmeric Curcuma longa L. powder (TP) on the body composition of black rockfish Sebastes schlegeli. Fish weighing g were fed to apparent satiation twice daily for 8 weeks. Adding TP decreased crude lipid levels and increased crude protein and ash levels. Abundant fatty acids in the TP-added group were C16:0, C18:1 n-9 (cis), and C22:6 n-3. The major amino acids in samples were glutamic acid, aspartic acid, glycine, leucine, alanine, lysine, and arginine.

무화과 잎 추출물 첨가 사료를 급이한 조피볼락(Sebastes schlegeli)치어의 영양학적 특성

The present study investigated the effect of diets supplemented with different levels (0, 1, 3, and 5 %) of fig leaf ethanol extract (FLEE) on the nutritional composition of black rockfish Sebastes schlegeli. Fish (<TEX>$10.05{\pm}0.44g$</TEX>) were fed to apparent satiation twice daily for 8 weeks. Adding FLEE decreased crude lipid levels and increased crude protein and ash. Among the three organic acids in the whole body of black rockfish, lactic acid was predominant, followed by citric acid and oxalic acid. Five free sugars were found in all groups. Fucose and glucose were the dominant free sugars in the FLEE-added group. The abundant fatty acids in the FLEE-added group were C16:0, C18:1-cis (n9), and C22:6n-3. The major amino acids in the samples were glutamic acid, aspartic acid, glycine, leucine, alanine, lysine, and arginine. The abundant free amino acids in the FLEE-added group were taurine, glutamic acid, alanine, leucine, and arginine.

Availability of squid viscera meal with cadmium removal treatment as a feed ingredient for fingerling black rockfish Sebastes schlegeli

Two 12-week feeding experiments were conducted to evaluate the nutritional value of squid viscera meal with cadmium removal treatment (dCSVM), which contained 1.5–2.0 mg/kg cadmium, as an alternative protein source to sardine meal in diets for fingerling black rockfish Sebastes schlegeli. Initial mean body weights in experiments 1 and 2 were 23.0 and 6.4 g, and the replacement rates of sardine meal with dCSVM in the test diets were 20–80 % and 30–60 %, respectively. In experiment 1, inclusion of dCSVM at 40 % and higher replacement rates of sardine meal retarded the growth of fish due partly to inferior dCSVM protein digestibility. The cadmium (Cd) concentrations in fish muscle of all treatment groups were below the detection limit (<0.1 mg/dry matter). In experiment 2 using dCSVM containing Cd at a lower level and having a higher protein digestibility than in experiment 1, no significant differences were observed in the growth between the control and 60 % replacement groups, although feed efficiency gradually decreased with the increase of dCSVM inclusion. These results show that dCSVM is safe and useful as an alternative protein source and could replace up to 60 % of sardine meal in fingerling black rockfish diets.

ECONOMIC RELATIONSHIPS BETWEEN AQUACULTURE AND CAPTURE FISHERIES IN THE REPUBLIC OF KOREA

Wild fish species are becoming scarcer and their market prices significantly increasing due to limited natural resources and increasing demand for sea food. In recent years, the Republic of Korea's (South Korea's) marine aquaculture production of finfish has drastically increased while prices have declined. This study conducts a comparative analysis of the economic relationships between wild-caught and farmed fish species, examining the relationship between fish price and supply resulting from the development of marine aquaculture. Major marine aquaculture species, in particular the most favored sashimi species in Korea, are evaluated. These are: flounder (Paralichthys olivaceus), black rock fish (Sebastes schlegeli), red sea bream (Pagrus major), and grey mullet (Mugil cephalus). This paper illustrates that the prices for both wild-caught and farmed fish declined as the farmed products entered the market and production expanded. However, the magnitude of price changes varied by species depending on if the farmed species has the same value or substitute value as the wild-caught fish and the development of aquaculture technology. The study shows aquaculture seems to play a role in helping to meet the demand for fish and can reduce the pressure on wild-stock fisheries.

Effects of Artemia Single Feeding Regime on Early Growth, Development and Survival of Black Rockfish Sebastes schlegeli Larvae

Effects of Artemia Single Feeding Regime on Early Growth, Development and Survival of Black Rockfish Sebastes schlegeli Larvae

Effects of Feeding and Temperature on Survival and Growth of Larval Black Rockfish Sebastes schlegeli in Rearing Conditions

Effects of Feeding and Temperature on Survival and Growth of Larval Black Rockfish Sebastes schlegeli in Rearing Conditions

Gonadal sex differentiation and effect of rearing temperature on sex ratio in black rockfish (Sebastes schlegeli)

Temperature-dependent sex determination has been demonstrated in some species of fish, and a high temperature during the period of sex differentiation typically produces a male-dominant population. This research investigated the gonadal sex differentiation and effect of rearing temperature on the sex ratio in larval black rockfish Sebastes schlegeli, which is a viviparous species. Two types of gonads were histologically distinguishable in fish 20 mm in total length (TL). The putative ovary started forming an ovarian cavity, while the putative testis was not clearly differentiated until 51 mm TL. In a temperature-controlled experiment, the proportions of females were 45% at 10°C, 46% at 14°C, 50% at 18°C, 63% at 22°C, and 83% (significantly different from 1:1 sex ratio) at 24°C. These results suggest that morphological sex differentiation in black rockfish occurs at approximately 20 mm in TL, and it is possible that high temperatures (24°C) induce not a male- but a female-dominant population in this species.

Effects of sodium cyanide (nacn) on the endogenous rhythm of the oxygen consumption rate in the black rockfishsebastes schlegeli

Laboratory bioassays were conducted to test the acute toxicity effects of sudden exposure to sodium cyanide (NaCN) on the endogenous rhythm of the oxygen consumption rate (OCR) in the black rockfishSebastes schlegeli. The OCR of the black rockfish (n = 14, total length = 20.4 ± 1.16 cm, wet weight = 158 ± 25 g) was measured with an automatic intermittentflow-respirometer. OCR decreased significantly when experimental fish were exposed to NaCN. When exposed to 10 ppb NaCN, fish were able to recover their OCR rhythmic activities. When fish were exposed to 20 ppb, however, the metabolic activity rhythms were not recovered. These results suggest that exposure to NaCN concentrations over 20 ppb cause severe physiological damage to the endogenous rhythms of black rockfish.

Effectiveness of stock enhancement of hatchery-released black rockfish Sebastes schlegeli in Yamada Bay — Evaluation by a Fish Market survey

Black rockfish Sebastes schlegeli is considered a promising species for stock enhancement because of its high growth rate and limited area of movement. This study evaluated the stocking effectiveness of black rockfish released in Yamada Bay, off the northeastern Pacific coast of Japan, using three indices estimated from survey data collected on all business days at the Yamada Fish Market over a period of 11 years. Eight annual cohorts of hatchery-raised, marked juveniles were released into the bay from 1989–1991 and 1993–1997. During the market census, all landed black rockfish were investigated for TL and presence or absence of marks. The census indicated that 51,512 fish out of 447,400 hatchery-released juveniles were landed commercially and recorded at the market. Of the returned fish, 1-year-old fish accounted for 61.2%, 2-year-old fish for 30.3%, and ≧3 year-old fish for 8.6%. Return rates of each year class ranged from 9.3% to 15.4% showing stable and rather high values. However, the economic return rate (landed sales values / hatchery costs) ranged between 0.68 and 1.25; 5 of the 8 year classes showed rates of less than 1, where hatchery costs exceeded their associated benefit. To make stocking of black rockfish feasible, raising the market price of this species through fishery management, decreasing hatchery production costs, and developing effective release strategies such as optimum release size are needed.

Movement Ranges and Routes of Black Rockfish Sebastes schlegeli in Summer and Autumn from Acoustic Telemetry

The movement range and diurnal behavior of 17 wild black rockfish (Sebastes schlegeli) were monitored within the marine ranching area of Tongyeong from 27 July to 7 November, 2005 using acoustic telemetry. Coded transmitters were surgically implanted into the abdomen of fish. Two of ten fish released in summer moved about 2 km away from the capture point for 1 day. The others stayed within a 500-m radius of the release point for 1 week after release. The seven fish released in autumn stayed within 500 m of the release point. Most fish were more active and had a greater range of horizontal diurnal movement at night than during the day. Additionally, the range of horizontal diurnal variation was greater in summer than in autumn. While fish released in summer were more vertically active at night than during the day, those released in autumn preferred to move vertically during the day.

Examination of Embryonic Developmental Stage by Cannulation to Synchronize the Timing of Parturition in Black Rockfish Sebastes schlegeli Broodstock Females

Examination of Embryonic Developmental Stage by Cannulation to Synchronize the Timing of Parturition in Black Rockfish Sebastes schlegeli Broodstock Females

Preliminary study on the water drag of Schlegel’s black rockfish Sebastes schlegeli

Drag forces acting on Schlegel’s black rockfish Sebastes schlegeli were studied. A new drag force transducer was designed and used to measure the water drag on Schlegel’s black rockfish in a vertical recirculating flume tank. Fourteen individuals were investigated, yielding two mean drag coefficients referred to the cross-sectional area and volume respectively at water velocities ranging from 0.3 to 1.0 ms−1. The drag coefficients can be used for estimating the drag forces acting on Sebastes schlegeli in water.