• Fisheries and Aquatic Sciences
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• v.12 no.2
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• pp.152-161
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• 2009

The largehead hairtail (Trichiurus lepturus) is one of the most common fisheries stocks in the East China Sea and the Yellow Sea. The species is caught using a variety of fishing tools, such as a stow net or a long line, as well as jigging and trawling. Scientific investigations have been conducted throughout the world to enable evidence-based estimations for the management and protection of the main fisheries biomass. For example, inshore and offshore hydro acoustic surveys are performed annually using bottom- and mid-water trawls around the Korean Peninsula. However, to date, no acoustic survey has been conducted to estimate fish size distribution, which is necessary to construct a data bank of target strength (TS) relative to fish species, length (L), and frequency. This study describes the frequency and length dependence of TS among fishes in Korean waters for the purpose of constructing such a TS data bank. TS measurements of the largehead hairtail were carried out in a water tank (L 5 m$\times$width 6 m$\times$ height 5 m) at frequencies of 50, 75, 120, and 200 kHz, using a tethering method. The average TS patterns were measured as a function of tilt angle, ranging from $-45^{\circ}$ (head down) to $+45^{\circ}$ (head up) every $0.2^{\circ}$. The length conversion constant ($b_{20}$) was estimated under the assumption that TS is proportional to the square of the length. In addition, in situ TS measurements on live largehead hairtails were performed using a split beam echo sounder.

• Fisheries and Aquatic Sciences
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• v.5 no.3
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• pp.183-190
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• 2002

To determine the effect of body size on the clearance rate and ingestion rate of small intertidal bivalves, Glauconome chinensis, feeding experiments were conducted on individuals of 12 different size classes, from 4 to 16 mm in shell length. Relationships between morphological parameters were also determined. The clearance and ingestion rates of G. chinensis responded similarly to their body size, ranging from 1.3 to 28.2 mL/hr/ind. and from 24.0 to 458.5, ${\mu}gC/hr/ind$., respectively. Both rates increased significantly (p<0.001) as shell length increased from 4 to 9 mm, although neither rate changed significantly when shell length was in the range from 12 to 16 mm. The weight-specific clearance rate $(CR_w)$ and ingestion rate $(IR_w)$ decreased with increasing body size, with values from 1.0 to 3.1 L/hr/g and from 17.9 to 51.3 mgC/hr/g, respectively. The $CR_w$ of G. chinensis was intermediate compared to those of larger bivalve species. The clearance rate (CR) relative to flesh dry weight (FDW) of G. chinensis were fitted well to the power function: $CR=0.43\times(FDW)^{0.71}\;(r^2=0.89)$. The exponent of fitting equation (0.71) of G. chinensis was higher than those of Mytilus edulis (Walne, 1972), Crassostrea gigas (Walne, 1972), and Placopecten magellanicus (MacDonald and Thompson, 1986).

• Fisheries and Aquatic Sciences
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• v.7 no.2
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• pp.58-63
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• 2004

Five urease-positive Vibrio parahaemolyticus strains were isolated from Kamak Bay in Yeosu in 2002 and 2003. V. parahaemolyticus YKB4 and YKB14 were isolated from seawater, YFB20 from black rockfish (Sebastes schlegeli), and YFO2l and YFO22 from olive flounder (Paralichthys olivaceus). The five urease-positive strains (YKB4, YKB14, YFB20, YFO21, and YFO22) did not show hemolysin and protease activity, while they did alter in color (to red) as the bacteria grew in the urea broth medium. All samples showed identical biochemical characteristics as a reference strain, V. parahaemolyticus KCTC2471, except in urease production. The five urease-positive strains showed urease activities at a mid stationary phase, and their activity was maximal in the late stationary phase of their culture supernatant. The addition of urea to the Luria-Bertani (LB) broth medium significantly affected the initial production of urease of V. parahaemolyticus isolates. Mortality by urease-positive V. parahaemolyticus YKB4, YKB14, YFO2l, and YFO22 was significantly high, being$60-80\%$, while YFB20 only reflected a rate of $20\%$. Protease-positive V. parahaemolyticus FM39 and FM50 showed a $40\%$ and $60\%$ mortality rate, respectively. However, hemolysin-positive V. parahaemolyticus had no mortality, like the non-pathogenic V. parahaemolyticus KCTC2471, while V. vulnificus resulted in a $40\%$ mortality rate. Injection with urease-positive V. parahaemolyticus strains showed mortality within 12 hrs in mice, and the strains could be isolated from the dead mice.

• Fisheries and Aquatic Sciences
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• v.8 no.1
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• pp.38-42
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• 2005

We evaluated the effects of different feeding strategies on the growth of young Nile tilapia, Oreochromis niloticus L., in a freshwater recirculating system during summer. Each of twenty fish (Mean body weight$\pm$ SD; 37. 7$\pm$0.10 g) were randomly distributed into each of 24 tanks. Eight treatments were prepared in triplicate. Control fish were hand-fed commercial feed twice daily without starvation. The other seven treatments employed different feeding and starvation strategies ranging from I day starved and 1 day fed (1DS+ 1DF) to 7 days starved to 7 days fed (7DS+7DF). All fish survived to the end of the 44-day feeding trial. The amount of food supplied was highest for the control fish in the control. Food supplied to fish in the 3DS+3DF and 4DS+4DF treatments was significantly lower than that of fish in the 1DS+1DF and 2DS+2DF treatments, but significantly higher than that of fish in the 5DS+5DF, 6DS+6DF and 7DS+7DF treatments. The weight gain of control fish was significantly higher than that of fish in other treatments. Feed efficiency ratio (FER) for fish in the 7DS+7DF treatment was significantly higher than that of fish in the control group, but it did not differ from that of fish in the 1DS+1DF and 2DS+2DF treatments. We concluded that young Nile tilapia raised with different starvation and feeding regimes during the summer in a freshwater recirculating system did not catch up in growth to fish fed daily. However, the enhanced FER of Nile tilapia in the 7DS+ 7DF, 2DS+ 2DF, and 1 DS+ I DF treatments partly explains the compensatory growth of the fish, although their weight gain was relatively low.

• Fisheries and Aquatic Sciences
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• v.10 no.4
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• pp.205-214
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• 2007

Surface water and sediment samples collected from the Mokpo coast of Korea were analyzed for molecular markers of organic municipal wastewaters, i.e., 11 fecal sterols including coprostanol (Cop) and nonylphenolic compounds (NPs), to characterize the main routes of these wastewaters to the coast and to assess contamination levels. Concentrations of Cop ranged from 94 to 7,568 ng/L in surface water and from 43 to 38,108 ng/g dry weight in sediments. Concentrations of NPs [nonylphenol (NP) and nonylphenol mono- and di-ethoxylates ($NP_{1-2}EOs$)] ranged from 123 to 4,729 ng/L in surface water and from 4 to 2,119 ng/ng dry weight in sediments. The levels of these compounds were much higher at stations near the rivers that pass through the urban center of Mokpo and the outfall of the wastewater treatment plant (WWTP). The spatial distribution of Cop levels was statistically similar to that of NPs (r=0.809 and 0.982 in surface water and sediments, respectively), indicating that these compounds may have similar discharge points, transport, mixing, and deposition in the study area. These results suggest that considerable amounts of organic wastewater compounds are discharged through rivers and WWTP effluent to the Mokpo coast.

• Fisheries and Aquatic Sciences
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• v.13 no.4
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• pp.332-339
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• 2010

Maturity and spawning of the snailfish, Liparis ochotensis was investigated based on samples collected by gill net in the East Sea of Korea from December 2008 to December 2009. The average total length of L. ochotensis was 63.4 cm and 64.1 cm for females and males, respectively. Gonadosomatic index (GSI) began to increase in July, reaching a maximum in November, then began to decrease in December. Monthly changes in the GSI values of L. ochotensis were similar for females and males. Annual reproductive cycle of this species can be divided into five successive stages in females: early growing stage (May), late growing stage (June to July), mature stage (August to September), ripe and spent stage (September to December), and recovery and resting stage (January to April). Males show four successive stages; growing stage (May to July), mature stage (August to September), ripe and spent stage (September to December), and recovery and resting stage (January to April). Relationship between total length (TL) and fecundity (F) was F=$0.00003TL^{4.002}$ ($R^2$ = 0.703), and F increased with TL. Total length at 50% group maturity was estimated to be 55.8 cm. Our findings suggest that the spawning period takes place from September to December, with the main spawning period occurring from October to December.

• Fisheries and Aquatic Sciences
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• v.9 no.4
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• pp.140-145
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• 2006

We measured activities of the ubiquitous tripeptide non-protein thiol (L-${\gamma}$-glutamyl-L-cysteinyl-glycine), glutathione (GSH), which is believed to playa fundamental role in detoxifying xenobiotics in biological systems, as a metabolic biomarker for benzo(${\alpha}$)pyrene and Aroclor 1254 exposure in the Pacific oyster Crassostrea gigas. Reproductive oysters were exposed to the pollutants for 50 days by the algal vectoring method in which the oysters were fed with concentrated standard algal foods grown in culture media containing Aroclor 1254 (0, 5, 50, 500 ng/g) or benzo(${\alpha}$)pyrene (0, 10, 100, 1,000 ng/g). Both pollutants induced maternal GSH activities in 10 days in a dosage-dependent manner (p<0.05), although Aroclor 1254 was stronger. The pollutant-driven GSH elevation persisted for 20 to 30 days depending on the pollutants and concentrations. Thereafter, a drastic decline in the GSH activity was observed due to metabolic failure, after which the oyster GSH remained at low levels throughout the remainder of the experiment. The pollutant exposures influenced maternal reproductive output in terms of fertilization, hatching, and morphology. These results imply that changes in activity of the GST-catalyzing molecule can be used as an oyster biomarker for Aroclor 1254 and benzo(${\alpha}$)pyrene exposure.

• Fisheries and Aquatic Sciences
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• v.12 no.1
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• pp.1-5
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• 2009

Crude saponin, extracted from the starfish Asterias amurensis, was assessed for its capacity as a biological pesticide. As part of this analysis, its insecticidal and repellent activities, in addition to its acute and chronic toxicities were tested. In comparison with the control group, insecticidal activity of saponin against tobacco cutworm, Spodoptera litura, in kale, Brassica loeracea was low at 36.4%. Repellent activities of the extracted saponin against green peach aphid, Myzus persicae, and S. litura, on soybean leaf, Glycine max and kale were 65.6% and 35.0% at $1^{st}$ day, and 54.5% and 30.0% at $3^{rd}$ day, respectively. Acute and chronic toxicity analysis was carried out using acute immobilizatioin test and reproduction impairment test, respectively. The saponin had 48 h-$EC_{50}$ of $65.21{\mu}g/mL$. Twenty-one day accumulative reproduction after treatment was lower in Daphnia magna at $7{\mu}g/mL$ saponin (78 youngs), compared with the control group (129 youngs). These results indicate that the extracted saponin exhibited some toxicity and has potential as a repellent against insects.

• Fisheries and Aquatic Sciences
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• v.8 no.4
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• pp.213-219
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• 2005

Vitellogenin (VTG) was purified from the blood plasma of estradiol-17$\beta$ ($E_2$)-treated male marbled sole (Limanda yokohamae) using gel filtration and anion exchange chromatography. The purity of the marbled sole VTG (msVTG) was confirmed by polyacrylamide gel electrophoresis (SDS-PAGE) and N-terminal amino acid sequencing. The purified msVTG was used to produce monoclonal and polyclonal antibodies in mice and rabbits, respectively, and the specificity of the polyclonal antisera for msVTG was confirmed by Western blot analysis. The antibodies cross­reacted with a protein of molecular mass approximately 160 kDa in the plasma samples of mature female marbled sole. No cross-reactivity was observed with the plasma of male fish. A direct non-competitive sandwich enzyme-linked immunosorbent assay (ELISA) was developed using the monoclonal anti-msVTG and polyclonal anti-msVTG antibodies, with purified msVTG as the standard protein. The values of the intra- and inter-assay variations were within the ranges of $8.l-9.8\%$ and $8.5-12.2\%$, respectively. The sensitivity was about 0.3 ng/mL. Serial dilutions of plasma from mature female sole reacted with the msVTG-antibodies in the sandwich ELISA, whereas the plasma from male fish did not. The results indicate that the maturation status of female marbled sole can be identified using a sandwich ELISA for msVTG.

• Journal of the East Asian Society of Dietary Life
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• v.24 no.3
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• pp.335-350
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• 2014

Compared to the large numbers of studies on the diabetes, hyperlipidemia and cancer therpeutic effects of ginseng, the anti-obese effect and mechanisms of ginsengs have not been studied as much. To determine the effects of ginseng on obesity, 14 keywords (ginseng, ginsenoside, obesity, weight, fat, diet, overeat, appetite, lipid, 3T3-L1, adipocyte, food intake, adipogenesis and lipolysis) were combined in searching a database. Fifty-six articles published from 1983 to 2012 as well as 656 patents registered until Aug $17^{th}$, 2012, were screened for anti-obese effects of ginseng. In the classification of experimental methods, 16 papers on 3T3-L1 cells, 38 papers on animals and three papers on human were reviewed. In terms of obese mechanisms of action, the most commonly used biomarkers were in order of lipid profiles > weight change > blood glucose > adipocytokine. Most ginseng studies on obesity focused on AMPK, $PPAR{\gamma}$, GLUT-4, PI3K and SREBP-1. Korean white ginseng extracts and Re repressed the lipogenesis genes such as PPARc2, SREBP-1c, LPL, FAS and DGAT1. However, ginseng or ginsenosides, PD (Rb1) and PT (Re), showed different or contradictory results. Water and ethanol extraction of ginseng showed contradictory effects on the secretion of inflammatory cytokines, wheras IL-6 was repressed by ethanol extracts and TNF-${\alpha}$ repressed by Re in vitro. Based on the literature, further studies on anti-obese mechanisms of ginseng, such as the inflammation-related obesity or cross signals between the adipocytes and the environments, are needed, instead of more studies on its hypolipidemic and hypoglycemic effects.