• Korean Journal of Fisheries and Aquatic Sciences
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• v.39 no.5
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• pp.404-409
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• 2006

This study investigated the reproductive cycle of the female hairychin goby, Sagamia geneionema, histologically. The fecundity of female hairychin goby ranged from 1,002 to 1,240 eggs when they reached a total length of 9.1-10.0 cm. Fecundity is related to total length. The gonadosomatic index (GSI) increased from December (1.87$\pm$0.46) and reached a maximum in April (11.57$\pm$1.92). The histological changes in the ovary were correlated with the GSI. Oocytes at the chromatin-nucleolus and peri-nucleolus stages were observed in the ovary year-round. In December, oocytes containing yolk appeared in the ovaries of a few fish. Most oocytes appearing in January were at the yolk globule stage. The frequency of oocytes appearing at the yolk globule stage from January to March was higher than in other months. Subsequently, empty follicles and atretic oocytes were observed in the ovaries in May. Based on the histological observations of gonad development and the monthly change in the GSI, the reproductive cycle was classified into the following successive stages: growing (October to November), mature (December to January), ripe and spawning (February to April), and degenerative and resting (May to September) stages. The histological observations of ovaries during the spawning period indicate that this species is a multiple spawner with abbreviated iteroparity based on the developmental pattern of oocytes.

• Asian-Australasian Journal of Animal Sciences
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• v.32 no.12
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• pp.1923-1932
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• 2019

Objective: We investigated visual marbling level (VML) influence on pork loin physicochemical traits, consumer palatability responses, VML liking, purchase intent, and their relationships. Methods: For each of five slaughtering dates, at 24-h postmortem, nine paired Duroc castrated male boneless Longissimus dorsi (LD) muscles were categorized into low (LM, score 1 to 2, n = 3), medium (MM, score 3 to 4, n = 3), and high (HM, score 5 to 6, n = 3) VML. Meat physicochemical quality traits and consumer responses (n = 389) on palatability and VML liking, and purchase intent were evaluated. The experiment was in randomized complete block design. Analysis of variance, Duncan's multiple mean comparisons, and correlation coefficients were determined. Results: VML correspond to crude fat (r = 0.91, p<0.01), but both were reversely related to moisture content (r = -0.75 and -0.91, p<0.01, respectively). As VML increased, ash (p<0.05) and protein (p = 0.072) decreased, pH and $b^{\star}$ increased (p<0.05), but drip, cooking (p<0.05) and thawing (p = 0.088) losses decreased. Among treatments, muscle fiber diameter, sarcomere length, total and insoluble collagen contents, $L^{\star}$, and $a^{\star}$ did not differ (p>0.05). Compared to the others, HM had lower collagen solubility percentage (p<0.05), but similar (p>0.05) Warner-Bratzler shear force (WBSF). No differences (p>0.05) were found in juiciness, overall flavor, oiliness, and overall acceptability, but HM was more tender (p<0.05) than the others. Based on VML, consumers preferred MM to HM (p<0.05), while LM was similar to MM and HM (p>0.05). Corresponding to VML preference (r = 0.45, p<0.01), consumers (83%) would (p<0.01) definitely and probably buy MM, over LM (74%), and HM (68%), respectively. Conclusion: Increasing VML in pork LD altered its chemical composition, slightly increased pH, and improved water holding capacity, thereby improving its tenderness acceptability. Marbling might reduce chewing resistance, as lower collagen solubility in HM did not impact tenderness acceptability and WBSF. While HM was rated as most tender, consumers visually preferred and would purchase MM.

• Ocean and Polar Research
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• v.40 no.4
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• pp.237-247
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• 2018

This study aims to estimate optimal harvests, fishing efforts, and stock levels of hairtail harvested by the large pair bottom trawl, the large otter trawl, the large purse seine, the offshore long line, and the offshore angling fisheries by using the surplus production models and the current value Hamiltonian method. Processes of this study are as follows. First of all, this study estimates the standardized fishing efforts regarding the harvesting of the hairtail by the above five fishing gears based on the general linear model developed by Gavaris. Secondly, this study estimates environmental carrying capacity (k), intrinsic growth rate (r), and catchability coefficient (q) by applying the Clarke Yoshimoto Pooley (CY&P) model among various surplus production models. Thirdly, this study estimates the optimal harvests, fishing efforts, and stock levels regarding the hairtail by the current value Hamiltonian method, including the average landing price, the average unit cost, and the social discount rate. Finally, this study attempts a sensitivity analysis to figure out changes in optimal harvests, fishing efforts, and stock levels due to changes in the average landing price and the average unit cost. As results induced by the current value Hamiltonian method, the optimal harvests, fishing efforts, and stock levels regarding the hairtail caught by several fishing gears were estimated as 33,133 tons, 901,080 horse power, and 79,877 tons, respectively. In addition, from the results of the sensitivity analysis, first of all, if the average landing price of the hairtail constantly increases, the optimal harvests of it increase at a decreasing rate, and then harvests finally slightly decrease as a result of decreases in stock levels. Secondly, if the average unit cost of fishing efforts continuously increases, the optimal fishing efforts decreases, but optimal stock levels increase. Optimal harvests start climbing and then decrease continuously due to increases in the average unit cost. In summary, this study suggests that the optimal harvests (33,133 tons) were larger than actual harvests (25,133 tons), but the optimal fishing efforts (901,080 horse power) were much less than estimated standardized fishing efforts (1,277,284 horse power), corresponding to the average of the recent three years (2014-2016). This result implies that the hairtail has been inefficiently harvested and recently overfished due to excessive fishing efforts. Efficient management and conservation policies on stock levels need to be urgently implemented. Some appropriate strategies would be to include the hairtail in the Korean TAC species or to extend the closed fishing season for this species.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.55 no.2
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• pp.102-110
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• 2022

This study was conducted to optimize the processing process for the oyster Crassostrea gigas gratin with cream sauce (OG-CS). The optimum concentration of added milk for oyster extract with milk (OE-M) was 35.0% based on the frozen-boiled oyster (F-BO), as suggested by the results of sensory evaluation. Response surface methodology was performed with whipping cream (WC)/[OE-M+mixed powder (garlic powder:onion powder=1:1) (MP)] (X₁) and OE-M/MP (X₂) as independent variables and viscosity (Y₁), amino acid nitrogen (Y₂), and overall acceptance for sensory evaluation (Y₃) as dependent variables. The optimal proportions were 74.55% of WC, 20.25% of OE-M, and 5.2% of MP, and the predicted multiple response optimal values for the dependent variables were 3,735.6 cP of Y₁, 197.0 mg/100 g of Y₂, and 6.2 score of Y₃. Under optimal conditions, the experimental values for Y₁, Y₂, and Y₃ were 3,711.9±30.0 cP, 198.1±1.9 mg/100 g, and 6.3±0.5 score, respectively, which were not significantly different from the predicted values (P>0.05). Further, the results of sensory evaluation suggested that the optimum concentration of macaroni:cheese (1:2) to be 46.2% based on the F-BO. The OG-CS prepared under these optimal conditions was superior to the commercial seafood gratin in overall acceptance.

• Fisheries and Aquatic Sciences
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• v.26 no.3
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• pp.204-215
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• 2023

The thermolabile haemolysin (tlh) of Vibrio parahaemolyticus (Vptlh) from V. parahaemolyticus is a multiple-function enzyme, initially describes as a haemolytic factor activated by lecithin and phospholipase A2 enzymatic activity (Shinoda, 1991; Vazquez-Morado, 2021; Yanagase et al., 1970). Until now, the tlh structure has hypothesized including N-terminal and C-terminal domain, but what domain of the Vptlh structure does the haemolytic activity has not been refined yet. In this study, a 450-bp VpTLH nucleotide sequence of the entire Vptlh gene encoded the C-terminal domain cloned firstly to examine its responsibility in the activity of the Vptlh. The C-terminal domain fused with a 6-His-tag named the His-tag-VpC-terminal domain was expressed successfully in soluble form in the BL21 (DE3) PlysS cell. Remarkably, both expression and purification results confirmed a high agreement in the molecular weight of the His-tag-VpC-terminal domain was 47 kDa. This work showed the His-tag-VpC-terminal domain lysed the erythrocyte membranes in the blood agar and the phosphate buffered saline (0.9%) media without adding the lecithin substrate of the phospholipase enzyme. Haemolysis occurred at all tested diluted concentrations of His-tag-VpC-terminal domain (p < 0.05), providing evidence for the independent haemolytic activity of the His-tag-VpC-terminal domain. The content of 100 ㎍ of the His-tag-VpC-terminal domain brought the highest haemolytic activity of 80% compared to that in the three remaining contents. Significantly, the His-tag-VpC-terminal domain demonstrated not to involve the phospholipase activity in Luria-Bertani agar supplemented with 1% (vol/vol) egg yolk emulsion. All results proved the vital responsibility of the His-tag-VpC-terminal domain in causing the haemolytic activity without the required activation by the phospholipase enzyme. Raw extracts of Phellinus igniarus and Phellinus pipi at 10^-1 mg/mL inhibited the haemolytic activity of the His-tag-VpC-terminal domain from 67.7% to 87.42%, respectively. Hence applying the His-tag-VpC-terminal domain as a simple biological material to evaluate quickly potential derivatives against the Vptlh in vivo conditions will accessible and more advantageous than using the whole of the Vptlh.

• Journal of Aquaculture
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• v.17 no.3
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• pp.228-232
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• 2004

This study evaluates red seabream quality using physicochemical and chemoenzymatic indices. Breaking strength was correlated with moisture content and lipid content of red seabram by a precedent experiment. Moisture content (X$_1$), lipid content (X$_2$) and breaking strength (Y) were optimized with multiple regression as, Y= -2.53539＋0.05544X$_1$-0.00161X$_2$. To test the equation, red seabream (n=13) were randomly purchased and measured moisture content, lipid content and breaking strength. The calculated breaking strength using the equation was similar to breaking strength measured using Rheo meter. Adenylate energy charge (AEC), a general biochemical index of stress, values of all sample were higher than 0.8 expect two fish. Fish's condition was a good. The equation developed in this study predicts breaking strength with moisture and lipid content measured. Moreover the equation may be used in grading cultured red seabream with calculated breaking strength. Grade according to breaking strength, when it came to over 1.4 kg, was measured as high grade; when it came to below 1.2 kg, was measured as low grade. Grade according to AEC, when it came to over 0.8, was measured as high grade.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.7
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• pp.4489-4497
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• 2015

This study aims at estimating the consumer's demand and willingness to pay(WTP) for horse meat in Korea. Three econometric models are employed to examine the multiple layers of the demand, including the current demand, the potential demand and latent demand. Findings indicate a substantial demand for horse meat. Dichotomous choice contingent valuation method is used to elicit the WTP. We assess the mean WTP for horse meat using a double-bounded logistic model. As a result, consumers are willing to pay at 67.8 percent of the beef prices of the third quality grade to purchase horse meat. And, for the factors that influence on WTP, only sex, age and recognition of horse meat are statistically significant.

• Ocean and Polar Research
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• v.33 no.2
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• pp.135-147
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• 2011

Zooplankton is an important constituent in assessing ecosystem responses to global warming. The northern East China Sea is an important ecosystem for carbon cycling with a net sink of carbon dioxide. Despite their importance as a major component in carbon cycling, relatively little is known about zooplankton biomass structure and its regulating factors in the northern East China Sea. This study examined zooplankton biomass distribution pattern in the region from multiple cruises encompassing various seasons between 2004 and 2009. Results showed that zooplankton biomass exhibits less cross-shelf gradient in general with declining biomass to the eastern shelf towards the Tsushima Current Water. Size-fractionated biomass showed that the 1.0~2.0 mm size group, mostly copepods, dominated zooplankton biomass, comprising 38 to 48% of total biomass. Smaller zooplankton (0.2~1.0 mm) biomass, consisting mainly of Paracalanus spp, a particle eating herbivorous copepod, was positively related to chlorophyll-a concentration, but no relationship was established for larger zooplankton (1.0~5.0 mm). Spatially-averaged mean total zooplankton biomass was also highly related to chlorophyll-a concentration. These result suggest that the long-term trend of zooplankton biomass increase in this region is partly accounted for by the increases of phytoplankton biomass and productivity underway in the region. However, the underlying mechanisms of how sea surface warming in the study area leads to increased phytoplankton biomass and productivity remains unclear.

• Journal of Aquaculture
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• v.17 no.3
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• pp.197-208
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• 2004

Five commercially valuable Korean Veneroid, Protothaca jedoensis, Ruditapes philippinarum, Saxidomus purpuratus, Cyclina sinensis and Meretrix lusoria were recognized by comparing internal and external morphological characters. As length of the primary tooth was directly grown proportional to shell size but all other characters were not measured according to size of shell. Hence, the morphological characters of these Veneroids may be estimated from the size of the unique primary tooth and it might be enough to be a good criterion for identification of species among Veneriods. Numerical index of hinge plate length of these species was assessed systematically, irrespective of measuring the length, height and width of the shell. The highest internal and external morphological similarity was observed between P. jedoensis and R. philippinarum and the lowest similarity was observed between P. jedoensis and M. lusoria. These similarities may be affected by multiple environmental factors as well as genetic characters. For artificial seed production of P. jedoensis, R. philppinarum, a closest relative among the five species, must be focussed.

• Korean Journal of Ichthyology
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• v.22 no.3
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• pp.195-200
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• 2010

A large volume of hatching jar was tested whether it is an effective to hatch fertilized eggs of Pacific cod. The volume of hatching jar did not show any significant differences in survival of the fertilized eggs; 48.3% for the jar of 15 L and 50.4% for that of 42 L. Survival rate of the fertilized eggs in a large volume of hatching jar ranged from 40.0 to 71.2%, which was higher than those of conventional small circular tank. A higher survival could be achieved even though stocking density of fertilized eggs was as high as 5,000 mL/jar. Consequently, the tested hatching jar allowed for incubation of a greater number of eggs with higher survival rate in a much smaller space. In addition, it reduces costs and manpower, and requires a relatively small amount of water per individual unit (6,700 mL/min), and provides a way to incubate multiple rearing groups in a quarantine environment.