• The Korean Journal of Malacology
• /
• v.31 no.2
• /
• pp.103-112
• /
• 2015

Bay scallop (Argopecten irradians) has been farmed only in the South Sea of Korea. East Sea Fisheries Research Institute (ESFRI) has developed bay scallop aquaculture technologies to extend its aquaculture area to the Southeast Sea of Korea. For the artificial spawning, the water temperature was maintained at $23^{\circ}C$. Over 100,000,000 eggs were spawned through artificial spawning inductions, such as air exposure and thermal shock by rising the water temperature. The fertilization rate was over 91% with nearly 94,000,000 fertilized eggs. The shape of fertilized eggs was spherical with an average diameter of $61.7{\pm}0.05{\mu}m(54.1-67.4{\mu}m)$. Five days after fertilization, the eggs developed into prodissoconch shell, and continuously grew into umbo stage and then umbones stage. After 8 days of fertilization, the size of larva became $179.7{\pm}8.4{\mu}m$ on average ($150.4-204.8{\mu}m$), and the larva formed a foot and an eye spot. The larvae grew to $235.4{\pm}9.7{\mu}m$ in 10 days and attached to adherence material, becoming juvenile bay scallop. The shells grew from 22.71 mm to 72.40 mm in 6 month (June-December). The total weight increased from 2.0 g to 32.7 g at the same period. The daily growth rates of young scallop were $0.35mm\;d^{-1}$ (Apr. to Jun.) and $0.41mm\;d^{-1}$ (Jun. to Aug.), which were comparable to those found in the South Sea. These findings suggest that the bay scallop aquaculture may be suitable in the Southeast Sea of Korea and may provide an additional crop to aquaculturists.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.26 no.5
• /
• pp.523-530
• /
• 2020

Based on the results of harmful algal blooms (HABs) monitoring by the National Institute of Fisheries Science and local governments, the effects of changes in the marine environment on HABs are described. Since the beginning of HABs monitoring in 1972, they continued to increase from the 1980s to the 1990s. After the largest number of HAB incidents (109) in 1998; the trend declined until the 2010s. Most HABs in the 1970s were caused by diatoms. In the 1980s, coastal dinoflagellates caused HABs; Cochlodinium polykrikoides blooms have been occurring continuously since 1993. There are three HAB species that cause damage to fisheries in Korea. The high-density bloom of Karenia mikimotoi caused mass mortality in shellfish in Jinhae Bay in 1981. Karenia sp. blooms occurring around Tongyeong in 1992 killed aquaculture fish. Since the occurrence of the largest fisheries damage of KRW 76.6 billion in 1995 caused by C. polykrikoides blooms, they have been occurring continuously. The concentration of nutrients in coastal waters was the highest in the 1980s and has declined since the mid-1990s. This reduction in nutrient concentration is a good explanation for the decreasing number of HABs. Since 2016, a summer high water temperature of 30℃ or more has appeared, and the range and scale of C. polykrikoides blooms have been greatly reduced. In 2016, K. mikimotoi blooms occurred around Wando, Jangheung and Goheung and small scale blooms of C. polykrikoides occurred around Yeosu. There were no C. polykrikoides blooms in 2017; however, Alexandrium affine blooms occurred from Yeosu to Tongyeong. There was a small-scale blooms of C. polykrikoides in 2018 compared to those in the previous years. Our results show that reduction in nutrients and the high water temperature owing to climate change are a good explanation for variation in HABs in Korean coastal waters.

• The Journal of Fisheries Business Administration
• /
• v.40 no.2
• /
• pp.49-70
• /
• 2009

This study proviedes GARCH model(Bollerslev, 1986) to analyze the structural characteristics of price volatility in domestic aquacultural fish market of Korea. As a case study, flatfish and rock-fish are analyzed as major species with relatively high portion in an aspect of production volume among fish captured in Korea. For analyzing, this study uses daily market data (dating from Jan 1 2000 to June 30, 2008) published by the Noryangjin Fisheries Wholesale Market which is located in Seoul of Korea. This study performs normality test on trading volume and price volatility of flatfish and rock-fish as an advanced empirical approach. The normality test adopted is Jarque-Bera test statistic. As a result, first, a null hypothesis that "an empirical distribution follows normal distribution" was rejected in both fishes. The distribution of daily market data of them were not only biased toward positive(+) direction in terms of kurtosis and skewness, but also characterized by leptokurtic distribution with long right tail. Secondly, serial correlations were found in data on market trading volume and price volatility of two species during very long period. Thirdly, the results of unit root test and ARCH-LM test showed that all data of time series were very stationary and demonstrated effects of ARCH. These statistical characteristics can be explained as a reasonable ground for supporting the fitness of GARCH model in order to estimate conditional variances that reveal price volatility in empirical analysis. From empirical data analysis above, this study drew the following conclusions. First of all, from an empirical analysis on potential effects of seasonality and the day of week on price volatility of aquacultural fish, Monday effects were found in both species and Thursday and Friday effects were also found in flatfish. This indicates that Monday is effective in expanding price volatility of aquacultural fish market and also Monday has higher effects upon the price volatility of fish than other days of week have since it has more new information for weekend. Secondly, the empirical analysis led to a common conclusion that there was very high price volatility of flatfish and rock-fish. This points out that the persistency parameter($\lambda$), an index of possibility for current volatility to sustain similarly in the future, was higher than 0.8-equivalently nearly to 1-in both flatfish and rock-fish, which presents volatility clustering. Also, this study estimated and compared and model that hypothesized normal distributions in order to determine fitness of respective models. As a result, the fitness of GARCH(1, 1)-t model was better than model where the distribution of error term was hypothesized through-distribution due to characteristics of fat-tailed distribution, was also better than model, as described in the results of basic statistic analysis. In conclusion, this study has an important mean in that it was introduced firstly in Korea to investigate in price volatility of Korean aquacultural fishery products, although there was partially a limited of official statistic data. Therefore, it is expected that the results of this study will be useful as a reference material for making and assessing governmental policies. Also, it is looked forward that the results will be helpful to build a fishery business plan as and aspect of producer, and also to take timely measures to potential price fluctuations of fishery products in market. Hence, it is advisable that further studies related to such price volatility in fishery market will extend and evolve into a wider variety of articles and issues in near future.

• Korean Journal of Food Science and Technology
• /
• v.53 no.6
• /
• pp.669-681
• /
• 2021

The content of major constituents and antioxidant activities of two lavers (Pyropia seriata, Pyropia dentata) selected through breeding at different regions (Jangsan-do, Amtae-do, Dali-do, Jin-do, Muan) were compared in this study. The mineral contents of both cultivars were in the following order: K>Na>Mg>Ca>Fe>Zn>Mn>Cu. The content of major fatty acids was as follows: eicosapentaenoic acid>palmitic acid>arachidonic acid>dihomo-ɣ-linolenic acid. Main constituents of total and free amino acids were as follows: alanine>glutamic acid>aspartic acid. In particular, the total amino acid content in P. dentata was higher than that in P. seriata and was the highest in the sample from Jangsan-do in January. In addition, in terms of total phenolic content, reducing power, and DPPH radical-scavenging activity of both samples collected in January and February, P. dentata showed better characteristics than P. seriata. This study may provide useful information for the selection of laver in high quality.

• Journal of Wetlands Research
• /
• v.20 no.4
• /
• pp.398-409
• /
• 2018

Organic farming practices including loach based ecosystem-farming have been demonstrated to be effective in conjunction with rice farming to increase yield and quality. This new form of farming combines agriculture and fishery and is quickly developing into a new industry. The current study investigated the effect of rice-fish mixed farming system on the vegetation-diversity function. Vegetation within the four study sites was surveyed and analyzed based on plant taxonomy. The vegetation survey demonstrated that 127 taxa of 38 families, 100 genera, 107 species, and 20 varieties occurred within the study sites. A total of 15 plant species taxa occurred in the rice-fish mixed paddy fields with a fish habitat and did not occur in the conventional paddy field lacking fish habitat. This difference is thought to arise from differences in moisture requirements for vegetation. Life form analysis demonstrated differences in hemicryptophytes, therophytes, and hydrophytes according to fish habitat. The naturalized plants identified were also determined to be species widely distributed throughout Korea. Frequency analysis demonstrated that the rice-fish mixed paddy fields with a fish habitat had a high ratio of both obligate and facultative wetland plants relative to the conventional paddy field. Based on the study results, it is likely that vegetation-diversity will increase with environment diversity. However, no statistical significance was observed according to paddy types. Future research should aim to identify additional environmental factors, including the existence of fish habitat, habitat area, depth of fish habitat, hydrological parameters, water quality, and paddy soil environment, to enhance vegetation-diversity and biocultural diversity.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.33 no.4
• /
• pp.339-347
• /
• 2000

An algicidal bacterium, Micrococcus sp. LG-5 against the harmful dinoflagellate, Cochlodinium polykrikoides was isolated. The optimal conditions for the highest algicidal activity of bacterial culture filtrate showed in the range of $20{\~}30^{\circ}C$, at pH 7.0 and $3.0{\%}$ of NaCl concentration. In addition, $IC_(50)(mean of 50{\%} inhibitory concentration)$ of the culture filtrate against C. polykrikoides after incubation of 5 days was $0.482{\%}$. To investigate heat and pH stability of the culture filtrate of Micrococcus sp. LG-5, the culture filtrate ($pore size, 0.1 {\mu}m$) was heated to $121^{\circ}C for 15 min$ and adjusted pH from 2.0 to 10.0. There were no significant changes in algicidal activity by heat treatment and the pH change between pH from 5.0 to 10.0. The algicidal substances produced from Micrococcus sp. LG-5 were mainly detected in the fraction of $10,000{\~}1,000$ MWCO (molecular weight cut-off). The culture filtrate of Micrococous sp. LG-5 showed antimicrobial activity against Enterococcus faecalis, Escheiichia coli, Uebsiella pneunioniae and Vibrio altinolyticus, but did not show against Pseudomonas aeminosa, P. Buorescens, Salmonella typhi, Staphylococcus aureus, V. cholerae and V parahaemolyicus. The culture filtrate of Micrococcus sp. LG-5 was examined against 16 phytoplankton species and showed the algicidal activity against Ajexandzium tuarense, Eutreptiella Drnnastin, Gymnodinium catenatum, G. mikimotoi, G. sanguineum, eyodinium impuaicum, Heterocapsa triquetra, Heterosipa akashiwo, Prorocentrum micans and Pyraminonas sp.. However no algicidal effects of Micrococcus sp. LG-5 were observed against Chlamydomonas sp., Cylindrotheoa closterium, P. mininum, P. triestimum, Pseudonieschia sp. and Sczipuiella trochoidea. On the other hand, algicidal activity on the tested marinelivefood was not detected except for Isochrysis galbana. In addition, physiological responses of cultured olive flounder (Paralichthys oliraceus) exposed to $1 and 10{\%}$ of the culture filtrate of Micrococcus sp. LG-5 were measured. There were no clear changes in AST, GGT, creatinine, urea, total cholesterol, total protein, albumine, $Mg^(+2), Ca^(+2), Na^+, K^+, and Cl^-$. These results indicate that olive flounders were not affected when they were exposed to the culture filtrate of Micrococcus sp. LG-5.

• The Korean Journal of Malacology
• /
• v.23 no.2
• /
• pp.217-225
• /
• 2007

This study was conducted to estimate the general genetic parameters, heritabilities, and genetic and phenotypic correlations on growth-related traits by studying multiple trait animal model in two Korean abalone species, Haliotis discus hannai and H. discus discus. The data was collected from the records of 3,795 individuals produced from 54 sires and 74 dams in Haliotis discus hannai and 399 individuals produced from 7 sires and 7 dams in Haliotis discus discus. The data was evaluated by the Genetics and Breeding Research Center, National Fisheries Research & Development Institute (NFRDI). Genetic parameters were estimated for two abalone species raised in Bukjeju branch, NFRDI, from May 20 to November 1, 2004. The heritability estimates for growth traits of shell length, shell width and body weight obtained from restricted maximum likelihood (REML) were ranging from 0.73 to 0.78 in Haliotis discus hannai, and from 0.87 to 0.89 in H. discus discus. The heritabilities for shell shape and condition factor were ranging from 0.17 to 0.20 in Haliotis discus hannai, and from 0.01 to 0.45 in H. discus discus. Genetic and phenotypic correlations were over than 0.96 between shell parameters and weight in both of abalone subspecies, indicating that breeding for weight gains could successfully be achieved by selecting for shell length.

• Journal of Aquaculture
• /
• v.9 no.2
• /
• pp.159-166
• /
• 1996

A feeding experiment was conducted using juvenile Korean rockfish (Sebastes schlegeli) to evaluate supplemental vitamin premix in a test diet containing fish meal as protein source for nutritional study. Four vitamin premixes were prepared by adjusting different quantity and combination of vitamins. Each vitamin premix contained (mg/kg diet) : premix-1 : ascorbic acid, 2666 ; a-tocopheryl acetate, 417 ; thiamin, 60 ; riboflavin, 200 ; pyridoxine, 40 ; niacin, 800 ; Ca-D-pantothenate, 280 ; myo-inositol, 4000 ; D-biotin, 6 ; folic acid, 15 ; p-amino-benjoic acid, 400 ; mennadione, 40 ; A, 16 ; $D_3$, 0.1 ; choline chloride, 8000 ; cyanocobalamin, 0.09 ; premix-2 : ascorbic acid, 270 ; a-tocopheryl acetate, 189 ; thiamin, 13.5 ; riboflavin,, 27 ; pyridoxine, 13.5 ; niacin, 135 ; Ca-D-pantothenate, 135 ; myo-inositol, 135 ; D-biotin, 1. 4 : folic acid, 4.9 ; mennadione, 5.4 : A, 5.4 ; $D_3$, 2.2 ; choline chloride, 3000 ; cyanocobalamin, 0.05 ; premix-3 : ascorbic acid, 570 ; a-tocopheryl acetate, 107 ; thiamin, 20 ; riboflavin, 14.3 ; pyridoxine, 14.3 ; niacin, 71,3 ; Ca-D-pantothenate, 57 ; myo-inositol, 456 ; D-biotin, 0.7 ; folic acid, 2.9 ; p-aminobenjoic acid, 285 ; mennadione, 5.7 ; A, 5.7 ; $D_3$, 1.1 ; choline chloride, 1500 ; cyanocobalamin, 0.03 ; premix-4 : ascorbic acid, 190 : a-tocopheryl acetate, 36 ; thiamin, 6.7 ; riboflavin, 4.8 ; pyridoxine, 4.8 ; niacin, 23.8 ; Ca-D-pantothenate, 19 ; myo-inositol, 152 ; D-biotin,0.2 ; folic acid, 1 ; p-aminobenjoic acid, 95 ; mennadione, 1.9 ; A, 1.9 ; $D_3$, 0.4 ; choline chloride, 500 ; cyanocobalamin, 0.01. Triplicate groups of the 50 fish averaging 4.25 g were fed one of four isoproteic ($47\%$) and isolipidic ($9\%$) experimental diets to satiation twice a day for 10 weeks. Weight gain, feed efficiency and protein retention in fish fed the diet with vitamin premix-1 were significantly higher than those in fish fed the other diets (P<0.05). Moisture, protein and lipid contents of muscle and whole body were not affected by different dietary vitamin premix (P>0,05). These results indicate that premix-1 can be used to adequate supplemental vitamin premix in test diet containing fish meal as protein source for juvenile Korean rockfish.

• Journal of Aquaculture
• /
• v.13 no.2
• /
• pp.129-135
• /
• 2000

Genetic variabilities of local populations of Anthocidaris crassispina and Hemicentrotus pulcherrimus were analysed by random amplified polymorphic DNA (RAPD) technique with phenotypic variabilities in timing of gonadal maturation, reproductive output and size of individuals in Cheju. H, pulcherrimus, collected from 4 locations during March 1997, indicated that Daepo individuals were significantly smaller than that at Hamdok, Wimi site A and Wimi site B (ANOVA, p>0.001). Gonodal-somatic index (GSI) of the Wimi site B population was significantly higher than that of three other locations (ANOVA, P>0.0001). An ANOVA test conducted on test size of A. crassispina, harvested from six different locations of Cheju during June 1997, indicated that the size of individuals from Pophwan was significantly smaller (P>0.0001) than that from five other locations. GSIs of urchin m Wimi and Hanlim were significantly higher than that from Pohwan and Oedo (ANOVA, p>0.0001). Genetic similarity, calculated from k13 primer analysis of total DNA, among the six different populations of A. crassispina varied from 0.67 to 0.92, and the values for H. pulcherrimus from 0.60 to 0.73; thus there was no genetic variation among different populations of the same species. Therefore, the populations are genetically homologous and the observed phenotypic variabilities were possibly associated with water temperature and food.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.23 no.3
• /
• pp.502-508
• /
• 1994

A total of 24 specimens of the pufferfish, Fugu xanthopterus, purchased at a fixhmarket in Pusan, korea were examined for toxicity using the assay method of tetrodotoxin (TTX). Also, the toxins isolated from the puffer liver were partially purified and analyzed for their chemical composition by instrumental behaviors. On the whole, when the level of toxicity in each organ was analyzed compared to that of liver, they were 100 % of the lover, 92 % for the intestine, 75% for the skin, 17% for the muscle, 785 for the testis, 87% for the ovary, and 71% for bile. The highest and average scores of toxicity for the liver were 917 and $231{\pm}51MU/g$ liver, respectively. The toxins of the puffer gave four peaks in HPLC whose retention times (10, 20, 22 and 25 min) were close to those of TDA, TTX, 4-epi-TTX, and and -TTX, respectively.