• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.2
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• pp.103-109
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• 2000

Complete senuences of the mitochondrial rRNA Benes were determined among six salmonines in Korean Waters (Brachpmystax lenok, Onoorhpchus keta, O. masou mason, O. mason ishikawae, O. mykiss, and albino mutant of O. mykiss). The purposes of this study were to provide the basic information on levels of mtDNA polymorphism among these species for genetic characterization; discuss phylogentic relationships among three Oncorhynchus sepecies; demonstrate the utility of rRNA gene sequence data as a genetic marker for disringuishinf among Korean salmonines. PCR/direct sequencing data indicated the following consistent results; 1) 12S rRNA genes was 945 bases long in Oncorhynchus species, and 946 bases in B. lenot including one insertion. 2) Of sequence variation in mitochondrial rRNA regions, transitional substitutions were superior to transversion. 3) The significant differences were not shown in the intraspecific variation values in these gene regions. The percentage sequence divergence values were ranged from $0.066 to 0.212{\%}$. 4) The interspecific divergences were greater than the intraspecific variation. Nevertheless, ribosomal RMh genes were more conserved among species than the other mitochondrial genes, and they showed potentiality as an intergenic marker for systematics. In addition, phylogenetic trees, constructed from this data, supported that cherry salmon was closer to chum salmon than to rainbow trout, and that lenok was most distantly related species in six salmonid species.

• Fisheries and Aquatic Sciences
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• v.20 no.11
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• pp.30.1-30.10
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• 2017

Small-scale fish farmers in developing countries are faced with challenges owing to their limited information on aquaculture management. Nile tilapia farmers in Teso North Sub-County recorded lower yields than expected in 2009 despite having been provided with required inputs. Water quality was suspected to be the key factor responsible for the low yields. This study sought to assess the effects of earthen pond water physico-chemical parameters on the growth of Nile tilapia in six earthen fish ponds under semi-intensive culture system in Teso North Sub-County. The study was longitudinal in nature with pond water and fish being the units of analysis. Systematic sampling was used to select five ponds while a control pond was purposively selected based on its previously high harvest. Four ponds were fed by surface flow and two by underground water. Each pond was fertilized and stocked with 900 fry of averagely 1.4 g and 4.4 cm. Physico-chemical parameters were measured in-situ using a multi-parameter probe. Sixty fish samples were randomly obtained from each pond fortnightly for four months using a 10 mm mesh size and measured, weighed and returned into the pond. Mean range of physico-chemical parameters were: dissolved oxygen (DO) 4.86-10.53 mg/l, temperature $24-26^{\circ}C$, pH 6.1-8.3, conductivity $35-87{\mu}S/cm$ and ammonia 0.01-0.3 mg/l. Temperature (p = 0.012) and conductivity (p = 0.0001) levels varied significantly between ponds. Overall Specific Growth Rate ranged between 1.8% (0.1692 g/day) and 3.8% (1.9 g/day). Ammonia, DO and pH in the ponds were within the optimal levels for growth of tilapia, while temperature and conductivity were below optimal levels. As temperature and DO increased, growth rate of tilapia increased. However, increase in conductivity, pH and ammonia decreased fish growth rate. Temperature and DO ranging between 27 and $30^{\circ}C$ and 5-23 mg/l, respectively, and SGR of 3.8%/day and above are recommended for higher productivity.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.6
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• pp.746-752
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• 2013

An 8-week feeding experiment was conducted to evaluate three types of squid Sepia esculenta liver powder (SLP) as a dietary protein source for replacement of fish meal (FM) in the juvenile black rockfish, Sebastes schlegeli. For replacement of FM, six experimental diets were formulated with 5 or 10% of either of three types (A, B, C) of SLP: SLP-$A_5$, SLP-$A_{10}$, SLP-$B_5$, SLP-$B_{10}$, SLP-$C_5$, and SLP-$C_{10}$. One of the control diets contained 100% FM as the protein source, and the other was a commercial diet (Com). Fish with an average body weight of $6.50{\pm}0.03g$ ($mean{\pm}SD$) were allocated randomly in triplicate groups of 50 to aquaria and fed the experimental diets until satiation. The weight gain (WG) and specific growth rate (SGR) of fish fed the FM, SLP-$A_5$, SLP-$A_{10}$, and SLP-$B_5$ diets were higher than those of fish fed the Com, SLP-$B_{10}$, SLP-$C_5$ and SLP-$C_{10}$ diets. No significant differences were observed in WG and SGR among the diet groups, with the exception of the SLP-$C_{10}$ diet group. The feed efficiency (FE) and protein efficiency ratio (PER) of fish fed the SLP-$A_5$, SLP-$A_{10}$, and SLP-$B_5$ diets did not differ from those fed the control diet. However, fish fed SLP-$B_{10}$ and SLP-$C_{10}$ had lower FE and PER than the fish fed the FM, commercial, SLP-$A_5$, SLP-$A_{10}$, and SLP-$B_5$ diets. Both the SLP-A and SLP-B diets, but not the SLP-C diets, replaced up to 10% and 5% of FM for juvenile black rockfish, respectively. The results of this experiment provide information that will assist in formulating an inexpensive and practical diet containing SLP for juvenile black rockfish.

• Korean Journal of Ichthyology
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• v.8 no.1
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• pp.83-89
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• 1996

The early life history of Korean bullhead, Pseudobagrus fulvidraco was studied to obtain some information required in aquaculture and reinforcement of natural population. The fertilized eggs were almost spherical in shape and demersal. The egg membranes were transparent with minute folds on the surface, causing them to stick to other substrates. Yolk is yellowish without oil droplets. The eggs just after fertilization were measuring $1.4{\pm}0.03mm$(1.3~1.5mm, n=10) and expanded to $1.7{\pm}0.08mm$(1.6~1.8mm, n=10) in diameter in 1.5 hr. The blastodisc was formed in 30 min and cleavage started in 1 hr after fertilization, and the intervals of each stage of cleavage was about 30 min at $25.0^{\circ}C$. The yolk from 32-cell stage to gastrula stage partly depressed and the depressed part moved clockwise. Hatching occurred in 53 hr after fertilization and hatched embryos had 18~19+20~21(38~40) myomeres measuring 4.2~4.3mm in total length. At the age 7 d after hatching, 4 pairs of barbels were already formed ; 1 pair on the posterior part of the nostril, 1 pair on the upper jaw, and 2 pairs on the lower jaw. And the posterior margin of caudal fin changed into two folds. The lateral band and the form of all fins were completed in 3 weeks.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.6
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• pp.773-784
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• 2018

In this study, we examined the UA (upwelling age) using wind data of AWS/ASOS in the East Sea coast and the correlation between UA and SST (sea surface temperature) from May to August in 1995 to 2016. The data used the 6 observations of the wind data of AWS/ASOS and the SST data of the COD/RISA provided by the National Institute and Fisheries Science near the East Sea coast. The UA was calculated quantitatively low but it rose when the actual cold water mass occurred. Correlation analysis between UA and SST showed the negative (-) r (correlation coefficient) predominately. At the time of cold-water mass in June to August 2013, the r had a very high negative value of -0.65 to -0.89 in the 6 observations. It proved that as the UA increases, the SST is lower. By knowing the UA, we were able to evaluate the trend of upwelling in the cold-water mass of the East Sea coast in the long term and it will contribute to minimizing the damage to aquatic organisms according to the size and intensity of the upwelling.

• Korean Journal of Ichthyology
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• v.10 no.1
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• pp.1-10
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• 1998

The early history of Korean mandarin fish, Siniperca scherzeri was studied to obtain some information required in aquaculture and reinforcement of natural population. During the period from June 1996 to July 1997, the mature adults of Siniperca scherzeri were collected from the middle Soyang Lake at Puksan - myon, Chunchon - shi, Kangwon - do, Korea. The eggs from females were obtained by injecting HCG or/and GnRH - a and fertilized by dry method in the laboratory. The fertilized eggs, measuring 1.70~2.10 mm in diameter and expanded to 2.20~2.66mm after absorption of water, were globosity, light orange yellow, separative, submergence and had one large oil globules of 0.5~0.7 mm. The blastodisc was formed in 1 hour and cleavage started in 1 hour 30 min. after fertilization, and the intervals of each stage of cleavage was about 50 min. at the water temperature of $21{\sim}24^{\circ}C$. Hatching occurred 131 hours 30 min. after fertilization and newly hatched larvae were 5.86~6.85 mm in total length(TL) and numerous stellate melanophores were distributed on the yolk and abdomen of caudal peduncle. The yolk was almost absorbed and the teeth development. 3 days after hatching, at 6.98~7.60 mm TL. The head spines and the teeth were largely developed and all fins were completely formed and became postlarva stage 15 days after hatching, at 10.10~12.90 mm TL. The body shape and the color pattern were similar to adult, 25 days after hatching, at 15.3~23.8 mm TL. In 5 months after hatching were reached at 154.10~175.02 mm TL and 49.32~82.67 g in body weight.

• Ocean and Polar Research
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• v.36 no.2
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• pp.121-134
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• 2014

Sessile marine bivalves including mussels, oysters and clams are often used as a sentinel species in coastal environmental monitoring since changes in the environmental quality are often well preserved in their tissues and shells. In this study, we investigated overall health condition of the Mediterranean Mussel, Mytilus galloprovincialis on the south coast using histology. Reproductive condition as gonad index (GI), condition index (CI) as a ratio of the tissue weight to the shell weight, digestive gland atrophy (DGA), types of parasites, and pathologic conditions including erosion, necrosis, hemocyte infiltration, and neoplasia were examined from each histological preparation. GI decreased from March to July then increased from July to September and spawning mussel could be observed as early as in April and the activity continued until September. CI also followed the monthly changes in GI, indicating that decrease in CI was associated with the weight loss due to spawning. DGA increased from March to June, decreased in July and increased from July to September. High DGA values observed in June and September were coincided with spawning and high water temperature. Histology also showed high prevalence of erosion in the digestive gland in June (36.0%) and September (56.4%), suggesting that high water temperature and spawning acted as environmental stressors. No parasitic organism was identified during the survey, although some symbiotic copepods were observed. Histology was found to be useful and affordable technique in monitoring the overall health of mussel, providing useful pathologic information of the cells and tissues.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.43 no.6
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• pp.715-722
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• 2010

The effects of temperature, salinity and irradiance on the growth of the harmful red tide dinoflagellate Cochlodinium polykrikoides Margelef isolated from the South Sea of Korea were examined in the laboratory. Growth was examined under the following combinations of temperature and salinity: 15, 20, 25 and $30^{\circ}C$, and 15, 20, 25, 30 and 35 psu at a constant irradiance of $180\;{\mu}mol/m^2/s$. No growth was observed with a temperature of $15^{\circ}C$ and a salinitiy of 15 psu. Moderate growth rates of more than 0.30 /day were obtained at $25^{\circ}C$ with salinities of 25.35 psu. These values are similar to in situ observations for this species. The maximum growth rate, 0.35 /day, was obtained at $25^{\circ}C$ and 30 psu. In light experiments, cell growth of C. polykrikoides was conducted with constant temperature ($20^{\circ}C$) and salinity (30 psu) under light photon flux densities (PFD) of 10, 25, 50, 70, 100, 150, 250 and $350\;{\mu}mol/m^2/s$. C. polykrikoides did not grow at $10\;{\mu}mol/m^2/s$. Cell growth was observed at irradiance values of $25\;{\mu}mol/m^2/s$ and above. The irradiance-growth curve was described as ${\mu}=0.30{\cdot}(I-15.27)/(I+27.22)$, (r=0.99). This suggests a compensation PFD of $15.27\;{\mu}mol/m^2/s$ and a maximum growth rate of 0.30 /day. In conclusion, C. polykrikoides prefers high salinity, temperature and irradiance in summer in Korea. These results provide important information for understanding the mechanism of C. polykrikoides blooms and developing technology to predict blooms of this organism in the field.

• Korean Journal of Environmental Biology
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• v.37 no.4
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• pp.474-482
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• 2019

Disease monitoring in wild aquatic animals is necessary to obtain information about disease occurrence, disease agents, and the transmission of diseases between wild and cultured species. In this study, we monitored viral diseases in wild marine fish and crustacea caught by trawl in Korea in April and October 2018. We monitored the viral diseases in 977 fish from 39 different species and 287 crustacea from 14 different species. In fish, we collected kidney and spleen to detect viral hemorrhagic septicemia virus (VHSV), red sea bream iridovirus (RSIV), marine birnavirus (MABV), hirame rhabdovirus (HRV), and lymphocystis disease virus (LCDV). In crustacea, we monitored white spot syndrome virus (WSSV), infectious hypodermal and hematopoietic necrosis virus (IHHNV), taura syndrome virus (TSV), infectious myonecrosis virus (IMNV), yellowhead disease virus (YHDV), and white tail disease virus (WTDV) using pleopods, pereiopods, gills, muscle, and hepatopancreases. Although none of the viral diseases tested in this study were detected in the samples, these results will help disease control between aquaculture species and wild aquatic animals.

• Journal of Aquaculture
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• v.16 no.1
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• pp.24-30
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• 2003

Studies of the seed production of Urechis unicinctus were conducted under the laboratory conditions to obtain some information for the U.unicinitus culture. The experiment included developmental studies of the egg development, larval culture, sediment preference and growth of young U.unicinctus. The experiment were conducted from March to August, 2000. The adults of U.unicinctus collected in Namhae-do, Korea. The developments of the fertilized eggs were observed under a light-microscope at intervals of one hour after containing with density of one individual per 1 $m\ell$. The larvae were fed with Phaeodactylum tricornutum cultured at the laboratory. The concentration of the phytoplankton for the feed was 30,000 cells per individual larva. With progress of development, the food concentration was gradually increased, up to 10,000 cells per individual for the young U.unicinctus. Trochophore larvae appeared on the 68 hours after hatching. On the 32 days after hatching, over 50% of fertilized eggs developed into young U.unicinctus. In order to investigate the effect of sediment on the growth and burrowing of U.unicinctus, the young worms were reared in tanks with different grain sizes. The highest value of sediment preference and survival rate of U.unicinctus was shown in the mixture sediment group with below 0.10 mm, 1.01∼12.00 mm, over 3.01 mm and shell. The lowest value in both sediment preference and survival rate of U.unicinctus was observed in 1.0l∼2.00 mm grain size.