• Korean Journal of Fisheries and Aquatic Sciences
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• v.56 no.6
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• pp.899-908
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• 2023

Droughts can alter the dynamics of aquatic ecosystems, including fish communities. This study compared the variations in fish communities in Juam reservoir before and after drought events. Fish sampling was conducted five times from April 2021 to April 2023 using three different sampling methods (kick net, cast net, and gill net). The water level in the reservoir reached its peak (103.73 EL.m, 62.2% capacity) in September 2021, before the drought, and dropped to its lowest point (88.84 EL.m, 17.6% capacity) in April 2023. The dissolved oxygen content in the reservoir decreased from 27 to 6.3 mg/L between the period with the lowest water level (April 2023) and the period with the highest water level (September 2021). In September 2021, 466 fish were collected, but after one year of drought, the number of individuals decreased to 105. Further, the number of fish collected and water levels were positively correlated. Dominant species exhibited a population decline of over 60% with decreasing water levels. These findings highlight the importance of fishery resource management during drought periods.

• Journal of Fisheries and Marine Sciences Education
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• v.26 no.2
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• pp.444-454
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• 2014

The range of optimization problem in aquaculture is very wide, resulting from the range of species, mode of operation. Quite a few studies focus marine net-cages, but studies on land based culture farm are few or no. This paper considers a allocation problem to meet production planning in land based aquaculture system. A water pool allocation model in land based aquaculture system was developed. The solution finds the value of decision variable to minimize yearly production costs that sums up the water pool usage cost and sorting cost. The model inputs were (1) the fish growth rate (2) critical standing corp (3) number of water pool (4) number of fish. The model outputs were (5) number of water pool in growing phase (6) cost of cultivation (6) optimal facility allocation(number of water pool for each growing phase). To solve the problem, an efficient heuristic algorithm based on a greedy manner is developed. Branch and bound and heuristic is evaluated through numerical examples.

• Journal of fish pathology
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• v.6 no.2
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• pp.205-218
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• 1993

On the development of hirame(Paratichtys olivaceus) culture, outbreak of scuticociliata infection was reported to cause severe damage in Japan. To establish effective measures for isolation and cultivation of this ciliate, we tried to culture this pathogenic ciliate using medium for bacteria and fish cell lines in vitro. Scuticociliata from the brain tissues of infected fish was aseptically inoculated to CHSE-214 cells cultured in MEM-10 without antibiotic. Scuticociliata grew well and the number of ciliate reached $10^6\;cells/ml$ at temperatures of $15^{\circ}C$ to $20^{\circ}C$ for 10d. The number of ciliate cultured in the cell lines is 10 times higher than the numbers cultured in the liquid medium alone. This ciliata could be cloned by dilution method. Scuticociliata isolated could grow well on 42 different cell lines that were established from marine fish, warm freshwater fish, and salmonids. This ciliate could be preserved in liquid nitrogen for more than 6 months. Subsequently, we observed the optimal temperature and salinity for growth, and tested the sensitivities of this organism to formaldehyde, flagyl(Metronidazole), Ekuteshin(Combination compound of sulfamonometoxin and ormethoprim), and ozonixation. Optimal temperature for growth was $25^{\circ}C$ and salinity was 1.0 to 1.5%. Washed scuticociliata was killed by formaldehyde at the concentration of 50ppm for 10min, but was not completely killed even at a high concentration of 400ppm for 20min in MEM-5. Flagyl and Ekuteshin can inhibit the growth of scuticociliata at the concentration of 1,000 and $100{\mu}g/ml$ in MEM-10, respectively. More than 99% of this scuticociliata could be killed by ozonization at a dose equivalent to $1.0mg/\ell$ oxidant for 30sec in sea water. Isolated scuticociliata showed the pathogenicity to the cultured hirame by artificial infection(I. P. injection, $10^5\;cells$/fish). The number of scuticociliata in the water could be counted by most probable number(MPN) method using tissue culture, and the minimum detectable number was $1.8\;cells/\ell$. The number in the reservoir tank for water supply to the culture tank was 110 cells/l. After cleaning by elimination of the sediments from of the reservoir tank and disinfected with formaldehyde, number of scuticociliata decreased and was counted less than $1.8\;cells/\ell$ and infection rate of cultured hirame was decreased.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.6
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• pp.948-956
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• 2013

Seasonal variations in species composition and abundance of the fish assemblages in the coastal waters off Gadeok-do were determined using monthly sample collection by a small otter trawl in 2010-2011. Of a total of 65 fishes collected, the dominant species were Leiognathus nuchalis, Clupea pallasii, Thryssa kammalensis, Engraulis japonicus, Repomucenus valenciennei, Sillago japonica, Trachurus japonicus, Pennahia argentatus, Okamejei kenojei, Cynoglossus joyneri, Pholis fangi, Pleuronectes yokohamae, and Zoarces gillii. These 13 fishes accounted for 92.8% of the total number of individuals collected. The number of fish species, number of individuals, biomass, and species diversity indices fluctuated with the seasons. The peak number of fishes occurred in April, whereas the biomass of fishes was highest in August. The numbers and biomass of fishes were lower in February corresponding with the low temperatures, and diversity indices were lower in January than in any other month.

• Korean Journal of Ichthyology
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• v.25 no.2
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• pp.106-118
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• 2013

Monthly variation in species composition of shallow water fish in Cheonsu Bay were determined using samples collected by a beach seine in the shallow water at Namdang beach from April 2010 to March 2011. The species composition were compared to the data obtained in 1885~86 and in 1993, and factors affecting the long-term change in species composition were analyzed. Fish collected during the study were 25 species, 2,194 individuals and 16,762 g. Chelon haematocheilus were predominated in abundance, accounting 68.5% in the number of individuals. A few number of fish were collected during the cold months from November to April. Abundance was high from July to September by a large catch of juveniles of pelagic fish. Species composition in 1993 did not differ significantly from that in 1985~86 although Fabonigobius gymnauchen living in the fine sediments were increased in abundance. Abundance increase of this gobiid fish was considered to be related to the sedimentation of fine particles due to weakened water circulation after dike construction. The number of species and catch amount in 2010~11 were significantly decreased comparing to those of the former periods; especially in pelagic fish and benthic fish, but C. haematocheilus were greatly increased in abundance. C. haematocheilus is an estuarine fish being able to survive in relatively poor quality of water. This increase seems to be related to fish larvae from the culture net cages recently installed in the inner bay. Recent decrease in abundance of shallow water fish suggested that water quality has been gradually getting poor and recently attained over a critical level for the nursery function of fish.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.5
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• pp.654-664
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• 1998

Seasonal variation in species composition and abundance of pelagic fish in Chonsu Bay were determined by analyzing monthly samples collected using a set net from March, 1992 to January, 1993. The data in this study were compared with those of 1981$\~$82. Of 63 species identified, Engraulis japonicus, Ammodytes penonatus, Enedrias fangi and Sardinella zunasi predominated in abundance. Especially E.japonicus occupied $87\%$ of total number of individuals. In spling, fish abundance increased by recruitment of lariat E. fanti as well as adults of E. japonicus, A. personatus and S. zunasi. These adults moved towards the open sea after spawning in early summer. A large number of juveniles was then collected from August until December. The seasonal change in species composition from the present study showed a similar trend to that occurred in 1981$\~$82. However, larger number of pelagic fish was caught in 1992$\~$93 than in 1981$\~$82. This result seems to be related to the higher water temperature (>$2^{\circ}C$) than the average mean temperature in spring and autumn, implying that higher temperature provides favorable conditions for spawning and growth of the fish.

• Fisheries and Aquatic Sciences
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• v.5 no.1
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• pp.1-4
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• 2002

The modulatory effects of oxytetracycline treatments at high concentrations on the infection potential of scuticociliates in cultured juvenile olive flounder (Paralichthys olivaceus) and density of the ciliates in culturing water were investigated. The groups bathed with 400 and 500 ppm of oxytetracycline showed significantly lower intensities of scuticociliates on the fish and considerably lower number of the ciliates in culturing water when compared with the control group. However, the intensity of scuticociliates on the fish in the group bathed with 300 ppm of oxytetracycline was not significantly different with that of the control group in spite of considerably lower number of scuticociliates in culturing water than in that of the control group. Although the intensities of scuticociliates on the fish intubated orally with 400 and 500 mg/kg of oxytetracycline were lower than that of the control group, there were no statistical significances. In contrast, the fish fed 300 mg/kg of oxytetracycline showed significantly lower intensity of scuticociliates when compared with other groups. The results of this study suggest that oxytetracycline treatments can modulate occurrence of scuticociliatosis in fish farms probably through change of bacterial density, damaging to scuticociliatosis and immuno-suppression of fish.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.28 no.2
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• pp.164-170
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• 1992

In order to understand and explain the spary combustion, it was necessary to understand the disintegration mechanisms of liquid jet. To understand the disintegration mechanisms of liquid jet, the disintegration phenomena and uniform droplet production regions of testing liquid jet was investigated by means of longitudinally vibration capillary nozzle, which was injected the testing liquids. The testing liquids were light oil and light oil and light oil blended with 25wt% fish oil (File fish oil, Sardine fish oil, Alaska pollac oil) The results can be summarized as follows: 1. The uniform droplet phenomena have been changed according to the frequency of capillary tube, the jet velocity and physical properties of testing oils. 2. Within the region of uniform droplet, Reynold number was increased as Weber number increases. 3. The lower limit of wave length in which uniform droplet was produced 0.8d which was lower than Rayleigh wave length 4. The light oil blended with file fish oil which has lower viscosity and surface tension had the widest uniform droplet production region on the frequency and velocity among testing oils. But light oil blended with sardine fish oil were similar with light oil in the uniform production region.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.17 no.1
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• pp.7-11
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• 1981

The author carried out an experiment to find out the responsing patterns of filefish, Stepha nolepis cirrhifer (Temminck et Schlegel) to the color lights. The experimental tank (360LX50WX55H cm) was set up in a dark room. Six Longitudinal sections each being 60 em intervals are marked in the tank to observe the location of the fish. Water depth in the tank was kept 50 em level. Light bulbs of 20W were placed at the both ends of the tank to be projected the light horizontally into the tank. Two different colored filters were selected in combination from four' colors-red, blue, yellow, and white, and were placed in front of the light bulbs to make\ulcorner different light of color. Light intensity were controlled by use of auxiliary filters intercepted between the bulb and the filter. The fish were acclimatized in the dark for 40 minutes prior to employ in the experiment. Upon turning on the light, the number of fish in each section was counted 40 times in every 30 seconds, and the mean of the number of fish in each section was given as the gathering rate of the fish. The results obtained are as follows: 1. Color of light, to which the fish gathered abundantly was found in the named order of blue, white, green, and red. 2. The differences of gathering rate upon arbitary combined two color lights were shown significant, and the differences increased remarkably in accordance with the lapse of illuminating period.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.47 no.2
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• pp.118-127
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• 2011

This study was investigated seasonal variation and species composition of fish species at artificial reefs (octangle three-stage compartment type and dice type)and natural rock in the Shinyang-Ri coastal waters off Jeju Island with visual census method in January 2009, April 2009, July 2009, September 2009, December 2009, March 2010, June 2010, and September 2010. A total of 44 fish species was occurred, and the dominant fish species were Apogon semilineatus, Chromis notata, Trachurus japonicus, Sebastes thompsoni and Apogon doederleini. The number of individuals of fishes was higher at April 2009 and March 2010, however, lower at June 2010 and September 2010. The number of fish speices was higher at artificial reefs than those of at natural rock. Apogon semilineatus was dominant at octangle three-stage compartment type and the dice type artificial reefs, whereas Chromis notata was for natural rock. These results indicated that artificial reefs were good habitats for a variety of fish species in the Shinyang-Ri coastal waters off Jeju Island.