• Korean Journal of Ichthyology
• /
• v.24 no.1
• /
• pp.41-47
• /
• 2012

In the present study, we investigated the characteristic of growth and the tolerance of cold temperature in small yellow croaker and yellow drum. The results shows that the growth of yellow drum were faster than those of small yellow croaker with high food convergency efficiency. In condition factor (CF), the results shows that the values of yellow croaker and yellow drum were significantly higher in September, respectively. In mortality according to cold shock, two fishes was died under $4.7^{\circ}C$ in slow temperature descending test, but was both died under $9^{\circ}C$ in acute temperature descending test.

• Journal of Aquaculture
• /
• v.21 no.2
• /
• pp.111-122
• /
• 2008

This study was conducted to assess the usefulness of the temperature characteristics of the tidal flat sediments during low tide as a environmental factor, and burrowing behaviour, fatness, total hemocyte counts(THCs) and differential hemocyte counts(DHCs) of hard clam Meretrix lusoria as biological activity indices for the management of hard clam farms located in Taean(Chungnam province) and Gimje(Jeonbuk province) tidal flat in Korea. Temperature ranges of the sediment at 1cm depth during spring(March to May) and summer(June to August) in Taean(where the exposure time was about $5.5{\sim}6$ hours during low tide) were $8.7{\sim}26.8^{\circ}C\;and\;27.6{\sim}32.8^{\circ}C$, respectively. Even though there was no significant difference(P>0.05), temperatures of the surface sediment where submerged with remained seawater were generally higher than that of uncovered with seawater. Burrowing depths of normally digged hard clams were 0.9{\sim}3.6cm from March to October, 2002. In the field experiment performed at Taean farming ground covered with seawater, burrowing times of the clams under natural water temperatures were $41.6{\pm}10minutes$ in February and $5.4{\pm}1.3minutes$ in August, respectively, and these were influenced by water temperatures. Fatness of hard clams began to decrease from May(at Taean tidal flat) and June(at Gimje tidal flat), showed the lowest level in August and increased again from September. Total hemocytes counts in the hemolymph of the hard clams were decreased to the lowest level in July($24.7{\times}10^4cells/mL$, at Taean tidal flat) and August($28.2{\times}10^4cells/mL$, at Gimje tidal flat), and significantly increased again from September(at Taean tidal flat, P<0.01) and October(at Gimje tidal flat, P<0.001), respectively. We observed three types of hemocytes from the hemolymph of hard clams according to whether hemocytes retain the granules or not and the size of the granules. As a results, we could found that periodical monitoring of the sediment temperatures, clam burrowing behaviour and hemocyte parameters were very helpful for the management of hard clam farming.

• Journal of Life Science
• /
• v.20 no.9
• /
• pp.1294-1298
• /
• 2010

White spot syndrome virus (WSSV) is one of the most virulent viral agents threatening the penaeid shrimp culture industry. This study was carried out to evaluate the susceptibility of the sand shrimp, Crangon affinis, to WSSV as an alternative experimental model. WSSV caused 100% mortality in C. affinis within 7 days after experimental infection by immersion. Based on challenge studies, it was confirmed that C. affinis could be a potential host in WSSV transmission. Also, the neutralization of WSSV was carried out using an antiserum raised against recombinant envelop protein rVP466 to evaluate the WSSV infection mechanism. A constant amount of WSSV (at $1{\times}10^4$ diluted stocks) was incubated with various amounts of antiserum and then mixed to 20 l reservoir for the immersion challenge of C. affinis for neutralization. At 5 days post challenge, the shrimp in the positive control immersed in the immersion reservoir containing WSSV stock showed 100% mortality. The shrimps challenged with the 3 different mixtures of WSSV and rVP466 antiserum (1:0.1, 1:0.5 and 1:1) showed 100%, 68.8% and 68.8% mortality at 14 days post challenge, respectively. These results indicated that the antiserum raised against rVP466 could block WSSV infection in C. affinis. Therefore, this study confirmed that C. affinis can be naturally infected by WSSV as another potential host and that C. affinis can be used as an alternative experimental animal instead of penaeid shrimps.

• Journal of Aquaculture
• /
• v.20 no.1
• /
• pp.60-64
• /
• 2007

We examined the effects of the vibration stress on oxygen consumption and ammonia excretion of cultured soft-shelled turtle, Pelodiscus sinensis. For the stressed group vibration of $45{\sim}78\;dB$ (V) from electric vibrator was turned on for 15 min with 2-h intervals during daytime hours ($08:00{\sim}18:00$) for 28 days. Two different sizes of soft-shelled turtle, large (carapace length: $12{\sim}16\;cm$, body weight: $300{\sim}600\;g$, large size turtle: LST) and middle ($16{\sim}20\;cm,\;700{\sim}1,000\;g$, middle size turtle: MST) were used. The oxygen consumption of LST the beginning of the experiment (1 day) was 124.30 mg $O_2/kg/hr$, and after 7, 14, 21 and 28 days of stress decreased by 47.2, 71.6, 79.1 and 86.0%, respectively. In MST, oxygen consumption of beginning day was 66.04 mg $O_2/kg/hr$, and after 28 days of stress decreased by 76.5%. Ammonia nitrogen excretion showed a similar pattern to that of oxygen consumption. Ammonia nitrogen excretion of beginning of the experiment was 0.537 mg N/kg/hr, and after 28 days of stress decreased by 75.4% for LST, and by 74.3% for the middle ones. From in this study it was showed that the physiological activity was reduced by 50% following 8.4 days of vibration stress for LST, and 15.5 days for MST.

• Journal of Aquaculture
• /
• v.11 no.4
• /
• pp.449-455
• /
• 1998

The small size food organism(under the size 150${\mu}m$) is needed as food for early stage of marine fish larvae of small mouse (e.g the group of grouper). This study was investigated to develop a method for copepod Apocyclops sp. culture in combination with the rotifer B. rachionus for stable culture of copepod species and harvest of various size food organisms. The culture conditions as temperature, salinity, culture volume, photo period, culture preiod and observation interval were 25${\circ}C$, 22ppt, 40ml, all dark except to observation time, 16 days and every two day during the experimental period, respectively. The Tetraselmis suecica was used as the food for the two testing orgtanisms. After every two day counting, theses two organisms were transferred to fresh culture tanks with Tetraselmis suecica of $7{\times}10^5$cells/ml. In the mixed culture of B. rotundiformis and A. sp., growth of rotifer was suppressed by mixed culture with A. sp. whereas the growth of copepod Apocyclops was promoted in the mixed culture with rotifer B. rotundiformis (the maximum density was 22 individuals/ml through the 16 culture days). Moreover, the number of copepod nauplius were promoted about 2 times in the mixed culture compared to the numbers in single species culture. With this combination culture, the havested two food organisms of variable sizes. This size variation of food organisms was useful tools for larval rearing of small mouse marine fish larvae and next step food organism size of post hatched larvae.

• Korean Journal of Ichthyology
• /
• v.29 no.1
• /
• pp.62-68
• /
• 2017

The Alaska pollock (Gadus chalcogrammus) belongs to the family Gadidae; it is a cold water fish, and has been developed as a novel aquaculture species in Korea. In this study, we describe ongoing surveillance for aquatic animal pathogens based on growth stages. We investigated bacterial flora in rearing water, and monitored pathogens; we also analyzed histopathological traits of abnormal fish. In rearing water, the total bacterial counts were $2.1{\times}10^3cfu/mL$ and Vibrio spp. (52%) were predominant in the larvae stage. In the juvenile and adult stages, the total bacterial counts were $3.4{\times}10^3$ and $3.2{\times}10^2cfu/mL$, respectively (with Pseudomonas sp. as the predominant species; 90% and 52%). This result revealed that the bacterial flora in rearing water changed depending on the feeding types. No virulent-bacteria or problematic viruses (VHSV, viral hemorrhagic septicemia virus; NNV, nervous necrosis virus; MBV, marine birnavirus) were detected from outwardly healthy fish using either culture or PCR assay. Some juveniles (less than 5%) had gas bubbles on the gill lamellae, degeneration of the corneal epithelium, and choroid gland degeneration, suggesting that these symptoms were caused by external injury and secondary infection by opportunistic bacteria. Disease management is important to cope with disease emergence in the novel aquaculture species Alaska pollock.

• Korean Journal of Environmental Biology
• /
• v.38 no.1
• /
• pp.40-46
• /
• 2020

Hybrid grouper(Epinephelus fuscoguttatus ♀×E. lanceolatus ♂) (mean weight 25.7±3.5g, mean length 11.2±0.9cm) were exposed to different ammonia concentrations of 0, 5, 10, 20, and 40mg L^-1 for 96 hours. The hematological hematocrit and hemoglobin parameters of the hybrid grouper were significantly decreased by 20 mg L^-1 ammonia exposure. In the organic plasma components, calcium was significantly decreased, whereas there was no change in magnesium. In the organic plasma components, the glucose and cholesterol values of the hybrid grouper were significantly increased by ammonia exposure. In the enzymatic plasma components, the ALP(Alkaline phosphatase) value of the hybrid grouper was also significantly increased by ammonia exposure. The results of this study demonstrate that acute ammonia exposure to hybrid grouper induced changes in hematological parameters and plasma components. Therefore, acute ammonia exposure over 20 mg L^-1 appears to be toxic to hybrid grouper and the results can be used as a major indicator in breeding hybrid grouper.

• Journal of fish pathology
• /
• v.22 no.1
• /
• pp.9-14
• /
• 2009

Fifteen diseased rockfish (Sebastes schlegeli) were collected from 4 net-cage farms in Huksan island. Some round transparent nodules were observed on gill filaments in fish. Bacteriological and histopathological examinations on the diseased fish were performed. Any pathogenic bacteria could not be isolated from the internal tissues and histopathological alterations were not found in any of the tissues except the gills. Rock fish were infected with epitheliocystis, Microcotyle sebastes and unknown aetiology on the gills. Cysts of epitheliocystis measuring 44.1-68.9 $\mu{m}$ in diameter were mainly found in the distal portion of the gill filaments and sometimes in the middle portion. But host responses were moderate in spite of formation of the epithelial cysts. Some Microcotyle sebastes captured the secondary filaments with clamps on the opisthohaptor. Attachment of the parasites provoked epithelial proliferation and resulted in gill lamellar fusion.Cysts of unknown origins measuring 26-425 $\mu{m}$ in diameter were found in the cartilage of gill filaments. These cysts contained eosinophilic materials and proliferation of cartilage cells was confirmed around the cysts. But there was no significant pathological changes associated with the presence of the cysts except enlargement of the gill filament with the cysts.

• Journal of Marine Life Science
• /
• v.4 no.1
• /
• pp.29-37
• /
• 2019

In order to control disease caused by multi-drug resistant bacteria in the aquaculture, the use of veterinary antibiotics, which are prohibited to fish, is increasing, instead of the existing fisheries antibiotics. Among them, tiamulin is illegally used in some cultured fish because it exhibits effective antibacterial activity against Gram-positive bacteria. To prevent unauthorized use, treatment of fish should be accompanied by a prescription from veterinarians or fisheries disease managers through research on fish of tiamulin. Tiamulin was injected intramuscularly at 5, 10 and 15 mg kg^-1 for the streptococcus-infected starry flounder, but did not show any therapeutic effect. Oral administration at a concentration of 15 and 30 mg kg^-1 was similarly ineffective. The concentrations of 30 and 60 mg kg^-1 resulted in death due to toxicity of antibiotics. Therefore, it is inappropriate to treat antibiotics with streptococcus-infected starry flounder.

• Journal of Aquaculture
• /
• v.20 no.4
• /
• pp.270-277
• /
• 2007

White spot syndrome virus (WSSV) which is the most serious threat to cultured shrimp around the world has given enormous economic damages to shrimp culture industry every year since it was found from the shrimp ponds in the west coast of the South Korea in 1993. WSSV has strong infectivity as well as virulence and it can be rapidly transmitted among shrimps in ponds by cannibalism of infected ones. Polyculture of shrimps with carnivorous fish has been applied in commercial shrimp farms to suppress or delay the viral outbreak because the fish may selectively eat the moribund shrimps infected by virus. To determine the selective predatory effect of a carnivorous fish, river puffer Takifugu obscurus on white shrimp Litopenaeus vannamei, polyculture trials in laboratory scale of WSSV-infected and non-infected shrimps with river puffer were conducted in concrete round tanks of $28.26\;m^2$ in surface area as followings: 1) juvenile shrimps (B. W. 0.62 g) with 5 months old puffer (B. W. 11.60 g) cultured for 8 days, and 2) sub-adult shrimps (B. W. 6.84 g) with 16 months old puffer (B. W. 85.82 g) cultured for 5 days in order to know the effects according to size difference of cultured animals. In polyculture of juvenile shrimp with 5 months old puffer, survival rates of infected and non-infected shrimps were 46.0% and 89.1% respectively and in that of sub-adult shrimp with 16 months old puffer those were4% and 48% respectively. The results showed that puffer tends to selectively prey on virus infected shrimps among infected and non-infected ones in a limited space with although there is difference in predatory rate with age and density of animals. Regardless of different densities and ages of animals as well as health condition of shrimps, however, there were low differences in daily biomass of shrimp consumed per kg body weight of puffer. This finding suggests that puffer preys on healthy shrimps when moribund shrimps were not sufficient. Therefore, farmers should consider the total biomass of puffer as well as density and stocking time when they stock puffer into shrimp ponds for polyculture.