• 한국패류학회지
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• 제29권3호
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• pp.245-250
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• 2013

We investigated the factors of mass-mortality in terms of water temperature and prey, in order to prevent the mass-mortality of cultured oysters at Gamak Bay in Yeosu City in 2007. The real-time water temperature was recorded as high, 28 to 31C, during late August. Nutrients, Dissolved Inorganic Nitrogen (DIN) and Dissolved Inorganic Phosphate (DIP) were downed in September. The analyzed results of chlorophyll a content were 0.78-1.50 ${\mu}gL^{-1}$ and phytoplankton for food resources was 81 cells $mL^{-1}$, both were low. The finding here indicate that Gamak Bay is in an oligotrophic state. The mass-mortality of cultured oysters occurred 43.6% in Gamak Bay. The mortality rate of oyster were above 67.0%, at Wanpo, however, it was showed 18.3% at Gumchun. Therefore, we believe the mass-mortality of cultured oysters at Gamak Bay comes from the destruction of bio-rhythms due to high water temperature and quantitatively and qualitatively decreasing food resources due to the limitation of nutrients.

• Journal of Ecology and Environment
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• 제45권1호
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• pp.10-16
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• 2021

Background: Ranavirus is an emerging infectious disease which has been linked to mass mortality events in various amphibian species. In this study, we document the first mass mortality event of an adult population of Dybowski's brown frogs (Rana dybowskii), in 2017, within a mountain valley in South Korea. Results: We confirmed the presence of ranavirus from all collected frogs (n = 22) via PCR and obtained the 500 bp major capsid protein (MCP) sequence from 13 individuals. The identified MCP sequence highly resembled Frog virus 3 (FV3) and was the same haplotype of a previously identified viral sequence collected from Huanren brown frog (R. huanrenensis) tadpoles in South Korea. Human habitat alteration, by recent erosion control works, may be partially responsible for this mass mortality event. Conclusion: We document the first mass mortality event in a wild Korean population of R. dybowskii. We also suggest, to determine if ranavirus infection is a threat to amphibians, government officials and researchers should develop continuous, country-wide, ranavirus monitoring programs of Korean amphibian populations.

• 한국환경보건학회지
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• 제29권4호
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• pp.1-3
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• 2003

Jinyangho is a natural water supply source of tap water in west Gyeongnam area, but mass mortality of crusian carp occurred during the time of temperature rise in spring. Examinations on diseased fishes were able to isolate four bacteria isolates and then identified the bacteria as a member of Aeromonas sp. Challenge experiment with mirror carp (Gyrinus carpiospecilaris) was proved the virulence, the isolates were in turn believed as the causative agent of mass mortality in Jinyangho.

• 환경생물
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• 제17권2호
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• pp.175-182
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• 1999

1996년 여름 제주도 서쪽 해안에서 전에 볼 수 없을 정도로 유용 대형저서동물이 대량으로 죽어, 전복, 오분자기, 소라, 해삼, 말똥성게에 큰 피해를 주었다. 제주도 해안에서 식물플랑크톤 대발생은 없었고, 대량폐사가 일어나기 전에 해안에서 표층 저염수가 나타났기 때문에 저염분 스트레스가 대량폐사에 결정적인 영향을 미쳤을 것으로 여겨진다. 같은 기간 관측된 강수량이 적어, 강수량으로 저염화를 설명하지 못한다. 국립수산진흥원(1997)이 관측한 자료는 1996년 8월 제주도와 중국 사이 해역에 표충 저염수가 나타난 것을 확실히 보여준다. 제주도 서쪽 해안에 나타난 표층 저염수는 다량으로 유출된 강물이 그 기원일 가능성이 가장 높다. 해류와 양자강에서 제주도까지 거리등도 표층 저염수가 양자강에서 방류된 강물에서 기원한 것이라는 가설을 지지한다.

• 한국수산과학회지
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• 제42권5호
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• pp.481-486
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• 2009

In 2007, 43.5% mortality of the cultured oyster population occurred in Gamak Bay. Mortality rapidly increase in September and peak in October. To prevent future mass-mortality event, we investigated spawning and variation of oyster body composition. The main spawning period of culture oyster occurred from August to September. Condition index and body composition (protein and glycogen) appeared to be influenced by the spawning activity. Condition index and glycogen content in September were lowest (13.5% and 5.6 mg/g, respectively). However, protein, lipid and glycogen contents did not rapidly recover after the spawning activity. The data indicates that mass-mortality of cultured oysters in Gamak Bay may be due to deteriorated health, spawning activity, stress of the high water temperature and decreasing food resources.

• 한국수산과학회지
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• 제45권6호
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• pp.723-729
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• 2012

On 3 February 2011, a mass mortality of finless porpoises Neophocaena asiaeorientalis occurred at a dike of the Saemangeum Sea dike. A total of 249 carcasses were collected; these had been stranded by a sea dike and had floated into the lake formed by the dike. Eight bodies were measured, and four of these were dissected to analyze stomach contents. The blubber thicknesses of five bodies were compared with those of caught finless porpoises in the Yellow Sea from 2010. Finless porpoises at the Saemangeum Sea dike exhibited better nutritive conditions than finless porpoises in the Yellow Sea. Air temperature in January 2011 was lower than the prior 5-year average (P<0.05). Water temperature when the mass mortality occurred was lower than values observed in 2009 and 2010: values below $0^{\circ}C$ had been recorded, and the majority of the dike lake had frozen over. The mass mortality of finless porpoises may have been caused by these unusually low temperatures.

• 한국패류학회지
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• 제25권2호
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• pp.93-96
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• 2009

Unexpected mass mortality has been one of the drawbacks in front of the stable production of Japanese scallop (Patinopecten yessoensis) on the Gangwon coasts of the East Sea. The preliminary data from our routine observation revealed that the mortality appeared to be related to variation of water temperature in the farming site and the degree of the mortality was dependent on scallop strain. The present study performed to verify the preliminary findings exhibited that the mortality was closely related to daily temperature variation rather than monthly variation. Daily temperature variation was particularly damageable to the scallop during the temperature elevation period. Scallops from hatchery seeds (Chinese strain) were more tolerant against the temperature variation over those from wild seeds. The hatchery scallop gain of the temperature tolerance was probably due to their larval experience to higher temperature in the hatchery as well as their maternal genetic acclimation to upper temperature extreme of the Chinese environment which was recently found.

• 한국어병학회지
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• 제34권2호
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• pp.255-259
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• 2021

This is the first report describing acute mass mortality occurred in juvenile olive flounder (Paralichthys olivaceus) caused by gas bubble disease (GBD). A total of 610 fish (average weight = 35 g), which were more than half of the fish acclimated at 17℃ in an aquarium, were killed within two days of acclimation. The dead and moribund fish showed excessively opened opercula and mouths, and occasionally, severe exophthalmia. Through microscopic observation, numerous gas emboli were found in the gills of the dead and live fish, while the fish were not infected with any microbial pathogens. The dissolved oxygen (DO) saturation level of the rearing water and seawater nearby the facility reached 145% and 286%, respectively, whereas other water quality parameters (such as salinity, pH, and chemical oxygen demand) were normal. The extreme saturation rate of seawater in the shore nearby seemed to be due to an enormous algal bloom that occurred there. Through molecular identification based on 18S rDNA sequences, the most dominant algal species was most closely related to Ulva californica (99.87% sequence identity) followed by U. prolifera, U. linza, and U. curvata (99.81%). Therefore, it can be concluded that supersaturated seawater due to mass algal bloom caused gas bubble disease in the olive flounder, leading to mass mortality. After technical adjustment, such as increased aeration, lowered water circulation rate, and inlet water filtration using micro-pore carbon filters, the DO level became normal, no further mortality occurred and the status of the fish was stabilized.

• 한국수산과학회지
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• 제47권6호
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• pp.978-982
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• 2014

A mass mortality of 249 finless porpoises Neophocaena asiaeorientalis occurred in the Saemangeum Dyke in February 2011. It was an extraordinary event, notable due to the death toll and the location of the occurrence, a semi-isolated lake enclosed by a man-made structure. We conducted sighting surveys that consisted of a land-based sighting survey recorded from three different platforms, and a ship-based sighting survey in the lake. The land-based survey was dedicated to clarifying the distribution of finless porpoises and whether they passed through two water gates (Shinsi and Garyek) of the dyke from 2011 to 2013. No finless porpoises were observed in the 2011 or January 2012 surveys. In April 2012, two months and one year after the mass mortality, one finless porpoise, swimming 400 m from the Shinsi water gate, was observed by a land-based survey. The number of observed individuals increased to nine in 2012 and reached 10 by May 2013 at the time of the surveys. Most of the porpoises were detected near the Garyek water gate. The density of the animals was $0.075/km^2$ in 2012 and $0.083/km^2$ in 2013. The density of porpoises was $2.063/km^2$ at the time of the mass mortality.

• 비만대사연구학술지
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• 제1권1호
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• pp.33-38
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• 2022

Although it has been confirmed that excessive body fat increases health risks and all-cause mortality, several epidemiological studies have reported that overweight or obesity in patients with chronic diseases and in older adults is advantageous with respect to mortality. Several mechanisms have been proposed to explain the biological basis of this obesity paradox. The marked heterogeneity of findings observed across studies and the possibility of systematic errors in these studies have cast doubt on the actual existence of the obesity paradox. However, the obesity paradox questioned the validity of body mass index as the best indicator for obesity in terms of predicting its comorbidities and urges clinicians to focus more on changes in body composition and related metabolic derangements, rather than body weight per se.