• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.8 no.2
• /
• pp.199-202
• /
• 2003

Monthly occurrence of the moon jellyfish (Scyphozoa: Ulmariidae: Aurelia aurita) was investigated in the southern coast of Korea in summer. The relationships not only between weight and length but also between length and food (rotifer and Artemia sp.) ingestion were also studied. Aurelia was monthly sampled 5 or 6 times at the coastal area between Jinhae and Geoje-do with a landing net (mouth: 30 cm, mesh size: 2 cm) at surface from June to August,2001. Aurelia aurita was dominated by 6-9 cm in June, 7-16 cm in July and 16 cm in August in bell diameter. The bell diameter was significantly related with weight (r=0.930, P<0.001). The ingestion rate was significantly different according to bell diameter and food density (ANOVA test: P<0.001).

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.49 no.4
• /
• pp.483-491
• /
• 2013

The sound-speed and density contrasts are important factors in estimating the target strength (TS) of moon jellyfish (Aurelia aurita). In this study, the sound-speed and density contrasts were measured using time-of-flight and neutral buoyancy methods, respectively. The sound-speed contrast of A. aurita was from 0.9966 to 1.0031 (mean${\pm}$SD, $0.9999{\pm}0.0017$) and no distinct differences in temperature or pulsation activity and weak were found. The density contrast was from 0.9994 to 1.0004 (mean${\pm}$SD, $1.0000{\pm}0.0002$). The density of A. aurita was substantially different but the density contrast of A. aurita was shown to be similar to that in the sampling location. The results can be used to estimate of TS of A. aurita by acoustic model.

• KSBB Journal
• /
• v.29 no.5
• /
• pp.336-342
• /
• 2014

Asexual benthic polyp reproduction plays a major role in the jellyfish bloom. Recent studies found that temperature is the most important factor to regulate the budding rate of the polyps. We established a simple dynamic model to count the number of polyps depending on the variation of temperature with two data sets from different places. The population of polyps was counted through the budding rate and the number of budding times by Fibonacci sequence. It is assumed that the budding rate depends on the temperature only. The budding rate of the asexual reproduction shows very sensitive to the distribution of the seawater temperature. The model was tested to the temperature data of Ansan located in the west sea of Korea. The results indicate that this model can be useful to predict the blooms of Aurelia aurita polyps, which may have considerable influence on the bloom of medusa. The shape of temperature curve plays a key role in the predicting the bloom of Aurelia aurita polyps.

• Ocean and Polar Research
• /
• v.34 no.1
• /
• pp.85-91
• /
• 2012

Physical properties such as sound speed contrast (h) and density contrast (g) of the interested target are key parameters to understand acoustic characteristics by using theoretical scattering models. The density and sound speed of moon jellyfish (common jellyfish, Aurelia aurita s.l.) were measured. Sound speed contrast (h) was measured from travel time difference (time-of-flight method) of an acoustic signal in a water tank for APOP studies (Acoustic Properties Of zooplankton). Density contrast (g) was measured by the displacement volume and wet weight (dual-density method). The sound speed remained almost constant as the moon jellyfish increased in bell length. The mean values${\pm}$standard deviation of h and g were $1.0005{\pm}0.0012$ and $0.9808{\pm}0.0195$), respectively. These results will provide important input for use in theoretical scattering models for estimating the acoustic target strength of jellyfish.

• Ocean and Polar Research
• /
• v.35 no.3
• /
• pp.205-217
• /
• 2013

We investigated the population dynamics of Aurelia aurita in Sihwa Lake from April to October in 2009. Salinity ranged from 5.9 to 30.7 psu at the surface. Abundance of mesozooplankton ranged from 3 to 111,874 indiv. $m^{-3}$. Ephyrae occurred from April to May with the peak in abundance occurring on 17 April. Maximum density of ephyrae was observed near the power transmission towers that are known to be habitats of polyps. Mortality of ephyrae was lower than in other areas because of the abundant prey concentration and the absence of predators. Young medusae occurred from April to July with the peak in abundance occurring on 8 May. Adult medusae occurred from May to July with the peak in abundance on 25 June and they disappeared before the rainy season. Planula occurred only in May and June with the peak in abundance on 25 June. Growth rates of Aurelia aurita ranged from -0.06 to 0.34 $d^{-1}$, and decreased rapidly after May. The period in which adult medusa occurred was restricted, compared with those in other area in Korea (e.g., Masan Bay) and Japan (e.g., Tokyo Bay). In the period of this study, the available food was limited in June and salinity decreased to ca. 20 psu in May because of the beginning of the wet season. We assumed that the exceptionally short period of occurrence of the medusa may be a response of adults to changes in temperature, salinity or food limitation which leads to the precocious maturation of young medusa and the release of planula and that the brief occurrence of medusa was caused by an abrupt decrease in activity after the release of planula.

• Ocean and Polar Research
• /
• v.32 no.2
• /
• pp.113-122
• /
• 2010

Understanding the abundance and distribution of massive jellyfish is necessary to forecast where or when their blooms will happen. The acoustic technique is one of the most useful methods of obtaining information if the acoustic characteristics of the targets are known. This study was conducted to determine the acoustic target strength (TS, dB) of two jellyfish species, Aurelia aurita and Cyanea nozakii, in the southern coast of Korea. For the ex situ measurements, 120, 200, and 420 kHz split beam transducers were used, and jellyfish with various bell lengths were arranged to prepare multiple jellyfish. Under 2 vertical individuals, the mean TS for multiple A. aurita at 120, 200, and 420 kHz was -72.7, -71.7, and -68.2 dB, respectively. In the case of 5 vertical individuals, the mean TS of the species was -71.3, -68.2, and -62.0 dB. Finally, the mean TS of C. nozakii at 120, 200, and 200 kHz was -62.0, -60.3, and -58.2 dB under 2 individuals and -58.1, -57.4, and -54.0 dB under 4 individuals, respectively. For both species, higher numbers of jellyfish resulted in a higher TS. In addition, higher frequencies were associated with a higher TS for the same jellyfish. These TS results for two species can be used as essential data for the acoustic detection of jellyfish in an open ocean or coastal area.

• Animal Systematics, Evolution and Diversity
• /
• v.16 no.1
• /
• pp.79-85
• /
• 2000

Some scyphomedusae were collected from the coasts of Busan (Gijang), Geojedo Island(Jangmok-ri) and Samcheok during the period from June 1989 to May 1999. They were identified into Stenoscyphus inabai of Stauromedusae and Aurelia aurita in Semaeostomeae. They are first recorded in Korea.

• Proceedings of the Korean Society of Fisheries Technology Conference
• /
• 2001.10a
• /
• pp.319-320
• /
• 2001

최근 서해안을 중심으로 한 한반도 주변해역에서 하계에 해파리류가 급증하면서 연안어장 및 생태계에 심각한 영향을 미치고 있는 실정이다. 우리나라 연안에서 우점하는 물해파리(Moon jellyfish: Aurelia aurita)는 전세계적으로 분포하는 종이며, 인체에 해를 미치는 유해한 종은 아니나 멸치와 같은 소형어류의 어장에 막대한 영향을 미치고 있는 실정이다. 물해파리는 소형일 때는 동물플랑크톤 중 요각류나 소형 갑각류를 먹다가 성장하면서 소형어류를 먹는 것으로 밝혀져있다( Purcell, 1985; sullivan et al., 1994). (중략)

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.51 no.3
• /
• pp.295-301
• /
• 2015

Target strength (TS) information is an important parameter that estimates the detection, distribution, and abundance of Aurelia aurita. In order to investigate the biological TS of jellyfish, some factors such as size (bell diameter), tilt angle, pulsation, and symbion should be known. In the ex situ TS measurements, the tilt angles and pulsation from synchronized swimming behavior of four live A. aurita (bell diameters in the air: 54.2 ~ 94.2 mm) were measured with the acoustic data at 70 kHz. The reduced target strength (RTS) of A. aurita was found to change ranged from 13.4 ~ 16.5 dB according to the incidence angles from $-30^{\circ}$ to $24^{\circ}$. When the change rate of bell diameter in the water was 0.2, the TS value showed a 7.2 dB change. These results could be utilized as an important data to understand the acoustic characteristic scattering of A. aurita.

• Journal of Life Science
• /
• v.17 no.3 s.83
• /
• pp.318-327
• /
• 2007

This study presents the molecular phylogenetic analysis of Korean Aurelia aurita Linnaeus collected from Yeosu in the southern waters of Korea using nuclear ITS1 region and mitochondrial COI gene sequences. The use of oligonucleotide primers F5 (forward) and R5 (reverse) targeted to ITS1 and LCO1490 (forward) and HCO2198 (reverse) targeted to COI amplified 267 bp and 643 bp fragments, respectively. The shortest genetic distance towards the ITS1 region is estimated at 0.023 when comparing Korean A. aurita to Aurelia sp. collected from California, USA. In particular, Korean and American/Swedish A. aurita were located far away in terms of genetic distance, ranging from 0.393 to 0.395. On the other hand, the genetic distance between Korean and English/Turkish/Swedish/American A. aurita regarding the mitochondrial DNA COI gene ranged from 0.201 to 0.205. However, a sister-ship with Korean and American A. aurita showed an extremely high bootstrap value (100%). The predicted secondary RNA structure of the mitochondrial DNA COI gene showed many different folding structures with a similar energy between Korean and American A. aurita. These results suggest that ITS1 and the mitochondrial DNA COI gene could be used as genetic markers for identification of the biogeographic populations.