• Journal of Aquaculture
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• v.18 no.3
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• pp.207-214
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• 2005

We report on the diagnosis, pathology, and taxonomy of Perkinsus sp. infection in Manila clams (Ruditapes philippinarum) from Korean waters. Amplimers were designed from internal portions of the non-transcribed spacer (NTS) of P. atlanticus for molecular diagnosis of Perkinsus infection. PCR-based identification methods and an in situ hybridization assay were developed for detection of Perkinsus sp. in live tissues as well as in histological preparations. Hybridization signals were observed around the nucleus of trophozoites. Positive results from PCR and in situ hybridization indicated that Korean Perkinsus sp. is genetically identical with P. atlanticus reported in Europe, which is currently synonymous with P. olseni reported from Australia. Microscopic morphological features of different lift stages of Perkinsus sp. appeared very similar to those of P. atlanticus. Severely infected clams often exhibited white nodules on their mantles and gills as a consequence of inflammation. In lightly to moderately infected clams, Perkinsus sp. was mainly found in gill tissues, whereas the protozoan parasites were found in digestive tracts, gonadal tissues, and foot tissues of heavily infected clams. It is likely that the gills are the portal of the infection and that P. olseni spreads to other tissues as the infection advances. In conclusion, by considering the taxonomic priority of P. olseni, Korean Perkinsus sp. is accepted as P. olseni. P. olseni appears to be common on tidal flats on the western and southern Korean coasts and is considered to be a pathogen capable of causing mass mortality of clams.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.14 no.2
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• pp.113-116
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• 1978

To ascertain the feasibility of the energy utilization in the sea adjacent to Korea, the distribution of the vertical temperature difference and the seasonal variation in the southeastern Yellow Sea are studied in relation to the sea water circulation. In summer, a region of high vertical temperature difference of approximately 16$^{\circ}C$ was found at a distance of approximately 40 miles from the western coast of Korea. It is located at the west of 125${\circ}$ 30`E and at the north of 34${\circ}$N. The vertical temperature structure is sustained by the inflow of Yellow Sea Warm Current water, the warming of the surface water of the Yellow Sea and the periodical renewal of the Yellow Sea Cold Water. It may be stated that power can be obtained from the sea water by making the use of the temperature difference. The vertical temperature difference was around 14$^{\circ}C$ in the western and southern waters of Jejudo Island. The vertical temperature difference decreases in autumn, and disappears due chiefly to the vigorous convective vertical mixing in winter when the northwest monsoon prevails. The power can be obtained from sea throughout the year, if power generation by the temperature difference is combined with that by wind and wave, and systemized in such a way that the former is employed in the hot season of summer, while the latter in winter and spring.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.48 no.6
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• pp.940-946
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• 2015

The Indo-Pacific bottlenose dolphin Tursiops aduncus commonly inhabits the coastal waters of Jeju Island, Korea. An investigation was conducted using data from vessel sightings and point sightings from land. During 40 days of vessel sighting surveys between 2007 and 2010, a total of 18 dolphin groups were encountered. The overall sighting rate was 0.01 group/n.m. Most Indo-Pacific bottlenose dolphins were sighted within 500 m of the northern coast of Jeju Island during surveys. Also, dolphin groups were observed 47 times during 109 days of shore-based surveys conducted between 2011 and 2015. The results of a dolphin distribution survey conducted in 2011 were generally similar to the results of previous surveys. However, there were no dolphin sightings from 2012 in Hanllim-eup, in the north-western part of the island, where dolphins were sighted frequently until 2011, whereas dolphin observations increased in the southern part of the island. The mean group size was 35.4 (SD=18.08) individuals. The most frequently sighted group size was 36-40 individuals. To conserve resident dolphins off Jeju Island, long term sighting surveys and environmental assessment are required to monitor their distribution patterns.

• Fisheries and Aquatic Sciences
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• v.9 no.4
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• pp.153-159
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• 2006

The ark shell (or 'blood clam') Scapharca broughtonii is a filter-feeding bivalve that has red blood and inhabits waters approximately 10m in depth off the southern coast of South Korea. This study was part of a larger research project investigating the causes of death and restoration of shellfish resources, which are important aquaculture products in South Korea. We examined physiological responses related to survival, respiration, excretion, and amino acid changes as a result of changes in salinity. The 9-day median lethal salinity ($LS_{50}$) was 16.5 psu with confidence limits of 14.9-18.1 psu. At $25^{\circ}C$, the oxygen consumption and ammonia-nitrogen excretion rates were increased with decreases in salinity. Although the osmolality of individuals was acclimated within 2 h at 26.4 psu and 12 h at 19.8 psu, it took more than 5 days at a salinity of 13.2 psu, whereas no individuals acclimated and all died at a salinity of 6.6 psu. Of the amino acids present in the blood, taurine and alanine increased in response to decreased salinity. Tissues of the gill and the mid-gut gland were affected by decreasing salinity. These data will provide important fundamental information for examining the causes of mass mortality of shellfish in the summer.

• Korean Journal of Ichthyology
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• v.9 no.2
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• pp.178-185
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• 1997

From November 1996 to April 1997, the rockfish, Sebastiscus marmoratus (Cuvier et Valenciennes) was reared in laboratory, and observed eggs development and morphology of larvae. The eggs of this species are demersal and adhesive, and their diameter were varied within 0.76 to 0.82 mm. The color of yolk is light yellow in early developmental stage, and then turned to orange before hatching out. The yolk contained numerous tiny oil globules. Hatching began about 33 hours and 30 minutes after insemination at $10.0{\sim}14.5^{\circ}C$ of waters. The newly hatched larvae were elongated in shape and 1.62~1.68 mm in total length (TL) with 7~8+16=23~24 myomeres. The larvae absorbed yolk material and oil globule completely in 14 days after hatching and became postlarvae. The spawning season of adult rockfish may be supposed to be from February to March in the southern sea of Korea.

• Korean Journal of Ichthyology
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• v.12 no.1
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• pp.62-70
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• 2000

Annual reproductive cycle of the file fish, Stephanolepis cirrhifer (Temminck et Schlegel), was histologically investigated. Samples were collected monthly in the coastal waters of Chungmun, south of Cheju Island, Korea from July 1997 to June 1999. In males and females of S. cirrhifer, the values of GSI (gonadosomatic index) were similar to the changes of water temperature and day length. GSI values in males and females were reached the maximum in June. Reproductive cycle could be divided into the following successive stages: in females, growing stage (February to May), mature stage (May to June), spawning stage (June to August), degenerative and resting stage (September to December), and in males, growing stage (February to April), mature stage (May to June), spent stage (June to August), degenerative and resting stage (September to January), respectively. Throughout histological observation of the ovary in the spawning period, the species belong to an asynchronous and multiple spawner.

• 한국해양학회지
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• v.26 no.4
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• pp.304-312
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• 1991

The distribution of dinoflagellate cysts have been investigated at 6 stations in Masan Bay, a well known area of red tide in the southern coastal waters of Korea, from May 1986 to March 1987. During the study, a total of 11 species in dinoflagellate cysts were isolated from surface sediments, representing 6 genera, 9 species and 2 unidentified species. The standing crops of dinoflagellate cyst varied extensively by month and station; ranging from 48 to 1,279 cells/cm$^3$ and showing major peaks in July. August and February. At stations, the distribution was most abundant at st. 4 (mouth of the bay), whereas it was very low at st. 1 (inner bay), where motile cell's blooms occur throughout the year. Thus, It is speculated that the distribution between the plankton and cyst populations of dinoflagellates show the different temporal and spatial patterns in a semi-closed bay like this survey area.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.3
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• pp.230-236
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• 1987

The correlation between tintinnid and dinoflagellate by means of seasonal variation of standing crops was investigated at two selected stations in Masan Bay, well-known as a red tide zone in southern coastal waters of Korea, during the period from January 1981 to December 1982. The most dominant dinoflagellates mainly belonged to $20-60\;{\mu}m$ of size class, and Gymnodinium and Prorocentrum were predominant from spring to summer season. Of tintinnid, Favella spp. were most dominant and associated with dinoflagellate blooms at the same season. Especially, Favella spp. were most positively correlated with $40-60\;{\mu}m$ size class of dinoflagellate, and also represented higher multiple corrleation with outer station (St.2), comprising relatively large species of Gymonodinium and Protogonyaulax, than with inner station (St. 1), dominated by Prorocentrum blooms. Thus, the interspecific food selection by size and morphology between tintinnid including Favella and dinoflagellate is recognized and it is considered to be an important factor influenecing on the prey-predator relationship in lower trophic level in the surveyed area.

• Journal of the Korean Society of Marine Environment & Safety
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• v.16 no.3
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• pp.259-268
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• 2010

Data on squid catches by the Korean jig fishery in sea blocks ($30'{\times}30'$), water temperatures at depth(30m, 50m and 100m) and zooplankton biomass in the East Sea from 1980 to 1999 were analyzed to examine the mechanism of formation of the high density stock area. Japanese common squid (Todarodes pacificus) catch in the East Sea was low in 1980s, while the catch was high in 1990s. The five sea blocks (No. 76, 82, 83, 87, 88) of the southern part in the eastern coastal waters of Korea showed high levels of percentage of total catch (35.1%), whereas the four sea blocks (No. 65, 71, 72, 78) of the coastal waters of Uleung Island showed high levels of percentage of CPUE (61.2%) for 20 years. Squid catches showed monthly fluctuations according to the vertical distribution of optimum water temperature for fishing ($14^{\circ}C{\sim}19^{\circ}C$). High total catch and high CPUE area matched well with $10^{\circ}C$ isothermal lines at 100m depth indicating northern limiting of Tsushima Warm Current, and temporal and spatial change in $10^{\circ}C$ isothermal line caused the change in total catch and CPUE. Horizontal distribution of zooplankton biomass by sea block was not matched well with those of total catch and CPUE, however pattern of time-series change in total zooplankton biomass was similar to that in total squid catch.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.6 no.1_2
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• pp.44-48
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• 1973

Since no medium-sized anchovies for skipjack baits are caught during the winter season in the Korean waters, the demand for the live baits in the winter season is met with crawl-stocked anchovies. Authors conducted a test on the wintering of the anchovies which were caught in the early November and acclimated for 22days in a crawl. The wintering crawl was kept in the inlet near Chungmu City, which is situated in the southern coast of Korea, for 4 months through December 1, 1971 to March 31, 1972. 1. The lowest water temperature of $7.2^{\circ}C$ recorded on March 1, caused no significant mortality of the wintering anchovies. However, two operations, moving the crawl and repacling the crawl webbing, brought about a considerable mortality. The mortality of the anchovies, due to the crawl moving to the wintering place two kilometers away from the transient acclimating place, amounted to 1.5 percent in 9 days following the crawl moving. The replacement of the fouled crawl webbing with a new one also caused a mortality amounting to 1.7 percent in 5 days. 2. It is judged that the favorable wintering waters lie in the south and southeast coasts of Keoje Island, the south and southwest coast of Chungmu City, coasts around Namhae Island, and the east coast of Dolsan Island. Jinhae Bay is not suited for the wintering because of its low water temperature in winter 3. The wintering anchovies wvere fed, once a day through the test period, with 4 kg of finely minced fresh anchovy for 57days in the early period, and with 2kg of compound pellet fish food for the rest of the period. Fatness coefficient of the wintering anchovies showed a slight increase in the latter half of the period.