• Journal of Aquaculture
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• v.22 no.1
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• pp.34-41
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• 2009

Gonadal development and reproductive cycle of the granular ark Tegillarca granosa were investigated by histological observations. Samples were collected monthly from January to Decemberry 2002 in the Yeoja Bay of Yeosu, Jeollanam-do, Korea. T. granosa was dioecious. The gonads consist of a number of oogenic follicle and acinus. Monthly changes in the gonad index reached a maximum in June and a minimum in August. Monthly changes in the condition index reached a maximum in July and a minimum in September. The reproductive cycle of this species can be divided into five successive stages: early active stage (March to May), late active stage (April to June), ripe stage (May to July), spent stage (July to August) and recovery and resting stage (September to March). The spawning of T. granosa occurred in July and August in Yeoja Bay. The sex ratio of female to male was not significantly different from 1:1.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.25 no.2
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• pp.44-53
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• 1989

In order to grasp the characteristics of a fishing ground at yeosu bay, the fluctuation in condition of the coast and that in catch by pound nets in the coast were investigated respectively. The results obtained are summarized as follows: 1. The water temperature in spring and summer was higher at the coast side than off shore, but in autumn and winter took the reverse. 2. The salinity was higher in spring and winter than in summer and autumn. A lower salinity zone was found at the Dolsan Do coast and higher ones were made off shore. 3. A eddy current was found at the Dolsan Do coast and a thermocline were made at the depth of 30 to 40 m in summer. But in autumn and winter the water became homogeneous. 4. The annual catch by the pound net was highest in 1984 and then decreased gradually. The monthly catch was highest in June and then decreased gradually. 5. The catches seemed to increase with the sea water temperature and salinity, and great catch was shown in 21$^{\circ}C$ to 27$^{\circ}C$ and 33.80% to 34.00%. 6. The component rate of fishes was 28.4% in spanish mackerel, 17.9% in anchovy, 19.5% in horse mackerel, 21.0% in sardine, 7.2% in hairtail, and 1% in common mackerel. 7. The fishes appeared continuously on way of fishing operation were spanish mackerel, hairtail, Yellow talil, crab, etc. An anchovy and sardine were caught mainly from March to July or August, horese mackerel and common mackerel from May to November. but puffer, swell fish, saury and filefish were caught mainly from April to October. 8. The sum of catch was largest in June, at which the wind direction was NE to SSW, the speed below 3.2m/sec, the atmospheric pressure below 1008mb, and precipitation beyond 154mm.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.41 no.1
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• pp.1-8
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• 2005

In order to find out the environmental factors influencing movement of common grey mullet, Mugil cephalus in funnel net fishing ground of the Dolsan-do, Yeosu southern sea area, the oceanographic factor such as the water temperature, isobath and tidal current were observed respectively, the water temperature was compared with the amount of common grey mullet caught by funnel net. Also, to investigate the movement direction of common grey mullet in same sea area, 160 common grey mullets of body length 22 to 51cm caught at funnel nets of the Dolsan-do southern sea area were marked and then released at 5 positions in 5 times. The results obtained are summarized as follows : 1. The water temperature at the funnel net fishing ground of Dolsan-do in 2002 was ranged from 6.9 to 27.4$^{\circ}C$. The water temperature was displayed a maximum value in August to increase from March and a minimum value in February of the ensuing year to decrease from September. The catches of gray mullet caught by funnel net were generally abundant from March to September, but decreased sharply from October. The optimum range of water temperature for the funnel nets fishing was situated between 15.0 to 25.0$^{\circ}C$. 2. The isobath from 6m to 13m in coast sea set up funnel nets were densely distributed and the depth more than 14m of isobath were widely spreaded to the open sea at Dolsan-do southern sea area. 3. The tidal current of the coast sea set up funnel nets flowed southward and northward along the coast ato ebb and flood tide respectively. The direction of tidal current to the open sea was southeast at ebb tide with the mean speed 43cm/sec, but northwest at flood with the mean speed 25cm/sec. 4. The recapture rate through the experiment duration showed 9.4%. The recapture rate in Gyedong area was very high value with 33.3% as compared with others. The movement of common grey mullet in Dolsan-do southern sea area trended toward a inner bay and north bound mainly.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.4
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• pp.253-266
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• 2014

The ECOM3D is used to study the circulation characteristics and density current from the Sumjin River runoff in the Kwangyang Estuarine System, South Sea, Korea. Annual mean value of $120m^3/s$ was imposed from the Sumjin River. The numerical model results in terms of tidal height, current and salinity field show satisfactory with skill scores over 90%. The current velocity showed the range of 1~2.5 m/s during flood and ebb phases. In particular, very strong flow occur in the narrow Channels of Noryang, Daebang and Changson exceeding over 2.0 m/s. The tidal residual currents in the various locations in the Kwangyang Estuary showed the range of 1~21 cm/s, The density-driven current through the Yeosu and Noryang Channels are about 12 cm/s and 4 cm/s, respectively. The current path through the Yeosu Channel is deflected toward west Bank. Based on budget analysis of the volume flux, the volume flux through the Yeosu Channel and the Noryang Channel were estimated to be 97.4 and $22.1m^3/s$ accounting for the 81.5% and 18.5% of total flux, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.6
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• pp.691-696
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• 2001

The first bloom of Cochlodinium polykrikoides was observed in the estuary of Nak-dong river near Pusan in Korea in 1982. Since then, there have been irregular blooms, sometimes spread over the adjoining .to Jinhae Bay even though it was confined to the bay and its vicinites until 1988. It had been outbroken frequently in the adjacent to Tongyeong, Geoje, Namhae and Yeosu coast since 1989. It became widespread along the coast of the South Sea to the East Sea of Korea in 1995. And in October in 1998 and 1999, the bloom had been taken place in Kunsan coast of Yellow Sea. According to the observations in situ, the frequency of occurrence has been increased year by year. The prevailing bloom season was from July to October with peak in September. The duration of the bloom became longer with the year, and sometimes lasted more than one month. The density of the bloom did not exceed 5,000 cells $mL^{-1}$until 1991, but it increased year by year to the highest of 43,000 cells $mL^{-1}$ in 1999. With respect to the assembleges of species in dinoflagellate blooms, C. polykrikoides was one of the important species with diatoms and the other dinoflagellates in 1980s. But since then, C. polykrikoides made an almost monospecific bloom. Based on two decadal observations of C. polykrikoides blooms, it became widespread throughout whole coast of the Korea, persistent for about one or two month long in some year, and monospecisc high density blooms. It was reported that significant fish mortalities were caused by this harmful dinoflagellate blooms especially in the fishfarms accomodating intensive fish cages such as Tongyeong, Namhae-do, Geoje, Yeosu and Geomun-do fishfarming yards. This widespread and persistent harmful algal blooms impede the development of marine aquaculture industries.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.40 no.3
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• pp.225-231
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• 2004

The power and scale of 950 hPa typhoon "Maemi" which struck the shore of Gosung in Kyungnam Province was same as that of 951 hPa typhoon "Saraho" in 1959. For the purpose of getting the safety of training ship "KAYA", we anchored at Jinhae Bay with riding at two anchors paid out 8 shackles of cable respectively. By the way when wind force being over 30m/s, we could not keep the safety of the ship "KAYA" by means of the holding power of an anchor only. Just by using the main engine moderately, we were able to maintain the security of the ship. The holding the main engine moderately, we were able to maintain the security of the ship. The holding power of an anchor according to the way of anchoring, the quality of sea bottom, the direction and speed of wind and current, and the length of an anchor cable were analyzed. The obtained results are summarized as follows : 1. When riding at two anchors rather than lying at single anchor we could get a good holding power. 2. There was a big difference in holding power according to the quality of the bottom. 3. It would be best anchoring in a soft mud area than in any other place as possible. 4. It would also be desirable to set anchor shackles much more than equipment number prescribed in regulation in order to get safety of a ship providing against typhoon.

• Korean Journal of Environmental Biology
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• v.36 no.1
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• pp.11-20
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• 2018

In planktonic ecosystems, the microplastics are considered as a potential food source for the zooplankton. To study a relationship between the zooplankton and the neustonic microplastics, a research experiment was carried out during May in the surface layers of the Yeosu coastal areas including Yeoja Bay, Gamak Bay, Yeosuhae Bay, and Botdol Sea. A neustonic zooplankton net (mesh size $300{\mu}m$; mouth area $30cm{\times}18cm$) was towed from the side of the ship in the event that it would not be affected by waves crashing by the ship at a speed of ca. 2.5 knots. All of the microplastic particles were separated from the zooplankton. The zooplankton and microplastics were appearing in a range of 61 to $763indiv.m^{-3}$ and 0.0047 to $0.3471particle\;m^{-2}$, respectively. It was noted that the Acartia omorii, Paracalanus parvus s. l., Labidocera euchaeta, A. hongi, decapod larvae, and cirriped larvae were predominantly seen in the experiment. For verifying relationships between zooplankton and environmental factors in addition to microplastics, a model redundancy analysis (RDA) was performed. The zooplankton were divided into two groups on the basis of feeding types (i.e. particle feeders, and carnivores), and the associated zooplankton larvae were also separately considered. A review of the additional environmental factors such as water temperature, salinity, turbidity, chlorophyll-${\alpha}$ concentration, diatom density, and dinoflagellate density were also contained in the analysis. The results showed that a noted zooplankton abundance had no close relation with the occurring number of microplastic particles, but rather was significantly related with other noted environmental factors such as temperature, salinity, turbidity, and chlorophyll-${\alpha}$ concentration. This fact implies that most zooplankton can feed themselves as a unit, by selecting the most likely available nutritious foods, rather than microplastics under the circumstance of food-richness areas, such what food resources are available as in the location of coastal waters.