• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.4
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• pp.269-275
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• 2003

In this paper, We examined auditory threshold and critical ratio of amberjack seriola dumerili, in the Jeju Island coastal waters, to find out hearing ability of the fish. The auditory threshold level, critical ratio and hearing index of amberjack were determinded by conditioning method using a sound coupled with electric shock in the condition of ambient noise or white noise in an experimental water tank. The audio-signals of pure tone and electric shock were from 80 HZ to 800 Hz and DC 7 V, respectively. Values for the critical ratios were calculated in terms of the masked thresholds using the noise projected to stable spectrum levels at all measurement frequencies of background noise. Masking noises were in the spectrum level range of 65 dB∼75 dB $(re 1{\mu}Pa\sqrt{Hz})$. The auditory thresholds of amberjack within the test the frequencies were most sensitive at 300HZ as 94.5 dB. The critical ratios of fishes ranged from 36.4 to 52.8 dB. The noise spectrum level that started masking was about 58∼72 dB within frequencies.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.43 no.5
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• pp.406-414
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• 2010

The impact of rainfall events on the sanitary indicator bacteria density of the shellfish-growing waters in Geoje Bay and Jaran Bay in Korea was investigated. The shellfish-growing area in Geoje Bay, which is a nearly closed basin, was not affected significantly, except near the stream mouth after 11.5 mm of rainfall in 1 day. However, most of the shellfish-growing water in the bay was polluted by fecal coliform bacteria after rain as heavy as 43.0 mm, and the levels of fecal indicator bacteria in some of the sea near the coast did not recover completely until 24 hours after the rainfall. By contrast, in Jaran Bay, which has no significant pollution source in the drainage area, although 9.3-490 MPN/100 mL of fecal coliform bacteria were detected near the stream mouth after rainfall of 33.5 and 81.0 mm, a very low level of the indicator bacteria was detected in the designated shellfish-growing area. During the investigation, the correlations between the sanitary indicator bacteria density and physical parameters, such as salinity and turbidity, were evaluated. Both the total coliform and fecal coliform densities were inversely correlated with salinity. Turbidity was positively correlated with the indicator bacteria density. The survey results suggest that for more efficient management of the shellfish-growing areas located in coastal areas, such as shellfish harvesting after rainfall, a detailed investigation of the effects of rainfall on the bacterial water quality in each growing area is needed.

• The Korean Journal of Malacology
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• v.20 no.1
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• pp.55-63
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• 2004

Gonadosomatic index, condition index and reproductive cycle with the gonadal development of the female Octopus ocellatus were investigated by histological observations and morphometric data, from January to December, 2000. And changes in biochemical components of the ovary and the trunk tissues including the digestive organ associated with gonadal development were studied by biochemical analysis from January to October, 2001. The specimens were collected at the coastal waters of Buan, Jeollabuk-do, Korea, from January 2000 to October 2001. O. ocellatus is a dioecious organism. The gonad of O. ocellatus locates medially in posterior region of the body. Morphology of the ovary shows round and oval in shape, the average diameter and external colour of ripe ovary was 32 mm and semitransparent light brown in colour. As the ovary was getting mature, transparent elongated eggs covered with chorion were present in the ovarian cavity. Monthly changes in the gonadosomatic index (GSI) showed a similar pattern with those of the condition index. The GSI and condition index began to increase in March and reached the maximum in April. And then, their values decreased from May and reached the minimum in September. Reproductive cycle of O. ocellatus can be categorized into five successive stages: early developing stage (September to December), late developing stage (November to March), ripe stage (March to May), partially spawned stage (April to June), and degenerative/resting stage (June to October). Follicle cells attached to an oocyte were involved in vitellogenesis in the cytoplasm of the vitellogeneic oocyte and formation of chorion (secondary egg membrane) of the ovarian eggs. Spawning occurred between April and June. The spawning period was once a year and the peak took place between May and June. This species belongs to semelparity. According to changes in biochemical contents of the ovary and the digestive organ, monthly variations of moisture, total protein, total lipid and glycogen contents (%) in the ovary showed a negative correlationship with those of the trunk tissues including the digestive organ. Accordingly, it is assumed that the ovary only may be received nutrient supply (total lipid content) for gonadal development from the trunk tissues including the digestive organ (r = -0.55, p < 0.05).

• Journal of the Korean Society of Marine Environment & Safety
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• v.14 no.2
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• pp.95-103
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• 2008

Heavy metals in the surface seawaters and sediments were measured in Gaduk channel of jinhae Bay. The high concentrations of heavy metals in the seawaters were found at the stations near the islands. In the seawaters, the mean concentrations of dissolved heavy metals except for Pb were not higher than previous data in this bay. Higher heavy metal contents in the surface sediments were observed at the stations adjacent to the Geojedo or Gadukdo of the Gaduk channel. The contents of Co,Ni,Zn,Cu,As and Cd in the surface sediments showed relatively high correlation coefficients with IL and COD. The order of enrichment factors(EFs) of heavy metals in the sediments on the basis of average shale values was As>Cd>Pb>Zn>Co>Cu>Hg>Ni, and the EFs of As,Cd,Pb and Zn at whole stations were higher than 1. EFs of Ni and Zn on the basis of natural background concentration in Korean coastal sediments were lower than EFs by average shale.

• Ocean and Polar Research
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• v.29 no.4
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• pp.401-410
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• 2007

In Korea the study of marine heterotrophic protists started in the late 1980s, and since the early 1990s many studies have been conducted in various marine environments. In this article, studies on the distribution and abundance of protists and the biotic interactions(bacteria-protists, phytoplankton-protists) conducted in Korean coastal waters are reviewed, and a field study is reported and discussed. The field study in Masan Bay was carried out from February 2004 to November 2005 at seven selected stations representative of the bay. During the study, the mean abundance of heterotrophic bacteria and the mean concentration of chlorophyll-a were $2.1{\times}10^6\;cells\;mL^{-1}$ and $9.8{\mu}g\;L^{-1}$, respectively. Heterotrophic protists consisted of heterotrophic dinoflagellates, heterotrophic nanoflagellates(excluding dinoflagellates) and ciliates, and their abundances were means of $7.9{\times}10^4\;cells\;L^{-1}$, $1.2[\times}10^3\;cells\;mL^{-1}$, and $4.0{\times}10^4\;cells\;L^{-1}$, respectively. Generally, the chlorophyll-a concentra+CZ14tions and the abundances of heterotrophic bacteria and protists were higher in the inner zone of the bay, where there are high concentrations of organic matters, than in the middle and outer zones. Using the grazing rates of heterotrophic nanoflagellates on bacteria previously reported in this area, it can be calculated that about 69% of bacterial producton was removed by HNF grazing activity. About 24% of initial chlorophyll-a concentration was removed by microzooplankton grazing activity. In conclusion, this study suggests that in Masan Bay heterotrophic protists control the growth of bacteria and phytoplankton, and heterotrophic protists represent an important link of bacterial & microalgal biomass to higher trophic levels.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.2
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• pp.198-203
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• 1999

Gonadal development and reproductive cycle off Gomphina melanaegis collected in the coastal waters of Chumunjin, Korea were investigated monthly from April 1996 to April 1997. G. melanaegis was dioecious, The gonads were located between the digestive diverticula and muscle tissues of the foot, The ovary was composed of a number of ovarian sacs, and the testis was composed of several testicular tubules. The flesh weight rate was reached the maximum in August ($23.0\%$), and then decreased to $19.8\%$ in September. In March, the value was reached the minimum ($17.8\%$) and then increased, The size of mature oocyte was ranged $50\~60\mu$m in diameter and had a germinal vesicle with a nucleolus. Mature oocyte contained a large number of yolk granules and lipid granules in its cytoplasm. The spermatozoon was consisted of a conical nucleus with acrosome, a middle piece containing four mitochondria and proximal and distal centrioles, and a flagellum, Sex ratio (male/female) and minimum size for sexual maturation of G. melanaegis were 0.79 and about 25 mm in shell length, respectively. The reproductive cycle could be classified into five succesive stages: multiplicative (December to March), growing (April and May), mature(June), sprawning (July and August), and degenerative and resting (September to November) stages.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.30 no.3
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• pp.432-441
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• 1997

Stomach contents of fat greenling, Hexagrammos otakii were analyzed to understand feeding ecology of the fish in the coastal waters, Shinsudo, Sarhon. Specimens were collected by angling and by gill net from February 1984 to September 1985. The fish consisted of 4 age groups from 0 to 3. The food items of the fish changed slightly by seasons and with growth of the fish. Main preys were copepods, gammarids and caprellids for the fish of age group 0, gammarids and caprellids for age group 1, and brachyurans and carideans for age group 2 and 3. The prey composition of the fish were more varied by seasons than by ages. Food items was not different between male and female of the fish. The fish positively selected for gammarids, polychaetes and brachyurans, but negatively selected for gastropods. The degree of selectivities for the other preys were changed with growth. As the fish grows it consumed larger preys in case of small preys such as gammarids and caprellids, however, it did not consumed larger preys beyond an optimal size in case of large preys such as sphaeromids, brachyurans and polychaetes.

• Journal of Korea Port Economic Association
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• v.32 no.2
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• pp.73-90
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• 2016

In Climate change is a global issue that requires global responses. As a key factor in climate change, greenhouse gas (GHG) emissions have attracted increasing attention the international community. One of the crucial global efforts to alleviate climate change is the establishment of an international climate change regime, comprising rules, norms, principles, procedures that are applicable to a wide range of activities. The International Maritime Organization (IMO) received a mandate from the Kyoto Protocol to regulate shipping GHG emissions. However, the IMO Convention and the UN Convention on the Law of the Sea also provide regulations on regarding GHG emissions. To execute its mandate, the IMO has developed various regulatory initiatives. In addition, the Chinese government has declared new regulations which designate parts of its coastal waters as emission control areas (ECA). Owing to the growing recognition of the benefits of ECA, ships, including ocean-going vessels that operate in areas near the Pearl River Delta, Yangtze River Delta, and the Bohai Sea will be obliged to use fuel containing less than 0.5% sulfur. China's shipping industry is playing a growing role in the international shipping market, and its response to these initiatives will have a substantial effect on the future application of these regulations. This study analyzed the GHG mandates of the IMO and the Chinese government, and then examines the main outcomes that have been achieved.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.5
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• pp.459-466
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• 2013

To understand the fishery characteristics by a beam trawl off the coast of the Chungnam province, covering $125^{\circ}$ 50'~$126^{\circ}$ 05'E, $36^{\circ}$ 15'~$36^{\circ}$ 25'N, a beam trawl was deployed 2~4 times a month from March 2008 to February 2009. The catch was consisted of 96 species of 63 families belonging to 19 orders. Among these, organisms were identified as 54 species of fish, 27 species of crustaceans, 9 species of gastropoda, bivalves, and 6 species of cephalopods. Trachysalambria curvirostris which is the target species of the beam trawl fishery occupied only 2.1% of the total catch, showing a low ratio of catches. Most of T. curvirostris was harvested from July to November while small amount of T. curvirostris was captured from May to December. In this study, we concluded that the bycatch ratio except T. curvirostris in T. curvirostris fishery was relatively high, thus the fishery of T. curvirostris might affect the fishery resource management of bycaught species off the coast of Chungnam province.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.7
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• pp.927-935
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• 2019

Screw-failure accidents in small ships frequently occur in coastal waters. In particular, vessels' propulsion systems are frequently coiled due to objects such as fish-nets and ropes that float on the sea. The failure of the ship's propulsion system can cause primary accidents such as ship operation delays and drifting due to loss of power; furthermore, the possibility of secondary accidents such as those involving operators in the underwater removal of rope stuck in a propeller. Ships that do not have the proper tools to solve these problems must be either lifted onto land to be repaired or divers must dive directly under the ship to solve the problem. Accordingly, some small vessels have been equipped with rope-cutter devices on the propeller shaft to prevent ship propeller system accidents in recent years; however, they are not being applied efficiently due to the cost and time of installation. To solve these problems, this study develops an underwater rope-cutter device and controller for the removal of propeller and shaft foreign material in small vessels. This device has simple structures that use the principle of a saw. Meteor gears and crank pins were used for the straight-line rotation of saw blades of the underwater rope-cutters to allow for long strokes. Furthermore, the underwater rope-cutting machines can be operated by being connected to the ship battery. The user, a non-professional, can ensure convenience and stability by applying reverse current prevention and a speed control circuit so that it can be used more conveniently and safely.