• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.16 no.2
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• pp.97-105
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• 2011

This study investigated the community structure and spatio-temporal variation of macrobenthic assemblages around Gijang Province, East Sea of Korea. Macrobenthos collected seasonally using a modified van Veen grab sampler from March to November 2006. A total of 157 macrobenthic fauna were collected. The overall average macrobenthos density were $552 \;ind/m^2$. The species number of macrobenthos was in the range from 62 in winter and spring to 122 in autumn. On the other hand, abundance fluctuated between 6,540 (in spring) and 17,920 (in autumn) inds./$18m^2$. Cluster analysis and non-metric multi-dimensional scaling (nMDS) were applied to assess the spatio-temporal fluctuation in the macrobenthic assemblages. Cluster analysis and nMDS ordination analysis based on the Bray-Curtis similarity identified 3 station groups. The group 1 (station 8~10, 12, 13, 17 and 18) was characterized by high abundance of the polychaete Lumbrineris longifolia, the bivalve Ennucula tenuis and the Amphipoda spp., with mean phi range from $6.2{\Phi}$ to $7.1{\Phi}$ (above 50m water depth). The group 2 (station 5~7, 11, 14~16) was numerically dominated by the po1ychaete Ampharete arctica and the bivalve Theorafragilis (mean phi: $6.0{\sim}7.0{\Phi}$; within 40 m water depth). Finally group 3 (station 1~4) was characterized by high density of the polychaetes Magelona japonica and Sternaspis scutata, with mean phi range from $3.5{\Phi}$ to $6.9{\Phi}$ (below 30 m water depth). In conclusion, the Macrobenthic community structure showed a distinct spatial and temporal trend, which seemed to be related to the water depth and sediment composition.

• Journal of Aquaculture
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• v.19 no.1
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• pp.25-32
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• 2006

An experiment was carried out to investigate changing of water quality during the seed production of dark-banded rockfish Sebastes inermis in large scale tanks. Ten broodstock of dark-banded rockfish were held in three circular tanks (diameter 6.5 m; depth 2 m; water volume 50 ton) each (stocking density $0.061kg/m^3$). During the experiment the temperature ranged from 14.2 to $16.1^{\circ}C$. The fingerlings were 134 with rotifers only during 1 to 9 days after parturition, rotifers with Artemia nauplii during 10 to 20 days after parturition, Artemia nauplii only during 21 to 35 days after parturition, Artemia nauplii with commercial diet during 36 to 80 days after parturition and commercial diet only during 81 to 85 days after parturition. Water quality (dissolved oxygen, pH, $NH_4^+-N,\;NO_2^--N,\;NO_3^--N\;and\;PO_4^{3-}-P$) in rearing tanks measured every 5 days in long term monitoring investigation or every 2 hours in diurnal monitoring investigation. In 85 days after parturition, the body weight of fish grew up to 0.88 f and specific growth rate was 8.0%/day in body weight. In long term monitoring investigation, with the increase of the amount of supplied commercial diet, the concentration of dissolved oxygen (DO) and pH decreased, but the concentration of $NH_4^+-N\;(4.5\;to\;76.3{\mu}M),\;NO_2^--N\;(0.02\;to\;0.06{\mu}M),\;NO_3^--N\;(3.0\;to\;5.9{\mu}M)$, and $PO_4^{3-}-P\;(0.41\;to\;0.59{\mu}M)$ increased. In the diurnal monitoring investigation, the concentration of $NH_4^+-N$ showed great fluctuation and ranged from 3.0 to $9.1{\mu}M$ when fed rotifers, 16.3 to $45.8{\mu}M$ when fed Artemia nauplii and 36.5 to $120.1{\mu}M$ when fed commercial diet. After daily feeding with each of feed, the amount of dissolved inorganic nitrogen (DIN) and phosphorus (P) wastage were 7.0 g and 0.7 g when fed rotifers, 24.7 g and 0.7 g when fed Artemia nauplii and 140.9 g and 2.2 g when 134 commercial diet. The amount of DIN and phosphorous wastage during 134 commercial diet was significantly higher than that of fed rotifer and Artemia nauplii (P<0.05). Results will provide valuable information far water quality management and culture of dark-banded rockfish in commercial seed production systems.

• The Korean Journal of Malacology
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• v.21 no.2 s.34
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• pp.121-132
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• 2005

We investigated the reproductive cycle with gonad developmental phases of Sinonovacula constricta by histological observations, and seasonal changes in biochemical component of the adductor muscle, visceral mass, foot muscle and mantle were studied by biochemical analysis, from January to December, 2004. The reproductive cycle of this species can be classifed into five successive stages: early active stage (March to May), late active stage (May to July), ripe stage (July to September), partially spawned stage (August to October) and spentfinactive stage (October to March). Total protein content was the highest in the following order: adductor muscle, visceral mass, foot muscle, and mantle. Except for mantle, it was generally higher during the ripe and spawning stages, while lower during the spent/inactive stage. There were positive correlations in total protein contents among adductor muscle, foot muscle, and visceral mass. However, the correlations were not statistically significant. Total lipid content was the highest in the visceral mass; it was more than 5 or 6-fold higher than those in the adductor muscle, foot muscle, or mantle. The monthly change was also most dynamic in the visceral mass. It first Increased during the early active stage (March to May), decreased during late active stage (May to July), and then increased again rapidly during the spawning stage (September). There were a strong negative correlation in total lipid contents between foot muscle and adductor muscle (r = -0.634, p = 0.027), and a strong positive correlation between adductor muscle and mantle (r = 0.665, p = 0.018). Glycogen contents showed more or less similar pattern to total lipid contents in the adductor muscle, foot muscle, and visceral mass. It was higher during the early active and spawning stages, while lower during the late active and spent/inactive stages. There was no statistically significant correlation in glycogen contents among different tissues. Especially, total lipid content showed a negative correlationship between the foot muscle, adductor muscle, visceral mass and mantle. Therefore, these results indicate that the nutrient content of the foot muscle, adductor muscle, viseral mass and mantle changed in response to gonadal energy needs.

• The Korean Journal of Malacology
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• v.19 no.1
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• pp.41-51
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• 2003

Reproductive cycle with the gonadal development of Ruditapes philippinarum can be classified into five successive stages by histological observations: early active stage (January to March), late active stage (February to May), ripe stage (April to August), partially spawned stage (May to October), and spent/inactive stage (August to February). Changes in total protein contents in the adductor muscle tissues reached the maximum in the early and late active stages (February) and appeared the minimum in the ripe and partially spawned stages (May), while changes in their contents in the visceral mass tissues reached the maximum in the ripe and partially spawned stages (June) and gradually decreased in the partially spawned stage (June to October). On the whole, changes in total protein contents showed a negative correlationship between the adductor muscle and visceral mass tissues (r = -0.292, p < 0.05). Changes in total lipid contents in the adductor muscle tissues reached the maximum in the inactive and early active stages (January) and sharply decreased in the early and late active stages (February), while their contents in the visceral mass tissues reached the maximum in the ripe and partially spawned stages (April) and gradually decreased in the partially spawned stage (to October). On the whole, changes in total lipid contents showed a negative correlationship between the adductor muscle and visceral mass tissues (r = -0.699, p<0.05). Changes in glycogen contents in the adductor muscle tissues reached the maximum in the late active and ripe stages (April) and rapidly decreased in the partially spawned stage (May to October), while their contents in the visceral mass tissues reached the maximum in the early and late active stages (February) and rapidly decreased in the late active stage (March). Thereafter, their levels gradually increased in the ripe and partially spawned stages (April to July). On the whole, changes in glycogen contents appeared no correlationship between the adductor muscle and visceral mass tissues (r = 0.062, p > 0.05). These results indicate that the adductor muscle and visceral mass tissues are an important energy storage and nutrient supply organ in the Manila clams, and the nutrient contents of the adductor muscle and visceral muscle tissues change in response to gonadal energy needs.

• Journal of Aquaculture
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• v.17 no.3
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• pp.187-196
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• 2004

This study was carried out to investigate changes in biochemical composition of rotifer, Brachionus plicatilis, enriched with the commercial enrichments (Enhance, Advantage, Algamac-2000, DHA-Selco and Advantage ＋ Chlorella) at various durations of enrichment (0, 6, 12 and 24 hr) to improve the growth and survival of marine fish larvae. Total lipid content of rotifers enriched with various enrichments tended to increase with an increase in durations of enrichment up to 6 hr, but after that, was not significantly affected by enrichment materials. However, total protein content of rotifers enriched groups except for Advantage＋Chlorella decreased with the increase in duration of enrichment. The highest protein/lipid ratio showed 2.7 in rotifer enriched with the Advantage ＋Chlorella. The phospholipid/lipid ratio of rotifer enriched with the Enhance, Advantage and Advantage＋Chlorella groups was significantly higher than that of enriched rotifer with the Algamac-2000 and DHA-Selco groups. The highest DHA level, 2.5%, of rotifer enriched for 24 hr was obtained in the Advantage, but was not significantly different among other groups, except for Algamac-2000. No significant difference in DHA level of rotifer enriched with the DHA-Selco, Algamac-2000 and Advantage＋Chlorella groups was observed between l2h and 24hr of enrichment. The DHA/EPA ratio in the enriched rotifers varied among enrichment material groups, ranged from a high level of 11.1：1 in the Advantage＋Chlorella group to a low level of 4.1：1 in DHA-Selco group. The results from this study indicate that rotifers enriched with Enhance, Advantage and Advantage＋Chlorella seemed to be effective to improve nutritional value of rotifer for marine fish larvae because phospholipid, DHAJEPA and protein/lipid ratios of rotifer enriched with Enhance, Advantage＋Chlorella were higher than those of rotifer enriched with either DHA-Selco or Algamac-2000. Especially, supplementation of the Chlorella to these enrichments would appear to be effective for improvement of fish larval performance because of no reduction of protein level in rotifer, which is critical for growth of fish larvae.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.5
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• pp.410-416
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• 2016

After the Sewol Ferry accident, the importance of maritime safety has been emphasized in Korea. In particular, educational and experience training are not only being conducted for maritime personnel but also in schools and at maritime-related organizations in order to broadly instill maritime safety awareness. Based on SOLAS regulations, safety education for sailors conducted every 10 days passenger boats, and fire-fighting drills and abandon-ship training should be conducted once a month on merchant ships. After the Sewol Ferry accident, the maximum number of trainees was reduced from 40 to 20 in order to improve the effectiveness of these training sessions by requiring all trainees to participate in the actual training. The current training process consists of two steps: textbook-based theoretical training and actual practice. Current training environment provides limited capability from human and facility recourses which limit the numbers of trainee participated and system operation time. By introducing the simulation training, it will improve the trainee skill and performance prior to the on-site training and allow the more effective and rapid progress on actual practice. Therefore, it will be proposed the three-step training method in order to improve the effectiveness on fire-fighting drill in Maritime Safety Education on this study. This study suggests a three step training method that would increase the efficiency of maritime safety education. An image-training step to enhance individual task awareness and equipment usage via simulation techniques after theoretical training has been added. To implement this simulation, a virtual training session will be conducted before actual training, based on knowledge obtained from theoretical training, which is expected to increase the speed with which trainees can adapt during the practical training session. In addition, due to the characteristics of the simulation, repeated training is possible for reaction drills in emergency circumstances and other various scenarios that are difficult to replicate in actual training. The efficiency of training is expected to improve because trainees will have practiced before practical training takes place, which will decrease the time needed for practical training and increase the number of training sessions that can be executed, increasing the efficiency of training overall. This study considers development methods for fire-fighting drill simulations using virtual reality techniques.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.16 no.4
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• pp.254-267
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• 2011

In order to assess structure changes of marine benthic communities in the Youngsan River Estuarine Bay for this 10-year period, we sampled macrobenthos in 2006 using the van Veen grab at the same 40 stations where a previous benthic community survey was conducted in 1995. The number of species and mean density of macrobenthos in 2006 decreased significantly than those of 1995. There were no significant differences in both the number and the density of polychaetous species between the two sampling periods, while both number and den-sity of molluscan species decreased significantly. Although the first two density-dominant species, semelid bivalve Theora fragilis and polychaete Tharyx sp. occurred as most dominant species, but the density of T. fragilis decreased significantly in many stations between 1995 and 2006. However, polychaete Tharyx sp. showed increment in density and percentage composition within community. The area dominated by T. fragilis was replaced by Tharyx sp.. Also, polychaete Poecilochaetus johnsoni and bivalve Raetellops pulchella which were pre-dominant in 1995 decreased significantly by 2006. Bivalve Yoldia johanni decreased its density and reduced its distribution area by 2006. Species diversity and rarefaction curves also revealed that overall species richness decreased. These results confirmed that the dominant species and species diversity of macrobenthic communities in the area should be changed due to anthropogenic stresses during 10 years.

• Journal of Aquaculture
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• v.19 no.3
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• pp.210-215
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• 2006

An experiment was conducted to investigate the effects of four water temperatures (10, 15, 20, and $25^{\circ}C$) in combination with three photoperiods (24L:0D, 12L: 12D, and OL:24D) on the oxygen consumption rate of juvenile dark-banded rockfish, Sebastes inermis (mean body weight $20.5{\pm}0.7g$). The oxygen consumption rates of S. inermis were measured in triplicate for 24 hours using a continuous flow-through respirometer. Different combinations of water temperatures and photoperiods resulted in significant differences in the mean oxygen consumption rate of S. inermis (P<0.001). The oxygen consumption increased with increasing water temperatures for all photoperiod treatments (P<0.01). Mean oxygen consumption rates at 10, 15,20 and $25^{\circ}C$ ranged $178.3\sim283.5,\;386.7\sim530.7,\;529.2\sim754.3$ and $590.0\sim785.5mg\;O_2kg^{-1}h^{-1}$, respectively. $Q_{10}$ values ranged $3.17\sim5.51$ between 10 and $15^{\circ}C,\;1.87\sim2.10$ between 15 and $20^{\circ}C$ and $1.08\siml.24$ between 20 and $25^{\circ}C$, respectively. Fish held in continuous darkness (OL:24D) used consistently less okygen than fish exposed to continuous light (P<0.05). The mean oxygen consumption offish in a 12L:12D photoperiod was higher than that offish in 24L:0D and 0L:24D photoperiods under all temperature treatments except $10^{\circ}C$. The oxygen consumption of fish exposed to the 12L:12D photoperiod was significantly higher during the light phase than during the dark phase under all temperature treatments except $10^{\circ}C\;(P<0.05)$. This study provides empirical data for estimating oxygen consumption of S. inermis under given condition. This result has application for culture management and bioenergetic model for growth of this species.

• Journal of the Korean Society for Marine Environment & Energy
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• v.8 no.2
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• pp.83-99
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• 2005

To evaluate environmental charateristics of the South Sea and East China Sea on summer, water and sediment quality were measured in June 2001-2003. Surface layer was affceted by Warm water originated from the high temperature and salinity-Tsushima Warm Current, on the other hand, Yellow Sea Cold Water was spread to the bottom layer in the south-western part of the Jeju island, and salinity at stations near the Yangtze River was decreased below 29psu because of a enormous freshwater discharges. Thermocline-depth was formed at about 10m, and chlorophyll maximum layer was existed in and below the thermocline. COD(Chemical Oxygen Demand), TN(Total Nitrogen), and TP(Total Phosphorus) concentrations showed seawater quality grade II in surface layer of the most area, but concentrations of such as COD, Chl. a, TSS(Total Suspended Solid), and nutrients were greatly increased in the effect area of Yangtze River discharges. Correlations between dissolved inorganic nitrogen, Chl. a and salinity were negative patterns strongly, in contrast, those of inorganic phosphorus, COD and Chl. a were positive, which indicates that phytoplankton biomass and phosphorus are considered as important factors of organic matter distribution and algal growth, respectively. in the study area. The distribution of ignition loss, COD, and $H_2S$ of surface sediment were in the ranges of 2.61-8.81%, $0.64-11.86mgO_2/g-dry$, and ND-0.25 mgS/g-dry, respectively, with relatively high concentration in the eastern part of the study area. Therefore, to effective and sustainable use and management of this area, continuous monitoring and countermeasures about major input sources to the water and sediment, and prediction according to the environmental variation, are necessary.

• Korean Journal of Ichthyology
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• v.20 no.4
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• pp.239-247
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• 2008

The objective of this investigation was to examine oxygen consumption (OC) and operculum movement number (OMN) of rainbow trout Oncorhynchus mykiss as a function of changes in water temperature (WT). The WT of the rearing facility was increased from $4^{\circ}C$ to $28^{\circ}C$ stepwise at $1^{\circ}C$ day at each WT (5, 10, 15, 17, 20, 23, 26, and $28^{\circ}C$) then OC and OMN were measured. The OC of the fish increased linearly with WT: O=25.0240 WT+17.5400 in the range of $4{\sim}23^{\circ}C$ However, at 26 and $28^{\circ}C$ the OC declined to around the level at $10^{\circ}C$. The OMN also increased linearly with temperature: OMN=4.4847 WT+59.2150 in the range of $4{\sim}23^{\circ}C$ but at 26 and $28^{\circ}C$ the OMN of the fish dropped slightly. The OC and OMN of the fish showed peak at $23^{\circ}C$ with the lowest values at $4^{\circ}C$. In the range of $4{\sim}23^{\circ}C$, the relationship between OC and OMN of the fish was expressed as a linear equation: OC=0.0923 OMN-308.2100. The OC of fish transferred from $15^{\circ}C$ to certain temperatures without acclimation showed a lower OC at 5 and $10^{\circ}C$ but above $15^{\circ}C$ the OC increased/decreased with temperature. The trout died in temperatures above $28^{\circ}C$ even when acclimated step by step with a $1^{\circ}C$ day increase in WT. In this experiment, a negative physiological changs occurred in the experimental fish at $23^{\circ}C$ suggesting that the optimal physiological temperature range of rainbow trout is $10{\sim}20^{\circ}C$.