• Korean Journal of Ichthyology
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• v.26 no.3
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• pp.185-193
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• 2014

To find the influence of water temperature, tank color and illumination in feeding, growth and blind-side hypermelanosis of starry flounder, Platichthys stellatus, in the present study, we performed a series of temperature, background color and illumination intensity test for 180 days (From June to December). The test was done in duplicate at 100 fish/tank (430% of initial covering area [PCA]) with the selected ordinary juvenile flounder (TL $17.3{\pm}0.5cm$, BW $82.5{\pm}0.2g$). The rearing was performed in darkgreen FRP aquarium tanks ($H100cm{\times}L100cm{\times}W100cm$; bottom area $1m^2$) lighten with average 1,000 lux and 230 lux, and in white FRP aquarium tank ($H100cm{\times}L100cm{\times}W100cm$; bottom area $1m^2$) lighten with average 230 lux of light intensity. We investigated correlation of daily food intake (DFI) with water temperature and salinity, and compared the influences of background colors and light intensity in DFI, food efficiency (FE), growth, survival rate, and ratio of malpigmented blind-side area and ambicolored fish ratio. In DFI, although it was not related with salinity, the amount was significantly decreased under 0.5 g/fish/day in summer and winter season, but was significantly increased over 1.5 g/fish/day in autumn season showing from $10^{\circ}C$ to $20^{\circ}C$ in water temperature. In background and illumination test, DFI, FE and survival rate showed no difference among three groups. The ratios of malpigmented blind-side area and ambicolored fish were also not significantly different among three groups, indicating that the blind-side hypermelanosis of starry may be governed not by background color (or light intensity) but by a genetics external trait inherited from parents.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.4 no.2
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• pp.55-60
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• 1971

There are a lot of kinds of shrimps for fishing baits, but Palaemon modestus is dominant species in the Karak River. The ecology in the natural environments was reported by the author (1970) and this work is an elemental task for the larval stage in shrimp farms. Shrimps were collected from the Karak River and carried to the laboratory. Hatched larvae were reared from June 6 to June 24, 1970 for pre-experiment, and main experiment was provided from August 10 to August 24, 1970. The following is a summary of the results: 1. Hatching period in the laboratory water tank was eight hours ($20^{\circ}C\~20.9^{\circ}C$). 2. The larvae died off from the sixth day after hatch without food. 3. Feeding begins on the third day after hatch. 4. The relationship between the density of food and the consumption was not concerned when the number of Artemia nauplii was 2 to 6 per ml of water. 5. The relationship between the day (X) and the food (Y) is: $$Y=6.49824X^{1.8384}$$ 6. The carapace growth curve is: $Y=1.1608X^{0.10024}$ 7. The relationship between the food (X) and the body length (Y) is: $$Y=2.8114X^{0.12767}$$ 8. The relationship between the carapace length and the body length(Y) is : Y= 3.7564X-0.4601

• Korean Journal of Environment and Ecology
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• v.29 no.3
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• pp.353-367
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• 2015

The goal of this study is to analyze the feedback structure of habitat changes of the Whooper Swan in Eulsukdo using system thinking to suggest a management plan for ecosystem health. Using the causal loop diagrams of population changes between Whooper Swan and other bird species in Eulsukdo, we found that the environmental changes in the roosting and foraging area affect the Whooper Swan's population. The causal loop diagrams of the Whooper Swan's roosting area indicated that the environmental changes (e.g., water level, noise, bird watching, and other experience activities) may influence their population density variation. In addition, the casual loop diagrams of the Whooper Swan's foraging area showed that the Whooper Swan's population was affected by various variables that included area factors such as surface area of freshwater, frozen water, salinity, and density of Scirpus planiculmis. Furthermore, through the integrated causal loop diagram, cumulative discharge of Nakdong estuary weir and building activities were identified as the variables that affect the population of the Whooper Swan. Thus, we selected this area as the strategic point to establish a management plan for the Whooper Swan's habitat. The results of this study will help in decision making of a long-term management plan for sustaining the environmental health of the ecosystem in Eulsukdo.

• Korean Journal of Environment and Ecology
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• v.28 no.6
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• pp.642-649
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• 2014

Mallard (Anas platyrhynchos) is the abundant winter visitor in South Korea. Mallard migrates long distances between Russian Siberia and Korea. This species prefers a rice paddy area as their winter habitat. We captured birds using cannon-net, and attached the GPS-Mobile phone based Telemetry(WT-200) on Seven Mallards in the winter of 2011~2013. We were monitored wintering home-range and movement distance. We analyzed the tracking location data using ArcGIS 9.0 and calculated Kernel Density Estimation (KDE) and Minimum Convex Polygon (MCP). The average home-range in the wintering ground by MCP was $118.8km^2$(SD=70.1, n=7)and the maximum home-rang was $221.8km^2$ and the minimum was $27.7km^2$. Extents of home-range by KDE were $60.0km^2$(KDE 90%), $23.0km^2$(KDE 70%) and $11.6km^2$(KDE 50%). Mallard moved an average of 19.4 km from start site(attach to WT-200 site), maximum moved was 33.2 km and minimum moved was 9.4 km. The average distance of 0.8 km between GPS fixed point(range 0.2~1.6 km), maximum moved was 19.7 km. Mallard moved a very short distance in wintering season and showed a very high water-dependent trends in wintering site.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.27 no.4
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• pp.255-265
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• 1991

In order to find the excavating performance of water-jet nozzle on the sand, the authors were carried out the excavating experiment with the model nozzles which were semi circular sectioned nozzles and rectangular nozzle in water tank. The results were as follows. 1) Excavating maximum depth and width on the sand by the water jet were straightly increased in proportion to the velocity of water jet and the section area of nozzle, and that, by the nozzle distance from the excavating point on the sand, the depth was decreased, while the width was increased straightly. 2) Rectangular nozzle which the thick of hole is 1mm, was a little bit better than the circular nozzle of the same sectioned area on the excavating performance. 3) Empirical equations between the velocity of water jet, the distance of nozzle, and the maximum excavating depth and width by angle of nozzle were expressed as linear, they were as follows on the 45$^{\circ}$ angle of the rectangular nozzle(1$\times$12mm); D=0.0093V sub(0)-0.23H+5.7. W=0.0147V sub(0)+1.06H+10.2. where, D is the maximum excavating depth(cm), W is the maximum excavation width(cm), V sub(0) is the velocity of water jet(cm/s); 926$\leq$V sub(0)$\leq$1504, H is the distance(cm) from nozzle tip to water-jetted point on the surface of sand.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.22 no.4
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• pp.201-213
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• 1989

This study is just to be carried out to grasp the efficiency of jet stream excavating for the ground. Changing the dynamic pressure, nozzle diameter, distance off the ground, we measured the impulse, the excavated depth, the excavated width. According as each dynamic pressure increases from 100 to $500gf/cm^2$, the impulse of the jet stream increases from 43 to 114gf, from 52 to 227gf, from 114 to 506gf, from 137 to 768gf, in 4, 6, 8, 10mm nozzles respectively, but it makes no difference in the value of distance within 50cm off ground. The excavated depth increases at the invariable rate in accordance with nozzle diameter, dynamic pressure, nozzle distance. We obtain the equations relevant to the ground I, II as follows: $$L_I=[0.01(H/r-100) -0.43\cdot\iota+11.78]{\cdot}D/4$$ $$L_{II}=[0.03(H/r-100) -0.34\cdot\iota+6.39]{\cdot}D/4$$ where, $L_I,\;L_{II}$ are respectively the excavated depths of the ground I, II, cm; H is the dynamic pressure, $gf/cm^2\;:\;\iota$ is the distance off the ground, cm; D is Nozzle diameter, mm; r is the specific weight, $1gf/cm^2$.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.6
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• pp.760-767
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• 2014

An experimental study is carried out to investigate the effect of jet stream in the gab of rectangular cylinders with different length in a parallel arrangement by using PIV method in a circulating water channel. The height(h) of the rectangular cylinder and the gap between the cylinder is 10mm, and the width(B) which is 300mm. The length of the model for flow direction was applied to 30mm, 60mm, 90mm & 120mm, The aspect ratio of a model on the basis of height(H=30mm) is 1, 2, 3 and 4. Reynolds number $Re=1.4{\times}10^4$, $Re=2.0{\times}10^4$, $Re=2.9{\times}10^4$ based on the height(H) of model for the distance of tidal distributions as of water depth have been applied during the whole experiments. The measurement area was set to 5H rear of the cylinder. As a result, Vortex size in the wake area were increased as velocity increased. and high aspect ratio increased through-flow velocity component in the near wake. Velocity deficit increased highly after near-wake area and low aspect ratio.

• The Korean Journal of Malacology
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• v.31 no.2
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• pp.83-92
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• 2015

The effect of different intermediated rearing method by expanding the attached floor space in order to highly density culture on the growth characteristics and survival rate of the juvenile abalone, Haliotis discus hannai, were investigated in land-based tanks. The intermediated culture methods was determined thru the shelter counts and layer for 10 month with two replicates : the single layer shelter (SLS), the double layer shelter (DLS), the triple layer shelter (TLS) and the single layer shelter under net cage (SLSNC). In addition, the culture on shallow race way tank had to set up as culture of the ditch raceway tank (CDRT) and the floor race way tank (CFRT). In the growth performance of reared abalone (initial mean shell length $54.18{\pm}7.39mm$ and weight $1.93{\pm}0.14g$) at experimental tanks, that the absolute growth rate (ARG), daily growth rate (DGR) and specific growth rate (SGR) to the shell length and shell breadth was not significant at each experimental tanks except SLSNC. As well as too, weight gain (WG), daily weight gain (DWG) and specific weight gain (SWG) to weight was not significant at each experimental tanks except SLSNC, too. Survival rates of CDRT and CFRT was lower than those of different experimental tanks (P < 0.05). Therefore, these results is showed that high density different intermediated rearing method by expanding the attached floor space for juvenile H. discus hannai was not have difference as growth performance and survival rate both one layer shelter and multi layer shelter. Also, it is considered that shallow race way tank was not useful rearing for the juvenile intermediate culture of H. discus hannai in land based.

• Proceedings of the Korean Aquaculture Society Conference
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• 2003.10a
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• pp.102-102
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• 2003

황복(Takifugus obscurus)은 주로 황해에 분포하며 봄철에 서해안으로 흐르는 금강, 한강 및 임진강으로 소상하여 강의 중상류에서 산란하는 소하성어류이다. 특히 황복은 바다와 하천을 오고 가는 관계로 해수뿐만 아니라 민물에서도 양식이 가능한 어종으로 다른 소하성어류와 마찬가지로 염분변화에 따른 삼투조절능력이 매우 우수할 것으로 생각된다. 본 연구는 황복이 급격히 염분을 달리하였을 때 나타나는 생리적 반응을 산소소비량과 암모니아 질소배설량의 변화로 염분변화에 따른 생리적 적응력을 살펴보고자 하였다. 본 연구에 사용한 황복은 전장 10cm(체중 15~25g) 전후의 치어로서 염분 32, 22, 12, 및 2 ppt로 조절되어 있는 FRP수조(500 L)에서 2개월간 사육 후, 각기 염분을 달리한(32, 22, 12, 2 ppt) 호흡측정 장치에 황복을 수용하여 산소소비량과 암모니아 질소배설량을 측정하였다. 한편, 사육 시스템내에서의 산소소비와 암모니아 질소의 배설경향을 보기 위하여 염분 16ppt에서 산소소비량과 암모니아 질소배설량을 25시간 관찰하였다. 산소소비 경향은 대체로 염분이 낮을수록 높은 산소소비 경향을 보였는데, 실험염분 32ppt에서는 2~32ppt 사육군 모두 다른 실험염분(22, 12, 2 ppt) 사육군보다 안정되고 낮은 산소소비량을 나타내었다. 그리고 실험염분 22, 12 및 2 ppt에서는 각기 실험염분과 동일한 염분 사육군에서 가장 높은 산소소비량을 나타낸 반면 32 ppt 사육군은 모든 실험염분에서 가장 낮은 산소소비량을 나타내었다. 암모니아 질소의 배설경향은 실험염분 2 ppt를 제외하고는 2 ppt 사육군에서 가장 높은 질소 배설율을 보였으나, 실험염분 2 ppt에서는 오히려 현저히 낮은 암모니아 질소 배설율을 나타내었다. 저 염분(2, 12 ppt)에서 사육한 황복은 22 및 32 ppt에서 사육된 황복에 비해 저염분에 노출될 경우 삼투조절을 위해 암모니아 배설에 상당한 차이를 보였다. 사육 시스템내에서 조사된 산소소비와 암모니아 질소 배설경향은 섭이와 관련하여 일간리듬을 보였는데, 산소소비는 섭이 3시간 후에 최고를 보였으며 암모니아 질소 배설은 섭이 4시간 후에 각각 최고를 나타내었다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.12
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• pp.1089-1096
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• 2015

A marine helicopter should remain sufficiently upright to permit safe evacuation of all personnel with a flotation system. And the rule requires that after ditching in water, the adequate flotation time will allow the occupants to leave the rotorcraft. To this end, stability test of the emergency flotation system for Korean marine helicopter was performed by using "Froude scaling method" in water tank. Test configuration and conditions were determined in consideration of the helicopter loading condition and related specifications. Test results meet the stability requirements at sea state code 4 and sea state code 2 with puncture conditions.