• Korean Journal of Fisheries and Aquatic Sciences
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• v.17 no.3
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• pp.197-205
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• 1984

From 1981 to 1982, a series of experiments on the optimum growth temperature, wintering temperature and lethal minimum temperature of the walking catfish Clarias batrachus, of about 12 to 40 g yearlings, were carried out using indoor recirculating aquariums at water temperature between $14^{\circ}C\;and\;34^{\circ}C$. The results are as follows. The optimum temperature of this species was turned out to be approximately $25^{\circ}C$ with highest feed intake and growth rates, and lowest conversion rate than at any other temperatures. The minimum temperature at which the fish can show growth turned out to be $18^{\circ}C$, At this temperature daily growth rate for 62 days was about $0.1\%$ and all fish survived. When this species was kept at $16^{\circ}C$ or lower, no fish survived more than one month and at lower than $14^{\circ}C$ all fish died out in 1 to 7 days. In accordance with these results it could be inferred that $18^{\circ}C$ is the minimum wintering temperature. Rearing this species at the minimum growth temperature for a long time, for wintering for instance, the sudden change of water temperature, especially decreasing to lower than $15^{\circ}C$ can be lethal for all fish.

• Journal of Aquaculture
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• v.11 no.1
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• pp.99-103
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• 1998

Artemia often observed as a co-existing organism in the mass culture tank of marine rotifer. The rotifer and Atremia are commonly used as food organisms in the marine fish larvae rearing. In this study, interspecific relation between the rotifer Brachionus rotundiformis (formely called S-type) and anostracan Artemia of the two developmental stages (0 and 19 day old after hatching) were investigated in the larboratory. The population growth of B. rotundiformis and one of the stage (nauplius or adult) of Artemia in mixed culture was compared with that of each single species culture. Culture period was 16 days. Every two days, the number of organisms in each species was counted and transferred to a fresh medium containing $7{\times}10^5$cells/ml of food Nannochloropsis oculata. Culture volume, temperature, salinity and photoperiod were set at 40ml, $25^{\circ}C.$, 22ppt and 24h all dark except to observation time, respectively. The rotifer population growth was greatly decreased by co-existence with Artemia. The coexisting Artemia suppressed the rotifer population growth due to it's high filtering speed for food (N. oculata). This study suggested that contamination by Artemia must be prevented for the stable rotifer production in the rotifer mass culture tank.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.3
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• pp.164-173
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• 2014

In underwater robotics, vision would be a key element for recognition in underwater environments. However, due to turbidity an underwater optical camera is rarely available. An underwater imaging sonar, as an alternative, delivers low quality sonar images which are not stable and accurate enough to find out natural objects by image processing. For this, artificial landmarks based on the characteristics of ultrasonic waves and their recognition method by a shape matrix transformation were proposed and were proven in Part 1. But, this is not working properly in undulating and dynamically noisy sea-bottom. To solve this, we propose a framework providing a selection phase of likelihood candidates, a selection phase for final candidates, recognition phase and tracking phase in sequence images, where a particle filter based selection mechanism to eliminate fake candidates and a mean shift based tracking algorithm are also proposed. All 4 steps are running in parallel and real-time processing. The proposed framework is flexible to add and to modify internal algorithms. A pool test and sea trial are carried out to prove the performance, and detail analysis of experimental results are done. Information is obtained from tracking phase such as relative distance, bearing will be expected to be used for control and navigation of underwater robots.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.40 no.1
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• pp.37-46
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• 2004

In order to increase fishing efficiencies of the fyke net used in the coast of Jeju Island, water tank experiment was caried out entering and escaping behavior using nets that were reduced to 1/20 of the size of the full scale fyke net and were improved to have antrance structure, and mackerel Scomber japonicus as experimental fish. The results of measurement are as follows : 1. Fish school behavior in the main net was showed two different patterns : swimming in a circle in the right space of the main net and swimming back and forth in ellipse in the right and left space. 2. The swimming speed of mackerel school was 23.9. 12.6 and 32.0cm/sec in the center space, right space of main net and in the mouth 3. The entering rate of fish school was 40% in net with 35cm length of the upper and funnel net in the mouth of fyke model net and 49% in conventional type fyke model net. 4. The escaping rate of fish school was 10% in net with 35cm length of the upper and funnel net in the mouth of fyke model net and 69% in conventional type fyke model net. 5. The remain rate of fish school was 90% in net with 35cm length of the upper and funnel net in the mouth of fyke model net and 31% in conventional type fyke model net.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.6
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• pp.748-752
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• 1999

This study was carried out to compare the growth and fatty acids composition of the rotifer (Brachionus rotundiformis) cultured in high density by the various enrichments and culture methods. The rotifer fed on condensed freshwater Chlorella was enriched with $\omega$-yeast, Algamac, Super Selco and marine Chlorella. In another culture method, the rotifer was cultured with enrichment supplements for 6 hours after feeding with condensed freshwater Chlorella supplement for 18 hour. The rotifer fed with condensed marine Chlorella for 24 hours without fieshwater Chlorella was used as a control group. Culture tanks (5 $\ell$ working volume) was immersed in a water bath ($28^{\circ}C$). The density of rotifer and dissolved oxygen level in water was stable in control group of rotifer cultured with condensed marine Chlorella for 24 hours and the n-3 HUFA content of rotifer was the highest among the rotifer culture methods. However, the density of rotifer and dissolved oxygen level in the groups of rotifers enriched with $\omega$-yeast, Algamac and Super Selco by methods were drastically decreased, The n-3 HUFA contents of rotifers enriched by Super Selco were higher than those of rotifer enriched by either $\omega$-yeast or Algamac in both methods. The results from this experiment indicated that supplementation of condensed marine Chlorella for 24 hour by the semi-continuous culture was effective for the improvement of the nutritional value of rotifer and it could provide the stable growth condition for rotifer culture in high density.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.12 no.4
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• pp.201-207
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• 1979

The stow net now used in the Yellow Sea, are traditional bag net with the opening held by a lighter upper and a weighted lower beams standing against the current. Such bag net anchored at the bottom are known in many countries, particularly in the estuaries of large rivers, but more rarely in sea fisheries, because they are too much affected by the weather, moreover a permanent strong current is necessary. Some scientists intended to improve this fishing gear, using the shearing devices instead of a lighter upper and a weighted lower beams in order to widen mouth of the stow net however they are unsuccessful. One-fortieth scale model net of the stow net was tested in a circular water tank with an effective volume of $5.67m\times1.76m\times1.00m$ of observing the configuration and tension of the net. Experiments were carried out under the various combination including water velocity, spherical floats and elevating floats with the shearing hoods instead of the upper beam. We found those devices offered a very low resistance per net area to current compared with the spherical floats or upper beam, and had a fairly good shearing power at any velocity and direction of the current. The total resistance (R) of the model net to which shearing hoods and floats are attached can be induced by the following formula under the condition of 0.25m/sec to 0.5m/sec, $$R(kg)=3.11V^{1.54}$$ The height (h) of the improved model net (m-B) is higher than traditional model net(m-A) with upper and lower beams, m-A: h(cm)=89.22-2.42(V-15). $V\geqq15,\;cm/sec$ m-B: h(cm)=89.20-0.78V (V:cm/sec) The catch efficiency of improved model net is 1.5 times traditional model net.

• Korean Journal of Poultry Science
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• v.31 no.3
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• pp.187-191
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• 2004

The experiment was performed to investigate the effect of heating temperature and shaking time on viscosity change of whole egg, yolk, and albumen. Shaking water bath was used at 35, 45, and 50$^{\circ}C$ and the viscosity was measured at 0, 3, 6, 9, and 12 hours. There were no significant differences in viscosity of whole egg between 35$^{\circ}C$ and 45$^{\circ}C$( over-all mean). However, the 50$^{\circ}C$ group showed significantly lower viscosity compared to 35 or 45$^{\circ}C$ groups(P < 0.05). Non-significant differences were noticed in yolk viscosity among temperature treatments, but there were significant differences among shaking times(P < 0.05). Heating temperature and shaking time did not show significant effect on the viscosity of albumen, but the lowest viscosity was shown at 0, 9, and 12 hours at 50$^{\circ}C$. The results suggest that whole egg, yolk, and albumen should be treated for more than 3 hours at 50$^{\circ}C$, more than 3 hours at 35$^{\circ}C$ and 45$^{\circ}C$ and 3～9 hours at 50$^{\circ}C$, and 0, 9, 12 hours at 50$^{\circ}C$, respectively and then can be used in the processing.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.33 no.4
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• pp.311-320
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• 1997

We selected horse mackerel Trachurus japonicus, mackerel Scomber japonicus and arrow squid Todarodes pacificus, to be used in the experiment. These fishes migrate to the Cheju coast and were caught by set-net. We studied on the attracting effect and the leading effect on the fish school using incandescent lights in an outdoor water tank at the Marine Research Institute Cheju National University. The results obtained are summarized as follows; 1. The horse mackerels, mackerels and arrow squids were actively attracted to the incandescent light. The optimum illumination and the reactions of each fish school were different though. 2. We turned the first attracting lamp on and turned it off after ten minutes. Then we turned the second attracting lamp on and turned it off after another ten minutes. The reaction of each fish school was a little bit different, but it worked to lead them to their destination. 3. We turned the three attracting lamps on at the same tune. After ten minutes, We turned the first attracting lamp off. After another ten minutes we turned the second attracting lamp off. The reaction of each fish school was a bit different, but it worked to lead them to their destination. 4. One incandescent light was moving. The reaction of each fish school was a little bit different, but it worked to lead them to their destination.

• Journal of the Korean Geotechnical Society
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• v.30 no.7
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• pp.27-40
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• 2014

So far, studies on the settlement of breakwater have mainly been conducted through numerical model tests focusing on an analysis or through the laboratory wave tank tests using a scaled model. There has not been a study on the settlement that is measured in an actual breakwater structure. This study analyzed the data of settlement that has been measured in an actual caisson breakwater for a long time and the characteristics and causes of wave-induced settlement in the caisson (including beneath ground), based on qualitative aspect, were examined. The analysis revealed that wave clearly has an effect on the settlement in caisson, especially in the condition of high wave such as typhoon. Caisson settlement is caused by the liquefaction of ground, which is due to the increase of excess pore pressure, the combination of oscillatory excess pore pressure and residual excess pore water pressure, and the solidification process of ground due to dissipation of the accumulated excess pore pressure. The behavior of excess pore pressure in the ground beneath the caisson is entirely governed by the behavior of the caisson. Ground that has gone through solidification is not likely to go through liquefaction in a similar or a smaller wave condition and consequently, the possibility of settlement is reduced.

• Journal of Life Science
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• v.23 no.3
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• pp.333-340
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• 2013

This study was performed to determine whether stem bark extract containing saponin of Albizzia julibrissin in the diet influences gonadal maturation and spawning in medaka (Oryzias latipes). The crude extraction containing saponin (HaBC) was partially purified from n-BuOH extraction of A. julibrissin stem bark by Diaion HP-20, Silica gel and Sephadex LH-20 chromatographies. We fed diets supplemented with HaBC to medaka. We then studied the effects of the HaBC supplement on the suppression of gonadal maturation and spawning in female medaka that were reared in aquaria with recirculation systems. In the experiment with immature female medaka, the periods of initiation of gonadal maturation and spawning were delayed in the fish that were fed diets supplemented with at least HaBC 20 mg/g-feed. In the experiment with mature female medaka, the fish that were fed diets supplemented with at least HaBC 20 mg/g-feed had lower GSIs than the control diet group did. The results showed that the growth of the immature medaka was not correlated with the amount of supplementation of HaBC in the diet. However, the condition factors (CF) in the medaka that were fed diets supplemented with at least HaBC 20 mg/g-feed were higher than in the medaka fed on the control diet. We concluded that extracts containing saponin from the stem bark of A. julibrissin have the potential to inhibit gonadal maturation in female medaka, but they did not act as growth stimulation. Further studies are required to determine the mechanism of the action.