• Korean Journal of Fisheries and Aquatic Sciences
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• v.42 no.4
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• pp.344-348
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• 2009

This study was conducted to investigate effects of dietary lipid level on growth and body composition of juvenile red sea bream in low temperatures. Duplicate groups of fish (initial body weight of 79 g) were fed one of three isonitronic diets (47% crude protein) containing different lipid levels (10%, 17% and 22%) for 25 weeks during the winter season. Weight gain and survival of fish fed 17% lipid diet were significantly (P<0.05) higher than those fish fed the 10% or 22% lipid diet. Protein efficiency ratio, daily feed intake, condition factor, hepatosomatic index and viscerasomatic index were not affected by dietary lipid level, but feed efficiency of fish fed 10% lipid diet was significantly (P<0.05) lower than those fish fed the 17% or 22% lipid diet. Proximate composition of the whole body, liver, viscera and dorsal muscle were not significantly different among all groups except for crude protein content of dorsal muscle. The contents of 16:0, 18:0, 20:4n-3 and 20:5n-3 of the whole body were significantly (P<0.05) affected by dietary lipid level. The results of this study suggest that an increased dietary lipid level from 10% to 17% can improve growth of juvenile red sea bream in low temperature periods.

• Ocean and Polar Research
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• v.34 no.2
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• pp.253-264
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• 2012

In the northwestern Pacific, spawning of the common squid, Todarodes pacificus, occurs at continental shelf and slope areas of 100-500 m, and the optimum temperature for the spawning and survival of paralarvae is assumed to be $18-23^{\circ}C$. To predict the spawning ground of Todarodes pacificus under future climate conditions, we simulated the present and future ocean circulations, using an East Asia regional ocean model (Modular Ocean Model, MOM version3), projected by two different global climate models (MPI_echam5, MIROC_hires), under an IPCC SRES A1B emission scenario. Mean climate states for 1990-1999 and 2030-2039 from 20th and 21th Century Climate Change model simulation (from the IPCC 4th Assessment Report) were used as surface conditions for simulations, and we examined changes in spawning ground between the 1990s and 2030s. The results revealed that the distribution of spawning ground in the 2030s in both climate models shifted northward in the East China Sea and East Sea, for both autumn and winter populations, compared to that of the 1990s. Also, the spawning area (with $1/6^{\circ}{\times}1/6^{\circ}$ grid) in the 2030s of the autumn and winter populations will decline by 11.6% (MPI_echam5) to 30.8% (MIROC_hires) and 3.0% (MPI_echam5) to 18.2% (MIROC_hires), respectively, from those of the 1990s.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.44 no.6
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• pp.709-716
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• 2011

To investigate the distribution and migrations of sea turtles occurring in Korean waters, an adult female green sea turtle Chelonia mydas was tagged with a satellite transmitter and released at Busan in October 2009. The confirmation was made for the first time that the released green sea turtle migrated back to Korea after visiting Jeju Island and Japan for approximately 9 months. The green sea turtle spent the winter in Jeju and Japan because of low water temperatures in the East Sea and South Sea during winter months, which were not suitable for turtle survival. Compared with an immature green sea turtle that was released at Jeju Island, the adult green showed a markedly different migration pattern, suggesting that juvenile and adult greens move differently because of their peculiar life cycle and their stage of maturity, in addition to responses to temperature changes. Additional satellite tracking with increased representation of species, sexes and sizes of turtles, and regions is required to gather information on the distribution and movements of sea turtles in Korean waters.

• Journal of The Korean Society of Grassland and Forage Science
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• v.43 no.2
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• pp.103-108
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• 2023

Due to the recent impact of global warming, heavy rainfall and droughts have been occurring regardless of the season, affecting the growth of Italian ryegrass (IRG), a winter forage crop. Particularly, delayed sowing due to frequent heavy rainfall or autumn droughts leads to poor growth and reduced winter survival rates. Therefore, techniques to improve yield through additional sowing in spring have been implemented. In this study, the growth of IRG sown in Spring and Autumn was compared and analyzed using vegetation indices during the months of April and May. Spectral data was collected using an Unmanned Aerial Vehicle (UAV) equipped with a hyperspectral sensor, and the following vegetation indices were utilized: Normalized Difference Vegetation Index; NDVI, Normalized Difference Red Edge Index; NDRE (I), Chlorophyll Index, Red Green Ratio Index; RGRI, Enhanced Vegetation Index; EVI and Carotenoid Reflectance Index 1; CRI1. Indices related to chlorophyll concentration exhibited similar trends. RGRI of IRG sown in autumn increased during the experimental period, while IRG sown in spring showed a decreasing trend. The results of RGRI in IRG indicated differences in optical characteristics by sowing seasons compared to the other vegetation indices. Our findings showed that the timing of sowing influences the optical growth characteristics of crops by the results of various vegetation indices presented in this study. Further research, including the development of optimal vegetation indices related to IRG growth, is necessary in the future.

• Journal of the Korean Society of International Agriculture
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• v.23 no.5
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• pp.520-530
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• 2011

This study was carried out to evaluate the possibility of rice double cropping in Korea by assessing the growth and yield performance of rice cultivars transplanted at the extremely-early date. When the transplanted rice seedling was exposed to low temperature below 0℃, the survival rate decreased drastically. However, short exposure to below 0℃ one or two times did not damage transplanted rice seedling so severely. Thus, the earliest transplanting in spring would be possible when minimum temperature rises above 0℃. Compared with the conventional seedling nursery tray (CSNT), seedling rearing with the potted nursery tray was more effective for increasing leaf age and seedling dry weight during nursery period. In the first rice cropping, rice cultivation with seedlings reared in PSNT showed shorter growth duration and cumulative temperature from transplanting to heading than that with seedlings reared in CSNT. The earliest heading date on July 4 in Jinbuolbyeo was earlier by two to three days than that of Dunaebyeo. If rice has not exposed to cold damage, the earliest heading date of Jinbujolbyeo can advance to June 30 or July 1. In this case, rice harvest would be possible on August 5, enabling the rice transplanting of the second rice cropping before August 10. At transplanting time with low temperature damage rice yield were less than 400 kg/10a while rice yield exceeded 400 kg/10a at transplanting time without low temperature damage.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.45 no.6
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• pp.382-386
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• 2000

This study was conducted to know the optimum conditions for overwinter culture of sweetpotato stems in PE film house. The stems will be used as transplant shoots in the next year instead of sprouts produced from storage roots. Sweetpotato stems were cut at field on harvest season and planted in PE film house under three different conditions of PE film mulching, tunnel, or mulching plus tunnel in comparison with the non-treatment of PE film on October 10 and November 10. The survival rate of sweetpotato stems, which was evaluated on April 10 after overwinter, was higher in the treatment planted on October 10 than that on November 10, and with PE film treatments, it was higher in tunnel or mulching plus tunnel than that of the non-treatment of PE film. The survival rate of sweetpotato stems to planting densities was 95-96% in 10$\times$2cm (333 stems/$m^2$) or in 10$\times$4cm (250 stems/$m^2$) when compared with 10$\times$2cm (500 stems/$m^2$). The survival rate under low temperature showed 95% until 20 days at 5$\pm$1$^{\circ}C$, and 0% within 5 days at 2$\pm$1$^{\circ}C$. From these results, it was concluded that there were optimum conditions that cutting time is middle October, planting density is 10$\times$3cm, and minimum maintenance temperature is 5$^{\circ}C$ in growing conditions of sweetpotato stems. Root yield produced by trans-planting shoots using the stems was similar to yield by shoots produced from roots, and the survival rate was not different among varieties.

• Journal of Korean Society of Forest Science
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• v.83 no.4
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• pp.531-539
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• 1994

We examined the in vitro rooting and survival of tissue cultured plantlets of Quercus acutissima Carr. and Pinus densiflora Sieb. et Zucc. after addition of Pisolithus tinctorius(Pt) ectomycorrhizal fungus inoculum to the medium and effects of three levels of sucrose and phosphorus in culture media. Shoots of Quercus acutissima were obtained from winter buds of a 30-year old tree and cuttings of Pinus densiflora from germinated seed, and they were inoculated with Pt in vitro. In both species, Pt enhanced shoot length, survival, number of adventitious roots, root length, and rooting percentage. Survival in Quercus acutissima was increased from 75% in control to 100% in Pt inoculation. Pt inoculation increased the percentage of rooting from 20% to 70% in Quercus acutissima cuttings and from 63% to 100% in Pinus densiflora cuttings. It is concluded that mycorrhizal inoculation to tissue cultured Quercus acutissima Carr. and to in vitro cutting of Pinus densiflora Sieb. et Zucc. has practical application to improvement of poor root development and initial period of reduced shoot growth in vitro.

• Journal of The Korean Society of Grassland and Forage Science
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• v.29 no.4
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• pp.321-328
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• 2009

This experiment was carried out to investigate the effect of cultivar and seeding date on the winter survival rate, quality and DM yield of Italian ryegrass on paddy field for three years in Suwon. Seeding started from 30th Sep. 2003. at intervals of five days and finished 20th Oct. New varieties of Italian ryegrass used in this experiment were "Kospeed", "Kowinmaster" and "Hwasan 101". The winter survival average rate of 5th Oct. seeding plot was 89.8% and it decreased with delayed seeding date. The heading date of "Kospeed" was 7th~13rd May, "Kowinmaster" was 16th May, but "Hwasan 101 ho" didn't show heading until 17th May. Dry matter (DM) yields of 30th Sep. seeding plot were Kospeed 7,909kg/ha, Kowinmaster 6,398 kg/ha and Hwasan 101 ho 5,204 kg/ha. DM yield was decreased with delayed seeding date. Total digestible nutrient (TDN) yield was also decreased with delayed seeding date. Crude protein (CP) content was the highest in Kospeed. seeding plot as 18.3% and in vitro dry matter digestibility (IVDMD) was not showed significant difference among seeding dates.

• Journal of The Korean Society of Grassland and Forage Science
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• v.17 no.2
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• pp.117-122
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• 1997

This experiment was conducted to evaluate the forage yield and quality and the possibility to provide Festulolium bmunii(Festuca pratensis $Huds{\times}Lolium$ mult~jlotum Lam.) as forage source in Korea. The Festuloliurn braunii were harvested at boot, heading and anthesis stage, respectively. The field trials were performed 6om 1994 to 1996 at the forage experimental field, College of agriculture, Chunpam National University. The results obtained were summarized as follows: 1. The date of boot, heading and anthesis stage of Festulolium bmunii observed in Taejon were May 12, May 23 and June 1 in 1995, and June 1, June 4 and June 9 in 1996, respectively. Winter survival percentage of Festulolium bmunii war ranged 6om 96% to 98% and summer survival percentage were 75-86%. It would suggest that Festulolium brawlii persisted well in the aspect of overwintering, while it wasn' t widely adapted to drought and high temperature in Taejon regions. 2. The CP content and DMD of Festulolium bmunii tended to decline as the growth stage advanced. The CP content and DMD of Festulolium bmunii were high at the boot stage and those at the anthesis stage were low. But fiber contents at the boot stage were lower than those at anthesis stage(P< 0.05). The yields of the DM and DDM with advancing the growing stage tended to increase, while there was no difference in the CPDM yields among stages. On the otherhand, the yields of DM and DDM at the anthesis stage were the highest (P< 0.05), but there was no difference in CPDM yield among stages. Based on the results mentioned above, it is suggested that Festulolium b m n i i has a possibility to use until the anthesis stage under the cutting regimes and that it has a potentiality to provide one of a good forage sources. %'ifqqiZ 43q *(College of Agriculture, Chungnam National Un~versity, Taejon 305-764, Korea)

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.53 no.1
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• pp.49-59
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• 2017

The objective of this study was to investigate the growth rate and the optimal stocking density of sea cucumbers. Grow-out was studied in situ by conducting a follow-up survey using visible implant elastomer (VIE) tags. The rearing systems were made of polypropylene pipe for the frames and netting. The experiment ran for 70 days near Yeosu, Korea in the water depth of about 7 m. A total of 576 sea cucumbers which have three groups of body sizes (small: 5.15, medium: 12.34 and large: 23.26 g) were used. The five groups of stocking densities (150, 300, 450, 600 and $850g/m^2$) in rearing system for sea cucumber were considered. Sea cucumbers were fed a mixed diet (mud, mineral, fish meal, etc.). The feed was supplied to 10% of their body wet weight once every 7 days. The survival rate (73%) of sea cucumber in $850g/m^2$ was lower than those of other density groups ($150g/m^2$: 89%, $300g/m^2$: 84%, $450g/m^2$: 78% and $600g/m^2$: 86%). The survival rate of medium size group was higher than those of small and large groups regardless of the density (P<0.05). Most of density groups have no significant difference except for $850g/m^2$ (P>0.05). The growth rate of small size group ($0.63%day^{-1}$) was higher than those of medium ($0.38%day^{-1}$) and large ($0.34%day^{-1}$) group regardless of the density (P<0.05). The threshold water temperature was $11.0^{\circ}C$ for sea cucumber growth in winter season.