• Korean Journal of Ichthyology
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• v.36 no.3
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• pp.209-219
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• 2024

A survey was conducted in 2011 to investigate the reproductive ecology and spawning behavior of the natural monumental and endangered species, Cobitis choii. C. choii exhibits sexual dimorphism with the development of lamina circularis on the second pectoral fin ray in males at one year old, facilitating easy differentiation between males and females. A total of 1,288 females and 881 males were collected from January to December, resulting in a sex ratio of 1 : 0.68. The spawning season was estimated to be from late June to early July (spawning peak from late June, with water temperatures ranging from 22 to 25℃), coinciding with a sharp decrease in the condition index. Gonadal maturity was observed with maturity indices of 17.5±2.11% for females and 2.9±0.46% for males, with fecundity of 2,444±838 eggs and egg size of 0.75±0.05 mm. Spawning behavior was induced by hormone injection (Human Chorionic Gonadotropin, HCG) in laboratory conditions. Experimental results revealed that males and females paired in a 1 : 1 ratio before spawning. Males pressed the abdomen of females using their lamina circularis to induce spawning, followed by immediate fertilization. Spawning behavior was repeated 15 to 25 (average 20) times per pair of males and females, and 80 to 120 eggs were spawned per time, and the total amount of spawned eggs were 2,500±250 on average.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.1
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• pp.63-70
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• 1999

The optimum sampling area which can be applied to the benthic community study is estimated from large survey data in the Songdo tidal flat and subtidal zone of Youngil Bay, Korea. A total of 250 samples by 0.02 $m^2$ box corer for the benthic fauna in Songdo tidal flat and 50 samples by 0.1 $m^2$ van Veen grab in Youngil Bay were taken from the total sampling area of 5 $m^2$. It was assumed that the sampling area could contain sufficient information on sediment fauna, if cumulative number of species, ecological indices, and similarity index by cluster analysis reflect the similarity level of 75% to those found at total sampling area (5 $m^2$). A total of 56 and 60 species occurred from Songdo tidal flat and Youngil Bay, respectively. The cumulative curve of the species number ($N_{sp}$) as a function of the sampling area (A in $m^2$ ) was fitted as $N_{sp}=37.379A^{0.257}$ ($r^2=0.99$) for intertidal fauna and $N_{sp}=40.895A^{0.257}$ ($r^2=0.98$) for subtidal fauna. Based on these curves and 75% of similarity to the total sampling area (5 $m^2$), the optimum sampling area was proposed as 1.6 $m^2$ for the intertidal and 1.5 $m^2$ for the subtidal fauna. Ecological indices (species diversity, richness, evenness and dominance indices) were again calculated on the basis of species composition in differently simulated sample sizes. Changes in ecological indices with these sample sizes indicated that samplings could be done by collecting fauna from < 0.5 $m^2$-1.5 $m^2$ on the Songdo tidal flat and from < 0.5 $m^2$-1.2 $m^2$ in Youngil Bay. Changes in similarity level of all units of each simulated sample size showed that sampling area of 0.3 $m^2$ (Songdo tidal flat) and 0.6 $m^2$ (Youngil Bay) should be taken to obtain a similarity level of 75%. In conclusion, sampling area which was determined by cumulative number of species, ecological indices and similarity index by cluster analysis could be determined as 1.5 $m^2$ (0.02 $m^2$ box corer, n=75) for Songdo tidal flat and 1.2 $m^2$ (0.1 $m^2$ van Veen grab, n=12) for Youngil Bay. If these sampling areas could be covered in the field survey, population densities of seven dominant species comprising 68% of the total faunal abundance occurring on Songdo tidal flat and six species comprising 90% in Youngil Bay can be estimated at the precision level of P=0.2.

• Korean Journal of Environmental Biology
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• v.41 no.4
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• pp.637-656
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• 2023

River estuaries are dynamic and productive ecosystems with high regional biodiversity. Environmental DNA (eDNA) has become a useful approach to assessing biodiversity in aquatic ecosystems. This study was conducted to investigate fish community characteristics and species diversity in two river estuary ecosystems, the Taehwa River and Changwon Stream. We further compared conventional and eDNA metabarcoding analyses of the fish communities. The conventional survey was performed in May, July, and October 2022, while the eDNA analysis was conducted only in May. We observed various fish species with different life histories, including carp, goby, and marine fish. We also found that migratory fish, such as dace Tribolodon hakonensis, sweetfish Plecoglossus altivelis, and eel Auguilla japonica, occurred in the Taehwa River, suggesting high river connectivity. Marine fish species were predominant in the Changwon Stream, as this river is located close to the sea. The diversity indices showed that the Taehwa River generally had higher species richness, evenness, and diversity values than the Changwon Stream. A total of 9-19 species were detected in the conventional survey for the three sites, whereas 11-18 species were found from eDNA analysis. The findings indicate that the sensitivity of eDNA was similar to or higher than that of the conventional method. Our study findings suggest the efficiency and efficacy of eDNA-based fish community monitoring, although with some shortcomings in applying the genetic marker to Korean fish, including no clear-cut distinction for Korean endemic species and/or genetically closely related species groups.

• Korean Journal of Ichthyology
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• v.19 no.4
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• pp.306-317
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• 2007

Reproductive cycle with the gonad developmental phases, first sexual maturity, spawning frequency, sex ratio of the dusky mud hopper, Periophthalmus modestus were investigated by histological observations. Monthly variations of the gonadosomatic index (GSI) began to increase in May and reached a maximum in June when the gonad was getting mature during the period of higher ground (water) temperature-long day length. Changes in the GSI showed a negative correlation to the HSI, but coincided with the fatness index. The reproductive cycle can be classified into five successive stages: in female, early growing stage (April to May), late growing stage (April to May), mature stage (May to June), ripe and spent stage (June to August), and recovery and resting stage (August to March); in males, growing stage (April to May), mature stage (May to June), ripe and spent stage (June to August), and recovery and resting stage (August to March); According to the frequency distributions of egg diameters during the breeding season, Periophthalmus modestus is presumed to be a summer breeder, asynchronous group and polycyclic species to spawn 2 times or more during the spawning season. Total eggs and mature eggs in absolute fecundity and relative fecundity (per cm) increased with the increase of body length. Total eggs and mature eggs in absolute fecundity and relative fecundity (per g) did not increase with the increase of body weight. Percentages of first sexual maturity of females and males ranging from 5.1 to 5.5 cm in body length are over 50%, and 100% for fish over 7.1 cm in body length. The sex ratios of females to males over 5.1 cm in body length were not significantly different from a 1 : 1 sex ratio.

• Development and Reproduction
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• v.12 no.2
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• pp.169-181
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• 2008

Reproductive ecology of the silver pomfret, Pampus argenteus were investigated by histological observations and morphometric data. Samples were collected by the stow net at the coastal area of Jaun-Do, Muan-gun, Korea, from January to December, 2006. P. argenteus is dioecious, the ovary is composed of many ovarian lobules, showing a pair of saccular structure, and the testis is composed of many seminiferous lobules, showing a pair of lobular structure. From February (growing stage) to September (after spawning), monthly changes in the gonadosomatic index, hepatosomatic index, and condition factor in females and males showed similar patterns with the gonad developmental phases. Judging from the results of their indice, it is assumed that spawning in females and males occur from May to July. The reproductive cycle can be classified into five successive stages in females: early growing stage (February to March), late growing stage (March to April), mature stage (March to July), ripe and spent stage (May to July), and recovery and resting stage (July to February); in males, the cycle can be divided into four successive stages: growing stage (February to April), mature stage (March to June), ripe and spent stage (May to July), and recovery and resting stage (July to February). According to the frequency distributions of egg diameters in the breeding season, P. argenteus is presumed to be spring-summer spawning species and polycyclic species to spawn 2 times or more during one spawning season. Number of total eggs in absolute fecundity were proportional to body length and body weight, respectively. Number of total eggs in absolute fecundity per body weight were also proportional to the body length, but if the increase of body weight considerably increased, rather total eggs in relative fecundity decreased with the increase of body weight. Percentage of first sexual maturity of P. argenteus were over 50% in females and males of 12.1 to 15.0 cm in body length, and 100% for fishes over 18.1 cm in length. Therefore, both sexes were regarded to be sexually mature at one year of age.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.11
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• pp.136-143
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• 2019

This study investigated the effects of environmental temperature and humidity on the physiological indicators such as respiratory rate, rectal temperature, and rumination time in cows. Twenty lactating Holstein cows were used for this study. The temperature/humidity index, which can be measured by the temperature and humidity of barns, was divided into three stages to distinguish the heat stress level of cows. The temperature and humidity indexes of each stage were classified into 70 ~ 75 for T1, 76 ~ 81 for T2, and 82 ~ 87 for T3, respectively. The respiratory rates per minute were 58.60 at T1, 66.12 at T2, and 84.05 at T3, respectively (P < 0.05), and the average rectal temperatures (℃) of the cows were 38.41 in T1, 38.69 in T2 and 39.05 in T3, respectively (P < 0.05). The body surface temperatures (℃) were 36.41 in T1, 36.51 in T2, and 37.39 in T3, respectively. The rumination times (minutes/day) were 473.10 in T1, 454.76 in T2, and 399.60 in T3, respectively (P < 0.05). As global warming continues to damage the dairy industry, further research is needed to improve the welfare of dairy cows and reduce their heat stress.

• Journal of Environmental Science International
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• v.8 no.1
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• pp.7-18
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• 1999

Fauna and biological water quality using benthic macroinvertebrates were analysed and estimated macroinvertebrates. Samples were collected 5 times from the 7 sites in the river between April and December 1997, and the results are summarized as follows. The taxa of benthic macroinvertebrates was totally composed 81 species, 45 genus, 37 families, 15 orders, 8 classes in 3 phyla. Among them, aquatic insects were mostly abundant as 65 species, and also, there were a species of oligochaetes, 2 species of hirundinida, 6 species of gastropods, 5 species of polecypoda, and 2 species of crustaceans. Average individual numbers in the whole sampling sites was 815 per square meter, and insects were abundant (Approx. 80%). Among the insects, the major taxa were respectively ephemeroptera (Approx. 70%) and trichoptera (Approx. 18%). According to the average individual numbers in each site, Chung-do stream (site 1) showed the highest appearance rate as 262 individual/ $m^3$ (32.2%), and the lowest value was at the end of Miryang River (site 7) as 38 individual / $m^3$(4.7%). The dominant species among the whole samples was Ecdyomurus levis Navas, and dominance indices was 0.3. In each site, Ecdyomurus levis Navas was dominant species from site 1 to site 5, and dominant species at site 6 and 7 was respectively Hirudinidae sp. 1. Species diversity index in total average of samples was 2.66. Average of species diversity index according to each study site was the highest value at site 4 (H'=3.47), and site 2, 1, 3, 5, 6, and 7 in that order. According to the water quality as biotic indices, GPI value was 1.49 in total average of Miryang river, and the pollution indices evaluated secondary water quality criteria as $\beta$-mesosaprobics. In each site, the best water quality was at site 3, and it revealed the first water quality criteria as Oligosaprobic. It was then site 1, 2, 4 and 5 in the order of water quality, and was evaluated secondary water quality criteria as $\beta$-mesosaprobics, respectively. Site 6 was also revealed the third water quality criteria as $\beta$-mesosaprobics. The worst water quality was at site 7, which revealed the third water quality criteria as a-mesosaprobics.

• The Korean Journal of Soil Zoology
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• v.6 no.1_2
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• pp.25-31
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• 2001

Oribatid mite communities in the process of litter decomposition were analyzed In Korean pine (Pinus koraiensis) forests of Namsan and Kwangreung, which were supposed to be under different environmental selective pressures. Oribatid mites were collected bimonthly from the litter bags (mesh size 0.4 mm, 1.7 mm) which was set up in the forest floor of study sites. This study had been carried out from Jan., 1997 to Sept., 1998. Species abundance of Kwangreung (mesh size 1.7 mm) was significantly higher than that of Namsan (mesh size 1.7 mm), but total no. of species did not exceed 30 species in all study sites. Concerning body length, medium sized oribatid mites (0.3-0.7mm) were more abundant than small ( < 0.3 mm) and large ( > 0.7 mm) sized mites. In Kwangreung, species whose body lengths were 0.2 mm to 0.5 mm were major group. However, a little larger species than Kwangreung's major group were dominant in Namsan. Sorenson similarity index and cluster analysis suggested that there were qualitative and quantitative differences in species composition in Namsan and Kwangreung. More species were collected in May through September than the other sampling times, but the pattern was rather different between first year and second year. Newly immigrant species were high in May in the first year and many of them regained on next year. Diversity indices suggested that species diversity of Kwangreung was higher than that of Namsan. Nearly 70% of total individual abundance was occupied by several dominant species in Namsan and Kwangreung . In the litter bags of mesh size 1.7 mm, the most dominant species was Trichogalumna nipponica in Namsan and Kwangreung, but in the litter bags of mesh size 0.4 mm in Kwangreung it was Ramusella sengbuschi which is smaller than T. nipponica. And important species related to litter decomposition were selected as follows; T. nipponica, Epidamaeus coreanus, Scheloribates latipes, Ceratozetes japonicus, Ramusella sengbuschi, Eohypochthonius crassisetiger, and Cultroribula lata.

• Korean Journal of Plant Resources
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• v.13 no.3
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• pp.227-242
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• 2000

Site characteristics, vegetation structure and dynamics of Kalopanax septemlobus forests in Mt. Heungjeong, Mt. Balwang and Mt. Gariwang were studied to provide the information need for national resources conservation and restoration of K. septemlobus forest in Gangwon-do of Korea. The K. septemlobus forests were distributed at 780m to 1,300m in altitude, steep slope, ridges-slope areas with facing northeast to northwest in good nutrition area. The annual diameter growth of those trees ranged 1.60mm to 2.41mm. Forty-three plots(20$\times$20m) were set up at three natural population of Kalopanax septemlobus forest and TWINSPAN method was used for vegetation structure analysis. The result of TWINSPAN ordination show that geographical features played a role in determining community types in the study areas. Community type of the study areas classified into three groups by TWINSPAN; K. septemlobus-Quercux mongolica- Acer mono community(Mt. Balwang), K. septemlobus-Q. mongolica- Tilia amurensis community(Mt. Heungjeong), K. septemlobus-Betula costata-Q. mongolica community(Mt. Gariwang). In most of the K. septemlobus forests, major woody species appeared predominantly were Q. mongolica, T. amurensis, Acer pseudo-sieboldianum, Lindera obtusiloba, A. mono, Magnolia sieboldii, Ulmus davidiana var. japonica. And also, Those species were surveyed in all the areas. Species diversity(H') of investigated areas ranged 0.3124~0.13992 and this value relatively higher than that of other forests with similar site. The range of similarity indices between surveyed areas was 64.1~64.54%. The distribution pattern of Morista's index show that Kalopanax septemlobus distributed randomly in tree and concentrated a few sample plots in subtree layer and shurb layer. K. septemlobus occupied 37.1~58.8% of tree layer story, 8.4~17.6% of subtree layer, 0~0.38% of shurb layer each surveyed area. The association analysis showed that Kalopanax septemlobus positively associated with Betula ermani, Deutzia glabrata, Carpinus cordata, Fraxinus mandshurica and negatively associated with Symplocos chinensis var. pilosa, Styrax obassia, Acer mono, Euonymus macroptera, Ulmus davidiana var. japonica. According to the diameter distribution of Kalopanax septemlobus community, the community of Mt. Gariwang will gradually decline and replaced by Quercus community. The communities of Mt. Heungjeong and Mt. Balwang has its seedlings and saplings, so it may be sustained.

• Korean Journal of Environmental Biology
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• v.39 no.3
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• pp.362-373
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• 2021

This study was conducted to establish mosquito distribution density and habitat in Sejong city for the prevention of mosquito-borne infectious diseases. The overall distribution of mosquitoes in the Sejong City was investigated, and the population density of mosquitoes in the old and new city was analyzed. Mosquito populations were determined using MOSHOLE and Blacklight traps once a week overnight. We also compared the mosquito population density of the old city and the new city, and the daily mosquito population was calculated using the data from the smart mosquito trap(DMS). Of all the study sites, Geumnam-myeon had the highest number of mosquitoes captured, and the dominant species were Armigeres subalbatus and Culex pipienspallens. Mosquito species with the potential for transmitting diseases were mainly found in Yeonseo-myeon (106 individual), and Geumnam-myeon (101). Mosquito collection rates by MOSHOLE trap and Blacklight trap were 58.49% and 41.51%, respectively. We concluded that using CO₂ would be the most suitable approach for collecting mosquitoes. The mosquito population density in the old city (92.05±7.04) was approximately twice that of the new city(51.50±4.05). Since Sejong City is divided into old city and new city, it is difficult to spot remarkable effects in a standardized way. For effective quarantine, differentiation of quarantine must be established. This study results provide a basis for Sejong City's integrated mosquito control guidelines, and therefore effective control of which we believe will help control the spread of mosquito-borne diseases and reduce damage from mosquitoes.