• Korean Journal of Ichthyology
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• v.13 no.3
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• pp.181-189
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• 2001

Spawning behavior of the Takifugu pardarlis (Temminck et Schlegel) was observed on the Jook-do coast in Tongyong from March 1997 to June 1999. The spawning ground was locted in the intertidal zone between Tongyong and Koje-do. Its bottom was mainly gravels and stones, and its depth was 0.5~1.0 m. Spawning season was from the end of the March to the middle of May. During the spawning season, the mature fishes formed school a of 10~30 individuals, then moved to the spawning ground together. When a mature female spawned eggs, the attendant males fertilized them at the same time. The fertilized eggs obtained from the parent fishes caught at the spawning ground were adhesive, opaque and spherical, measuring 1.14~1.24 mm (mean 1.19 mm, n = 50) in diameter with numerous tiny oil globules. Hatching period was about 205 hours after fertilization at water temperature of $18.0{\pm}0.5^{\circ}C$. The newly hatched larvae were 2.92~3.10 mm (mean 3.01 mm, n = 20) in total length (TL), had a large yolk, and 11~13+14~15 = 25~28 myomeres. At 5 days, the larvae had attained 3.79~3.85 mm (mean 3.82 mm, n = 20) in TL and had transformed into the postlarval stage. At 15 days, the postlarvae had attained 7.78~7.90 mm (mean 7.84 mm, n = 20) in TL. At 21 days, had larvae attained 10.15~10.27 mm (mean 10.21 mm, n = 20) in TL and had reached the juvenile stage. All fins were formed with a complete set of fin rays having the following counts: dorsal fin rays 11~12; anal fin rays 9; pectoral fin rays 14~15; caudal fin rays 11~12.

• Journal of Aquaculture
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• v.11 no.2
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• pp.193-201
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• 1998

This study was carried out to investigate the enviromental quality and the growth of transplanted pen shell, Atrinna pectinata japonica. Followings are the results of growth of transplanted pen shell with respect to the shell size groups from the natural habitat (Usando) in May 1995, and cultivated upto November in the transplantated area (Soomoonri). The water depth of transplantated area andnatural habitat were 3m, 20~25m, respectively. The seawater temperature of the two culturing farms were ranged of 10.9~$27.8^{\circ}C.$, 8.5~$30.0^{\circ}C.$, respectively at the lowest in November adn the highest in July. The seawater salinity of the two areas were ranged of 29.54~35.26$^0\prime\infty$, 28.75~36.31$^0\prime\infty$, respectively at the lowest in July and the highest in November. The phosphoric acid ($PO_4$-P) of the two areas were 0.09~$1.14 ^{\mu}$g-at/l, 0.23~$1.33 ^{\mu}$g-at/l, respectively at the lowest in June and the highest in September. The bottom type of the two areas was a silty mud, 85.23% (82.17~87.26%) in natural habitat and 92.12% (90.76~92.94$^0\prime\infty$) in transplanted area. In this study area, phytoplankton were composed of 19 species. Of these 19 species, Skeletonema costatum was dominant species in seawater between natural habitat and transplantatied area, and 157 cells/ml, 165 cells/ml at August respectively. Stock of phytoplankton in transplantated area were more than those of natural habitat except June and November. The growth of shell length, shell height, total weight, soft part weight and posterior adductor muscle weight of pen shell on different size groups (SL 10, 10~15, 15~20, 20cm) were excellent in shell length of 10cm group, and 99.32%, 107.66%, 871.09%, 951.26% and 1,223.76%, respectively. The survival rate of pen shell was 98.10% in the shell length of 10cm groups, 90.35~94.76% in the others groups. The growth of shell length, total weight, soft part weight and posterior adductor muscle weight of pen shell in transplantated area were more 1.3, 2.6, 2.7 and 4.5 times than those of natural habitat.

• Korean Journal of Environmental Biology
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• v.36 no.4
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• pp.647-658
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• 2018

The aim of this study is to investigate the seasonal changes of phytoplankton communities based on the environmental changes in a dense oyster farming area (Hansan-Geoje Island) from June to December 2016. The water temperature varied from $14^{\circ}C$ to $28.8^{\circ}C$ and its salinity ranged from 29.4 to 34.2 psu. Nitrate+nitrite was kept at c.a. $3.0{\mu}M$ on the surface layer from June to July, below the concentration limit in August and early September, and then gradually increased from late September. Ammonia was high on July 20 and August 10, and its seasonal characteristics were not clear. Phosphate ranged from 0.01 to $0.7{\mu}M$ on the surface layer, and its seasonal changes were similar to those of nitrate+nitrite. Mean silicate concentrations were $10.7{\mu}M$ on the surface and $15.7{\mu}M$ in the bottom layer, and it was not acted as a limiting factor for the growth of phytoplankton. Among the phytoplankton community, Bacillariophyceae, Dinophyceae and Cryptophyceae was 61.2%, 22.5%, and 13.6%, respectively. In late June, dinoflagellate Prorocentrum donghaiense was dominant in the outer waters(St. T1), later on, Cryptomonas spp. and Chaetoceros spp. were dominant, respectively. From late September to October, diatoms Pseudo-nitzschia spp. and Chaetoceros spp. were stimulated under non-stratified condition after the typhoon. In December, A. sanguinea was found to be $1.7{\times}10^5cells\;L^{-1}$. Seasonally, relative high phytoplankton biomass may be favorable to maintain high production of filter feeder oyster in the dense oyster farming areas of Hansan and Geoje Island.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.14 no.3
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• pp.134-144
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• 2009

Paleoproductivity changes in the central part of the Bering Sea since the last glacial period were reconstructed by analyzing opal and total organic carbon (TOC) content and their mass accumulation rate (MAR) in sediment core PC23A. Ages of the sediment were determined by both AMS $^{14}C$ dates using planktonic foraminifera and Last Appearance Datum of radiolaria (L. nipponica sakaii). The core-bottom age was calculated to reach back to 61,000 yr BP. and some of core-top was missing. Opal and TOC contents during the last glacial period varied in a range of 1-10% and 0.2-1.0%, and their average values are 5% and 0.7%, respectively. In contrast, during the last deglaciation, opal and TOC contents varied from 5 to 22% and from 0.8 to 1.2%, respectively, with increasing average values of 8% and 1.0%. Opal and TOC MAR were low ($1gcm^{-2}kyr^{-1}$, $0.2gcm^{-2}kyr^{-1}$) during the last glacial period, but they increased (>5 and >$1gcm^{-2}kyr^{-1}$) during the last deglaciation. High diatom productivity during the last deglaciation was most likely attributed to the elevated nutrient supply to the sea surface resulting from increased melt water input from the nearby land and enhanced Alaskan Stream injection from the south under the restricted sea-ice and warm condition during the rising sea level. On the contrary, low productivity during the last glacial period was mainly due to decreased Alaskan Stream injection during the low sea-level condition as well as to extensive development of sea ice under low-temperature seawater and cold environment.

• Korean Journal of Environment and Ecology
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• v.31 no.6
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• pp.537-548
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• 2017

The purpose of this study was to investigate the species composition and the aquatic environment of Jojong Stream and Sudong Stream, which were the original habitats of Zacco koreanus population and restored population re-introduced in Bongseonsa Stream. It also compared and analyzed the states of the growth and reproductive ability of Z. koreanus habiting in each of the three streams. The investigation was conducted in June 2016 which was known as the spawning season of Z. koreanus. The results of the physical aquatic environments showed the slight differences in altitude, width and depth of water among three streams, but the bottom structure was found to be quite different in the composition of the boulder, cobble, and pebble among the streams. The result of the physicochemical aquatic environment analysis showed that there were no significant differences in water temperature, pH, DO, BOD, and EC among the three stream. In the fish fauna investigation, 530 individuals of 11 species of 3 families were collected in Bongseonsa Stream, 293 individuals of 12 species of 4 families were collected in Jojong Stream, and 361 individuals of 11 species of 4 families were collected in Sudong Stream. All three streams were dominated by Z. koreanus and Z. platypus. Six Korean endemic species appeared in each of the three streams, showing the high occurrence rate of indigenous species of 50.0% or more. The aggregation index analysis revealed that the mean dominance index ranged from 0.63 (${\pm}0.05$, BS) to 0.72(${\pm}0.01$, JJ), mean diversity index from 1.55 (${\pm}0.06$, JJ) to 1.78 (${\pm}0.11$, BS), mean evenness index from 0.71 (${\pm}0.03$, JJ) to 0.76 (${\pm}0.02$, BS), and mean richness index from 1.61 (${\pm}0.33$, JJ) to 1.73 (${\pm}0.24$, SD). The result indicated that the observed differences between the stream community indices were statistically nonsignificant. The similarity analysis showed that 75.4% similarity was divided into two groups of A and B and that the fish fauna on each analyzed point was similar. The quantitative habitat evaluation index (QHEI) analysis showed that the average value of QHEI was 151.0 (${\pm}46.0$), which means that it was a suboptimal habitat environment. The result of length-weight analysis of Z. koreanus populations showed that the regression coefficient b of the restoration population and the original habitat population were at 3.0 or higher while the condition factor had a positive slope. Moreover, it was found that the slopes of the regression coefficient b and condition factor of the original habitat population were larger than the restored population. The analysis of the length frequency distribution of the Z. koreanus population revealed that all three streams maintained the stable life cycle although it was found that the growth rate of the original habitat population was faster than the restored population in the one-year-old class. The result of the gonadosomatic index (GSI) analysis showed that the GSI median value of the Z. koreanus population in the restored habitat Bongseonsa Stream was higher than the population in the original habitat Jojong Stream and Sudong Stream for both of males and females.