• Korean Journal of Ichthyology
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• v.25 no.1
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• pp.9-16
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• 2013

Egg development and early life history of the endangered species, Gobiobotia naktongensis were investigated to provide basic information regarding biological characteristics and restoration. Eggs were obtained from the females with Ovaprim (0.5 mL/kg) injecting and then fertilized using the dry method in the laboratory. Number of spawned eggs were $1,015{\pm}199$. Spawned eggs were strongly adhesive, opaque and grayish and measured $0.74{\pm}0.08mm$ (mean${\pm}$SD) in diameter. Fertilized egg size continuously increase until $2.94{\pm}0.10mm$ for 9 h 30 min at $23^{\circ}C$. Fertilized eggs hatched 26 h after fertilization, and newly hatched larvae an average were $3.4{\pm}0.07mm$(TL). The yolk sacs of the larvae were of most absorbed of 3 days after hatching and $4.4{\pm}0.1mm$ (TL). About at 13 days after hatching, they became to juvenile stage and reached $16.8{\pm}0.50mm$ (TL). At 80 days after hatching, the band patterns and external form of juveniles were similar to those of adults, and they averaged $27.7{\pm}2.32mm$(TL).

• Korean Journal of Ecology and Environment
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• v.33 no.3 s.91
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• pp.282-294
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• 2000

The reproductive ecology and the early life history of Macropodus chinensis were investigated in aquarium. Mature male made the bubble nest and spawned with wrapping the female and reverse posture. The parental male protected the offspring until the larvae depart the bubble nest. Egg productivity and egg hatching rate were the highest at water temperature in $28^{\circ}C$ and $26^{\circ}C$ respectivity than any other artificial temperature. The eggs were buoyant, globular and 0.95${\sim}$1.05 mm in diameter. Cleavage was progressed at intervals of 15 minutes. Eggs hatched in 42${\sim}$44hours after fertilization and the newly hatched larvae were 3.0${\sim}$3.2 mm in total length. The lawae were 4.5${\sim}$5.4 mm in 4${\sim}$5 days after hatching and fed on the food with dispersion from the nest. In 40${\sim}$45 days after hatching, all fin rays completely developed, and juveniles reached 18.2${\sim}$23.5 mm in total length. In 90${\sim}$110 days after hatching, body from of young fishes were similar to adult with 37.4${\sim}$48.2 mm and represented secondary sexual characters longer than 45.0 mm in total length, and about 120 days, fishes began spawning(water temperature for ontogenesis: $26.0{\pm} 1^{\circ}C$).

• Korean journal of applied entomology
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• v.59 no.4
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• pp.361-369
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• 2020

This study aimed to investigate the differences in the effects of nematicidal materials (Burkholderia rinojensis, fluazaindolizine, fluopyram, fosthiazate, hydrogen peroxide, and imicyafos) on eggs and larvae of the sugar beet cyst nematode, Heterodera schachtii and clover cyst nematode, H. trifolii, which have recently become problematic in highland Chinese cabbage cultivation areas in Korea. Comparison of the hatching rates according to the test materials showed differences between treatments. In the treatment with fluopyram, fosthiazate, and imicyafos, a very high hatching inhibitory effect of 99% was observed in both nematodes, and there was no difference in the efficacy of treatments between nematode species except for that with hydrogen peroxide. Regarding the nematocidal activity of treatments against hatched larvae, only the fluazaindolizine treatment, despite showing a high hatching inhibitory effect, showed a low nematicidal effect of less than 30% against both nematodes, whereas a mortality rate of more than 90% was observed in the other treatments. There was no difference between nematode species in the reactions of the 2nd instar juveniles to all nematicidal test materials after 24 and 48 h of treatment. Although there are limitations to the laboratory experiment, the reaction to the nematicidal materials of the two cyst nematodes that damage the same host was similar, and simultaneous control is suggested in the areas where the two nematodes occur together.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.1
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• pp.24-32
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• 1987

Bluegill, Lepomis macrochirus RAFINESQUE, has bred widely in the various districts of Korea since the Office of Fishery transplanted it into our country from Japan in December, 1969. On August 17, 24 in 1985, bluegill were caught in the reservoir of Habuk-Myon, Yangsan-Gun, $Ky\breve{o}ngsangam-Do$, Korea. They spawned in the rearing aquarium on July 13 and August 2 in 1986. The eggs of this species are adhesive and demersal. The size of the egg diameters were varied from 1.18 to 1.30 mm. Hatching took place in 40 hours after fertilization at the water temperature of $24.3-25.4^{\circ}C$. The newly botched larvae were 3.75-4.05 mm in total length possessing yolk sac, and 29-30 mytomes. Many melanophores were evenly distributed on the entire body. Ten days after hatching, the postlarvae attained 6.05-6.35 mm in total length. The yolk sac was completely absorbed and the width of the pectoral finfold had reached the maximum size. One month fifteen days after hatching, the juvenile attained 25.20 mm in total length.

• Ocean and Polar Research
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• v.44 no.1
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• pp.39-59
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• 2022

How in the Antarctic icefish, generally, and Pseudochaenichthys georgianus, in particular, otoliths increase in size and build new material as the fish ages and passes through different life phases is largely unexplored. Morphometric details of 3418 otoliths of Ps. georgianus from S. Georgia and 318 from S. Shetland, were processed and proportions of the amounts of collagen and aragonite removed by EDTA were determined for different age groups. Microstructural investigations showed that characteristics of the 3-dimensinal collagen net are the reason for the radial direction and orientation of the aragonite needles of approximately 1.0 ㎛ in length in larval and 2.3 ㎛ in length in adult specimens. Earlier generated increment layers from the primordial centre (PC) in the dorsal direction restrict those of the secondary centre (SC), causing new growth layer accretion in different directions. In the otoliths of larval Ps. georgianus, aragonite layers are 0.89 ㎛ wide while in juveniles and adults they measure 1.45-2.86 ㎛. Otoliths change from a sphere shape in the larvae to a longish object of irregular outline in the older stages. It is tentaively suggested that the observed otolith shape differences at distinct growth stages are due to physical effects related to swimming speeds at particular water depths and locations. To confirm that otoliths, apart from being useful for age analyses, could also serve to establish correlations between developmental stage and the oceanic environment the fish spend time in, further analyses using additional species and state-of-the-art methods like µCT imaging to evaluate otolith volumes and shapes are required.

• Korean Journal of Ecology and Environment
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• v.40 no.2
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• pp.337-345
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• 2007

Changes of feeding habitat and feeding organ of a land-locked sweetfish, Plecoglossus altivelis related to their growth process were investigated in the Lake Okjeong, Sannae-myeon, Jeongeup-si, Jeollabuk-do, Korea from 2004 to 2005. In the lake, the post-larvae from 25 to 40 mm in standard length fed mainly on animal organisms such as Copepoda, Branchiopoda and Rotatoria. Also, the juveniles from 50 to 60 mm (SL) fed on Chironomidae of Diptera, Copepoda and Branchiopoda. However, the juvenile from 60 to 70 mm (SL) in the Churyeong Stream fed on animal organisms and aquatic algae, the immature fishes more than 70 mm (SL) fed on only periphyton such as Synedra, Cymbella, Navicula and Pinnularia. Also, the feeding organs of the tooth and stomach were changed according to its growth and food change.

• Korean Journal of Ichthyology
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• v.7 no.2
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• pp.128-134
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• 1995

In order to study the taxonomic status of Cottus species from Korea, 19 morphological characters, egg number and size and hatched juvenile form in C. poecilopus and C. hangionsis were compared. The two species of C. poecilopus and C. hangionsis overlap each other in morphometric characters mostly, but snout length, caudal peduncle length and pectoral fin ray number were distinguished between them. Moreover the C. poecilopus and C. hangionsis specimens were differ from each other in the number of egg and size. The newly hatched juvenile form of C. hangiongensis produced many small eggs from which pelagic larvae were formed. In contrast, C. poecilopus produced well - developed juveniles. Two species have distinctly different life - cycles ; amphidromous for C. hangionsis and fluvial land - locked for C. poecilopus.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.22 no.5
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• pp.332-341
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• 1989

Stomach contents and microstructures in otolith of Chaenogobius laevis were analyzed for the determination of age, growth and food. By comparaing structural similarity in a series of growth increments from three samples collected in a two-week interval, daily deposition of growth increments in otolith can be validated. Growth in length as daily basis was well represented by Gompertz curve: $L= 5.73{\cdot}\;e^{15.06}(1-e^{-0.0015t})$ for the fish age of $46\~102$ days. Mean growth rate increased from 0.40 mm/day for the age of $50\~60$ days to 0.85 mm/day for the age of $80\~100$ days. Chasnobius laevis showed a carnivorous feeding behavior and its major food items were polychaetes, amphipods and copepods. Small individuals ($15\~30$ mm SL) preyed heavily on copepods as well as polychaetes. However, the portion of copepods in stomach contents was decreased with increasing fish siEe, and this decrease was compensated by an increased consumption of amphipods.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.1
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• pp.22-31
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• 1994

Fish aggregating devices(FAD) or artificial fish reefs deployed in the ocean space have been developed in various forms. The objective of FAD is to aggregate, cultivate and proliferate aquatic resources by making changes in ocean flows around it. developing spawning grounds, improving feeding areas and protecting larvae and juveniles. Most floating fish aggregating devices(FFAD) are in the form of surface buoys or subsurface buoys with a single point mooring system(SPMS). The mooring line of SPMS for the secure positions of FFAD is expected to keep great stresses as a result of the harsh ocean environment. Laboratory static tests on synthetic fiber ropes used for the SPMS were run. The Nylon wet rope specimen tests under increasing-and-decreasing loads showed about 20% strength drop. Also the logarithmic creep-tie behavior of fiber ropes was observed in the constant load test and compared with Flessner's formula.

• Korean Journal of Ichthyology
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• v.32 no.3
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• pp.166-181
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• 2020

The egg development, early life history and spawning site characters of Korean endemic fish, Coreoleuciscus splendidus (Gobioninae), were investigated at the part of Jo-jong stream in Korea from May 2020. The fertilized eggs were 2.05~2.23 mm (mean, 2.13 mm) in diameter and had no oil globules. The embryo began to hatching about 98 hrs after fertilization under water temperature of 20±1℃. The newly-hatched larvae were 5.03~5.68 mm (mean, 5.31 mm) in total length (TL), and their mouth and anus were not opened. 4 days after hatching, Several rod-like cupulae were observed on the head and lateral side of the body at 6.95~7.89 mm (mean, 7.51 mm). 7 days after hatching, the post-larva stage were 8.39~9.29 mm (mean, 8.78 mm) in total length, and their york were completely absorbed. The cupulae were completely distinguished. They entered the juvenile stage when all fin-rays were formed at 29 days after hatching, and their TL were 14.16~17.04 mm (mean, 14.99 mm). Squamation was initiated on the caudal body at approximately 18.21~23.74 mm (mean, 30.28 mm), 38 days after hatching, and completed at 26.82~33.33 mm (mean, 19.42 mm), 73 days after hatching, the external characteristics from of juveniles were same to adults. The spawning site was characterized by bottom structure of pebble (64~16 mm) and gravel (16~2 mm), environmental conditions of the spawning sites were 6~18 cm in water depth, 0.43~0.73 m/sec in bottom water velocity. In spawning sites, an egg mass or separated eggs were located a small gap of under the pebble and gravel.