• Korean Journal of Ichthyology
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• v.9 no.1
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• pp.48-60
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• 1997

The species composition and seasonal variations of fish community in the Zostera marina belt at the coastal water off Hamduck, northern part of Cheju Island, were analyzed based on day and night samples collected by a small beam trawl from May 1993 to May 1994. The dominant species among the 58 fish species in 35 family were tubesnout, Aulichthys japonicus, gobie, Pterogobius zonoleucus, filefish, Rudarius ercodes, pipefish, Syngnathus schlegeli and sea catfish, Plotosus lineatus. These species comprised 86.1% in the number of individuals and 62% in biomass. The number of individuals and biomass were high between October and December, and low between January and April. About 90% of fishes were noncommercial and small-sized fishes, less than 14cm in total length. The larvae and juvenile fishes were collected in the study area throughout the year. The recruitments of dominant species were related to the seasonal variations of Z. marina utilized as a shelter or feeding ground. A japonicus, P. zonoleucus, Zoarchias glaber and Hexagrammos agrammus recruited between January and June, and R. ercodes, S. schlegeli, P. lineatus and Petroscirtes breviceps between July and December.

• Ecology and Resilient Infrastructure
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• v.2 no.3
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• pp.216-223
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• 2015

The conservation project to protect an endangered fish, Gobiobotia naktongensis was executed against declining the gene diversity of the fish after the construction of Youngju Dam in a sand-bed stream (Naeseongcheon Stream). We tried to move the populations of G. naktongensis from submerged planned sites to alternative habitats, bred artificially and augmented the juveniles to optimal habitat, and monitored the results of the restoration implementation. No entity of G. naktongensis was confirmed at the planned submerged sites despite attempting to capture more than 8 times and eventually the movement to alternative habitat could not be implemented. About 40 individuals of G. naktongensis were captured in the Naeseongcheon Stream and a total of 5,000 individuals were artificially spawned up. The population of juvenile inherited the genetic diversity from the brood stock. The bred juveniles were discharged at the selected optimal site that had a habit condition what was similar to their natural habitat. The micro-dispersion around the discharging area was found at the early stages of the augmentation. The re-capturing rate of discharged juveniles was reduced as time passed. The discharged juveniles seemed to adapt to the natural environment of Naeseongcheon Stream. The observation of their high abdominal distension and excrement demonstrated that the juveniles fed successfully in the discharging area. Therefore, securement of genetic homogeneity and enhancement of restoration population of G. naktongensis in upstream and downstream of Youngju Dam site from the artificial seed producing seemed to be primarily successful and long-term monitoring and analysis of the effect was expected to be necessary.

• Korean Journal of Ichthyology
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• v.33 no.4
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• pp.262-272
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• 2021

The egg development and early life history of Tribolodon hakonensis that collected from the Seomjin River were studied. The fertilized eggs of the T. hakonensis were slightly adhesive and separated with a yellow yolk and no oil globule. The size of the eggs was an average of 2.89 mm (2.79~2.96) in diameter. Fifty percents of the embryos were hatched in about 63 hrs after fertilization at water temperature of 20℃. The newly hatched larvae showed average 6.92 mm (6.09~7.60) in total length. At 8 days after hatching, they were 13.75±0.67 mm (n=10) in total length and their yolk sacs were completely absorbed, opening mouth and anus (postflexion larvae stage). At 40 days after hatching, they became juvenile and reached 26.99±1.82 mm (n=10) in total length and all their fin rays were formed. At 137 days after hatching, the young fish were 72.63±10.7 mm (n=10) in total length and their body shape, color and behavior were similar to those of adult fish. The size of eggs and the larva after hatching significantly affected the initial growth among groups of genus Tribolodon, and the hatching time of fertilized eggs and the growth rate of the early life history according to the water temperate were different.

• Journal of Aquaculture
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• v.20 no.4
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• pp.270-277
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• 2007

White spot syndrome virus (WSSV) which is the most serious threat to cultured shrimp around the world has given enormous economic damages to shrimp culture industry every year since it was found from the shrimp ponds in the west coast of the South Korea in 1993. WSSV has strong infectivity as well as virulence and it can be rapidly transmitted among shrimps in ponds by cannibalism of infected ones. Polyculture of shrimps with carnivorous fish has been applied in commercial shrimp farms to suppress or delay the viral outbreak because the fish may selectively eat the moribund shrimps infected by virus. To determine the selective predatory effect of a carnivorous fish, river puffer Takifugu obscurus on white shrimp Litopenaeus vannamei, polyculture trials in laboratory scale of WSSV-infected and non-infected shrimps with river puffer were conducted in concrete round tanks of $28.26\;m^2$ in surface area as followings: 1) juvenile shrimps (B. W. 0.62 g) with 5 months old puffer (B. W. 11.60 g) cultured for 8 days, and 2) sub-adult shrimps (B. W. 6.84 g) with 16 months old puffer (B. W. 85.82 g) cultured for 5 days in order to know the effects according to size difference of cultured animals. In polyculture of juvenile shrimp with 5 months old puffer, survival rates of infected and non-infected shrimps were 46.0% and 89.1% respectively and in that of sub-adult shrimp with 16 months old puffer those were4% and 48% respectively. The results showed that puffer tends to selectively prey on virus infected shrimps among infected and non-infected ones in a limited space with although there is difference in predatory rate with age and density of animals. Regardless of different densities and ages of animals as well as health condition of shrimps, however, there were low differences in daily biomass of shrimp consumed per kg body weight of puffer. This finding suggests that puffer preys on healthy shrimps when moribund shrimps were not sufficient. Therefore, farmers should consider the total biomass of puffer as well as density and stocking time when they stock puffer into shrimp ponds for polyculture.

• Journal of Aquaculture
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• v.19 no.3
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• pp.210-215
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• 2006

An experiment was conducted to investigate the effects of four water temperatures (10, 15, 20, and $25^{\circ}C$) in combination with three photoperiods (24L:0D, 12L: 12D, and OL:24D) on the oxygen consumption rate of juvenile dark-banded rockfish, Sebastes inermis (mean body weight $20.5{\pm}0.7g$). The oxygen consumption rates of S. inermis were measured in triplicate for 24 hours using a continuous flow-through respirometer. Different combinations of water temperatures and photoperiods resulted in significant differences in the mean oxygen consumption rate of S. inermis (P<0.001). The oxygen consumption increased with increasing water temperatures for all photoperiod treatments (P<0.01). Mean oxygen consumption rates at 10, 15,20 and $25^{\circ}C$ ranged $178.3\sim283.5,\;386.7\sim530.7,\;529.2\sim754.3$ and $590.0\sim785.5mg\;O_2kg^{-1}h^{-1}$, respectively. $Q_{10}$ values ranged $3.17\sim5.51$ between 10 and $15^{\circ}C,\;1.87\sim2.10$ between 15 and $20^{\circ}C$ and $1.08\siml.24$ between 20 and $25^{\circ}C$, respectively. Fish held in continuous darkness (OL:24D) used consistently less okygen than fish exposed to continuous light (P<0.05). The mean oxygen consumption offish in a 12L:12D photoperiod was higher than that offish in 24L:0D and 0L:24D photoperiods under all temperature treatments except $10^{\circ}C$. The oxygen consumption of fish exposed to the 12L:12D photoperiod was significantly higher during the light phase than during the dark phase under all temperature treatments except $10^{\circ}C\;(P<0.05)$. This study provides empirical data for estimating oxygen consumption of S. inermis under given condition. This result has application for culture management and bioenergetic model for growth of this species.

• Korean Journal of Ichthyology
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• v.13 no.2
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• pp.129-135
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• 2001

Matured adults of Siniperca scherzeri were collected from Soyangdam and Hongchun river, Gangwon-do, Korea. The fertilized eggs were hatched and reared in the laboratory of the Korea Ocean Research and Development Institute. Osteological development of the larvae and juveniles of Siniperca scherzeri were investigated. Three days after hatching, the larva (6.12 mm in total length: TL) had partly ossified parasphenoid, clavicle, hyomandibular, preopercle, opercle and jaw bones with 7 to 8 canine teeth. The ascending process of premaxillary and ca 19 and 23 teeth on the premaxillary and dentary, respectively, were ossified at 10 days after hatching. Also at 10 days, the vertebral columns of the larvae (6.85 mm in TL) were posterioly ossified to the 5~7th vertebra, and ossification was completed in the juvenile (10.99 mm in TL) on the 22 nd day. Thus ossification began 3 days after hatching, and was completed 22 days after hatching.

• Korean Journal of Ichthyology
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• v.27 no.2
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• pp.71-77
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• 2015

Morphological changes in eggs and larvae of spotted knifejaw, Oplegnathus punctatus were observed by cultivation of fertilized eggs to juvenile stage. Fertilized egg was demersal and transparent. The egg has one oil glouble and its size ranged 1.01~1.15 mm ($1.08{\pm}0.10mm$; $mean{\pm}SD$, n=20). Culture chambers were maintained $22.5{\sim}24.5^{\circ}C$ in water temperature and 33.5~34.5ppt in salinity. It took 25 mins from fertilization to the blastoderm stage, 55 mins to 2 cell stage and 20 hrs 50 mins to hatching. Newly hatched yolksac larvae ranged 2.59~3.02 mm ($2.81{\pm}0.25mm$, n=5) in total length, and mouth and anus were not still open. Yolk and oil globule were absorbed 2 days after hatching (DAH). Flexion larvae in 12 DAH ranged 3.02~3.07 mm TL ($3.04{\pm}0.04mm$), and the caudal fin grew to fan-shaped, melanophores appeared on top of digestive canal.

• Korean Journal of Ichthyology
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• v.28 no.3
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• pp.156-163
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• 2016

Egg development and early life history of Korean southern spine loach, Iksookimia hugowolfeldi, were observed in the present study. Eggs were obtained after injecting females with 0.5 mL/kg of Ovarprim. Eggs were artificially fertilized using the dry method in the laboratory. Number of spawned eggs were $1,933{\pm}530per$ individual. Mature eggs were slightly adhesive with light yellowish coloring, and they measured $1.35{\pm}0.03mm$ in diameter. Hatching of the embryo occurred 56 h (50%) after fertilization at water temperature $25^{\circ}C$, and newly hatched larvae were averaged of $5.6{\pm}0.18mm$ in total length. At 5 days after hatching, larvae averaged $7.8{\pm}0.31mm$ in total length and their yolk sacs had been completely absorbed. Beginning at 15 days after hatching, the fish entered the juvenile stage and reached $13.2{\pm}0.87mm$ in total length. At 100 days after hatching, the band patterns and external form of juvenile were similar to those of adults, and they averaged $49.2{\pm}4.29mm$ in total length.

• Journal of Aquaculture
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• v.11 no.1
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• pp.19-29
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• 1998

An 18-week growth trial was conducted in flow-through aquarium system to evaluate the practical dietary protein sources for juvenile abalone (Haliotis discus hannai). Three replicate groups of the abalone averaging 0.11g were fed one of ten diets containing casein, white fish meal (WFM), meat meal (MM), feather meal (FM), blood meal (BM), soybean meal (SM), corn gluten meal (CGM), cotton seed meal (CSM), Undaria powder (UP), or wheat flour (WF) as a dietary protein source. In addition, these dietary protein sources were cmpared with algae such as raw Undaria or dried Laminaria. Weight gain of abalone fed the diets containing casein, WFM, SM, CSM, or UP was significantly higher (P<0.05) than those of abalone fed other diets, and this value of abalone fed FM, BM, CGM, or algae was lower than other groups. Shell length, shell width, body wt./shell length ratio, and body wt./shell width ratio of abalone fed casein, WFM, SM, CSM, UP, and WF were also highe (P<0.05) than those of other groups. There were no significant difference (P>0.05) in moisture and protein contents of soft body among all diets. The data obtained in this study indicate that each of the casein, WFM, SM, CSM or UP is good dietary protein source for juvenile abalone.