• Korean Journal of Ichthyology
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• v.34 no.1
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• pp.16-24
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• 2022

The eggs development and early life history of Sarcocheilichthys variegatus wakiyae was investigated. The adult fishes were collected in Yeongsangang River, Damyang-gun, Jeollanam-do, Korea, and their spawning inducement was carried by sex maturation hormone (Ovaprim) injections. Spawning amount was mean 31±3.5 Mature eggs were cicular in shape and mean 2.40±0.05 mm in diameter. Hatching period of the embryo was 230 to 240 hours after fertilization under water temperature of 22℃. The newly hatched larvae were 10.7±0.19 mm in total length (TL). 3 days after hatching, postlarvae was measured 12.0±0.13 mm in TL and the tip of the caudal fin was bent at 45°. 11 days after hatching, it was measured 14.6±0.13 mm in TL, and transferred to juvenile as the number of fins (iii7 dorsal fin, iii6 anal fin, i7 ventral fins) reached a constant number of each part.

• Korean Journal of Ichthyology
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• v.35 no.1
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• pp.39-43
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• 2023

The water temperature and salinity have an important effect on the growth and survival of rearing fish. This study investigates the effect of water temperature and salinity on larvae and juveniles of Platycephalus indicus. The experimental water temperature was set to 13, 16, 19, 22, and 25℃, respectively, and the salinity was set to 7, 14, 21, 28, and 32 psu, respectively. Ten individuals were randomly collected daily and measured the total length using a stereo microscope. The growth rate was the highest at 25℃ (21.62±0.14 mm), 28 psu (15.02±0.05 mm) and the lowest at 13℃ (7.04±0.05 mm), 7 psu. The survival rate was the highest at 22℃ (69.2%), 32 psu (84.1%) and the lowest at 13℃ (15.1%), 7 psu. This study demonstrates that the water temperature and salinity affected the survival and growth of Platycephalus indicus larvae and the juvenile.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.4
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• pp.407-412
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• 2013

We performed four sets of feeding trials to establish optimum feed size (Exp-I), stocking density (Exp-II) and feeding frequency (Exp-III and IV) for Korean rockfish. In Exp-I, three different particle sizes of a commercial diet (small, 2.0-2.1 mm; medium, 2.4-3.2 mm; and large, 4.0-5.3 mm) were fed to four replicate groups of fish ($22.8{\pm}0.1g$), each of which was fed to apparent satiation for six weeks. In Exp-II, fish ($44.3{\pm}0.4g$) were reared at four stocking densities (1.5, 3.0, 4.5 and 6.0 $kg/m^3$) and fed a commercial diet to apparent satiation for four weeks. In Exp-III, fish ($14.8{\pm}0.1g$) were fed a commercial diet once, twice, thrice, $4{\times}$ or $5{\times}$ a day at a feeding ratio of 3.25% of body mass. Another group of fish was fed the same commercial diet $5{\times}$ a day to apparent satiation; this treatment was designated FS (five times satiation/day). In Exp-IV, fish ($31.3{\pm}0.1g$) were fed a commercial diet once, twice, thrice or $4{\times}$ a day to apparent satiation. Another group of fish was fed to apparent satiation once every 48 hours. In Exp-I, fish fed the large particle (4.0-5.3 mm) diet had a significantly higher feed conversion ratio and lower protein efficiency ratio than fish fed the small particle diet. In Exp-II, groups of fish reared at densities of 4.5 and 6.0 $kg/m^3$ had significantly higher feed intake and growth performance than fish reared at 1.5 and 3.0 $kg/m^3$. In Exp-III, fish fed to apparent satiation had significantly higher growth performances than fish fed once or $4{\times}$ a day. A significantly higher feed conversion ratio and a lower protein efficiency ratio were obtained in the FS group. In Exp-IV, growth performance and feed utilization efficiency were not significantly affected by experimental variation in feeding frequency. Fish fed to apparent satiation once every 48 hours had better feed utilization than those in other treatments and growth performances of those were comparable. Therefore, the optimum feed particle size, stocking density and feeding frequency for Korean rockfish under conditions we used were 2.0-3.2 mm, 4.5-6.0 $kg/m^3$, and once a day or once every 48 hour, respectively.

• Korean Journal of Ichthyology
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• v.35 no.4
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• pp.263-269
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• 2023

This study aims to contribute to the research on resource recovery for the rapidly declining population of Liparis tanakae by observing the larval development process and the morphology of juveniles based on their growth. Natural spawning eggs collected in Yeosu were used for observing the process of egg development and larval morphology. The water temperature during the rearing process was maintained at 12.3~13.5℃ (average 12.7℃). The fertilized eggs had an egg diameter ranging from 1.57 to 1.79 mm (average 1.71 mm) and were spherical and adhesive. Within 4 hours 35 minutes after fertilization, they reached the two-cell stage, and after 74 hours 10 minutes, the formation of the yolk sac began. At 106 hours post-fertilization, a caudal fin appeared at the tail tip. Hatching began at 526 hours, and the larvae developed with the yolk sac positioned just behind the eyes. The newly hatched larvae had both the mouth and anus open. Melanophores appeared inside the lower jaw and around the tail on the third day after hatching. By the 16th day after hatching, most of the yolk was absorbed, and melanophores were visible in the head region. Finally, on the 63rd day after hatching, the head region significantly developed, and the body shape and mouth were similar to those of an adult fish, signifying the transition to the juvenile stage. This study will serve as valuable data for aquaculture techniques related to the conservation and restoration of fish species based on the hatching and juvenile morphology of Liparis tanakae.

• Journal of fish pathology
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• v.24 no.3
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• pp.237-245
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• 2011

Disease survey was conducted to investigate the cause of high mortality in 23 farms of eel, Anguilla japonica, during the period from 2000 to 2010. Seven kinds of fish pathogens were confirmed in the tested fish, which included: Pseudodactylogyrus sp. (infection rate: 65.5%, 19/29 samples), aquabirnavirus (ABV, 62.5%, 15/24 samples), Edwardsiella sp. (44%, 11/25 samples), anguillid herpesvirus 1 (AngHV1, 16.7%, 2/12 samples), Heterosporis sp. (10.3%, 3/29 samples), Vibrio sp. (8%, 2/25 samples), Trichodina sp. (3.4%, 1/29 samples). The rate of single infection was 44.8% (13/29 samples), while 62.1% (18/29 samples) showed mixed type of infection with 2 to 5 different pathogens. The most predominant mixed infection were Pseudodactylogyrus sp.-Edwardsiella sp. (10.3%, 3/29 samples), Pseudodactylogyrus sp.-ABV (10.3%, 3/29 samples), Edwardsiella sp.-ABV (6.9%, 2/29 samples). Infection by the above infectious parasites, bacteria and virus was confirmed in tested eels of juvenile to adult sizes that were cultured at $25{\sim}30^{\circ}C$ in almost the examined farms.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.312-320
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• 2021

In this study, we aimed to develop a feed additive that can promote the growth of stone flounder (Kareius bicoloratus). To this end, we fermented mealworm medium (5%, w/v) with lactic acid bacteria (LAB) with antibacterial function (HeTm_LpWpPa) and evaluated its efficacy as a feed additive. Fish (approximately 5-6 g) were reared in six completely recirculating tanks (100 fish/tank) for 6 weeks. The total length of fish with and without HeTm_LpWpPa supplementation was 8.26 and 8.42 cm and body weight was 19.71 and 20.28 g, respectively, at 6 weeks. The weight gain of the control and experimental groups was 223.26 % and 248.76 %, respectively. The specific growth rate at 6 weeks was 2.79 % (control) and 2.98% (experimental), and the growth rate of the experimental group was slightly higher (0.19 %) than that of the control group. At the end of the experiment (i.e. 6 weeks), the number of fish below the mean weight in the experimental group was 3 (1 %) and that in the control group was 17 (5.7 %). These results indicate that feed supplementation of 10 % HeTm_LpWpPa could be utilized to promote the growth of flounder in farming.

• Journal of Aquaculture
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• v.21 no.4
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• pp.272-277
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• 2008

We investigated the growth and survival in seedling production, and growth performance was compared with the different rearing tanks and protein source of formulated feed for juvenile Pacific bluefin tuna Thunnus orientalis (PBT). The survival rate at the end of nursery culture at 30 days after hatching was $0.69{\pm}0.40%$, and total length and mean body weight were $49.83{\pm}2.52\;mm$ and $1.03{\pm}0.09\;g$, respectively. Growth performance has no significant difference in fish reared by different tanks forms for 10 days. In order to develop an artificial diet, we evaluated the dietary utility of enzyme treated fish meal (Bio-CP, BIO) for juvenile PBT. Only diet BIO sustained similar growth and higher feed efficiency, and final carcass lipid content as compared to those of Sand lance (SL) These results revealed that BIO-CP a suitable dietary protein source, could sustain growth of PBT.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.1
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• pp.16-23
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• 1987

The cyprinid loach, Misgurnus mizolepis $G\ddot{u}nther$, a freshwater teleost, is a member of the family Cobitidae and is known to distribute in Korea and China. This fish is considered to be an excellent food fish in Korea. This report is a description of the gross morphology of the embryos and larvae up to the development of juvenile period of life. The eggs were obtained by injecting gonadotropin and fertilized by wet method in the laboratory on July 10 in 1986. The inseminated eggs were rinsed with tap water and incubated at $25^{\circ}C$. Live, freshly laid eggs were separative, demersal, adhesive, light yellow and average 1.1mm in diameter. The hatching took place in about yellow and average 1.1mm in diameter. The hatching took place in about 24 hours after fertilization. The newly hatched larvae were average 2.7 mm in total length possessing yolk sac and 35-36 myotomes. Ten hours after hatching, the prelarvae attained 3.5 mm in total length. The first heart pulse and melanophores at the side of the body were observed at this stage. Yolk sac was completely reserved at four days after hatching. The larvae that was cultured 24 days after hatching, 15.4-16.4 mm in total length, entered the juvenile period of life. All the un rays were already peresent; D. III 6, A. III, 5, P.10, V. 4-5, C.14.

• Journal of Aquaculture
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• v.16 no.2
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• pp.88-93
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• 2003

Diets containing 3000 kcal/kg at the crude protein (CP) level of 40% (Diet 1) and 4000 kcal/kg at the CP level of 50% (Diet 2) were fed to the juvenile rockfish, Sebastes schlegeli (35.6 g) at 3-4% body weight for a period of 28 days. Diet 2 promoted significantly higher growth and feed efficiency than Diet 1. Oxygen uptake increased with increasing body weight. The oxygen uptake-body weight relationship of diets 1 and 2 were best expressed by y=0.3218 $e^{0.0592x}$ (R=0.8494) and y=0.3612 $e^{0.0532x}$ ($R^2$=0.8805), respectively. Assimilation efficiency (AE), gross growth efficiency ( $K_1$) and net growth efficiency ( $K_2$) of the fish fed on Diet 2 were 73.8, 16.0 and 22.6%, respec- tively. Fish fed on Diet 2 showed significantly higher AE, $K_1$ and $K_2$ than those fed on Diet 1. Hence Diet 2 con- taining 4000 kcal/ kg with crude protein of 50% is recommended for the Korean rockfish.kfish.

• 한국해양학회지
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• v.19 no.2
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• pp.217-227
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• 1984

Fish samples were collected by a trap net during 1981∼82 at the mouth of Cheonsu Bay to determine seasonal fluctuations in abundance and species composition. Examination of a series of trap net catches indicated that trap net data could be used, at least, for a qualitative analyses of a fish community and for a quantitative study of some pelagic fishes of Cheonsu Bay. Of the 64 species collected, a few temporal components predominated in abundance because of great seasonal fluctuations of water temperature. The early spring catch showed a low abundance value, and two cold weather seasonals, juvenile Enedrias fangi and Ammodytes personatus predominated in number and in weight. The number of species, abundance value in number and in biomass showed a peak in late spring when fishes move into bay for spawning and feeding after over-winterinig in the sea. Three pelagic species or warm weather seasonals, Harengula zunasi , Ammodytes personatus and Konosirus punctatus, predominated in abundance values. In this period night catch was significantly larger than day catch in terms of number of species, abundance in number and in weight Summer data showed a marked reduction of the number of species and abundance due to the loss of spawners probably by mortality or wide dipersion after spawning. A slight increase in abundance was observed in autumn by recruitment of the young-of-the-years. This catch was predominated by three juvenile fishes, H. zunasi, E. japonica and K. punctatus, which were the same species as in spring. The autumn catch showed no significant difference between day and night compositions.