• Journal of Aquaculture
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• v.19 no.2
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• pp.125-132
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• 2006

Black rockfish larvae and juveniles were reared for 95 days after parturition (DAP) in order to determine four enzyme activities (trypsin, pepsine-like enzyme, lipase, amylase) during ontogeny. Larvae were fed rotifers Brachionus plicatilis from 1 to 25 DAP, Artemia nauplii from 10 to 78 DAP and then gradually changed to pelleted feed from 30 DAP. Temperature was kept between $13.5{\sim}14.9^{\circ}C$. Trypsin and lipase activities were found in 2 DAP larvae ($7.0{\pm}1.5$ unit and $4.5{\pm}1.4$ unit, $mean{\pm}SD$, respectively). The evolution of both enzymes activities showed a profile marked by drastic increases between postflexion and juvenile stage. There is an increment on specific trypsin activity at 10 DAP, corresponding with the beginning of Artemia feeding. Pepsin-like enzyme activity was found at 11 DAP and increased drastically from 56 DAP, cor-responding with the initiation of juvenile stage. Amylase activity was also found at 11 DAP and maintained at a low level up to 38 DAP followed by a drastic increase from 39 DAP to 50 DAP. Considering our results of both trypsin and pepsin-like enzyme activities, it might be concluded that higher somatic growth of Sebastes inermis could be possible with the initiation juvenile of stage and the early juvenile stage is a suit-able period for feeding an artificial diet for fish.

• Korean Journal of Ichthyology
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• v.28 no.3
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• pp.179-185
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• 2016

To develop cultivation technique for Acipenser ruthenus and secure basic taxonomic materials, this study examined egg development and larva morphological development. This study used a couple of male and female broodstork matured in a PVC circle water tank (Ø 5 m) with the water temperature of $16.0{\pm}1.0^{\circ}C$ in June 2005. They were oval opaque and sinking cohesive eggs and the sizes of them were between $3.83{\sim}3.85(3.84{\pm}0.01)mm$ (n=10). As for the egg development, the dry process was adopted with artificial insemination in this study, and an hour after the insemination, the embryo disks were developed, 31 hours after the insemination, they reached the end of gastrula stage, and 82 hours (50%) after the insemination, they were hatched. Right after the hatch, the total lengths of larvae were $10.1{\sim}10.3(10.2{\pm}0.11)mm$ (n=10) with big yolks in the venter. 17 days after the hatch, the total lengths of them were $26.2{\sim}32.4(29.3{\pm}4.39)mm$ (n=10) and in the front of a dorsal fin there were 11 scute scales that started to make tracing development. As 50 days after the hatch, the total lengths were $86.4{\sim}93.1(89.8{\pm}4.71)mm$ (n=10), and fin rays all reached integer, they were moved to the larva apparatus.

• Korean Journal of Ichthyology
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• v.9 no.1
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• pp.99-107
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• 1997

The early life history and reproductive ecology of Siniperca scherzeri were studied to obtain fundamental information in aquaculture and reinforcement of natural population in Soyang Lake, Buk-myon, Chunchon-shi, Kangwon-do from June to October 1996. Symptric species with adult fishes (+1 ages) of Siniperca scherzeri were 11 species belonging to 6 families and 10 genera and those with Juveniles (2~3 months) were 5 species belonging to 4 families and 5 genera. The sex radio of this species were 1 (female, 85) : 1.24 (male, 105). Adult and juvenile of this species were predominantly piscivores. Bluegill, Lepomis macrochirus, Zacco platypus, common carp, Cyprinus carpio, unidentified fish and shrimp were important components of the food items. The spherical eggs were demersal and separative without a colorless transparent chorion and slightly yellowish yolk containing one large oil globule (0.5~0.7mm). The egg just after fertilization were measuring 1.72~2.05mm (n=30), and expanded to 2.27~2.58mm (n=30) in diameter after 30 min. Hatching occurred 130~155 hrs after fertilization at water temperature of $20{\sim}25^{\circ}C$ and newly hatched larvae measuring 5.5~7.1mm in total length. In the newly hatched larvae, numerous branched malanophores were distributed on the yolk and abdomen of caudal peduncle. In ten-day old larvae, the yolk was mostly absorbed and the head spines and the teeth were well developed. All fin rays were formed and total length of the larvae were reached 13.6~15.6mm at 20 days after hatching. In fifty-five day old larvae were similar in both body shape and color to adult. The juvenile stage at 4 months after hatching were attained 86.4~95.3mm (n=7) in total length and 8.77~14.78g (n=7) in body weight.

• Korean Journal of Ichthyology
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• v.19 no.4
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• pp.318-323
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• 2007

The feeding habits of Pacific cod (Gadus macrocephalus) were studied based on the examination of stomach contents of 192 specimens collected from November, 2005 to January, 2006 in the coastal waters off Gadeok-do, Korea. The size of Pacific cod ranged from 35 to 82 cm in standard length (SL). Pacific cod mainly consumed shrimps such as Eualus spathulirostris, Crogon hakodatei and C. affinis and fishes. Its diet also included small quantities of cephalopods, amphipods, hermit crabs and crabs. Individuals between 35 cm and 45 cm SL mainly consumed shrimps. The portion of shrimps decreased with increasing fish size, and this decrease was paralleled with increased consumption of fishes and cephalopods. In this study we found Syngnathus schlegeli in the stomach contents of many Pacific cod specimens. S. schlegeli is a typical seagrass fish species which inhabits in seagrass beds, This fact means that Pacific cods stay in the seagrass beds during spawning period. Therefore migration of Pacific cod to coastal waters off Gadeok-do during spawning period seems to be a survival strategy for its larvae and small juveniles to stay in seagrass beds which provide with abundant foods and shelters to many commercial fish species.

• Korean Journal of Ichthyology
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• v.29 no.1
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• pp.62-68
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• 2017

The Alaska pollock (Gadus chalcogrammus) belongs to the family Gadidae; it is a cold water fish, and has been developed as a novel aquaculture species in Korea. In this study, we describe ongoing surveillance for aquatic animal pathogens based on growth stages. We investigated bacterial flora in rearing water, and monitored pathogens; we also analyzed histopathological traits of abnormal fish. In rearing water, the total bacterial counts were $2.1{\times}10^3cfu/mL$ and Vibrio spp. (52%) were predominant in the larvae stage. In the juvenile and adult stages, the total bacterial counts were $3.4{\times}10^3$ and $3.2{\times}10^2cfu/mL$, respectively (with Pseudomonas sp. as the predominant species; 90% and 52%). This result revealed that the bacterial flora in rearing water changed depending on the feeding types. No virulent-bacteria or problematic viruses (VHSV, viral hemorrhagic septicemia virus; NNV, nervous necrosis virus; MBV, marine birnavirus) were detected from outwardly healthy fish using either culture or PCR assay. Some juveniles (less than 5%) had gas bubbles on the gill lamellae, degeneration of the corneal epithelium, and choroid gland degeneration, suggesting that these symptoms were caused by external injury and secondary infection by opportunistic bacteria. Disease management is important to cope with disease emergence in the novel aquaculture species Alaska pollock.

• Korean Journal of Ichthyology
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• v.10 no.1
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• pp.106-114
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• 1998

In order to estimate energy budget of the rockfish, Sebastes schlegeli juvenile, during the period from parturition to juvenile, of rockfish were reared at constant condition of water temperature($16^{\circ}C$ and $20^{\circ}C$). Energy used by the reared juveniles were calculated from estimates of data on growth, oxygen consumption, nitrogen excretion, feeding and energy content. After parturition, total length of juvenile was 4.56~5.49mm(average 4.97mm, n=20), and the average dally growth rates were 0.50mm at $20^{\circ}C$. The weight-specific oxygen consumption and nitrogen excretion rates decreased with increasing body weight. Temperature significantly affected oxygen consumption and nitrogen execretion rates, with the higher rates at $20^{\circ}C$ than $16^{\circ}C$. During the 25 days from parturition to jllveniles, feeding rates were 65.8cal at $16^{\circ}C$, and 89.2cal at $20^{\circ}C$. The assimilation effeciency estimated by nitrogen content of food and egested feces were 85.21% at $16^{\circ}C$ and $20^{\circ}C$. During the period from parturition to juvenile, energy was used the higher in body growth than in oxygen consumption. The gross growth efficiencies($K_1$)and net growth efficiencies($K_2$) of the rockfish, Sebastes schlegeli juvenile ranged from 43% to 47% and from 50% to 55%, respectively.

• Korean Journal of Ichthyology
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• v.36 no.2
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• pp.120-128
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• 2024

In this study, the characteristics of the early life history were investigated for the Hypomesus nipponensis in the west coast Daeho Bay. Egg's were adhesive eggs that had the property of sinking in water in a circular shape. The size of mature eggs was 0.52~0.66 (average of 0.59±0.03, n=30) mm. The hatching time took 140 hours at a water temperature of 22~23℃. Immediately after hatching, the yolk sac larvae was 4.78~5.60 (average of 5.25±0.26, n=30) mm in total length, and the mouth and anus were not completely opened. On the 7 days after hatching, the preflexion larvae was 5.91~6.64 (6.32±0.21) mm in total length, and the mouth and anus were opened, and feeding activities were started. On the 25 days after hatching, the flexion larvae was 9.70~12.3 (10.2±0.63) mm in total length, and the end of the spine at the tail end began to bend upward. On the 42 days after hatching, the postflexion larvae was 14.1~18.8 (16.9±1.44) mm in total length, and the end of the spine at the tail was completely bent at 45°. On the 56 days after hatching, it reached the integer with 10 dorsal fins, 16 anal fins, 7 ventral fins, and 19 caudal fins. According to the study, there were spot-shaped melanophore vesicles under the pectoral fins during the incubation period, the different positions of the egg yolk compared to the battlefield, the deposition of melanophore vesicles on the back and under the body of the caudal part during the postflexion larvae period, and the absence of melanophore vesicles on the torso between the head and the starting point of the dorsal fin. It was distinguished from related species in that melanophore vesicles were deposited in one row from the back of the body to the caudal part during the juvenile period.

• Korean Journal of Ichthyology
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• v.24 no.1
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• pp.48-55
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• 2012

Egg development and early life history of the slender shinner, $Pseudopungtungia$ $tenuicorpa$ were investigated to provide basic information regarding biological characteristics and restoration in 2010. Eggs were obtained by injecting females with Ovaprim and then fertilized using the dry method in the laboratory. Matured eggs were strongly adhesive, opaque and grayish and measured $1.96{\pm}0.08mm$(mean${\pm}$SD) in diameter. Fertilized eggs hatched 240 h after fertilization at $23^{\circ}C$, and newly hatched larvae an average $8.6{\pm}0.25mm$ in total length. At 2 days after hatching, larvae averaged $9.0{\pm}0.37mm$ in total length and their yolk sacs had been completely absorbed. About at 10 days after hatching, they beacme to juvenile stage and reached $10.6{\pm}0.44mm$ in total length. At 70 days after hatching, the band patterns and external form of juveniles were similar to those of adults, and they averaged $36.0{\pm}2.13mm$ in total length.

• Korean Journal of Ichthyology
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• v.26 no.2
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• pp.89-98
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• 2014

Eggs development and early life history of the endangered Korean dwarf loach, Kichulchoia brevifasciata (Teleostei: Cobitidae) was investigated to provide basic information regarding biological characteristics and restoration. Adult fish specimens were sampled using a spoon net at Geurnsan-myeon, Goheung-gun, Jeollanam-do, Korea from June to July 2011. Since, spawning characteristics were analyzed, and females were induced to spawn by injecting Ovaprim (0.5 mL/kg) and their eggs were artificially fertilized with sperms by the dry method in the laboratory. Total length of mature female were 46~76 mm with GSI $9.6{\pm}3.77%$, and total length of mature male was 42~52 mm with GSI $3.5{\pm}1.04%$. Sex ratio (♂/♀) was 0.10, and there were no secondary sexual characteristics. The number of mature eggs was averaged $60{\pm}28.7$ per female. The lemon yellow eggs were slightly adhesive $1.46{\pm}0.07mm$ in diameter. The embryo hatched approximately 66 h after fertilization at $25^{\circ}C$, and the hatched larvae were averaged $5.5{\pm}0.07mm$ in total length (TL). At 6 days after hatching, the larvae averaged $9.0{\pm}0.29mm$(TL) and their yolk sac was completely absorbed. At 17 days after hatching, they entered the juvenile stage and reached $12.6{\pm}0.24mm$ (TL). At 80 days after hatching, the band patterns and external form of the juveniles were similar to those of adults, and they averaged $33.0{\pm}2.19mm$(TL).

• 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).