• 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.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.12 no.3
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• pp.159-169
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• 2007

Excessive input of organic matters from fish cage farms to the coastal waters has been considered as one of the major factors disturbing their benthic ecosystem. Sediment samples were taken from around the two fish cage zones (A and B) in Tongyeong coast in June and August 2003, to evaluate the ecological impacts of fish cage farming activity on the macrobenthic polychaete communities. Polychaete accounted for $81{\sim}87%$ of the total macrofauna individuals from each of the sampling stations. The number of species, abundance, diversity and dominant species of polychaete were rapidly changed with the distance from the fish cages. Within 10 m from the fish cages, Capitella capitata, which is a bio-indicator for the highly enriched sediments, was a dominant species and the lowest diversity was recorded. In particular, the maximum density (${\sim}18,410\;ind.m^2$) of C. capitata was found at Farm A where fish cages were more densely established within a semi-enclosed bay system. The sampling zone between 10 m and 15 m showed a rapid decrease of C. capitata with a rapid increase of the numbers of species, implying that this zone may be an ecotone point from a highly to a slightly enriched area. In the sampling zone between 15 m and 60 m, a transitional zone, which represents slightly enriched condition before normal one, was observed with additional increase and maintenance of the number of species and density of polychaete. In addition, the potential bio-indicators of organic enrichment, such as Lumbrineris longifolia and Aphelochaeta monilaris were the predominant species in the sampling zone. Multidimensional scaling (MDS) ordination plots and k-dominance curves confirmed the above results on the gradual changes in the macrobenthic polychaete communities. Our findings suggest that the magnitude of impact of fish cage farming activity on polychaete communities is probably governed by a distance from fish cage, density of fish cage and geomorphological characteristics around fish cage farm.

• Korean Journal of Environment and Ecology
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• v.38 no.1
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• pp.55-66
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• 2024

This study conducted a survey to investigate the characteristics of fish communities and the inhabiting status of endangered species in the Byekgye Stream, Korea from April to September 2020. A total of 3,415 fish of 9 families and 31 species were collected from 7 survey stations during the survey period. The dominant species was Zacco koreanus (relative abundance of 31.2%), and the subdominant species was Z. platypus (15.0%), followed by Pungtungia herzi (11.7%), Acheilognathus yamatsutae (5.4%), A. lanceolata intermedia (4.8%), Rhinogobius brunneus (4.4%), and Pseudopungtungia tenuicorpa (4.3%). Among the fish species collected, 19 (61.3%) were identified as Korean endemic species, and two cold-water fish species sensitive to climate change (Rhynchocypris kumgangensis and Cottus koreanus) were collected. Four species were designated as class II endangered wildlife by the Ministry of Environment: A. signifer, P. tenuicorpa, Rhodeus pseudosericeus, and C. koreanus. A. signifer and P. tenuicorpa mainly inhabited the mid to lower streams, R. pseudosericeus in the midstream, and R. pseudosericeus in the upstream. P. tenuicorpa inhabited in large numbers, and estimating the age by total length-frequency distribution in July, the total length of the 26-35 mm group was estimated as 0 years old, the 54-75 mm group as 1 year old, 82-97 mm group as 2 years old, 104-109 mm group as 3 years or older. The cluster analysis showed that the dominance index decreased from upstream to downstream, but the diversity, evenness, and richness index increased. The water quality of Byekgye Stream was evaluated as good overall since the river health (fish assessment index, FAI) using fish was evaluated as excellent (5 stations) and good (2 stations). Byekgye Stream has relatively well-preserved habitats, but conservation measures are required as habitats are disturbed by river repair work in some parts of the midstream and downstream areas where many endangered species inhabit.

• Journal of the Korean Society of Marine Environment & Safety
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• v.30 no.1
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• pp.13-19
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• 2024

An analysis of the coastal water temperature in the Tongyeong waters, the eastern sea of the South Sea of Korea, revealed that the water temperature rose sharply before the typhoon made landfall. The water temperature rise occurred throughout the entire water column. An analysis of the sea surface temperature data observed by NOAA(National Oceanic and Atmospheric Administration) satellites, indicated that sea water with a temperature of 30℃ existed in the eastern waters of the eastern South Sea of Korea before the typhoon landed. The southeastern sea of Korea is an area where ocean currents prevail from west to east owing to the Tsushima Warm Current. However, an analysis of the satellite data showed that seawater at 30℃ moved from east to west, indicating that it was affected by the Ekman transport caused by the typhoon before landing. In addition, because the eastern waters of the South Sea are not as deep as those of the East Sea, the water temperature of the entire water layer may remain constant owing to vertical mixing caused by the wind. Because the rise in water temperature in each water layer occurred on the same day, the rise in the bottom water temperature can be considered as owing to vertical mixing. Indeed, the southeastern sea of Korea is a sea area where the water temperature can rise rapidly depending on the direction of approach of the typhoon and the location of high temperature formation.

• Korean Journal of Environment and Ecology
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• v.38 no.3
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• pp.246-262
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• 2024

The survey conducted from 2018 to 2020 aimed to investigate the changes in fish fauna and community characteristics in the upper reaches of the Seomgang River, Korea. During the survey period, 35 sites were selected, resulting in the collection of 7,817 fish belonging to 12 families and 40 species. The dominant species was Zacco koreanus, with a relative abundance of 34.5%, followed by Z. platypus at 28.7%. Other significant species included Rhynchocypris oxycephalus (10.2%), Pungtungia herzi (5.3%), and Squalidus gracilis majimae (4.3%). Notably, four protected species - Acheilognathus signifer, Gobiobotia brevibarba, and Cottus koreanus, designated as class II endangered wildlife by the Ministry of Environment- were identified. These species predominantly inhabit the middle and lower reaches, except for Gobiobotia brevibarba, which is found in the upper reaches. Nineteen species, accounting for a 47.5% endemism rate, were endemic to Korea. The study also noted the presence of one climate-sensitive species, Cottus koreanus, and two exotic species, Carassius cuvieri and Micropterus salmoides. Community analysis indicated a trend of decreasing dominance and increasing diversity and richness from upstream to downstream, with a distinct division into uppermost reaches, upper reaches, middle and lower reaches, and lakes. The construction of the Hwaseong Dam has had a significant direct and indirect impact on the fish community. The habitat and abundance of endangered species such as R. pseudosericeus, A. signifer, and G. brevibarba decreased dramatically immediately after the dam's construction, transforming the submerged area from lotic to lentic environments. Approximately 20 years later, the habitats have stabilized, leading to an increase in the fish population and a recovery of the previously diminished endangered species. The river health (FAI) was also evaluated, with 27 sites rated as very good (A), seven as good (B), and one as fair (C). However, endangered species such as A. signifer continue to face threats from dam and river construction, while C. Koreanus has experienced a severe population decline due to river works. Additionally, the presence of the ecosystem-disrupting species M. salmoides in Hwaseong Lake raises concerns. To ensure a stable habitat for fish in the upper reaches of the Seomgang River, it is crucial to avoid indiscriminate river construction, urgently implement restoration policies for endangered species such as A. signifer, and develop management strategies to control the spread of invasive species such as bass.

• Journal of the Korean Society of Food Science and Nutrition
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• v.26 no.2
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• pp.270-284
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• 1997

Effects of dietary carotenoids were investigated on the metaboβsm and body pigmentation of rainbow trout(Salmo gairdneri), masu salmon(Oncorhynchus macrostomos), eel(Anguilla japonica), rock fish(Sebastes inermis) and black rock fish(Sebastes schlegeli). Three weeks later after depletion, these fishes were fed diet supplemented with ${\beta}-carotene$, lutein, canthaxanthin', astaxanthin or ${\beta}-apo-8'-carotenal$ for 4 to 5 weeks, respectively. Carotenoids distributed to and changed in integument were analyzed. In the integument of rainbow trout. zeaxanthin, ${\beta}-carotene$ and canthaxanthin were found to be the major carotenoids, while lutein, isocryptoxanthin and salmoxanthin were the minor carotenoids. In the integument of masu salmon, zeaxanthin was found to be the major carotenoids, while triol, lutein, tunaxanthin, ${\beta}-carotene$, ${\beta}-cryptoxanthin$ and canthaxanthin were the minor carotenoids. In the integument of eel, ${\beta}-carotene$ was found to be the major carotenoids, while lutein, zeaxanthin and ${\beta}-cryptoxanthin$ were the minor carotenoids. In the integument of rock fish, zeaxanthin, ${\beta}-carotene$, tunaxanthin$(A{\sim}C)$ and lutein were found to be the major carotenoids, while ${\beta}-cryptoxanthin$, ${\alpha}-cryptoxanthin$ and astaxanthin were the minor carotenoids. Likely in the integument of black rock fish, ${\beta}-carotene$, astaxanthin and zeaxanthin were found to be the major carotenoids, whereas ${\alpha}-cryptoxanthin$, ${\beta}-cryptoxanthin$, lutein and canthaxanthin were the minor contributor. The efficacy of body pigmentation by the accumulation of carotenoids in the integument of rainbow trout and masu salmon were the most effectively shown in the canthaxanthin group and of eel, rock fish and black rock fish were the most effectively shown in the lutein group. Based on these results in the integument of each fish, dietary carotenoids were presumably biotransformed via oxidative and reductive pathways. In the rainbow trout, ${\beta}-carotene$ was oxidized to astaxanthin via successively isocryptoxanthin, echinenone and canthaxanthin. Lutein was oxidized to canthaxanthin. Canthaxanthin was reduced to ${\beta}-carotene$ via isozeaxanthin, and astaxanthin was reduced to zeaxanthin via triol. In the masu salmon, ${\beta}-carotene$ was oxidized to zeaxanthin. Lutein was reduced to zeaxanthin via tunaxanthin. Canthaxanthin was reduced to zeaxanthin via ${\beta}-carotene$. and astaxanthin was reduced to zeaxanthin via triol. In the eel, ${\beta}-carotene$ and lutein were directly deposited but canthaxanthin was reduced to ${\beta}-carotene$, and cholesterol lowering effect by Meju supplementation might be resulted from the modulation of fecal axanthin, astaxanthin and ${\beta}-apo-8'-carotenal$ were oxidized and reduced to tunaxanthin via zeaxanthin. In the black roch fish, ${\beta}-carotene$ was oxidized to ${\beta}-cryptoxanthin$. Lutein was reduced to ${\beta}-carotene$ via ${\alpha}-cryptoxanthin$. Canthaxanthin was reduced to ${\alpha}-cryptoxanthin$ via successively ${\beta}-cryptoxanthin$ and zeaxanthin. Astaxanthin converted to tunaxanthin via isocryptoxanthin and zeaxanthin, and ${\beta}-apo-8'-carotenal$ was reduced to ${\alpha}-cryptoxanthin$ via ${\beta}-cryptoxanthin$ and zeaxanthin.

• Journal of Aquaculture
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• v.19 no.2
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• pp.84-89
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• 2006

Effect of dietary inclusion of various sources of green tea on growth, immune system and challenging test of juvenile olive flounder Paralichthys olivaceus was investigated. Five experimental diets with triplicates were prepared: control, raw leaves, dry leaves, by-product and extract. Twenty five (an initial body weight of 52.5 g) were randomly distributed into 15 of 180 L flow-through tanks. Nutrient requirements of the experimental diets satisfied growth of juvenile olive flounder. The feeding trial lasted for 7 weeks. After 7-week feeding trial, blood were sampled from three randomly chosen fish for serum analysis of Iysozyme and bactericidal activity, and ten fish were infected with Edwardsiella tarda for challenging test from each tank. Weight gain (g/fish) of fish fed the diet containing extract and control diet was significantly higher than that of fish fed the other diets. Feed efficiency ratio for fish fed the diet containing extract and control diet was significantly higher than that for fish fed the diets containing raw leaves and by-product, but not significantly different from that for fish fed the diet containing dry leaves. Serum Iysozyme activity (units/ml) of fish fed the diets containing dry leaves and extract was significantly higher than that of fish fed the diets containing raw leaves and by-product, but not significantly different from that of fish fed the control diet. Serum bactericidal activity (${\times}10^6$ bacteria/ml) of fish fed the diet containing dry leaves and extract was significantly lower than that of fish fed the diets containing raw leaves, by-product and control diet in 3 hour. However, serum bactericidal activity of fish fed the diet containing extract was significantly lower than that of fish fed the other diets in 6 hour. And serum bacterial activity was low in fish fed the diets containing dry and raw leaves, by-product, and control in 6 hour in order. Accumulative mortality (%) of fish fed the control diet was low compared to that of fish fed the diets containing raw leaves and by-product, but high compared to that of fish fed the diets containing dry leaves and extract although no significant difference was found among treatments. In considering above results, dietary inclusion of extract and dry leaves of green tea seemed to be highly effective to improve immune system and endurance against E. tarda infection of juvenile olive flounder.

• Journal of Aquaculture
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• v.11 no.4
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• pp.529-546
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• 1998

Gonadal part that developed by indifferentiation period for 6 months after hatching is made as gonad and fat body. These gonad are thin semi-transparant and undistinguished germ cell. Germinal epithelium is distinguished by development of gonad epithelial tissue from 7 months after hatching. Sex differentiation is begun by oogonia develoment at 8 months after hatching. Primary oocytes grow over germinal epithelium of gonadal cavity, at 9 months after hatching, gonadal cavity become ovarian cavity as they increasing. As soon as oocytes at 13 months after hatching are filled with the whole part of gonad, degeneration of oocyte is begun. And then, gonad has cavity tissue, a small number of oocyte are located in gonadal cavity. At 15 months after hatching, new primary oocyte develop and cavity of ovarian tissue in the central of ovarian cavity. Spermatogonia multiplicate and cavity tissue consist of testicular tissue. These gonad become hermaphrodite and then ditermine the sex of female and male. These results show the red sea bream is juvenile hermaphrodite and undif-ferentiated gonochoristic teleost. Male and female differentiation type of gonad is divided in undifferentiation stage, oogonia-like stage, ovary-like stage, ovary development stage, hermaphroditic testis stage, hermaphroditic ovary stage, and testis development stage. Undifferentiation stage is continued total lenth 18cm at 13 months after hatching. ovary-like stage is continued total length 11~18cm at 13 months after hatching. Ovary-like stage is continued total length 14~26cm at 10~14 months after hatching. Ovary development stage begins from total length 20cm, 14 months after hatching. At 20 months after hatching, 44 percent of total sampled individuals had ovary. Hermaphroditic ovary stage first begins total length 19~20 cm at 15 months after hatching, but it is not observed total length 28~29cm at 20months after hatching. Hermaphroditic testis stage first begins total length 21~22cm at 20months after hatching and is continued for 20months. Testis development stage first begins total length 20~21cm at 20 months after hatching, and is occupied 33 percent total length 28~29cm at 20 months. The beginning of sex differentiation more than 50 percent is from total length 16cm at 11 months after hatching. Sex determination begins total length 20cm, 14months after hatching in female and total length 20cm, 15 months after hatching in male. Sex determination more than 50 percent begins total length 23cm,, 17 months after hatching. Undifferentiated gonadal part of red sea bream consist gonad and fat body. As differentiation is going on and gonad is growing, fat body shrinks. This appearence is showed the same tendency in 3-year old red sea bream. 1.9mm larvae after hatching grow about 19mm larvae for 47 days. The relationship between the total length and body weight of larvae and juveniles in $BW=4.45{\times}10^{-6}TL^{3.4718}$ r=0.9820. Fishes in cage culture grow to maximum total length 28.4cm. The relationship between the total length and body weight of these fishes is $BW=2.36{\times}10^{-2}TL^{2.9180}$, r=0.9971. Undifferentiated gonadal part of red sea bream consist gonad and fat body. As differentiation is going on and gonad is growing, fat body shrinks.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.4
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• pp.599-607
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• 1998

To clarify annual reproductive cycle of Korean dark sleeper, Odontobutis platycephala (Iwata et Jeon), we examined the seasonal changes of gonadosomatic index (GSI), the proportional frequency of oocyte development stages in the ovary and the changes of sex steroid hormone levels in blood from December 1995 to November 1997. In July and August, GSI was 0.35 to 0.72 and most oocytes in the ovary were chromatin-nucleolus stage and perinucleolar stage (proportional frequency: $87\%\~96\%$). In September, GSI was 1.20 $\pm$ 0.12, some oocytes in the ovary were yolk vesifle stage (proportional frequency: $22.8\%$) and vitellogenic stage which appeared very rarely(proportional frequency: $2.2\%$). GSI increased gradually from October and reached 4.59± 0.61 to December. During this period, oocytes of vitellogenic stage increased slightly (proportional frequency in December: $22.1\%$). In January, GSI was 4.32 $\pm$ 0.72 but the proportional frequency of oocytes in vitellogenic stage increased (proportional frequency: $51.2\%$). from February, GSI was increased sharply and reached to 10.51 $\pm$ 1.04 in March, the highest value throughout the year and the proportional frequency of oocytes in vitellogenic stage also reached the highest levels (proportional frequency: $60\%$). From April, GSI was gradually decreased and fell down to 1.11 $\pm$ 0.35 in June. During this period, the proportional frequency of mature oocytes was the highest in April (proportional frequency of mature oocyte stage: $40\%$ in April, $12\%$ May, $5\%$ June) throughout the year, and atretic ovarian follicles were appeared. The blood level of estradiol-17$\beta$ ($E_2$), which stimulates the hepatic synthesis and secretion of vitellogenin, was $0.84{\pm}0.20\;ng/m{\ell}$ in August, and thereafter was not changed until December. from January, it increased sharply and reached the highest level of $ 2.85{\pm}0.35\;ng/m{\ell}$ in March throughout the year, but fell to $0.14{\pm}0.02\;ng/m{\ell}$ in July(P<0.05), 17$\alpha$-hydroxprogesterone(17$\alpha$-OHP) was the peak $13.37{\pm}0.52ng/m{\ell}$ in March, but no significant changes in other period(below $3ng/m{\ell}$, P<0.05). 17$\alpha$, 20$\beta$-dihydroxy-4-pregnen-3-one(17$\alpha$, 20$\beta$-P), which was known as the final maturation inducing hormone in teleost, was $0.74{\pm}0.09ng/m{\ell}$ in April and $0.54{\pm}0.07ng/m{\ell}$ in May, but no significant changes in other period (below $0.26\;ng/m{\ell}$, p<0.05). Taken together these results, the annual reproductive cycle of O. platycephala divided into 4 periods as follows: 1) ripe and spawning period from April to June, main spawning period was from April to May, 2) Resting period from July to August, 3) Growing period from September to December, 4) Maturing period from January to March. Moreover, It was showed that the changes of sex steroid hormone in blood played a important roles in the annual reproductive cycle of O. platycephala.

• Journal of Aquaculture
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• v.5 no.1
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• pp.29-67
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• 1992

Life cycle and seed production of the freshwater prawn, Macrobrachium nipponense, were studied and the results are as follows : 1. Larval development : Embryos hatched out as zoea larvae of 2.06 mm in mean body length. The larvae passed through 9 zoea stages in $15{\~}20$ days and then metamorphosed into postlarvae measuring 5.68 mm in mean body length. Each zoea stage can be identified based on the shapes of the first and second antennae, exo- and endopodites of the first and second pereiopods, telson and maxillae. 2. Environmental requirements of zoea larvae : Zoea larvae grew healthy when fed with Artemia nauplii. Metamorphosing rate was $65{\~}72{\%}$ at $26{\~}28\%$ and $7.85{\~}8.28\%_{\circ}Cl.$. The relationship between the zoeal period (Y in days) and water temperature (X in $^{\circ}C$) is expressed as Y=46.0900-0.9673X. Zoeas showed best survival in a water temperature range of $26{\~}32^{\circ}C$ (optimum temperature $28^{\circ}C$), at which the metamorphosing rate into postlarvae was $54{\~}72\%$ The zoeas survived more successfully in chlorinity range of $4.12{\~}14.08{\%_{\circ}}Cl.$, (optimum chlorinity $7.6{\~}11.6\;{\%_{\circ}}Cl.$.), at which the metamorphosing rate was $42{\~}76{\%}$. The whole zoeal stages tended to be longer in proportion as the chlorinity deviated from the optimum range and particularly toward high chlorinity. Zoeas at all stages could not tolerate in the freshwater. 3. Environmental requirements of postlarvae and juveniles : Postlarvae showed normal growth at water temperatures between $24{\~}32^{\circ}C$ (optimun temperature $26{\~}28^{\circ}$. The survival rate up to the juvenile stage was $41{\~}63{\%}$. Water temperatures below $24^{\circ}C$ and above $32^{\circ}$ resulted in lower growth, and postlarvae scarcely grew at below $17^{\circ}C$. Cannibalism tended to occur more frequently under optimum range of temperatures. The range of chlorinity for normal growth of postlarvae and juveniles was from 0.00 (freshwater) to $11.24{\%_{\circ}}Cl.$, at which the survival rate was $32{\~}35\%$. The postlarvae grew more successfully in low chlorinities, and the best growth was found at $0.00\~2.21{\%_{\circ}}Cl.$. The postlarvae and juveniles showed better growth in freshwater but did not survive in normal sea water. 4. Feeding effect of diet on zoea Ilarvae : Zoea larvae were successfully survived and metamorposed into postlarvae when fed commercial artificial plankton, rotifers, and Artemia nauplii in the aquaria. However, the zoea larvae that were fed Artemia nauplii and reared in Chlorella mixed green water showed better results. The rate of metamorphosis was $68\~{\%}75$. The larvae fed cow live powder, egg powder, and Chlorella alone did not survive. 5. Diets of postlarvae, juveniles and adults : Artemia nauplii and/or copepods were good food for postlarvae. Juveniles and adults were successfully fed fish or shellfish flesh, annelids, corn grain, pelleted feed along with viscera of domestic animals or fruits. 6. Growth of postlarvae, juveniles and adults : Under favorable conditions, postlarvae molted every five or six days and attained to the juvenile stage within two months and they reached 1.78 cm in body length and 0.17 g in body weight. The juveniles grew to 3.52 cm in body length and 1.07 g in body weight in about four months. Their sexes became determinable based on the appearance of male's rudimental processes (a secondary sex character) on the endopodites of second pereiopods of males. The males commonly reached sexual maturity in seven months after attaining the postlarvae stage and they grew to 5.65 cm in body length and 3.41 g in body weight. Whereas the females attained sexual maturity within six to seven months, when they measured 4.93 cm in body length and 2.43 g in body weight. Nine or ten months after hatching, the males grew $6.62{\~}7.14$ cm in body length and $6.68{\~}8.36$ g in body weight, while females became $5.58{\~}6.08$ cm and $4.04{\~}5.54$ g. 7. Stocking density : The maximum stocking density in aquaria for successful survival and growth was $60{\~}100$ individuals/$\ell$ for zoeas in 30-days rearing (survival rate to postlarvae, $73{\~}80{\%}$) ; $100{\~}300$ individuals/$m^2$ for postlarvae of 0.57 cm in body length (survival rate for 120 days, $78{\~}85{\%}$) ; $40{\~}60$ individuals/$m^2$ for juveniles of 2.72 cm in body length (survival rate for 120 days, $63{\~}90{\%}$) : $20{\~}40$ individuals/$m^2$ for young prawns of 5.2 cm in body length (survival rate for 120 days, $62\~90{\%}$) ; and $10\~30$ individuals/$m^2$ for adults of 6.1 cm in body length (survival rate for 60 days, $73\~100{\%}$). The stocking density of juveniles, youngs and adults could be increased up to twice by providing shelters.