• Journal of Aquaculture
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• v.16 no.1
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• pp.24-30
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• 2003

Studies of the seed production of Urechis unicinctus were conducted under the laboratory conditions to obtain some information for the U.unicinitus culture. The experiment included developmental studies of the egg development, larval culture, sediment preference and growth of young U.unicinctus. The experiment were conducted from March to August, 2000. The adults of U.unicinctus collected in Namhae-do, Korea. The developments of the fertilized eggs were observed under a light-microscope at intervals of one hour after containing with density of one individual per 1 $m\ell$. The larvae were fed with Phaeodactylum tricornutum cultured at the laboratory. The concentration of the phytoplankton for the feed was 30,000 cells per individual larva. With progress of development, the food concentration was gradually increased, up to 10,000 cells per individual for the young U.unicinctus. Trochophore larvae appeared on the 68 hours after hatching. On the 32 days after hatching, over 50% of fertilized eggs developed into young U.unicinctus. In order to investigate the effect of sediment on the growth and burrowing of U.unicinctus, the young worms were reared in tanks with different grain sizes. The highest value of sediment preference and survival rate of U.unicinctus was shown in the mixture sediment group with below 0.10 mm, 1.01∼12.00 mm, over 3.01 mm and shell. The lowest value in both sediment preference and survival rate of U.unicinctus was observed in 1.0l∼2.00 mm grain size.

• Journal of Aquaculture
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• v.20 no.1
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• pp.60-64
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• 2007

We examined the effects of the vibration stress on oxygen consumption and ammonia excretion of cultured soft-shelled turtle, Pelodiscus sinensis. For the stressed group vibration of $45{\sim}78\;dB$ (V) from electric vibrator was turned on for 15 min with 2-h intervals during daytime hours ($08:00{\sim}18:00$) for 28 days. Two different sizes of soft-shelled turtle, large (carapace length: $12{\sim}16\;cm$, body weight: $300{\sim}600\;g$, large size turtle: LST) and middle ($16{\sim}20\;cm,\;700{\sim}1,000\;g$, middle size turtle: MST) were used. The oxygen consumption of LST the beginning of the experiment (1 day) was 124.30 mg $O_2/kg/hr$, and after 7, 14, 21 and 28 days of stress decreased by 47.2, 71.6, 79.1 and 86.0%, respectively. In MST, oxygen consumption of beginning day was 66.04 mg $O_2/kg/hr$, and after 28 days of stress decreased by 76.5%. Ammonia nitrogen excretion showed a similar pattern to that of oxygen consumption. Ammonia nitrogen excretion of beginning of the experiment was 0.537 mg N/kg/hr, and after 28 days of stress decreased by 75.4% for LST, and by 74.3% for the middle ones. From in this study it was showed that the physiological activity was reduced by 50% following 8.4 days of vibration stress for LST, and 15.5 days for MST.

• Journal of Aquaculture
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• v.21 no.3
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• pp.133-138
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• 2008

We evaluated the effects of dietary supplementation of scoria on growth performances and apparent protein digestibility in juvenile parrot fish Oplegnathus fasciatus and olive flounder Paralichthys olivaceus. In experiment, parrot fish at initial average weight of $7.6{\pm}0.01g(mean{\pm}SD)$ were divided into 9 groups(three groups per dietary treatment) and fed one of three isonitrogenous diets which contained 0%, 1% and 2% of scoria, respectively. Experiment was conducted with juvenile olive flounder to demonstrate the improved apparent digestibility of protein found in the experiment. Five experimental diets were formulated to contain different levels of scoria: Diet 1(control), 0% scoria; diet 2, 1% scoria; diet 3, 2% scoria; diet 4, 3% scoria; and diet 5, 4% scoria. After 9 weeks of feeding trial(Exp), no significant differences were observed on growth performances between Scoria 2% and the control group. However, the growth was significantly lower in scoria 1% compared to that of the control group. Hematological parameters were not affected by the supplementation of scoria. Interestingly, apparent protein digestibility was improved by dietary supplementation of scoria both in parrot fish and olive flounder. The findings suggest that dietary supplementation of 2-3% scoria is optimum levels in order to improve the protein digestibility in the diets for juvenile parrot fish and olive flounder.

• Journal of Aquaculture
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• v.6 no.4
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• pp.295-310
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• 1993

As a part for the development of effective mass production techniqne of the puffer, Takifugu rubripes. seedfish, an investigation was carried out in 1989. 1991 and 1992 to determine the optimum starting feeding time of rotifers as a starting food for the fish larvae, and to find out the influences of the light intensitiy and LD cycles on the Artemia consumption by the larvae. The optimum starting time of feeding with rotifer. Brachionus Plicatilis was 2nd to 5th day from hatching resulting in survival of $96.5\~90.0\%$. Optimum light conditions for maximum feeding for fish larvae with Artemia were 1000 lux in 6mm, 600 lux in 8mm, and 200 lux in total length of 10-12 mm larvae. Relationship between total length (X: mm) of fish (6-12 mm in total length) and light intensity (Y: lux) for maximum feeding was:Y=2200-200X (r=-1.000). Relationship between days from hatching (X) and total length (Y: mm) of puffer fry was :Y=1.6427+0.2540X(r=0.9814) for 3 to 36 days after hatching, Y=-33.1452+1.1867X(r= 0.9854) for 36 to 68 days after hatching. Survival rate for 68 days after hatching was $24.1\%$ and the range of water temperature during this period was $21.25\pm1.67^{\circ}C$.

• Journal of Aquaculture
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• v.6 no.4
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• pp.273-284
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• 1993

Ion concentrations and osmolarities of the body fluid and oxygen consumption of the larvae of the freshwater crab, Eriocheir japonicus under the influence of various salinities and water temperatures were studied. The levels of $Na^+\;and\;Cl^-$ ions in the body fluid of the crab placed in the low salinities (freshwater and $30\%$ seawater) were higher at the low temperature $(16^{\circ}C)$ than high temperature $(30^{\circ}C)$. However, the crab in the high salinity $(90\%\; seawater)$, those ions in the body fluid were higher at the high temperature $(30^{\circ}C)$ than the low temperature $(10^{\circ}C)$ When the zoea larvae were young (first and second stages), the ion concentrations of the body fluid were more affected by salinities and temperatures of the media. The salinity levels of the media more influenced the levels of $K^+$ ions of the body fluid of the larvae than the temperature. The osmolarities of the body fluid of the larvae were almost isotonic when they were placed at $70\%$ seawater $(24.5\%o)$. Oxygen consumption of individual larva was lower in zoea 1 and 2 stages than the other stage larvae. The high oxygen consumption of the larvae was observed at $70\%$ seawater compared to the other salinity levels.

• Journal of Aquaculture
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• v.19 no.3
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• pp.188-196
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• 2006

Annual reproductive cycle of small yellow croaker, Larimichthys polyactis were histologically investigated based on samples captured nearby the coast around Chujado, Youngkwang and Kanghwa, South Korea from February $2004{\sim}February$,2005. By histological survey, the annual reproductive cycle was classified into the following successive stages: The primary growth stage from September to October, the second growth stage from October to December, the mature stage from January to April, the final mature, ovulation and spawning stage from May to June, the degeneration stage from June to July and the rest stage from August to September. Throughout anatomical observation of the ovary, it is found that the small yellow croaker, L. polyactis belongs to an asynchronous and multiple spawner from late spring to early summer.

• Journal of Aquaculture
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• v.19 no.3
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• pp.166-172
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• 2006

Induced androgenesis, a form of artificial parthenogenesis is an important tool for the generation and use of genetically isogenic or clonal fish strain. An optimized protocol for the genetic inactivation of mud loach (Misgurnus mizolepis) oocytes (i.e. production of androgenetic haploid) was developed using UV-irradiation. Various dose levels of UV significantly affected the fertilizing capacity of the eggs, hatchability of embryos and incidence of haploidy. Based on the extensive examinations of treatment conditions on embryo viability and haploid incidence, the optimum dose level of UV irradiation was turned out to be $10,800ergs/mm^2$ with 56.9% of hatching success and 94.6% of haploidy. The overall yield of putative androgen under optimized treatment condition was more than 50% out of total eggs inseminated. The success of androgenetic reproduction of haploid genome was verified by flow cytometry and PCR amplification of transgene that is exclusive to either one of parental sexes. However, a small portion $(8\sim11%)$ of presumed androgenetic haploid larvae was proven to contain residual DNA fragment(s) from maternal parent.

• Journal of Aquaculture
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• v.19 no.3
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• pp.157-165
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• 2006

Expression of major antioxidant enzyme (AOE) including Cu/Zn superoxide dismutase (Cu/Zn-SOD), catalase (CAT), glutathione-S-transferase (GST) and 3 glutathione peroxidase isotypes (GPXs) at mRNA levels during heat stress was examined in mud loach (Misgurnus mizolepis) liver. Based on the semi-quantitative RT-PCR, real-time RT-PCR and/or northern dot blot hybridization, the antioxidant enzyme genes were generally up-regulated during elevation of water temperature from $23^{\circ}C$ up to $32^{\circ}C$. GPXs and SOD displayed the most significant elevation of mRNA levels (up to 3 and 2 folds, respectively) while CAT showed the steady-state expression irrespective of thermal conditions. GST represented the relatively moderate response (1.3-fold increase) in its transcription to thermal stress. The transcriptional activation of AOE genes was not significant at the treatment temperature lower than $29^{\circ}C$. Increased mRNA levels of GPX (extracellular form) and SOD genes in the fish exposed to $32^{\circ}C$ was readily detectable 1 day after exposure to heat stress.

• Journal of Aquaculture
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• v.19 no.3
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• pp.216-221
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• 2006

The Effect of different temperatures and photon irradiance on the growth of crust and the regeneration of tissue fragments of the commercially important red alga Grateloupia acuminat Okamura were examined in laboratory cultures. The tetraspore developed into basal crusts and produced upright thalli. Crust grew very fast at $25^{\circ}C$ and $80{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ after one week in indoor culture. However, they stopped growing after three weeks. Maximum growth was $275{\mu}m$ in diameter. They required four weeks to get upright thalli at $5^{\circ}C$, while only three weeks were required at $10^{\circ}C$. When different light intensities were compared at $15^{\circ}C$, cells of the crusts were well differentiated $80{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ and consistently divided so that upright thalli were produced. In aeration culture, the upright thalli grew up to 6.5 cm in length within 4 months. Thus, it is possible to produce mass cultures of Grateloupia in the field. In addition, female and male gametophytes developed from the tetraspores and they were fertilized to produce tetrasporohyte thalli. By this procedure, the normal life cycle of the red alga G. acuminata was completed.

• Journal of Aquaculture
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• v.11 no.4
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• pp.421-428
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• 1998

This study was performed to determine the level of soybean meal (SM) or feather meal (FM) that could substitute for fish meal in fat cod(Hexagrammos otakii Jordan et Starks) diet. A control diet with fish meal as protein source was included. The amount of 5, 10, 15 and 20% of SM or FM substituted for fish meal in the control diet, respectively. Amino acids supplementation in the 20% SM diet was compared. In addition, combination of 5% SM, 5% corn gluten meal, 5% meat meal, 5% blood meal and 5% FM was substituted for fish meal in the control diet. Duplicate groups of the 40 fish averaging 21g were fed one of 11 isoproteic (45%) and isolipidic (15%) experimental diets to satiation twice a day for 2 months. No significant differences were found among fish fed the control, substituting up to 20% SM or 10% FM in weight gain, feed efficiency, daily feed intake, and protein efficiency ratio (P>0.05). It is concluded that SM or FM can be used as a partial substitute for fish meal up to 20% or 10% in the control diet, respectively.