• Development and Reproduction
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• v.17 no.2
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• pp.79-85
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• 2013

To understand the sex reversal characteristics in the longtooth grouper (Epinephelus bruneus), this study examined the sex reversal and artificial masculinization of wild caught E. bruneus reared in indoor rearing tank after a 17${\alpha}$-methyltestosterone injection. To domesticate a broodstock, 64 wild caught E. bruneus, between 47.0 to 110.0 cm in total length and from 1.5 to 21.4 kg in body weight, were reared in indoor rearing tank (4.0 to 5.0 m wide, and 2.5 to 3.0 m depth) for four years. Seven specimens showed sex reversal from female to male during indoor rearing condition, whose total length and body weights were from 63.0 to 99.0 cm and from 4.4 to 13.2 kg, respectively. After inducing artificial masculinization in 14 female E. bruneus with a 17${\alpha}$-methyltestosterone (2.0 mg/kg BW) implants for 3 years, spermiation occurred in 9 specimens (total length: 54.0 to 68.0 cm, body weight: 2.3 to 4.3 kg). Among the female to male sex reversals, two specimens returned back to being female, whose body weights were 2.8 kg (initially 2.6 kg) and 2.7 kg (initially 2.3 kg). Therefore, this study suggested that E. bruneus (> 3.0 kg) was more effective in masculinizing by 17${\alpha}$-methyltestosterone implants.

• Fisheries and Aquatic Sciences
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• v.14 no.2
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• pp.123-129
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• 2011

To determine whether rearing density affects the hypermelanosis on the blind side (ambicoloration) of olive flounders Paralichthys olivaceus, we reared fry with an unpigmented non-eyed (blind) side in duplicate at densities of 150 individuals/$m^2$ (commercial production density: control) and 450 individuals/$m^2$ (high density group) for 90 days in 1-t dark-green fiberglass reinforced plastics (FRP) tank. We recorded feed intake, feed conversion efficiency (FE), growth and survival, and measured the ratios of staining blind-side area (staining area) and ambicolored fish every 30 days. Daily feed intake (DFI), feed conversion efficiency (FE), growth rate, condition factors, and survival rate were calculated at the end of the experiment. Although the FE was higher in the high-density compared to the control, the two density groups showed similar feed intakes, growth, and survival. The ratio of staining area as well as the ratio of ambicolored fish significantly were significantly higher in the high-density group than in the control from days 30 to 60, but significantly increased and evened out by the end of the experiment (P<0.05). In conclusion, we determined that rearing density is not the main cause of the blind-side hypermelanosis, but found that increasing the rearing density can accelerate the ambicoloration in olive flounders.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.36 no.6
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• pp.661-668
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• 2003

Performance of an airlift bioreactor (ABR) containing the immobilized microorganisms was evaluated in an integrated pilot scale recirculating aquaculture system stocked with Nile tilapia (Oreochromis niloticus) at an initial rearing density of $5\%$ and compared to a rotating biological contactor (RBC) for 40 days. The TAN concentration of rearing tank for ABR and RBC were maintained at $0.4\;g/m^3$ and $0.5\;g/m^3,$ respectively, The nitrite nitrogen was completely removed by the ABR. The ABR's aeration was more stable than the RBC's. On the whole, the feasibility of ABR as an aquacultural water treatment unit was recognized.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.4
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• pp.457-468
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• 1995

In order to develop a more practical culture system from the present running seawater tank system, two experiments of environmental factors, growth, survival rate and rearing density of olive flounder (Paralichthys olivaceus) were carried out for two consecutive years. Two groups of fish in initially averaging 7.5cm of total length, and 3.4g of body weight (EXP. I) and 5.0cm and 1.8g (EXP. II) were reared in the semi-closed recirculating seawater system equipped with the rotating biological contactors with the commercial culture scale. The dissolved inorganic nitrogen concentrations is EXP. I ranged 0,247-0.512 ppm of $NH_4-N$ (0.010-0.043 ppm of$NO_2-N$, and 0.108-0.342 ppm of $NO_3-N$, and those in EXP. II were 0.091-0.715 ppm, 0.002-0.045 ppm, and 0.007-0.277 ppm, respectively. Daily feeding rates of the fish were $0.67-2.41\%$ in EXP. I and $0.69-2.22\%$ in EXP_ II, and teed efficiency were $34.8-59.8\%\;and\;40.5-88.4\%$ in EXP. I and II, respectively. The average total ten說h and body weight were 40.0-42.8cm and 695.0-852.69g after 340 days culture in EXP. I, and 36.7-39.7cm and 552.4-706.4 g after 365 days culture in EXP. II, respectively. Survival rates of the fish at the end of EXP. I and II were $92.0\%\;and\;96.0\%,$ respectively. The ratio to body surface area of non-ocular side in all fish to bottom area of rearing tank, so-called covering rate, was used as an indicator of rearing density. The highest cowering rate and weight density of fish per $m^2$ of rearing tank at the end of experimental period were 2.2 and 34.1kg in EXP. I, and 2.6 and 36.3kg in EXP. II, respectively. For the commercial culture of olive flounder, the semi-closed recirculating seawater system was found to be more effective than the running seawater tank system in aspect to the fish productivity and protection of marine environment.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.14 no.4
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• pp.233-238
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• 1981

A recirculating water system without filter bed was used for a high density experimental rearing of common carp, Cyprinus carpio, during the summer of 1981. Of the water system, 3 tanks were used for stocking each tank with 10,000, 20,000 and 30,000 common carp fingerlings which averaged 0.6 g. The water in the system was maintained in dark green colour by heavy growth of phytoplankton during the most period of the experiment. In this experiment, the best daily growth rate, $3.7\%$, was obtained from the 10,000 fish group followed by $2.8\%\;and\;3.0\%$ from the 20,000 and 30,000 fish groups respectively. Thus there was no significant difference between the latter two groups. Especially, notably high concentration of total ammonia, $5\sim7$ ppm ammonia-N, in the culture water appeared during the most experimental period, but this did not seem to have affected feeding and growth of the fish when the water was kept at heavy bloom. It was also obvious that the outbreak of columnaris disease was effectively depressed in this green water recirculating system compared to that in clarified recirculating system. One tank ($7m^2$) of this system was stocked with 446 common carp of intermediate size averaging 352.2 g and after 40 day rearing they grew to 486.3 g in average with a daily growth rate of $0.8\%$. This result was a little inferior to that reared in a tank of the clarified water system as control which showed $1.0\%$ daily growth rate. Therefore, before an initiation of the commercial production of fish in this method, further studies concerning the amount of ammonium with its effect on the fish under rearing in this system and the columnaris disease problem should be carried out.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.5
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• pp.465-472
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• 2001

The effects of water level reduction in rearing tank and fish transference during fish selection process on the stress response (hematological factors, cortisol, glucose, lactic acid and osmolality) of tank-reared olive flounder Paralichthys olivaceus of large (FL), small (FS) and Japanese croaker, Nibea japonica (JC) were examined in running seawater culture system. The water level of rearing unit was lowered from 33 cm to 8 cm in the course of 2 minutes in the water level reduction experiment. The fish were removed from rearing tank (12 ton) to 450 L tank in 30 seconds after capture in the fish transference experiment, In water level reduction, the hematocrit of FL was significantly increased from $14.6\%$ at beginning to $23.5\%$ after 10 hours, However, it decreased to the value of beginning after 46 hours. Plasma cortisol concentration of FL was the highest concentration (13.7 ng/mL) after 22 hours, but it decreased to 4.0 ng/mL at the end of experiment. Cortisol concentration of FS did not show any significant difference during the experiment. The cortisol concentration of JC were significantly higher at 4 hours (282.3 ng/mL) and 22 hours (350.5 ng/mL), Glucose concentration of JC was the highest (138.0 mg/dL) at 22 hours. Lactic acid concentration was not different between experimental groups. In the fish transference experiment, red blood cell of FL was increased from $1.9\times10^6\;cell/{\mu}\;L\;to\;4.2\times10^6\;cell/{\mu}L$ in 24 hours. Blood hemoglobin of JC were significantly elevated in 24 hours. At 1 hour after transference, plasma cortisol concentrations in both fish species were increased to 95.3 ng/mL in FL and 175.5 ng/mL in JC. Glucose concentration of JC was increased to 132.5 mg/dL at 1 hour, 129.5 mg/dL at 3 hours after transference.

• The Korean Journal of Malacology
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• v.31 no.2
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• pp.83-92
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• 2015

The effect of different intermediated rearing method by expanding the attached floor space in order to highly density culture on the growth characteristics and survival rate of the juvenile abalone, Haliotis discus hannai, were investigated in land-based tanks. The intermediated culture methods was determined thru the shelter counts and layer for 10 month with two replicates : the single layer shelter (SLS), the double layer shelter (DLS), the triple layer shelter (TLS) and the single layer shelter under net cage (SLSNC). In addition, the culture on shallow race way tank had to set up as culture of the ditch raceway tank (CDRT) and the floor race way tank (CFRT). In the growth performance of reared abalone (initial mean shell length $54.18{\pm}7.39mm$ and weight $1.93{\pm}0.14g$) at experimental tanks, that the absolute growth rate (ARG), daily growth rate (DGR) and specific growth rate (SGR) to the shell length and shell breadth was not significant at each experimental tanks except SLSNC. As well as too, weight gain (WG), daily weight gain (DWG) and specific weight gain (SWG) to weight was not significant at each experimental tanks except SLSNC, too. Survival rates of CDRT and CFRT was lower than those of different experimental tanks (P < 0.05). Therefore, these results is showed that high density different intermediated rearing method by expanding the attached floor space for juvenile H. discus hannai was not have difference as growth performance and survival rate both one layer shelter and multi layer shelter. Also, it is considered that shallow race way tank was not useful rearing for the juvenile intermediate culture of H. discus hannai in land based.

• Korean Journal of Organic Agriculture
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• v.8 no.1
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• pp.79-88
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• 1999

In order top investigate the growth of water dropwort grown by sandculture irrigated with recirculated tilapia aquaculture water, these experiments were carried out. Fish(tilapia) production and biofiltration provided by sand cultured water dropwort(Oenanthe stolonifera DC.) were linked in a closed system of recirculation water. Water dropwort was irrigated with water drawn from the tilapia tank and drainage from sand beds was returned to the fish tank. The temperature, pH and EC of tilapia culture water were stable. The growth of water dropwort grown by sandculture with aquaculture water was normal. Microbial activity of the biofilterbed irrigated by tilapia rearing water was higher than that of biofilterbed irrigated by tapwater. The feasibility of an integrated, recirculatory system for concurrent production of water dropwort and fish with no additional fertilization application was demonstrated.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.5
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• pp.622-630
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• 1998

Rotating Biological Contactor (RBC) was tested for the removal of total ammonia nitrogen (TAN) by using simulated aquaculture system. RBC performance was evaluated by controlling revolution rate of disk and hydraulic residence tile (HRT). The optimum revolution rate of disk was 4 rpm, As HRT of RBC was increased, TAN removal efficiency of RBC and TAN concentration of rearing water were increased. HRT for maintaining lowest TAN concentration of rearing water was 9.5 minutes and at that condition TAN concentration of rearing tank was $1.03 g/m^3$

• Development and Reproduction
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• v.24 no.3
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• pp.225-230
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• 2020

This study reports the presence of mature and bi-sexual phase gonads in red spotted grouper, Epinephelus akaara after less than a year of cultivation in a commercial indoor tank and a net cage. In December 2018, juveniles were placed in an indoor tank and cultured for five months. In June 2019, the fish were transferred to a net cage and cultured until September. The rearing temperatures ranged from 19.86℃-24.65℃ in the indoor tank and 21.86℃-27.65℃ in the net cage. During the net cage culture period, specimens were randomly selected for histological gonad examination. The highest gonadosomatic index (GSI) value was measured in July (3.38±2.53), and dramatically decreased in August (0.44±0.21) and September (0.42±0.30). In July, some mature fish showed signs of vitellogenic stage oocyte development (vitellogenic and oil droplet stage oocytes), but immature fish were in an early developmental stage containing peri-nucleolus stage (PNS) oocytes. Bi-sexual phase gonads containing spermatocytes and spermatids were observed in the lumen and several PNS oocytes. By August and September, most specimens showed early-stage ovary development. However, mature testis (in August) and bi-sexual phase gonads (in September) were also observed. These results provide evidence for early puberty and hermaphroditism in the red spotted grouper.