• Fisheries and Aquatic Sciences
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• v.21 no.1
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• pp.2.1-2.8
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• 2018

This study evaluated hemato-histological changes of black porgy in recirculating aquaculture systems (RAS) with three different ozone doses (no ozone, 20 g, and $40g\;ozone/kg\;feed\;day^{-1}$). During the 44-day study, black porgy did not show significant behavior changes or mortalities in both the ozonated systems displaying average total residual oxidants concentrations of 0.12 and 0.25 mg/L. There were no differences in growth and blood parameters among the systems. However, histological alterations on gills and livers were observed in both the treatment systems. In the higher ozone dose, signs of cellular damage were more apparent. Although the ozone doses did not manifest a serious adverse effect on growth and hematological observations in this short-term study, an ozone dose should not exceed $20g\;ozone/kg\;feed\;day^{-1}$ for black porgy based on the histological result. In order to use ozone in a seawater RAS, further studies will be needed to evaluate long-term effects of total residual oxidants.

• Journal of Aquaculture
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• v.19 no.1
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• pp.14-18
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• 2006

The objective of this study was to evaluate food value and profitability of black porgy (Acanthopagrus schlegeli) cultured in freshwater. In fish flesh, muscular hardness of black porgy reared in freshwater $(9210{\pm}1215g/cm^2)$ was slightly lower than those of fish in seawater $(9987{\pm}6549g/cm^2)$, but there was no significant difference. Also, there was no difference between muscular strength of fish reared in freshwater and seawater. When the flesh qualities of black porgy reared in freshwater was compared with those of fish reared in seawater through the questionnaire, there were no significant differences between fish reared in freshwater and seawater in appearance, texture, taste and flavor. For 10 months of black porgy culture in fresh water, the gross profit in culturing from juvenile (5.5 g) to adult size (100g), and from adult to marketable size (400 g) were 24,000,000 won (30.0%) and 53,870,000 won (36.9%), respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.43 no.5
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• pp.474-481
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• 2010

The sperm collection time, sex steroid hormones, and gonadal development of protandrous black porgy, Acanthopagrus schlegeli, acclimated in freshwater for more than 2 years were investigated to evaluate its reproductive capability. The gonadal development of black porgy reared in seawater and freshwater could each be classified into four successive stages. For black porgy reared in seawater (BSW) as the control, these were the growing (December to February), mature (February to March), spent (March to June), and degeneration and resting (July to December) stages; for black porgy reared in freshwater (BFW), these were the growing (November to January), mature (January to February), spent (February to May), degeneration and resting (June to November) stages. In both BSW and BFW, the plasma cortisol levels were the highest in March. The plasma testosterone (T) levels of BSW and BFW were the highest in March and February, respectively. The plasma estradiol-$17{\beta}$ ($E_2$) levels did not differ significantly between BSW and BFW. The 11-ketotestosterone (11-KT) levels in the plasma of BSW and BFW were the highest in April. Sperm was collectible from March to June in BSW and from February to May in BFW. The results indicated that the gonadal maturation of BFW was about 1 month faster than that of BSW.

• Animal cells and systems
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• v.13 no.4
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• pp.439-445
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• 2009

Cytochrome P450 aromatase (P450arom) catalyzes the conversion of androgens to estrogens and plays an important role in reproduction and development in vertebrates. We investigated the expression patterns of ovarian P450arom (P450aromA) and brain P450arom (P450aromB) mRNA during sex change in black porgy. Maturity was divided into seven stages from male to female (immature testis, mature testis, testicular portion of mostly testis, ovarian portion of mostly testis, testicular portion of mostly ovary, ovarian portion of mostly ovary, and mature ovary). P450aromA expression was significantly higher in the ovarian portion of mostly-ovarian stage fish, and P450aromB expression was highest in the brain of black porgy with mostly-ovarian gonads. Histology showed that testicular tissues were disintegrated with the development of ovarian tissue associated with an increase in the expression of the two P450arom mRNAs during sex change. Interestingly, among various tissues, P450aromA was only expressed in the ovary, and P450aromB was only expressed in the brain. To understand the role of gonadotropin-releasing hormone (GnRH) and estradiol ($E_2$), we injected exogenous hormone (GnRH analogue [GnRHa] and $E_2$) into immature black porgy. In the GnRHa group, expression of the two P450arom genes decreased 12 h after injection, and expression of the two P450arom genes were significantly higher at 6 dafter $E_2$ injection. These results provide useful baseline knowledge on the mechanism of natural sex change in black porgy.

• Journal of Aquaculture
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• v.19 no.3
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• pp.149-156
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• 2006

Stress responses, osmoregulation and growth of black porgy reared in freshwater or seawater were investigated by supplying the feed (10 mg/kg feed) treated with the $T_3$ (3,5,3'-triiodo-L-thyronine) for 90 days. Plasma $T_3$ in black porgy reared for 60 days in freshwater with (FT) or without (FN) $T_3$, treatment was lower than that in black porgy reared in seawater with (ST) or without (SN) $T_3$ treatment. The concentration of $T_3$ in FT was significantly more than that in FN. Plasma cortisol in FT, at the same day, was 4 times higher than that in FN, whereas the differences of the hormone between ST and SN was not significant. Although the levels of plasma glucose in FN and FT tended to be lower than that in ST and SN, no differences were found between fish reared in freshwater and seawater after $T_3$ treatment. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) of black porgy reared in seawater showed no difference throughout the experimental period. However, at the beginning stages of the experiment, the plasma levels of these enzymes in FN and FT were higher than in SN and ST. Recovering of AST level to the level of SN or FT was laster in FT than in FN. However, no effects of the exogenous $T_3$ treatment on osmoregulatory capacity and growth of black porgy reared in freshwater or seawater were observed in this study.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.48 no.2
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• pp.137-146
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• 2012

Black porgy and fat greenling are commercially important fish species due to the continuously increasing demand in Korea. When estimating acoustically the fish length by a fish sizing echo sounder, it is of crucial importance to know the target strength (TS) to length dependence. In relation to these needs, the target strength experiments for live fishes were conducted in an acrylic salt water tank using two split-beam echo sounders operating at 70 and 120kHz. The target strength under well-controlled laboratory conditions was simultaneously measured with the swimming movement by digital video recording (DVR) system and analyzed as a function of fish length (L) and frequency (or wavelength ${\lambda}$). Equations of the form TS-alog (L)+blog (1)+c were derived for their TS-length dependence. The best fit regression of TS on fork length for black porgy was TS=20.62 log (L, m)-0.62 log (${\lambda}$, m)-30.68 ($r^2$=0.77). The best fit regression of TS on fork length for fat greenling was TS=12.06 log (L, m)-5.85 log (${\lambda}$, m)-22.15 ($r^2$=0.44).

• Journal of Aquaculture
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• v.22 no.1
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• pp.122-125
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• 2009

Salinity tolerance on survival rate of 2, 4 and 6-week-old larvae and juvenile of black porgy Acanthopagrus schlegeli was investigated at 0, 7.5, 15, 22.5 and 30 psu for 21 days. In the 2 and 4-week-old larvae and juvenile (TL: 1.23 and 1.72 cm) were all died within 12 and 26 hours after to the 0 psu transfer, respectively. However, survival rate of other experimental group (7.5, 15, 22.5 and 30 psu) was significantly difference in the range between 27.3% and 95% (P<0.05). However survival rate of 6-weeks-old juvenile (TL: 2.83 cm) were over 99.0% during experimental periods and they appeared in good health. There was no significant difference in survival those reared to the salinities of all experimental groups (P>0.05). The present study suggests that the freshwater and saline groundwater of low salinity could be used to grow early juveniles of black porgy and it may be possible to culture in freshwater.

• Journal of Fisheries and Marine Sciences Education
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• v.24 no.3
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• pp.387-394
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• 2012

Fertilization rates were over 90% when sperm from black porgy Acanthopagrus schlegelii acclimated and raised in freshwater and black porgy raised in seawater were fertilized with eggs from female black porgy raised in seawater, although cryopreserved sperm were significantly lower in fertilization rates than non-cryopreserved sperm. From the observations of embryos development at different salinities (0, 10, 20 and 32 psu) within 3 hours upon fertilization (16 cell stage), all were dead at 0 psu. However, the development process and speed at 10 and 20 psu were the same as at 32 psu. But, many developing embryos were egg envelope injury at low-salinities of 10 and 20 psu unlike at 32 psu. This is attributable to osmotic shock. Hatching rate of embryos at 32 psu was 60% or so, whereas low as 5% or less were successfully hatched at 10 and 20 psu, implying that osmotic shock could be responsible for the failure of embryo development.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.28 no.1
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• pp.1-9
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• 1992

The author has examined the response of sting fish, Sebastes inermis and black porgy, Acanthopagrus schlegelii to the attraction lamps(1 W) line in an experimental water tank(550 L$\times$ 58 W $\times$ 73H cm). Attraction lamp was set up at intervals of 55 cm for each section. The frequency rate was investigated at the illuminated section in accordance with the intervals of lighting on and putting out that was 1, 3 and 5 minutes under two conditions of light stimulus. The results are as follows: 1. Frequency rate at the last section when each of the attraction lamps was gradually switched on and off: (1) Sting fish was 27.2 % in case of 3 minutes interval, and 17.4 % in 1 minutes interval, and 15.8 % in 5 minutes interval. (2) Black porgy was 28.5 % in case of 5 minutes interval, and 25.8 % in 3 minutes interval, and 12.0 % in 1 minutes interval. 2. Distribution of fish at the illuminated section when each of the attraction lamps was gradually switched off after they were switched on all at once: (1) Sting fish was much gathered in the section adjacent to the extinguished section under the condition of 1 and 3 minutes interval, and not regular trend under 5 minutes interval. (2) Black porgy was much gathered last section under the condition of 1 and 3 minutes interval, and almost evenly distributed under 5 minutes interval. 3. Each of the attraction lamps was gradually switched off after they were switched on all at once, and only the last one was on: (1) The frequency rate of Sting fish was 27.2 % in case of 5 minutes interval, and 16.0 % in 1 minute interval, and 8.0 % in 3 minutes interval. (2) The frequency rate of Black porgy was 10.7 % in case of 1 minute interval, and 8.9 % in 3 minutes interval, and 0.8 % in 5 minutes interval.

• Fisheries and Aquatic Sciences
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• v.8 no.3
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• pp.177-181
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• 2005

Fishing selectivity is determined by the level of voluntary escaping behavior in accordance with decision-making based on the relationship between fish size and mesh size. This study examined movement during the swimming behavior of black porgy in a trawl's towing cod-end and analyzed the movement components such as swimming speed, angular velocity of turning, and distance to the net over time. Most of the observed fish exhibited an optomotor response, maintaining position and swimming speed without changing direction. Others exhibited erratic or 'panic' behavior with sudden changes in swimming speed and direction. The latter behavior involved very irregular and aperiodic variations in swimming speed and angular velocity, termed 'chaotic behavior.' Thus, the results of this study can be applied to a chaotic behavior model as a time series of swimming movements in the towing cod-end for the fishing selectivity.