• Korean Journal of Fisheries and Aquatic Sciences
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• v.52 no.2
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• pp.134-140
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• 2019

A feeding trial was conducted to investigate the effects of dietary fish meal replacement by a blend of lysine cell mass, corn protein concentrate and poultry by-product meal on the growth and blood chemistry of the starry flounder Platichthys stellatus. The fish meal replacer (FMR) was prepared to have the same level of protein as fish meal (FM). With a commercial diet as a positive control, five experimental diets (basal, FM42, FM32, FM22 and FM12) were formulated to contain 52% protein and 10% lipid. The dietary FM levels decreased from 52% (basal) to 42, 32, 22 and 12% with concomitant increase in the FMR to 10, 20, 30, 40 and 50%, respectively. Juvenile starry flounder with an average body weight of 177.3 g were randomly distributed in each (30 fish/tank) of 18 plastic tanks ($139{\times}99{\times}54cm$). After a 45-day feeding trial, the survival rate ranged from 95.6% (FM22) to 100% (control and FM42), while the weight gain of the fish groups varied from 49.7 to 58.4 g. The results clearly revealed that starry flounder can grow well on a diet containing low FM (12%) with a high level of FMR (50%) without any adverse effects.

• Journal of fish pathology
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• v.28 no.2
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• pp.87-92
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• 2015

Juvenile Paralichthys olivaceus (mean length $17.3{\pm}2.2cm$, mean weight $46.5{\pm}6.3g$) were exposed for 10 days to tributyltin (TBT) at various concentrations (0, 1, 2, 4 and $8{\mu}g/L$). Hematological parameters, such as red blood cell (RBC) count, hematocrit (Ht), and hemoglobin (Hb) concentration, were considerably decreased by high TBT concentrations. In plasma constituents, inorganic components such calcium and magnesium were also significantly altered. Plasma calcium was notably decreased, whereas plasma magnesium was increased. The enzyme components, glutamic oxalate transaminase (GOT) and glutamic pyruvate transaminase (GPT), were significantly decreased by TBT exposure. The present findings suggest that TBT exposure can cause significant alterations in hematological parameters and plasma constituents of flatfish Paralichthys olivaceus.

• Journal of Ecology and Environment
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• v.44 no.1
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• pp.54-61
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• 2020

Background: Most fish undergo prey switch from juvenile to adult. It is thought that slightly different feeding habits occur among adult fishes due to growth, spawning, habitat change, and so on. Therefore, the diet of the John Dory Zeus faber (≥ 24 cm TL) was studied in the coastal waters of Korea by analysis of stomach contents, with comparison by season and size class of diet composition and prey diversity. Monthly samples were taken from February 2017 to January 2018. Results: The results showed that the John Dory was a piscivorous predator, and pisces had occupied 82.3% of IRI%. Trichiurus lepturus and Trachurus japonicus were important preys in all size classes and seasons. Diet composition differed among the size classes and seasons (Chi-square test, P < 0.05). As body size of Z. faber increased, the occurrence of benthic fish (Glyptocephalus stelleri) tended to increase. The seasonal prey composition also changed depending on the abundant species of each season. Conclusions: Z. faber is a piscivorous predator. The consumption habits of Z. faber appear to different results by their size and seasons. This study suggests that Z. faber could be considered an opportunistic predator.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.39 no.4
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• pp.326-332
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• 2006

To investigate the effects of environmental salinity on the expression of the genes for growth hormone (GH) and prolactin (PRL) in the pituitary, and their receptors (GHR, PRLR) In the kidney, intestine, and gills in teleosts, we acclimated juvenile olive flounders (Paralichthys olivaceus) to different salinities (5, 15, 25, or 32 psu) for 3 days and examined their mRNA levels using the reverse transcription-polymerase chain reaction (RT-PCR). In the fish adapted to low salinity, the PRL mRNA levels in the pituitary were elevated dramatically, whereas the GH mRNA levels did not differ significantly. PRLR mRNA increased significantly in fish exposed to low salinity, whereas GHR mRNA levels did not differ. These results suggest that PRL is an important hormone for flounders that are acclimated to brackish water and it may control ion homeostasis with PRLR in the osmoregulatory organs.

• Korean Journal of Ichthyology
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• v.20 no.1
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• pp.74-77
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• 2008

Three juvenile specimens (38.8~51.5 mm SL) of the opistognathid fish, Opistognathus hongkongiensis Chan were collected off the Jeju Island, southern Korea. O. hongkongiensis is characterized by having a large mouth, dark brown vertical bands on sides, and yellow dorsal fin without a black blotch. We described it as the first record to Korean fish fauna, and proposed the new Korean name, "Jul-hu-ak-chi" for this species.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.56 no.5
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• pp.676-683
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• 2023

The development of the egg, larvae, and juveniles of Acheilognathus macropterus from the Wicheon stream of Nakdonggang River was investigated for early life history characteristics. The fish used in the study were collected from Wicheon stream located in Bian-myeon, Uiseong-gun, Gyeongsangbuk-do. The fertilized egg was 1.88±0.09 mm (n=30) in long diameter and 1.34±0.06 mm (n=30) in short diameter. After fertilization at a water temperature of 20℃, the egg took 31 h and 40 min to hatch. Newly hatched larvae had an average total length of 3.92±0.13 mm (n=30) and possessed a yolk sac the mouth and anus were not developed. Twenty days after hatching, the postflexion larvae had an average total length of 8.08±0.29 mm (n=30), with the tail tip fully bent at 45° and began feeding. Thirty-three days after hatching, the number of fin stems reached an integer with an average total length of 15.0±1.08 mm (n=30). In this study, differences in the egg size, hatching time, melanophore development period, and distribution location were confirmed between A. macropterus and allied species.

• Development and Reproduction
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• v.15 no.4
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• pp.365-371
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• 2011

Water temperature governs various biological events in many aquatic animals including fish. Temperature changes the rates of gametogenesis and development, in some cases, is even capable of reversing fish sex. Treatments of fish with unusually high temperature are known to induce the expression of HSP70 gene. Development of an effective inhibitor for HSP70 gene expression is, thus, crucial to study the role of HSP70 in the temperature sensitive biological events. We have investigated the inhibitory effect of quercetin, 3,3',4',5,7-pentahydroxyflavon, a natural flavonid, on the expressions of HSP70 gene induced by high temperature ($36^{\circ}C$) in the Nile tilapia, Oreochromis niloticus, larvae and juveniles (10~13 cm in total length). The expression of HSP 70 gene was significantly decreased in tilapia larvae immersed in 50 ${\mu}M$ or 100 ${\mu}M$ quercetin solution for 6 hours before the exposure to high temperature (P<0.05). In particular, the level of HSP70 expression in fish treated with 100 ${\mu}M$ was as low as that of fish without high temperature treatment. Juveniles of tilapia were individually injected with 0.1 $m{\ell}$ of either 0.5 mM, 5 mM or 20 mM of quercetin solution before the exposure to high temperature. As the results, the expression of HSP70 gene in the gonad and brain of juvenile fish was significantly inhibited by the injection of 0.5 mM quercetin solution (P<0.05), but not by higher concentrations. We report, for the first time in the fish, that quercetin effectively inhibits the expression of HSP70 gene induced by high temperature and 100 ${\mu}M$ for the immersion of larvae and 0.5 mM for the injection to juvenile can be used for the effective concentrations for the study of temperature sensitive biological events in tilapia.

• Journal of Aquaculture
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• v.21 no.4
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• pp.265-271
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• 2008

Upper temperature tolerance of the turbot Scophthalmus maxim us, one of the popular aquaculture species in European community and China, was evaluated in terms of survival and growth at $20^{\circ}C$, $23^{\circ}C$, $26^{\circ}C$, or $29^{\circ}C$. Best growth was achieved at temperature $20^{\circ}C$ in this experiments. The fish exposed to $20^{\circ}C$ or $23^{\circ}C$ were comparable in survival, condition factor and feed conversion efficiency reminiscent of the latter temperature to be agreeable for the fish. The temperature over $23^{\circ}C$ appeared to be the temperatures beyond the fish can tolerate. For instance, the fish exposed to 26 showed mortality of 60.9% by day 60; none of the fish exposed to $29^{\circ}C$ survived beyond day 7. Culture densities between 80 and $200\;fish/m^2$ did not influence the survival, growth, condition factor and specific growth rate of the fish. The final production of the culture density experiment was $10\;kg/m^2$ on average. These results imply that the location where water temperature remains lower than $25^{\circ}C$ during summer can be a candidate site for the turbot aquaculture.

• Journal of Aquaculture
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• v.17 no.2
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• pp.122-127
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• 2004

On protein equivalence base, fishmeal (FM) was replaced by lysine cell mass (LCM) in selected different diets in Korean rockfish, Sebastes schlegeli (Hilgendorf) Eight experimental diets were formulated to contain 100% FM (LC $M_{0}$), 90% FM+10% LCM (LC $M_{10}$),80% FM+20% LCM (LC $M_{20}$), 70% FM+30% LCM (LC $M_{30}$), 60% FM+40% LCM (LC $M_{40}$ ), 70% FH+30% LCM+lysine (LC $M_{+Lys}$), 60% FM+40% LCM+lysine (LC $M_{40+Lys}$), and 50% FM+50% LCM+lysine (LC $M_{50+Lys}$). Experimental individuals of the fish (12.6 g) were randomly fed on one of the experimental diets. After 6 weeks of feeding trial, weight gain (WG) and feed efficiency (FE) of fish fed LC $M_{0}$ diet was significantly (P〈0.05) higher than those of fish fed LC $M_{20}$, LC $M_{30}$, LC $M_{40}$ , LC $M_{30+Lys}$, LC $M_{40+Lys}$, and LC $M_{50+Lys}$ diets, however, there was no significant difference in WG of fish fed LC $M_{0}$ and LC $M_{10}$ diets. Supplementation of lysine has no effect on WG. There was no significant difference in condition factor (CF) of fish fed LC $M_{0}$, LC $M_{10}$ and LC $M_{20}$ diets. Hemoglobin (Hb) of fish fed LC $M_{0}$, LC $M_{10}$, LC $M_{20}$, LC $M_{30}$, LC $M_{40}$ , LC $M_{30+Lys}$, and LC $M_{40+Lys}$, diets were not significantly different from each other. No significant differences were observed in hematocrit (PCV) and hepatosomatic index (HSI) among all dietary treatments. Apparent digestibility of dry matter (ADM) and protein (ADP) of diets significantly decreased with increase in dietary LCM level, though there was no difference in ADM and ADP between LC $M_{0}$ and LC $M_{10}$. These results indicate that LCM could replace up to 10% of fishmeal in Korean rockfish diets.ish diets.iets.ish diets.s.ish diets.

• Ocean and Polar Research
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• v.26 no.3
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• pp.415-423
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• 2004

An experiment was conducted to investigate the differences of total ammonia nitrogen (TAN) excretion rates and feces production rates among the offsprings from cultured Japanese strain (JJ, mean BW; $17.1{\pm}0.1g$), intraspecific hybrid strain between cultured Japanese and selected Korean strain (JK, mean BW: $17.1{\pm}0.1g$) and selected Korean strain(KK, mean BW: $21.5{\pm}0.1g$) of red sea bream in order to compare their dietary protein utilization efficiency. Fish were hand-fed with a commercial diet containing 46.7% crude protein for 2 weeks, three times daily 09:00, 13:00 and 17:00. After daily feeding, the TAN excretion rates reached peaks of 49.03, 58.75 and 36.26mg/kg fish/hr for the JJ, JK and KK strain, respectively, during the daytime. The value of the KK strain was significantly lower than that of the JJ and JX shuin (P<0.05), however daily TAN excretion rates of the JJ, JK and KK strain were not different (P>0.05). When fish were fed at satiation after 4 days of starvation, TAN excretion rates reached the maximum values 4 hours after the feeding fur the KK (31.23 mg/kg fish/hr) and 6 hours after the feeding fur the JJ (44.19 mg/tg fish/hr) and JK strain (41.70 mg/kg fish/hr). After 3 days of starvation, the daily endogenous TAU excretion rates (ETE) for the JJ, JK. and KK strain were 286.91, 215.66 and 179.29mg/kg fish/day, respectively. The value of the KK strain was lower than that of the JJ and JK strain (P<0.05). The total feces production rates of the JJ, JK and KK strain were not significantly different, however the proportions of feces production rates by time for the JJ, JK and KK strain were different (P<0.05). As overall results, efficiency of dietary protein utilization of JJ, JK and KK seems to be different and KK strain could offer a desirable option for aquaculture purpose.