• Korean Journal of Fisheries and Aquatic Sciences
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• v.52 no.5
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• pp.474-481
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• 2019

This study evaluated the chronic effects of $NO_3-N$ on juvenile blackhead seabream Acanthopagrus schlegelii. The experiment used six identically configured recirculating aquaculture systems (435 L), with three tanks (70 L) each. The $NO_3-N$ concentrations studied were 0 (control), 62.5, 125, 250, 500, and 1,000 mg/L $NO_3-N/L$. Thirty juvenile blackhead seabream ($18.8{\pm}2.2g$) were stocked in each tank. Growth and hematological changes were evaluated after 120 days. At the end of the experiment, the growth, survival, and cortisol levels indicated that blackhead seabream were healthy in 500 mg $NO_3-N/L$. However, insulin-like growth factor I (IGF-1) and the IGF-1 receptor were significantly lower at 250, 500, and 1,000 mg $NO_3-N/L$ than in controls (62.5 and 125 mg $NO_3-N/L$). Juveniles were likely affected at a much lower $NO_3-N$ concentration than 250 mg/L $NO_3-N/L$ in terms of IGF-1 and the IGF-1 receptor. Therefore, for the sake of long-term fish welfare, the $NO_3-N$ should be maintained at lower than 250 mg/L for blackhead seabream in recirculating aquaculture systems.

• Journal of Life Science
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• v.25 no.1
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• pp.16-20
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• 2015

During the storage of these two species in a large conservation tank, fertilized eggs were collected and the offspring were raised. During culturing of the offspring, individuals with mixed characteristics of these two species were observed, and 96 individuals were randomly tested using microsatellite markers applicable to both species. Among the 96 individuals, 15 individuals with mixed morphological characteristics were confirmed to be hybrids showing both of genotypes red seabream and blackhead seabream. Additionally, based on sequence analysis of mitochondrial cytochrome oxidase subunit 1 (mtDNA CO1), 81 showed 99% nucleotide sequence identity to that of black sea bream, and the remaining 15 individuals showed over 99% sequence identity to that of red seabream. So, hybrids were produced by female red seabream and male blackhead seabream. These results suggest that hybrids may form in nature between these two species if their habitats overlap due to the influence of humans or global climate change.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.52 no.3
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• pp.268-273
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• 2019

This study evaluated acute nitrate nitrogen ($NO_3-N$) toxicity in juvenile blackhead seabream Acanthopagrus schlegelii. Seventy juveniles (Trial A, $7.1{\pm}0.6g$) and nine juveniles (Trial B, $71.3{\pm}3.5g$) per 70 L tank were exposed to $NO_3-N$ concentrations of 0, 500, 1500, 2500, 3500, and 4500 mg/L and 0, 600, 1200, 1800, 2400, and 3000 mg/L, respectively, in triplicate for 7 days. In Trial A, all fish exposed to 3500 and $4500mg\;NO_3-N/L$ died within 48 h; in Trial B, all fish exposed to $3000\;NO_3-N/L$ died after 120 h. The $96\;LC_{50}$ and $168\;LC_{50}$ were 2505 and $1806mg\;NO_3-N/L$, respectively, in Trial A, and 2663 and $2377mg\;NO_3-N/L$ in Trial B. Large juveniles were more resistant to $NO_3-N$ than small juveniles. The results of acute $NO_3-N$ toxicity studies provide important data for subsequent chronic toxicity studies.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.48 no.4
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• pp.474-482
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• 2015

This study aims to investigate the patterns and incidence rates of morphological deformities during artificial fingerling production of blackhead seabream (BSB, Acanthopagrus schlegeli) juveniles by visual and soft X-ray observations of BSB juveniles (n=881) collected from four industrial hatcheries. Using both methods, we observed seven types of external deformity ($11.2{\pm}4.4%$) and eight types of skeletal deformity ($53.4{\pm}5.1%$). Lordosis occurred in all hatcheries with the highest frequency and the mean frequency was $13.1{\pm}4.4%$ (24.5% in total abnormal) by soft X-ray. Although they had a similar standard length (SL), juveniles with lordosis had a significantly lower condition factor and body weight than normally developed juveniles (P<0.05); normal distribution curves of histogram of body proportions, i.e., body height (BH)/head length (HL) and trunk (=SL-HL)/BH, indicated differences between normally developed juveniles and those with lordosis. In addition, 59% of juveniles with lordosis had vertebral curvature of less than $20^{\circ}$, generally at the $17^{th}$ vertebrae. It is expected that the above results will be used as basic data necessary for determining the cause of lordosis and for developing techniques to prevent this symptom in the fingering production industry of BSB juveniles.

• Journal of Species Research
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• v.8 no.4
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• pp.373-379
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• 2019

Two parasitic copepods, poecilostomatoid Colobomatus mylionus Fukui, 1965 and siphonostomatoid Clavellisa chinensis ($Y{\ddot{u}}$, 1933), were reported for the first time from Korea and redescribed based on the females collected from the marine fish of Korean waters. The C. mylionus was collected from the blackhead seabream, Acanthopagrus schelegelii(Bleeker). Colobomatus mylionus had been frequently reorded from marine teleost fishes from of Eden, Newcastle, Brisbane, Yelloon, and Point Sampson. The second record was C. chinensis redescribed based on the speciemens collected from the gills of a Japanese grenadier anchovy, Coilia nasus Temminck and Schlegel. Some differences were observed between the orginal description of known specimens examined in this study, these differences do not warrant a change in the taxonomic staus of the two species. The attachment site of all two copepods reported from Korea were the cephalic sensory canals and gills.