• Journal of fish pathology
• /
• v.20 no.3
• /
• pp.257-267
• /
• 2007

The hypo-salinity effects on fertilized eggs, embryos and larvae were investigated in olive flounder (Paralichthys olivaceus) obtained from hatcheries in Cheju-Island, Yeosu and Chungnam. Those were treated to eight concentration; 0, 3.4, 6.7, 10.1, 13.4, 20.2, 27.4 and 33.6 ‰. It was not discrepancy in the survival rate and hatching success rate of fertilized embryos obtained from different regions. Also, in the larvae, the regional difference was not appeared. The survival rate and hatching ability of embryos significantly diminished in the lower groups than 13.4 ‰ compared to 33.6 ‰. After fertilization, namely embryos are tolerant of a wide range of salinity (13.4 - 33.6 ‰). Reduced salinity induced an increase of the malformed embryo and larvae including various deformities; irregular embryos membrane (or yolk sac depression), fin erosion and swim bladder inflation in the flounder embryo. The hatching success of embryos was significantly reduced in lower salinity than 13.4 ‰. Notably, the reduction of larval survival rate significantly was observed in ≤10.1 ‰ treated groups with the same manner of survival rates of the embryos. Additionally, olive flounder was found to be adequate model for measuring external impulses because there are no the regional differences.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.48 no.2
• /
• pp.207-220
• /
• 2015

This study identified the species-specific, frequency-dependent characteristics of broadband acoustic scattering that facilitate classifying fish species using the pulse compression (PC) technique. Controlled acoustic scattering laboratory experiments were conducted with nine commercially important fish species using linear chirp signals (95-220 kHz) over an orientation angle range of ${\pm}45^{\circ}$ in the dorsal plane at approximately $1^{\circ}$ increments. The results suggest that the angular-dependent characteristics of the broadband echoes and the frequency-dependent variability in target strength (TS) were useful for inferring the fish species of interest. The scattering patterns in the compressed pulse output were extremely complex due to morphological differences among fish species, but the x-ray images strongly suggested that spatial separation correlated well with scattering for the head, skeleton, bone, otoliths, and swim bladder within each specimen.

• Applied Microscopy
• /
• v.40 no.4
• /
• pp.253-259
• /
• 2010

The ultrastructure of sperms in testes of the pond smelt (Hypomesus nipponensis) was investigated using electron microscopes. The whitish testis was located between swim bladder and intestine. Especially, the left testis was larger than the right testis. The sperm was approximately $26\;{\mu}m$ in length. The sperm had an oval head and the acrosome was not found. The nucleus was about 400 nm in diameter and chromatin was incompletely condensed. The nuclear fossa deeply formed in sperm head and two centrioles were located in the fossa. The mitochondrium was observed only one in midpiece of the sperm and a motile flagellum consisted of an axoneme with a typical 9+2 pattern of microtubule. Also, the tail of the sperm has axonemal fins.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.47 no.3
• /
• pp.234-240
• /
• 2011

In order to obtain the fundamental data about the behavior of sharks by underwater audible sound, this experiment was carried out to investigate the auditory characteristics of tiger shark Scyliorhinus torazame which was caught in the coast of Jeju Island by heart rate conditioning method using pure tones coupled with a delayed electric shock. The audible range of tiger shark extended from 80Hz to 300Hz with a peak sensitivity at 80Hz including less sensitivity at 300Hz. The mean auditory thresholds of tiger shark at the frequencies of 80Hz, 100Hz, 200Hz and 300Hz were 90dB, 103dB, 94dB and 115dB, respectively. The positive response of tiger shark was not evident after the sound projection of over 300Hz. At the results, the sensitive frequency range of tiger shark is narrower than that of fish that has swim bladder. In addition, it is assumed that the most sensitive frequency in auditory thresholds of Chondrichthyes is lower than that of Osteichthyes. Critical ratios of tiger shark measured in the presence of masking noise in the spectrum level range of about 60-70dB (0dB re $1{\mu}Pa/\sqrt{Hz}$) increased from minimum 27dB to maximum 39dB at test frequencies of 80-200Hz. The noise spectrum level at the start of masking was distributed at the range of about 65dB within 80-200Hz.

• Korean Journal of Ichthyology
• /
• v.11 no.2
• /
• pp.149-154
• /
• 1999

To use of the precise scientific name of the genus Hypomesus from Korea, taxonomic revison of the genus Hypomesus was studied based on the specimens collected at 11 sites of the reservoirs and estuaries from Korea. The most population of the Hypomesus nipponensis was taken the pneumatic duct that connected between the anterior part of swim bladder and stomach. The number of pyroric caeca of the specimens was zero to five. The number of chromatophore at isthmus was fifty to one hundred. And authors were confirmed with the membrane structure across the nasal cavity. Then, we think that the scientific name of the pond-smelt at Korea is Hypomesus nipponensis by these characters. The Yangyang population that have the sixty-two to sixty-three of vertebrae, was confirmed with H. japonicus.

• Korean Journal of Ichthyology
• /
• v.22 no.4
• /
• pp.273-278
• /
• 2010

Partial nucleotide sequences of nuclear protein-coding recombination activating gene 1 (RAG1) gene of two Abbottina and five Microphysogobio species residing in Korea were analyzed to elucidate the molecular phylogenetic position of A. springeri Banarescu and Nalbant. In RAG1 tree A. rivularis was clearly separated from the monophyletic lineage composed of A. springeri, Biwia zezera and Microphysogobio species. Within this lineage B. zezera showed sister-group relationship to the monophyletic group composed of A. springeri and five Microphysogobio species. Thus, our phylogenetic tree revealed the polyphyletic nature of two Abbottina species from Korea, which result is well congruent with the previous phyletic assumption based on osteological features. The current classification of Abbottina and Microphysogobio based on morphological criteria, such as the presence or absence of papillae on lips and size of swim bladder with or without encapsulation, does not reflect their true evolutionary history.

• Development and Reproduction
• /
• v.20 no.2
• /
• pp.51-63
• /
• 2016

The landmark-based morphometric and meristic analysis of the kelp grouper (Epinephelus bruneus), red spotted grouper (E. akaara) and seven-banded grouper (E. septemfasciatus) were performed to compare the differentiation of overall body shape and structure. The measurements of the morphometric dimensions were observed in 25 parts (truss dimension: 16 parts; head part dimension: 9 parts) of 38 morphometric dimensions and also meristic differences observed in 3 parts (dorsal fin, anal fin and caudal fin) of 6 meristic counts (P < 0.05). Observed morphometric characteristics primarily involved in truss and head part dimension, kelp grouper have larger values in caudal part of truss dimension, kelp grouper, red spotted grouper and seven-banded grouper have similar values in pectoral part of truss dimension, in addition to, results of head part dimension showed that red spotted grouper have smaller values in overall dimensions (P < 0.05). As meristic characteristics, kelp grouper have more number of anal fin rays than other fish, red spotted grouper have more number of dorsal soft rays than other fish, and seven spotted grouper have more number of anal soft rays, and caudal fin rays than other fish (P < 0.05). Photographed under the x-ray, kelp grouper have the most curved vertebral column and largest swim bladder than other fishes (P < 0.05). Our results of this study confirmed that 3 subfamily fishes adequately can distinguish with external body shape, and we hope that the results of our study could be used to identify in Serranidae family as taxonomical parameters.

• Fisheries and Aquatic Sciences
• /
• v.16 no.4
• /
• pp.253-260
• /
• 2013

We investigated the toxicological effects of Aroclor 1254 on the fertilized eggs, embryos and larvae of the olive flounder Paralichthys olivaceus. The survival rate and hatching success of the embryos decreased significantly in treated groups in an Aroclor 1254-dose-dependent manner. Significant differences were found at ${\geq}5{\mu}g/L$ Aroclor 1254 compared to the control group. Hatching success occurred at ${{\leq}}10{\mu}g/L$ Aroclor 1254, which was not significantly different to the control. Embryo malformation increased significantly at ${\geq}1{\mu}g/L$, and included yolk-sac and tail-flexure abnormalities. There was a significant decrease in the survival rate of the larvae at ${\geq}5{\mu}g/L$, which was accompanied by the malformations described above. Notably, concentrations as low as $1{\mu}g/L$ caused a significant increase in abnormalities in the larvae, including incidences of multi-focal hemorrhages, pericardial and yolk-sac edema, inhibition of swim bladder inflation and severe developmental delay. The responses to Aroclor 1254-induced toxicity were generally similar among fertilized eggs, embryos and larvae from three separate flounder hatcheries: Cheju Island, Yeosu and Chungnam, South Korea. These results indicate the high acute toxicity of Arolcor 1254 concentrations of which as low as $1{\mu}g/L$ in olive flounder larvae can affect unhatched embryos. To conclude, the average $LC_{50}$ values for Aroclor 1254 in the embryos and larvae were 50.92 and $3.08{\mu}g/L$, respectively. Additionally, the average $EC_{50}$ values, based on the rate of damage were 14.72 and 5.6$1{\mu}g/L$, respectively.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.48 no.4
• /
• pp.479-486
• /
• 2012

In order to obtain the fundamental data about the behavior of conger by underwater audible sound, this experiment was carried out to investigate the hearing ability of Conger eel Conger myriaster which was in the coast of Jeju Island by heartbeat conditioning method using pure tones coupled with a delayed electric shock. The audible range of conger eel extended from 50Hz to 300Hz with a peak sensitivity at 80Hz including less sensitivity over 200Hz. The mean auditory thresholds of conger eel at the frequencies of 50Hz, 80Hz, 100Hz, 200Hz and 300Hz were 105dB, 92dB, 96dB, 128dB and 140dB, respectively. The positive response of conger eel was not evident after the sound projection of over 200Hz. At the results, the sensitive frequency range of conger eel is narrow in spite of swim bladder. Auditory masking was determined for Conger eel by using masking stimuli with the spectrum level range of about 60~70dB (0dB re $1{\mu}Pa/\sqrt{Hz}$). According to white noise level, the auditory thresholds increased as compared with thresholds in a quiet background noise including critical ratio at 68dB of white noise from minimum 26dB to maximum 30dB at test frequencies of 80Hz and 100Hz. The noise spectrum level at the start of masking was distributed at the range of about 68dB within 80~100Hz.

• Korean Journal of Ichthyology
• /
• v.29 no.3
• /
• pp.157-164
• /
• 2017

In 2015, a nervous necrosis virus (NNV) was isolated from sevenband grouper, Epinephelus septemfasciatus, maintained in land-based aquaculture system at below $12^{\circ}C$ in winter. Mortality was up to 30% in brood fish, over 4 kg of body weight. Moribund fish showed clinical sings typical of viral encephalopathy and retinopathy (VER), also called viral nervous necrosis (VNN), such as uncoordinated, corkscrew-like swimming behavior, belly-up at rest, darkening of body, cloudy eyeball and hyperinflation of the swim bladder. Aetiology of the disease was confirmed by gross observation of clinical signs, histopathology and molecular diagnosis. Histological studies revealed severe vacuolation and necrosis in the brain. Molecular diagnosis by revere transcription-polymerase chain reaction (RT-PCR) specific to batanodavirus yielded a positive result. The nucleotide sequences of the PCR-amplified fragment were 99.48~100% similar to barfin flounder nervous necrosis virus (BFNNV) genotype and most closely aligned with Pacific cod betanodavirus (PCNNV). This is the first report of natural batanodavirus, NNV infection in sevenband grouper reared in low water temperature during winter (below $12^{\circ}C$) in Korea.