• Journal of Ecology and Environment
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• v.37 no.4
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• pp.185-194
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• 2014

Seasonal monitoring was implemented to understand the influence of macrophyte bed structure on the composition and trophic interaction of aquatic organisms (algae, zooplankton, macro-invertebrate, and fish) in a shallow wetland (Upo Wetland, South Korea). Distinct division of the plant assemblage (reed zone and mixed plant zone) was observed. The reed zone was composed solely of Phragmites communis, whereas the mixed plant zone comprised a diverse macrophyte assemblage (Salvinia natans, Spirodela polyrhiza, Trapa japonica, Ceratophyllum demersum, and Hydrilla verticillata). Most of the aquatic organisms were more abundant in the mixed plant zone than in the reed zone, and this was positively associated with the seasonal development of macrophyte cover. Stable isotope analysis showed seasonal interactions among aquatic organisms. The majority of aquatic animal (zooplankton, Odonata, and Ephemeroptera) were dependent on epiphytic particulate organic matter (EPOM), and the dependence on EPOM gradually increased toward autumn. Interestingly, Lepomis macrochirus consumed Ephemeroptera and zooplankton in both macrophyte zones, but Micropterus salmoides depended on different food items in the reed zone and the mixed plant zone. Although, M. salmoides in the reed zone showed food utilization similar to L. macrochirus, it consumed Odonata or small L. macrochirus in the mixed plant zone. Based on these results, it appears that differences in the structure of the two macrophyte zones support different assemblages of aquatic organisms, strongly influencing the trophic interactions between the aquatic organisms.

• Journal of fish pathology
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• v.34 no.1
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• pp.117-121
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• 2021

An ayu (Plecoglossus altivelis) farm in Korea recently experienced an epidemic of vertebral column deformities where about 90% of fry displayed a vertebral column that was grossly opaque along either the cranial part of the column or its entire length. Abnormal fish were lordotic, scoliotic and/or kyphotic about midway down the spine. Examination of serial sections of whole fish showed only histological lesions in the vertebral column and suggested some disturbance in the early development of the vertebral centrum. Such abnormalities included a frayed spinal or notochord sheaths with irregular thickening and compression, mal-absorbed notochord cells, thickening of around cell layer and hypercellularity on both facets of the notochord sheath. No parasites, fungi, or bacteria were detected. While this lesion has only been reported once in the past, this is the first report of histopathological findings.

• Korean Journal of Environmental Biology
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• v.36 no.2
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• pp.99-106
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• 2018

Extensive monitoring of aquatic organisms in rice paddy fields has been difficult due to laborious sampling methods such as quadrat sampling using a hand net. This study aimed to analyze temporal and regional community compositions of aquatic organisms collected with a less time-consuming sampling method. This method involved using submerged funnel traps in rice paddy fields. Submerged funnel traps were useful for capturing taxa containing species that are indicative of environmental changes and highly mobile species that feed on waterbirds. Fifteen taxa including Ampullariidae, Cobitidae, Chironomidae, Hydrophilidae and Dytiscidae determined the community compositions. Among the major taxa, only Chironomidae resistant to environmental disturbances represented temporal variations of aquatic organism communities in rice paddy fields. Ampullariidae, Dytiscidae, and Hydrophilidae, which are prone to be affected by anthropogenic activities, differed among regions.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.2
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• pp.174-178
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• 2014

In this study, 6-10 clinically healthy farmed abalone, Haliotis discus hannai were obtained from Jeollanam-Do Wando Soan-myeon, Bogil-myeon, and Nohwa-eup monthly for 1 year 7 months and were examined histopathologically. As a result, the adductor muscle had severe cellular swelling and myonecrosis. These lesions were stained with hematoxylin and eosin and Giemsa. The lesions were not caused by infection of bacteria or parasites. We investigated the relationship between lesion frequency and water temperature and discovered that increased water temperature was associated with increasing lesion frequency. As water temperature is related to growth rate, increased growth rate was closely related to increased lesion frequency. We considered that these lesions could be a useful factor in measuring shellfish health.

• Proceedings of the Korean Aquaculture Society Conference
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• 2006.05a
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• pp.163-165
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• 2006

• Journal of Fisheries and Marine Sciences Education
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• v.27 no.1
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• pp.49-62
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• 2015

As methods reducing damages by jellyfish which enter the coastal areas of Korea, attaching cutting devices to towing nets of otter trawls or pair trawls and/or using a canvas type of cutting nets of small fishing boats have been widely utilized. In order to reduce shut-down damages of power plants in coastal areas due to the mass influx of marine organisms including jellyfish, a possible improvement of the traveling water screen system and various jellyfish influx blocking devices were suggested in this study. The results could be utilized as an important index for reducing damages by jellyfish bloom which cause on a massive scale in summer in Korea.

• Journal of Fisheries and Marine Sciences Education
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• v.26 no.1
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• pp.10-21
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• 2014

The aquatic disease inspector is not classified as an occupation in the current Korean Standard Classification of Occupations(KSCO). Therefore, the roll of the aquatic disease inspector in the medical treatment and the prevention against the aquatic organism disease is underestimated. The aquatic disease inspector is in a more disadvantageous position than the pharmacist and the veterinarian. The purpose of this study is to approve the aquatic disease inspector as an occupation in KSCO. The important contents of this study are as follows. In the first place, this study looks around the general requirements of classifying the occupations in KSCO. The aquatic disease inspector satisfies the most general requirements. But, because of the similarities of job between the aquatic disease inspector and the veterinarian, the aquatic disease inspector do not satisfy the requirement for 'the principle of exclusiveness'. In the second place, this study looks around the classification system of KSCO. The classification system of KSCO is consists of multi steps. This study makes the plan for the appropriate occupation classification of the aquatic disease inspector. In the third place, this study looks for the legal methods to classify the aquatic disease inspector as an occupation in KSCO. In order to classify the aquatic disease inspector as an occupation in KSCO, many regulations of the laws about the aquatic disease inspector and the veterinarian are to be amended and the number of the aquatic disease inspectors is to be increased by the innovative measures.

• Fisheries and Aquatic Sciences
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• v.19 no.4
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• pp.19.1-19.7
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• 2016

A laboratory experiment was conducted to determine hexavalent chromium ($Cr^{6+}$) accumulation in the mullet and investigate $Cr^{6+}$ toxicity using a panel of biomarkers including metallothioneins (MTs), glutathione (GSH), glutathione S-transferase (GST), and superoxide dismutases (SODs) for 4 weeks. $Cr^{6+}$ bioaccumulation in all tissues, except muscle, was consistently time- and dose-dependent. The accumulation of $Cr^{6+}$ for 4-week exposures was in the following order: $kidney{\approx}liver$ > $intestine{\approx}gill$ > spleen > muscle. Compared with the control, $Cr^{6+}$ bioaccumulation was increased in ${\geq}200{\mu}g\;L^{-1}$ groups (P < 0.05). An independent relation was observed between accumulation factors (AFs) and exposure concentration. But AFs increased with exposure time. In the liver and gill, GST and SOD differed from the control at a high $Cr^{6+}$ concentration at 2 and 4 weeks (P < 0.05). This study indicated that the gills were as sensitive as the liver to $Cr^{6+}$ toxicity. However, the latter appeared to influence largely on the organism's adaptive response to $Cr^{6+}$, since $Cr^{6+}$ may elevate GSH and MT levels by enhancing the hepatic uptake of metal in the mullet.

• Journal of fish pathology
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• v.26 no.1
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• pp.45-50
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• 2013

Enrofloxacin is one of the normally used flouroquinolones in mammalian and fish but its withdrawal time and studies were remain obscure. The residual contents of enrofloxacin in fish muscle were analyzed by using HPLC-FLD. More than 0.1 mg/kg of ENR was detected in muscle tissues and the residues were found over 1 year after treatment. The concentration of ENR in Paralichthys olivaceus was not affected by water temperature and lasted for an extended amount of time. The spike recoveries of ENR in the muscle tissue ranged from 78% to 85%. From this results, we need the prescription by veterinarian or aquatic organism disease inspector in ENR usage to assure safety of fish. Future research is required to determine the recommendation dose of ENR for side effects and safety.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.55 no.5
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• pp.688-696
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• 2022

Obesity could cause immune-physiological disorders in fish. Yet, little is known about the impact of obesity on stress and histological responses. This study aimed to determine histological and physiological changes in and vulnerability of overfeeding-induced obese rainbow trout Oncorhynchus mykiss exposed to stress condition. Control, intermediate and overfed groups were fed at 1.5, 2.5 and 3.09% of their body weight per day, respectively, for eight weeks. Weight gain, body mass index, hepatosomatic index and serological parameters, and histology of liver were measured in five fish from each group at week 0, 2, 4, and 8. At week 8, 20 fish from each group were exposed to heat stress by increasing water temperature at a rate of 3℃ per day from 15 to 25℃ and maintaining the final temperature for 10 days. Overall, overfed fish showed significantly higher weight gain, body mass index, and serological parameters than those of fish in the other groups. Fish in the overfed and intermediate groups displayed multifocal infiltration of inflammatory cells in hepatic parenchyma. Mortality rate and serological parameters of fish in the overfed group exposed to heat stress were significantly higher than those of fish in the other groups, indicating increased vulnerability to environmental stress.