• Fisheries and Aquatic Sciences
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• v.6 no.3
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• pp.160-163
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• 2003

Mortality of several species of fish and shellfish exposed to Harmful Algal Blooms (HABs) caused by Cochlodinium polykrikoides, Heterosigam akashiwo, Alexandrium tamarense, Eutreptiella gymnastica, Heterocapsa triquetra and Prorocentrum micans was studied. When fish were exposed to a cell density of 8,000 cells $mL^{-1}$ in C. polykrikoides, $35\%$ of flatfish and darkbanded rockfish died within 48 hrs. However, jacopever rockfish had mortality of higher than $85\%$. Rock bream, filefish and red sea bream showed $100\%$ mortality within 10 hrs with an exposure cell density of 8,000 cells $mL^{-1}$. The rest of HABs except for C. polykrikoides showed that there was no fish and shellfish death throughout the 48 hrs even in the maximum cell density of 100,000 cells $mL^{-1}$ These results imply that C. polykrikoides can have a serious impact on fish mortality and it is regarded as an ichthyotoxic dinoflagellate. The fish death may be attributed to anoxia caused by a combination of the production of reactive oxygen species (ROS) and polysaccharide from C. polykrikoides during blooms.

• Journal of fish pathology
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• v.16 no.2
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• pp.81-90
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• 2003

High mortality with signs similar to viral haemorrhagic septicemia (VHS) such as severe haemorrhages in the skin, muscle and air bladder occurred in the farmed adult rainbow trout, Oncorhynchus mykiss, in Ku-mi and Je-chun area in Korea. The isolates were neutralized by an antiserum against IHNV but not by antisera against VHSV. Electron micrograph of an ultrathin section showed large numbers of bullet-shaped virus particles. The newly isolated rhabdovirus was composed of five structural proteins. In the western blot analysis Ihe anti-DiNV serum strongly reacted with G. N and MI protein. The cumulative mortalities of RTK infected rainbow trout (10-12cm.9-12g) with $10^{3.5}\;and\;10^{1.5}TCID_{50}/m{\ell}$ were 80% and 30%. respectiveIy_ RTJ infected fish showed 50% mortality by infection with $10^{3.5}TCID_{50}/m{\ell}$. Control group and IHNVChAb exhibited no mortality. From these results, the viruses were identified lHNV although diseased fish showed similar sign. with VHS and caused high mortality in large-sized fish.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.56 no.4
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• pp.407-418
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• 2020

Mass mortality of mariculture fish due to high summer temperatures is a major issue in the mariculture industry in many coastal waters of Korea, yet measures to mitigate the impact are generally limited. We injected a micro-bubble of liquefied oxygen into the bottom of rockfish cages (about 6-8 m deep) in order to maximize the dispersal of micro-bubbled seawater and reduce fish mortality. The injection of low-temperature oxygen in micro-bubbles lowered the water temperature at the injection area by as much as 1℃ and increased dissolved oxygen concentration by 0.5 ppm. In early August, following a week with persistent high water temperature (above 28.5℃), there was an increase in fish mortality despite the micro-bubble system, which resulted in approximately 7% death of the total introduced fish population. However, this mortality appeared to be much lower than mortality reported in a neighboring mariculture facility (approximately 50% mortality). We also estimated the volume that can be recirculated with pumped seawater using a micro-bubble system. We suggest that this approach of injecting liquefied oxygen through a micro-bubble system may reduce fish mortality during high temperature periods.

• Korean Journal of Ecology and Environment
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• v.45 no.3
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• pp.314-321
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• 2012

To quantitatively assess the effects of turbidity on egg development and larval fish survival, a laboratory fish rearing experiment was applied to different life stages (newly hatched larval stage, juvenile stage and pre-adult stage) of the Zacco platypus, one of the most universal and tolerant species in Korea. According to the stress index of turbidity in water with exposure time, three different treatments, including a reference condition (1~7 NTU) as well as intermediate (20~150 NTU) and high turbidity conditions (400~1,000 NTU) were applied, and egg hatching and larval fish mortality rates were observed. The mortality rates of newly hatched larval fish were significantly different among treatments (ANOVA, $F_{2,3}$=17.79, p<0.05). Average rates of survival to hatching were 20.9% (${\pm}0.1%$) for reference condition, 11% (${\pm}6.9%$) for intermediate level and 3.2% (${\pm}3.7%$) for high level conditions, respectively. A sudden change of mortality at the high level was observed within 5 days of the experiment. About 84% of juvenile fish survived until 20 experimental periods under conditions of reference turbidity, while survival under conditions of intermediate turbidity was over 80% of larval fish until day 13 of the experiment, but dropped to less than 10% after day 14 and 15 of two experiments. Fish mortality appeared from day 6 of the high turbidity experiment, and 50% mortality was achieved at day 9 to 10 of experiment. Full mortality occurred at day 14 of the experiment (RM-ANOVA, $F_{2,38}$, p<0.005). In the pre-adult stage experiment, no mortality was observed during the experiment at reference level treatment (20 days), while only slight mortality rates were observed for both intermediate and high levels until day 5 of the experiment, however, no further fish died in either experiment. It was significantly different compared to reference condition (RM-ANOVA, $F_{2,20}$=8.28, p<0.01), but no difference was observed between intermediate and high level conditions. Consequently, this tolerant species has been determined to be well adapted to high levels of turbidity in its adult stage, but more vulnerable throughout earlier life stages.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.14 no.2
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• pp.107-115
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• 2011

The purpose of the study is to analyze the environmental characteristics of fish acute toxicity that is dependent on the harmfulness of ACQ (Alkaline Copper Quat)-Treated Wood and Oryzias latipes mortality in a comprehensive way, provide objective verification method on the eco-toxicity and environment-friendliness of landscaping materials and methods, and utilize it as a basic datum for evaluation criteria. The main results are summarized as follows : 1. As a result of analysis on the harmfulness characteristics, each experimental plot showed different values respectively. In particular, it has been found that in proportion to the volume of testing materials, COD and Cu increases at a constant rate, compared to the input water. In the plot C with three testing materials, COD increased 67 times more than that of the input water, and Cu increased up to 12.36mg/L. 2. In case of fish toxicity, plot C, B, A all showed a mortality rate of 100%, indicating that fish toxicity is strong. In particular, the mortality rate of each plot within the initial time of one and a half hour showed clearly, which suggests that the fish toxicity is influenced by the increased concentration of hazardous substances depending on the volume ratio of testing materials. 3. As a result of comparison and analysis on the harmfulness and fish toxicity, the harmfulness showed different values on each experimental plot but, we found that the changing rate of values of toxicity of COD and Cu is mutually similar to that of mortality in the initial hour according to the experiment of fish toxicity, which shows that COD and Cu are major factors to increase fish toxicity.

• Journal of fish pathology
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• v.34 no.2
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• pp.255-259
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• 2021

This is the first report describing acute mass mortality occurred in juvenile olive flounder (Paralichthys olivaceus) caused by gas bubble disease (GBD). A total of 610 fish (average weight = 35 g), which were more than half of the fish acclimated at 17℃ in an aquarium, were killed within two days of acclimation. The dead and moribund fish showed excessively opened opercula and mouths, and occasionally, severe exophthalmia. Through microscopic observation, numerous gas emboli were found in the gills of the dead and live fish, while the fish were not infected with any microbial pathogens. The dissolved oxygen (DO) saturation level of the rearing water and seawater nearby the facility reached 145% and 286%, respectively, whereas other water quality parameters (such as salinity, pH, and chemical oxygen demand) were normal. The extreme saturation rate of seawater in the shore nearby seemed to be due to an enormous algal bloom that occurred there. Through molecular identification based on 18S rDNA sequences, the most dominant algal species was most closely related to Ulva californica (99.87% sequence identity) followed by U. prolifera, U. linza, and U. curvata (99.81%). Therefore, it can be concluded that supersaturated seawater due to mass algal bloom caused gas bubble disease in the olive flounder, leading to mass mortality. After technical adjustment, such as increased aeration, lowered water circulation rate, and inlet water filtration using micro-pore carbon filters, the DO level became normal, no further mortality occurred and the status of the fish was stabilized.

• Journal of fish pathology
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• v.35 no.1
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• pp.77-92
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• 2022

Aquaculture development is based on the ideas of increasing production while reducing economic losses. Bacterial diseases are the leading source of fish cases. Citrobacter freundii has been linked to septicemia and mortality all over the world. In the current study, the cause of mortality in O. niloticus was C. freundii MW279218. External hemorrhages were seen on the affected fish, as well as paleness in the liver and kidney congestion. C. freundii MW279218 had a median lethal dosage of 1.5×10⁵ CFU/mL. Zinc oxide and zinc oxide nanoparticles (ZnO-NPs) were tested for their biocidal effectiveness against C. freundii MW279218. The lethal effect of ZnO-NPs for C. freundii MW279218 was 100% when compared to zinc oxide compound, and the inhibition zone width was 2.31.1mm at the highest tested concentrations (70 mg/L) compared to the lowest (35 and 45 mg/L, respectively). Fish were fed three different diets for 28 days: diet 1 (no additives), diet 2 (100 mg of ZnO-NPs/kg of feed), and diet 3 (200 mg of ZnO-NPs/kg of feed). Organs were also collected for histopathology 96 hours after injection (P<0.05). In the groups given 200 mg of ZnO-NPs, there was 10% mortality and 80% RPS. The group fed 100 mg of ZnO-NPs/kg, on the other hand, had 20% mortality and 60% RPS, compared to 50% mortality in the control positive group. Histopathological examinations demonstrated significant alterations in the control positive group and mild lesions in the hepatopancreas of the groups administered 100 mg ZnO-NPs/kg of feed. The groups fed 200 mg of ZnO-NPs/kg diet, on the other hand, showed no histological alterations. ZnO-NPs were found to be effective in the up regulation of both IL-10 and complement 5 immune-related genes.

• The Journal of Fisheries Business Administration
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• v.48 no.3
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• pp.47-59
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• 2017

Fish mortality is the most important success factor in aquaculture management. To order fingerlings considering the effect of mortality is a important problem in aquaculture farm. This study is aimed to decision the number and size of fry in aquaculture farm. This study build the mathematical model that finds the value of decision variable to minimize total cost that sums up the fingerling purchasing cost, aquaculture farm operating cost and feeding cost under mortality constraint. The proposed mathematical model involve biological and economical variables: (1) number of fingerlings (2) fish growth rate (3) mortality (4) price of a fry (5) feeding cost, and (6) possible order period. Numerical simulation model presented here in. The objective of numerical simulation is to provide for decision makers to analyse and comprehend the proposed model. When extensive biological and cost data become available, the proposed model can be widely applied to yield more accurate results.

• The Journal of Fisheries Business Administration
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• v.47 no.4
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• pp.1-13
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• 2016

Fish mortality is the most important success factor in aquaculture management. To analyze the effect of mortality considering biological and economic condition is a important problem in land-based aquaculture. This study is aimed to analyze the effect of mortality for duration of cultivation in land-based aquaculture. This study builds the mathematical model that finds the value of decision variable to minimize cost that sums up the water pool usage cost, sorting cost, fingerling cost and feeding cost under critical standing corp constraint. The proposed mathematical model involves many aspects, both biological and economical: (1) number of fingerlings (2) timing and number of batch splitting event, based on (3) fish growth rate, (4) mortality, and (5) several farming expense. Numerical simulation model presented here in. The objective of numerical simulation is to provide for decision makers to analyse and comprehend the proposed model. When extensive biological and cost data become available, the proposed model can be widely applied to yield more accurate results.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.13 no.4
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• pp.42-51
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• 2010

The purpose of this study is to analyze the characteristics of environment-friendliness of Root Barrier materials based on comprehensive experiments on harmfulness of Root Barrier materials and fish toxicity of Oryzias latipes mortality to verify eco-toxicity of each method of construction and Root Barrier material, which are to be applied by taking eco-toxicity into account when building ecological flows in upper areas on natural and artificial grounds. As a result, the following conclusions have been reached in this study: 1. In regard of the harmfulness analyzed, each material showed a different result of analytical value in each lab tank. Compared to lab tank, pH (la), DO (lb), T-N (VI) and T-coli (la) were in the same grade, but COD, SS, T-P and F-coli were less than that of control, respectively increased or decreased by material were analyzed. 2. In the experiment of fish toxicity, Barrier sheet was found to have 66.7% of fish mortality, indicating strong fish toxicity. Synthetic rubber system root barrier sheet (20.0%) was analyzed to have medium fish toxicity, while Synthetic resin system root barrier-waterproof sheet (3.3%), Synthetic rubber system membrane root barrier sheet (3.3%) and Synthetic resin system root barrier sheet (0.0%) showed relatively lower mortality and fish toxicity. To sum up such results as found in the experiment mentioned so far, the values of harmfulness and root penetration resistance analyzed were different in each lab tank, but there was absolutely little correlation with the mortality gained from the experiment on fish toxicity. In the experiment of fish toxicity, environment-friendly root barrier materials were analyzed, and it was found that Synthetic resin system root barrier sheet, Synthetic resin system root barrier waterproof sheet and Synthetic rubber system membrane root barrier sheet are highly environment-friendly. In contrast, Synthetic rubber system root barrier sheet was found to have medium-level environment-friendliness. Also, Barrier sheet was analyzed to have low environment-friendliness.