• 한국수산과학회지
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• 제43권2호
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• pp.159-168
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• 2010

This paper presents a mathematical model and simulation method for investigating the performance of set net systems and fish cage systems influenced by currents and waves. Both systems consist of netting, mooring ropes, a floating collar and sinkers. The netting and ropes were considered flexible structures and the floating collar was considered an elastic structure. Both were modeled on a mass-spring model. The structures were divided into finite elements and mass points were placed at the mid-point of each element, and the mass points were connected by mass-less springs. Each mass point was subjected to external and internal forces and the total force was calculated at every integration step. An implicit integration scheme was used to solve the nonlinear dynamic system. The computation method was applied to dynamic simulation of actual systems simultaneously influenced by currents and waves in order to evaluate their practicality. The simulation results improved our understanding of the behavior of the structure and provided valuable information concerning the optimized design of set net and fish cage systems exposed to an open ocean environment.

• Journal of Nutrition and Health
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• 제29권1호
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• pp.32-40
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• 1996

To investigate the effect of dietary docosahexaenoic acid(DHA) and environmental enrichment on brain fatty acid composition and acetylcholinesterase(AChE) activity, two groups of was fed isocaloric diets containing 10 or 12% dietary lipids for 7 weeks. A third group was fed 10% (w/w) dietary lipids with supplemented 2% DHA-rich fish oil. Each diet group was housed either in a stainless steel cage individually or in a large enriched cage with toys where 7 rats were kept together. The fatty acid composition of plasma and brain was significantly affected by dietary lipid composition but not by environmental enrichment. Fish oil supplementation significanlty decreased plasma levels of monounsaturated fatty acids(MUFA) and increased polyunsaturated fatty acids(PUFA). Fish oil supplemented groups also maintained lower plasma n-6 fatty acids and higher n-3 fatty acids levels than unsupplemented groups. The fish oil supplementation significantly decreased arachidonic acid and increased eicosapentaenic, docosapentaenoic acids, and DHA in brain fatty acid composition. In addition, brain DHA level in supplemented groups tended higher than the unsupplemented. Brain, AChE activity significantly increased by the environmental enrichment but not by the fish oil supplementation. These finding suggest that the 2% fish oil (0.57% DHA & 0.31% EPA, per diet weigth) supplementation is enough to accumulate n-3 fatty acids and to change the n-6 n-3 ratio in brain and environmental enrichment might promote the learning ability.

• 한국해양학회지:바다
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• 제2권2호
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• pp.151-159
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• 1997

1995년 6월, 남해안 통영지역 가두리양식장 해수-퇴적물 경계면에서 입자상유기물의 수직유입량과 용존산소의 소모량, 영양염류의 용출량을 관측하였다. 입자상유기물의 수직유입량은 저층고정식 sediment trap을 이용하였으며, 용존산소의 소모량과 영양염류의 용출량은 benthic chamber method로 측정하였다. 가두리양식이 연안부영양화에 미치는 영향과 가두리에서 유출된 입자상유기물의 확산강도를 정량하기 위해, 가두리 아래(수심 약 18 m, Cage Site)와 가두리에서 수평으로 약 100 m 가량 떨어진 곳(수심 약 32 m, Control Site)의 해수-퇴적물 경계면에서, 암모니아와 인산염, 규산염의 용출량을 비교하고, 탄소와 질소와 인의 mass balances를 추정하였다. 관측결과, 가두리정점(Cage Site)으로는 6400 mg C $m^{-2}d^{-1}$의 입자상유기물이 유입되었고, 동시에 230 mmol $O_2\;m^{-2}d^{-1}$ 이상의 용존산소가 소모되었다. 따라서 탄소의 경우, 가두리 아래 해저면으로 공급되는 유기 입자의 약 40%에 달하는 양이 해수-퇴적물 경계면에서 분해되며 (ca. 2400 mg C $m^{-2}d^{-1}$), 나머지 약 60%는 퇴적되어 매몰되는 것으로 보인다. (ca. 4000 mg C $m^{-2}d^{-1}$) 그러나 대비정점(Control Site)에서는 가두리정점에 비해 상대적으로 적은 양의 유기물유입과(ca. 4000 mg C $m^{-2}d^{-1}$), 낮은 용존산소소모율이 관측되었다(75 mmol $O_2\;m^{-2}d^{-1}$). 관측결과는 가두리에서 투기되는 대부분의 입자상유기물이 가두리 아래 해저면에 집중적으로 퇴적되고 있음을 보여주며, 가두리 부근 해저면으로 확산되는 입자상유기물의 양은 가두리에서 멀어질수록 급속히 감소함을 시사한다.

• 수산해양교육연구
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• 제24권5호
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• pp.609-615
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• 2012

A histo-pathogical examination was carried out to evaluate the effect of commercial extruded pellet (EP) and a raw fish moist pellet (MP) diet on the health of juvenile rockfish cultured in marine net-cage for 7 months. Fish were distributed randomly to each net cage as a group of 76,000 fish (initial mean body weight 5.9 g). After 2 months, the hypertrophy or swelling of liver parenchymal cells was identified in most individuals and lasted until 7 months. Livers in EP fed group frequently showed hypertrophic parenchyma and fatty change with occasional atrophic cells. However, after 4 months, lymphocytic infiltration in splenic parenchyma was seen in a number of individuals. In addition, the gastric glandular epithelium was atrophied and in the lumen of renal tubules protozoan parasites were frequently identified but there was no correlation with the type of feed. Moreover, juvenile rockfish on EP diet showed gross and microscopic hypertrophy of the liver which would be due to oversupply of feed. Severe hepatic cellular hypertrophy or swelling could lead to the damage of microcirculation. Especially fatty change and atrophic change of liver could be the result from the damage, which could be responsible for immunological problem. Lymphocytic infiltration of spleen on the MP diet suggests that juvenile rockfish could be frequently exposed to infectious antigens.

• 한국어류학회지
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• 제29권1호
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• pp.41-51
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• 2017

어류양식용 가두리로서 동합금가두리망의 현장활용 가능성을 파악하기 위해 양식어류인 2년산 참돔을 동합금망과 합성섬유망에서 9개월 동안 각각 사육관리하면서 참돔에 미치는 양식생물학적 및 병리학적 영향을 조사하여 생물학적 안전성을 평가하였다. 동합금가두리망은 지름 25 m, 깊이 10 m의 규모로 제작하여 경남 통영시 욕지면 주변해역 연구교습어장에 설치하였다. 동합금가두리망과 합성섬유망에서 사육한 참돔의 생존율은 각각 99.75%와 99.70%로 유의한 차이는 나타나지 않았다. 일일체중성장률은 동합금가두리망과 합성섬유망에서 각각 2.13 g/day와 1.65 g/day로 동합금가두리망에서 사육한 참돔의 성장률이 빠른 것으로 나타났다. 혈액성분 분석에 따른 건강도 평가는 합성섬유망에 비해 동합금가두리망에서 양호한 것으로 나타났다. 가두리망 종류별 사육중인 참돔의 구리와 아연의 축적은 다른 기관에 비해 생식소에서 축적이 높게 나타났으며, 가용부분인 근육내 중금속 축적은 허용기준치에 비해 매우 낮았다. 또한 병원체 감염조사결과 동합금가두리망과 합성섬유망에서 기생충은 Microcotyle tai, 세균은 Vibrio alginolyticus 외 5종 등이 공통적으로 관찰되었으나, 동합금가두리망에서 Vibrio속의 세균 감염률에는 다소 차이를 보여 항균작용이 있을 것으로 예상된다. 따라서 동합금가두리망의 시스템안정성, 재활용가능성, 항균성 및 식품안전성 등을 고려할 때 어류양식용 가두리로 현장에서 활용이 가능할 것으로 여겨진다.

• 한국어병학회지
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• 제35권1호
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• pp.1-25
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• 2022

지난 30년간 전세계 양식업은 비약적으로 발전하였다. 양식업은 인간이 요구하는 동물성 단백질 섭취량의 15% 이상을 공급하는 중요한 산업이므로 수요 충족을 위하여 어류와 수산생물의 지속적인 생산 증가가 필요하다. 우리나라 남해안(경남과 전남)에 위치한 어류 가두리양식장 수면적 비율은 전국 대비 약 90%로 어류 양식업의 측면에서는 매우 중요한 곳이다. 그러나 최근의 양식환경은 전지구적 문제인 기후변화에 의한 영향을 점진적으로 받고 있으며, 이러한 영향이 더욱 심화될 것으로 예측되고 있다. 그러므로 지금의 시점에서 기후변화가 우리나라 산업계, 특히 양식산업에 미칠 영향을 정확히 평가하여야 할 시점일 뿐만 아니라 나아가 어업피해를 최소화하기 위한 사회적 및 국가적 전략이 필요하다. 남해안 가두리양식장에서 양식되는 어류의 피해는 해마다 늘어나고 있는데 주요피해의 원인 인자는 기후변화와 직·간접적으로 관련이 있는 고수온, 저수온 및 적조의 발생 등으로 알려져 있다. 현재의 시점에서 지구 온난화는 경제적 한계를 가지는 어종이나 새로운 종에 대한 양식산업화의 기회를 제공할 수 있다. 그러나 이러한 긍정적인 기회의 존재에도 불구하고 새로운 종의 유입에 의한 생태 교란, 적조 등 미세조류의 번식빈도 증가, 질병 발생 기회의 증가, 여름철 고수온 발생 및 기간의 장기화 등 부정적인 문제가 발생하며, 이러한 원인들의 복합적인 영향으로 인해 양식어류의 폐사 규모와 사례가 증가하고 있다. 어류의 폐사 피해의 증가는 양식산업계에 심각한 경제적 영향을 줄 뿐만 아니라 피해 대응과 후속 조치를 위한 사회적 비용 또한 증가하게 된다. 그러므로 어류양식장에서 발생하는 폐사 피해는 원인 인자들에 대한 적극적이고 능동적인 대응으로 줄일 수 있으며, 양식생물의 사육 및 관리기술 향상, 효율적인 먹이 관리, 질병 차단과 능동적 대응, 제도개선 등 다양한 영역에서 이루어져야 한다. 본 총설에서는 우리나라 남해안에 위치한 어류 가두리 양식장에서 발생한 대량폐사 사례를 분석하고 폐사 원인에 대한 대응 능력을 향상시키기 위한 방안을 제시하고자 하였다.

• 수산해양기술연구
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• 제44권1호
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• pp.46-56
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• 2008

A numerical model analysis was performed to analyze the motion and mooring tension response of submersible fish cage systems in irregular waves and currents. Two systems were examined: a submersible cage mooring with a single, high tension mooring and the same system, but with an additional three point mooring. Using a Morison equation type model, simulations of the systems were conducted with the cage at the surface and submerged. Irregular waves(JONSWAP spectrum) with and without a co-linear current with a magnitude of 0.5m/s were simulated into the model as input parameters. Surge, heave and pitch dynamic calculations were made, along with tension responses in the mooring lines. Results were analyzed in both the time and frequency domains and linear transfer functions were calculated.

• Ocean Systems Engineering
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• 제7권2호
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• pp.143-155
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• 2017

For complex flexible structures such as nets, the determination of drag forces and its deformation is a challenging task. The accurate prediction of loads on cages is one of the key steps in designing fish farm facilities. The basic physics with a simple cage, can be addressed by the use of experimental studies. However, to design more complex cage system for various environmental conditions, a reliable numerical simulation tool is essential. In this work, the current load on a cage is calculated using a Morison-force model applied at instantaneous positions of equivalent-net modeling. Variations of solidity ratio ($S_n$) of the net and current speed are considered. An equivalent array of cylinders is built to represent the physical netting. Based on the systematic comparisons between the published experimental data for Raschel nets and the current numerical simulations, carried out using the commercial software OrcaFlex, a new formulation for $C_d$ values, used in the equivalent-net model, is presented. The similar approach can also be applied to other netting materials following the same procedure. In case of high solidity ratio and current speed, the hybrid model defines $C_d$ as a function of Re (Reynolds number) and $S_n$ to better represent the corresponding weak diffraction effects. Otherwise, the conventional $C_d$ values depending only on Re can be used with including shielding effects for downstream elements. This new methodology significantly improves the agreement between numerical and experimental data.

• 수산해양교육연구
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• 제27권4호
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• pp.1184-1193
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• 2015

Monitoring for megalocytivirus infection was conducted for ten months from March to December in 2013 in 15 aquatic farms culturing, red sea bream, rock bream, rock fish and black sea bream around Tongyoung coastal area in Korea, to assess spatial and temporal variability of detection prevalence, and to explore possible links with seawater temperature. In nested-PCR targeted major capsid protein (MCP) gene, asymptomatic megalocytivirus infection was detected in the externally healthy farmed fish with a significant prevalence in range from 0 to 58.3% for ten months. Higher prevalence of megalocytivirus (46.7% - 57.1%) was observed in high water temperature season from September to November than that in other months with lower prevalence of 0.0% to 20.0%. Even though an acute infection of megalocytivirus was occurred in rock bream (positive in the first PCR) with high mortality in one of fifteen farms, there was no expansion or transmission of the disease to the rock fish and red sea bream culturing in net cage just proximal to the rock bream cage in which disease outbreaked. Nucleotide sequence analysis of the cloned MCP gene isolated asymptomatically infected rock fish revealed that the megalocytivirus in this study was clustered together with the rock bream iridovirus (RBIV) under the subgroup II of the genus megalocytivirus (Iridoviridae), which is known to be the major megalocytivirus strain in Korea. The typical histopathological signs were not found in the spleen of rock fish asymptomatically infected by megalocytivirus. Experimental infection of rock bream with the spleen homogenate of the rock fish infected asymptomatically did not induce any mortality unlike the homogenate of infected rock bream with hih mortlity. However, these results may suggest that the asymptomatic infection of megalocytivirus in other fish species can be a potential risk threatening aquaculture industries as a transmission factor of megalocytivirus to susceptible fish species, especially rock bream.

• 한국음향학회:학술대회논문집
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• 한국음향학회 2000년도 하계학술발표대회 논문집 제19권 1호
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• pp.233-236
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• 2000

The acoustical response of fish depends on size and physical structure na, most important, on the presence or absence of a swimbladder. Acoustic scattering models for swimbladdered fish represent a fish by an ideal pressure-release surface having the size and shape as the swimbladder. Target strength experiments of red seabream (Chrysophrys major) have been conducted using 38 (split-beam), 120 (split-beam) and 200kHz (dual-beam) frequencies. At each start of each experiment, the live fish are placed in the cage at the surface, then the cage is lowed to about $4{\cal}m$ depth where it remains during the measurements. To test the acoustic models, predictions of target strength based on swimbladder morphometries of 10 red seabream offish total length from $103{\cal}mm{\;}to{\;}349{\cal}mm$ ($3 <$TL/\lambda$ < 45)are compared with conventional target strength measurements on the same, shock-frozen immediately after caged experiments. X-ray was projected along dorsal aspect to know the morphological construction of swimbladder. and fish body. At high frequencies, Helmholtz-kirchhoff(HK) approximation would greatly enhance swimbladdered fish modeling. Sound scattering model [HK-ray approximation model] for comparison to experimental target strength data was used to model backscatter measurements from individual fish. The scattering data can be used in the inverse method along with multiple frequency sonar systems to investigate the adequacy of classification and identification of fish