• Journal of Aquaculture
• /
• v.7 no.3
• /
• pp.177-187
• /
• 1994

The objective of the present study were to evaluate nitrification characteristics and determine optimum treatment conditions of three phase fluidized bed reactor for recycling water treatment of aquaculture. When the loading rates were 2.739-0.086kg $COD/m^3/day$ and 1.575-0.128kg $NH_4\;^+-N/m^3/day$, COD and ammonia removal efficiencies were $56.3-94.7\%\;and\; 67.3­92.6\%$, respectively. The maximum removal rates of COD and ammonia were 1200mg/l/day and 488mg/l/day, respectively. Ammonia removal rates were more than $90\%$ beyond 1hr HRT. The ammoniaremoval efficiency was sensitive to the variation of media concentration and air flowrate.

• Journal of Aquaculture
• /
• v.3 no.1
• /
• pp.89-125
• /
• 1990

In order to improve top shell seed production techniques spawning and larvae rearing were done in rearing tanks. Growth of young top shell in the nursing ground were also investigated. For induced spawning, top shells were maintained in still water during night time. Then they were treated with ultra violet iradiated sea water after dried up in air for 60 minutes. Spawning rate were 10 to $39.77\%$. It was found that young top shells moved in the growing grounds from nursing grounds when they reached approximately 30-40mm in shell heignt. Among main food algae for top shell in the natural growing grounds, sea mustard were melted away during June. Therefore, presence of another food algae such as Ecklonia cava or Sargassum spp. seems to be the main limiting factor for survival of top shell during summer. The tolerance of top shells ranging from 30mm to 60mm to low density of seawater for were tested at the temperature between 29.5 and $31.4^{\circ}C$. Hundred percent mortality occoured in 20, 55 and 90 hours after first stocking at the specific gravity of 1.010, 1.015, and 1.020, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.25 no.3
• /
• pp.176-180
• /
• 1992

Nitrification Is an important facet of water recycling fish culture system, because the toxic cation ammonia is converted to the innocuous anion nitrate. This study was attempted to find the optimal design factor of submerged filter for ammonia removal in water recycling fish culture system. The experimental system was designed submerged filter with corrugated skylight plate, and operated in the fish farm, National Fisheries University of Pusan. When the influent ammonia concentration was about 10mg/l (9.43-13.66mg/l) nitrification rates were tested for the removal of ammonia over a four stage of the hydraulic loadings. The submerged filter removed 76.24, 62.88, 39.09 and $9.20\%$ of the ammonia to hydraulic load of 0.028, 0.037, 0.056 and $0.111m^3/m^2$. day, respectively. We can apply the above data to the material balance on the ammonia concentration in a fish reservoir, and conclude that the maximum allowable ammonia production was 1.52mg/min, and the optimal hydraulic loading was $0.047m^3/m^2$\;\cdot day$, in order to maintain the ammonia concentration below 10mg/l in the fish reservoir.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.29 no.7
• /
• pp.779-793
• /
• 2023

Intensive and long-term aquaculture activities in Korea have generated considerable amounts of organic matter, deteriorating the sedimentary environment and ecosystem. The Korean government enacted the Fishery Management Act to preserve and manage the environment of fish farms. Based on this, a fisheries environment assessment has been conducted on fish cage farms since 2014, necessitating the development of a scientific and objective evaluation method suitable for the domestic environment. Therefore, a benthic health index (BHI) was developed using the relationship between benthic polychaete communities and organic matter, a major source of pollution in fish farms. In this study, the development process and calculation method of the BHI have been introduced. The BHI was calculated by classifying 225 species of polychaetes appearing in domestic coastal and aquaculture areas into four groups by linking the concentration gradient of the total organic carbon in the sediment and the distributional characteristics of each species and assigning differential weights to each group. Using BHI, the benthic fauna communities were assigned to one of the four ecological classes (Grade 1: Normal, Grade 2: Slightly polluted, Grade 3: Moderately polluted, and Grade 4: Heavily polluted). The application of the developed index in the field enabled effective evaluation of the Korean environment, being relatively more accurate and less affected by the season compared with the existing evaluation methods like the diversity index or AZTI's Marine Biotic Index developed overseas. In addition, using BHI will be useful in the environmental management of fish farms, as the environment can be graded in quantified figures.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.30 no.1
• /
• pp.20-31
• /
• 2024

This study was conducted to investigate the changes in the structure of benthic communities resulting from aquaculture activities and to assess the benthic health status of surface sediment in Gangjin Bay, a region known for concentrated shellfish aquaculture on the southern coast of Korea. Survey stations were divided into longline culture, bottom culture, and non-cultivation areas. The spatiotemporal distribution of physiochemical factors such as the grain size, water temperature, salinity, and total organic carbon in Gangjin Bay showed no significant differences between sampling stations. However, the species number, density, and diversity were relatively lower at the sampling stations in the bottom culture areas than at the other stations throughout the entire survey period. Cluster analysis and principal coordinates analysis also clearly distinguished the benthic communities in the bottom culture areas from those in the other sampling areas. At the sampling stations in the longline culture and non-cultivation areas, Scolectoma longifolia and Sigambra tentaculata, which are indicator species of organically enriched areas, appeared as dominant species. However, excluding some stations influenced by physical factors such as the water depth and current speed, the occupancy rate was not high. The health assessment results, conducted using the fisheries environment assessment method, revealed good conditions with Grades 1 and 2 across the entire area. However, an examination of the spatiotemporal changes in benthic communities and the benthic health index indicated that the benthic environment in the bottom culture areas was affected by physical disturbances.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.8 no.2
• /
• pp.61-67
• /
• 1975

Oceanographic conditions of the coastal water around Chungmu, one of the most important oyster farming areas in Korea, were studied from May to November in 1974 to find out the environmental influence to oyster farming. Six localities, Goseong Bay, Jaran Bay, off Saryangdo, Hansilpo, Tong-yeong Bay and Juklimpo were selected for monthly oceanographic observation and biological sampling. Flood current running westward brings saline water from the south-east and ebb current brings the low salinity water of Jinju Bay into this area. The waters in Juklimpo, Hansilpo and Tong-yeong Bay are slightly cooler and more saline than the waters in Goseong Bay, Jaran Bay and off Saryangdo. The amount of dissolved oxygen is lowest in September and Hansilpo has the least oxygen during summer. Silicate content is lower in waters of Tong-yeong Bay, Juklimpo and off Saryangdo than those of Goseong Bay, Hansilpo and Jaran Bay. Suspended matter in this area ranges from 7.4 to 16.6 mg/l and scarce in Jaran Bay, Juklimpo and off Saryangdo. Chlorophyll a shows large seasonal variation and local fluctuation. Composition of phyto-plankton reveals the difference between the waters of Goseong Bay, Jaran Bay and off Saryangdo and the waters of Hansilpo, Tong-yeong Bay and Juklimpo. The growth of oyster was good in Juklimpo, Tong-yeong Bay and Goseong Bay and worst in Hansilpo. The highest mortality was observed $82\%$ in the waters off Saryangdo.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.7
• /
• pp.299-309
• /
• 2019

This study was designed to assess the quality and quantity of food resources such as the chlorophyll a concentration (Chl-a), the particulate organic carbon (POC) and the particulate organic nitrogen (PON), on blood cocke (Tegillarca granosa Linnaeus) farms from May to November 2017 in the northwestern area of Yeoja Bay, Korea. The values of Chl-a, POC and PON were $1.69-7.68{\mu}g{\cdot}L^{-1}$ (average: $3.48{\mu}g{\cdot}L^{-1}$ in the surface), 0.88-2.58 mM (average: 1.97 mM) and 0.17-0.90 mM (average: 0.54 mM), respectively, and these values were higher in the spring and summer and lower in the autumn. Furthermore, Chl-a and POC had higher values on the bottom layer than those vales on the surface, while PON had higher values on the surface than those values on the bottom. The POC/PON ratio and POC/Chl-a ratio were 1.56-7.88 (average: 3.71 on the surface of the water) and 216-967 (average: 700 on the bottom of the water), respectively, with most of the carbon sources being sediment-accumulated particle organic matter, and the contribution by phytoplankton was assessed as being low. These results show that the food source of the blood cockle farms in the northwest area of Yeoja Bay seems to be abundant in quantity, but this is considered to be very poor in quality.

• Journal of fish pathology
• /
• v.25 no.3
• /
• pp.249-256
• /
• 2012

Disease occurrence and dead cell ratio of Porphyra cultivated at Seocheon area were studied. Seaweed samples were collected monthly at 12 cultivating sites of Porphyra from Nov. 2008 to Mar. 2009. Although disease occurrence was low at the beginning of cultivation at the most of collecting sites, the occurrence increased with time. The most common symptom of Porphyra disease in this area was diatom attachment, followed by white rot disease. Licmophora sp. was the most common species of diatom and its attachment was the highest on November, the beginning of cultivation. Although the occurrence ratios of green spot disease and white rot disease were high on November, chytrid disease was increased at the end of cultivation period. Dead cell ratio of Porphyra thalli was different at each study site and cultivating time, but normally the ratio was high at the end of cultivating season. The changes of dead cell ratio could be related to the nutrition supplement and currents, and the more precise reason of dead cell ratio would be revealed by further research related to cultivating environment conditions.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.17 no.4
• /
• pp.315-322
• /
• 2011

The importance of aquafarming is increasing all over the world, however the coastal environment in the semi-closed inner bay has been aggravated due to the long term production and the high stocking density. For the sustainable aquafarming, there is a requirement for a eco-friendly fishery management by the estimation of ecological carrying capacity. The model development and application is still in the initial step, because it has to consider the whole ecosystem and all culture activities. As an alternative, there is a requirement for ecological indicator to assess the ecological performance. This study tried the estimation of ecological carrying capacity using ecological indicator. The production and the facility of the oyster farms was 4,935M/T, $49ind./m^3$ in Geoje-Hansan Bay(2008). Filtration pressure indicator was 0.203 which could provide a guidance on the present level of culture development. According to the environmental characteristics and the present oyster farms in Geoje-Hansan Bay, the newly assessed filtration pressure for the acceptable ecological carrying capacity was 0.102. Consequently, ecological carrying capacity in Geoje-Hansan Bay was 2,480M/T, $25ind./m^3$ and this represents the level of culture that can be introduced into Geoje-Hansan Bay without leading to significant changes to ecological process, species, populations or communities. Our study utilized the ecological indicator to estimate ecological carrying capacity of oyster farming for sustainable productivity and this could be the scientific basis for the eco-friendly fishery management.

• Proceedings of the Korean Aquaculture Society Conference
• /
• 2003.10a
• /
• pp.23-23
• /
• 2003

김 붉은갯병은 김 엽체에 난균류 Pythium속의 Pythium porphyrae의 기생에 의해 발생되어 매년 김 양식에 큰 피해를 주는 매우 심각한 김 갯병중의 하나이다. 최근에는 이들 병해의 발생 및 억제를 위한 김 산처리제 (활성처리제) 남용에 따른 연안 양식어장의 생태계 파괴 및 김의 자연식품에 대한 이미지 훼손 등의 문제점이 대두되고 있다. 따라서 본 연구에서는 김 양식시 발생되는 붉은갯병의 병해를 억제하고자 활성처리제 처리시 고염분해수 처리를 병용함으로써 활성처리제의 사용을 최소화하면서 처리효과를 배가시키고자 하였다. 시험에 사용한 김 엽체는 2002년 10월에 전라남도 해남군 황산면 지선에서 채묘한 방사무늬김 (Porphyra yezoensis)을 육묘해 엽장 1cm 내외에서 냉동망을 제작하여 -2$0^{\circ}C$에 저장한 엽체를 자연해수 (약 27$\textperthousand$), 15$^{\circ}C$, 100$\mu$mol photon m$^{-2}$ s$^{-1}$, 광주기 9L : 15D의 배양조건하에서 15일간 배양한 엽장 3-4cm 정도의 것이었다. 활성처리제와 고염분해수처리제의 병용에 의한 붉은 갯병 억제효과는 붉은갯병 병원균의 유주자를 김 엽체에 감염시킨 후 27$\textperthousand$의 자연해수에 12일간 배양하면서 염분농도를 3-25%, 처리주기를 1-2회로 하여 각 시험구별 병해정도로 평가하였다. 고염분해수 처리에 의한 붉은갯병균 균사의 생장억제 효과는 김 엽체를 붉은갯병 병원균의 유주자로 감염시킨 다음 감염 12시간 후 염분농도를 3-25%로 처리한 후 27$\textperthousand$의 자연해수에 4일간 배양하면서 각 시험구별 배양시간에 따른 병원균 균사에 의한 김 엽체의 감염세포수로 평가하였다. 활성처리제와 고염분해수처리제의 병용이 김 엽체 생장에 미치는 영향은 건전한 김 엽체의 절편을 27$\textperthousand$의 자연해수에 배양하면서 시험구별로 활성처리와 고염분해수 (5, 10, 15, 20, 25%) 처리를 3일 간격으로 하면서 12일간 배양한 후 엽체의 엽면적 증가율로 평가하였다. 활성처리제와 고염분해수처리제의 병용에 의한 붉은갯병의 억제효과는 대조구 (활성처리 1회)와 비교해 주 2회의 활성처리구와 염분농도 20, 25% 처리구에서 병해 억제효과가 월등히 높았다. 고염분해수 처리에 의한 붉은갯병균 균사의 생장억제 효과는 염분농도 5, 10% 처리구의 경우 무처리구에 가까운 감염세포수를 보였으나, 염분농도 20, 25% 처리구의 경우 활성처리제 처리와 비슷한 감염세포수를 보여 뚜렷한 생장 억제효과를 나타냈다. 활성처리와 고염분해수 처리의 병용이 김 엽체 생장에 미치는 영향은 대조구 (활성처리 1회)의 3.4배 생장율과 활성처리와 염분농도 5-20%의 고염분해수 병용 처리구의 3.1-3.6배 생장율은 유의한 생장차이를 보이지 않았다 (P<0.05).