• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.43 no.2
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• pp.126-139
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• 2007

In the autumn of 2000 and spring of 2001, field surveys were conducted to estimate the effectiveness of artificial reefs (type cube, $2{\times}2{\times}2m^3$) that were established in the four islands of Bangnyeong, Socheong, Daeyeonpyeong and Ganghwa in Kyonggi Bay, the west coast of Korea during 1995 and 1996. The condition of reefs was examined through SCUBA diving and a side-scan sonar. Much of the reefs in Daeyeonpyeong and Ganghwa area were buried in bottom sediment. Despite an intensive search in Bangnyeong area, even a cluster of reefs was not found and most of them seemed to be buried by sand waves. Thus an appropriate investigation on the sediment transport should be included in pre-assessment for the expected performance and protection of artificial reefs. Distribution of average CPUE in natural fishing ground (control) was estimated by bootstrapping simulation and possible comparison of CPUE between control and reef areas (treatment) were made in Bangnyeong and Socheong (Experiment I). Positive reef effect was detected in Socheong but CPUE of treatment in Bangnyeong was varied between or lower than the 99% CPUE confidence intervals of the control. Control/treatment abundance and biomass of fishes and invertebrates were tested by paired t-test and sign test (Experiment II). Only four cases among 22 showed significant positive effect. Based on the results, the cube artificial reef in Socheong was inferred as an affirmative one. Floor type was hypothesized to be one of the probable agents in determining the effectiveness of artificial reefs.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.47 no.2
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• pp.146-152
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• 2011

Underwater CCTV camera systems are increasingly replaced the traditional net approach of assessing the species, numbers and aggregation patterns of marine animals distributing around the artificial reefs installed in the inshore fishing grounds, in particular, in relation to the biological investigation of behavior and distribution patterns of target fishes. In relation to these needs, we developed a multi-directional underwater CCTV camera system to use in detecting and tracking marine animals in the artificial reef ground. The marine targets to be investigated were independently tracked by using a camera module toward the bottom and four camera modules installed in the interval of $90^{\circ}$ in horizontal plane and inclination of $45^{\circ}$ in vertical plane of the CCTV system without the overlap of video frames by each camera module. From the results of several field tests at sea, we believe that the developed multi-directional underwater CCTV camera system will contribute to a better understanding in evaluating the effect of artificial reefs installed in the inshore fishing grounds.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.27 no.5
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• pp.535-548
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• 1994

Community structures and fish densit were investigated on three different types of artificial reefs, dice, turtle artificial reef and tubes, constructed in the Korean waters. Variations of fish fauna according to type of artificial reef and the proper artificial reef in each area for optimizing harvest were discussed. Fish were captured by trammel gill net during May, June, September and November, 1988 and both identified and counted. Fourty-five fish species were found in the artificial reefs. Of these, Sebastes spp., Hexagrammos otakii, Pleuronectidae, Navodon modestus and Stephanolepis cirrhifer showed high occurrence-frequency. The dominant species groups were coastal settlement, demersal or rock fishes such as Pleuronectidae, Rajiformes, Stephanolepis cirrhifer, Navodon modestus, Hexagrammos otakii and Sebastes spp. in all of the Artificial reefs except the oceanic area of southern waters. Scomber japonicus was predominant in the oceanic area of southern waters. Composition of demersal, rock and pelagic fishes were different depending on the types of artificial reef. Dice artificial reefs were occupied by rock fish, on the other hand turtle artificial reefs were dominated by dermersal fish. Fish density was high at the dice artificial reef in all survey areas except the middle area of Eastern waters, with high fish density evident in the Tube artificial reef. Fish community structures were remarkably different between Dice and Turtle artificial reefs. The Tube artificial reef showed intermediate characteristics between the above two types of artificial reefs. The coastal areas of Southern waters and the middle and southern areas of Western waters revealed similar fish fauna. Results from the oceanic areas of Southern waters were well associated with the middle and southern areas of Eastern waters.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.40 no.1
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• pp.31-38
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• 2007

This study investigated the fluid force acting on an artificial reef and the scour pattern at the bottom of the artificial reef in a steady-flow field using the finite difference method (Flow-3D). The structure was tetragonal in shape, like similar objects found in nature. The numerical analysis showed that the hydrodynamic characteristics and incipient scouring pattern matched natural phenomena. The velocity distribution around the tetragon was symmetric and wake occurred inside the tetragon and behind the bottom of the tetragon. The length of the recirculation flow behind the tetragon for each velocity was about 4-5 cm and the magnitude of the recirculation flow inside the tetragon generally increased with the Reynolds' number, although it decreased slightly for Reynolds' numbers from 11,000 to 12,000. In addition, the total fluid force acting on the tetragon increased with the inflow velocity, although the increment was smaller when the velocity exceed 18 cm/sec. The incipient pattern for the scouring of sediment matched the natural phenomenon.

• Fisheries and Aquatic Sciences
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• v.5 no.4
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• pp.281-286
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• 2002

Artificial reefs were set on a sandy bottom substratum at 8m, 10m and 13m depths along the coast in Muronohana, Ikata, Japan. Succession of seaweed communities was observed monthly or bimonthly from February 1999 to August 2000 on artificial reefs. Within one month, the diatom colonized on the reefs with coverage of $100\%$. After three months, Enteromorpha intestinalis and Colpomenia sinuosa dominated on the reef in the spring. Seaweed flora decreased during the summer and the dominant species were several species of Melobesioidea. In the winter, the seaweeds grew up again and the dominant species on the each reef were Sargassum spp., Ecklonia kurome and Padina arborescens after one year. The dominant species in the algal succession process changed from diatoms to the perennial seaweeds such as Sargassum spp., E. kurome and P. arborescens. Thus, the pattern of succession of the dominant species and the degree of domination were changed by the season, water depth and the recruitment of spores and eggs from the mature alga around the reefs.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.1
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• pp.200-205
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• 2008

Stability and durability of the artificial reefs (ARs) installed for wildstock enhancement have been a key issue. We surveyed the stability of 4,044 artificial reefs installed at 5 sites (Gangeung, Donghae, Samcheok, Goseong. and Yangyang) along the Gangwon coast of the East Sea (Sea of Japan) through which 1 to 5 typhoons pass annually. The ARs surveyed were 7 types aging 1 to 4 years. The side scan sonar (SSS) and scuba diving surveys confirmed that the ARs stability was age and type-dependent. A total of 85.56% ARs remained safe. the rest 14.44% being influenced by physical parameters of the waters such as wave extremes mostly caused by typhoons. An interesting observation was that the AR were particulatly vulnerable to the wave extremes in the first year of installation, thereafter being less damageable. Representative damages of the ARs were capsized (0.20%). broken (5.79%), sunk (0.27%), and buried (8.18%). By type, dice reef was most stable. while semicircle branch reef was most vulnerable.

• Journal of Ocean Engineering and Technology
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• v.24 no.2
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• pp.18-24
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• 2010

Submerged rubble structures include artificial reef and the mound part of the rubble mound breakwater. Artificial reef is a type of the submerged wave absorbing structure installed in a coastal zone to prevent beach erosion and designed to initially reduce the energy of incoming waves so that its run-up height and overtopping quantity can be decreased. In order to ascertain the stability of such submerged rubble structures, minimum weight of the rubble has to be calculated first from the incoming wave height using Hudson's formula or Brebner-Donnelly formula. Based on the calculated minimum weight, a model is built for use in a hydraulic model test carried out to check its stability. The foregoing two formulas used to calculate the minimum weight are empirically derived formulas based on the result of the tests on the rubble mound breakwater and it is, therefore, difficult for us to apply them directly in the calculation of the minimum weight of the submerged structures. Accordingly, this study comes up with a numerical simulation method capable of deformation analysis for rubble structures. This study also tries to identify the deformation mechanism of the submerged rubble structures using the numerical simulation. The method researched through this study will be sufficient for use for usual preparations of the design guidelines for submerged rubble structures.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.8
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• pp.5327-5332
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• 2014

In Korea, the quantitative growth rate of artificial reef construction is supposed to reach the peak point. Therefore, new approach is needed to the point of artificial reefs business. Functional reefs, such as shellfish reefs, recreational reefs, seaweed reefs, and fish reefs, are beneficial alternatives. This study conducted hydraulic testing to assess the stability of corrugated artificial reefs (ARs) that were constructed to promote the growth of shellfish and seaweed. The results of this study showed that some dimensionless design parameters affected the stability of corrugated artificial reefs under a range of wave and water depth conditions in a fixed bed condition. The findings also highlight the importance of hydraulic experiments in solving the problems that have emerged in the design and construction of artificial reefs.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.47 no.2
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• pp.139-145
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• 2011

Hydro-acoustic survey was carried out to estimate a fish distribution at marine ranching area and aggregated fish schools at artificial reef area in Oeyeondo, Korea. The survey system was set up with DGPS system, scientific echo sounder (EK60, Simrad Co.), and ECDIS (Mecys. Co. LTD). A track survey and a random survey was respectively applied to the marine ranching area (474.4ha) and to the artificial reef area (within a radius of 300m). As the result, fish distribution and MVBS values in marine ranching area showed that created fisheries resources didn't come to be abundant yet as to appear fish distribution in all of the area. In the artificial reef area, it was, however, able to detect many fish school signals on the top of and around artificial reefs and to confirm the luring effect of artificial reefs.

• Ocean and Polar Research
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• v.23 no.3
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• pp.255-264
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• 2001

Development process of benthic community on experimental substrata attached on a newly installed artificial reef complex in Jeju Island was observed for 27 months from 1992 to 1994. Among 34 species of algae and 64 species of zoobenthos obtained from the study, Ecklonia cava dominated with a maximum biomass of about $10kg/m^2$. It was able to smother the other animals, however it provided a new substrate for the new settlers. Opportunistic bryzoans such as Likenopora radiata and Dexiospira spirillum occurred during the early stage were substituted by poriferans, banacles and other bryzoans. Young barnacles were smothered by bryozoans, on the contrary, bryozoans were bulldozed by adult barnacles. No apparent differences have been observed between vertically and horizontally installed substrates in terms of species composition and biomass during the early stage of succession. Thereafter owing to the rapid growth of E. cava, the horizontal substrata carried on a higher biomass while the vertical showed a higher coverage. The benthic process on the experimental substrata can be classified into three stages: initial stage, build up stage and regulatory stage. Important mechanisms involved were canopying of E. cava, suffocation by bryozoans and poriferans, and bulldozing of adult barnacles.