Economic benefits and management implications of reducing the harvest of juvenile mackerel in Korea

LEE, Jungsam,KIM, Dae-Young,SEO, Young-Il,KIM, Do-Hoon The Korean Society of Fisheries and Ocean Technolo 2016 수산해양기술연구 Vol.52 No.4

It is essential to provide good environment for juvenile fish to grow and spawn in order to keep reproduction mechanism of fisheries resources. However, harvesting juvenile fish deprives adult fish of the opportunity to reproduce, thereby changing self-regulating renewable resources into non-renewable ones and preventing sustainable harvesting as well as reducing fishers' income. We reviewed the catch status of Korea on juvenile mackerel and analyzed how reducing the catch ratio of juvenile mackerel may affect the spawning stock and Korean fishermen's revenue. In addition, we analyzed the problem of caching juvenile mackerel in Korean fisheries and current efforts to protect and reduce the catch ratio of juvenile mackerel in Korea. Furthermore, we suggested future efforts to protect juvenile mackerel. The result of the study showed that reducing the catch ratio of juvenile mackerel from 44.4% to 30.0% would increase fishers' revenue by 60.6 billion KRW. We suggest the changing of purse seine fishery's catching methods from night operation to day operation, relocation of fishing vessels to move to other fishing grounds when fishing vessels meet high density of juvenile mackerel, and consumers' clever choice of consuming adult mackerel in order to accelerate the move toward protecting juvenile mackerel in Korea.

Vibration analysis of a DWT 1,000-ton ocean-research vessel with electric propulsion

Bae, Dong-Myung,Cao, Bo,Chen, Tuo-Han The Korean Society of Fisheries and Ocean Technolo 2014 수산해양기술연구 Vol.50 No.1

In vibration analysis of ships, the principle aim is to determine the natural frequencies and excitation frequencies, and use this information to avoid resonances and vibration damage. The simplest method is to prevent resonance conditions, which is effective as long as the natural frequencies and excitation frequencies can be regarded as independent from environmental conditions. For ships that use electric propulsion systems, the sources of vibration are reduced compared with those caused by a diesel engine or other combustion-based propulsion systems. However, the frequency spectrum of these vibrations may be different; therefore, to understand the characteristics of the electric propulsion, we also should investigate how the ship responds to these vibrations. We focused on a 1,000-ton deadweight (DWT) ocean-research vessel using an electric propulsion system and analyzed the response to vibration.

Structural analysis of a Korean-designed cruiser-class sailing yacht

Bae, Dong-Myung,Cao, Bo,Kim, Dong-Jun The Korean Society of Fisheries and Ocean Technolo 2015 수산해양기술연구 Vol.51 No.1

A Korean-designed cruiser class sailing yacht, based on the form of traditional yachts, has been developed. In this paper, structural design procedures for the yacht are studied. The scantling of structural members and loads is carried out based on the guidelines suggested by Australian Standard 4132-1993, the American Bureau of Shipping (ABS) and the International Organization for Standardization (ISO). Patran/Nastran finite element analysis is performed on models of the trial sailing boat, and from these results, the structural strength of the ship's hull is verified.

Comparison of catches and species composition for flounders caught using gillnets, gillnets with supporting lines, and trammel nets

Park, Hae-Hoon,Millar, Russell B.,Park, Chang-Doo,Park, Seong-Wook,Lee, Sung Il,Bae, Bong-Seong,An, Heui-Chun,Cho, Sam-Kwang,Lee, Kyounghoon The Korean Society of Fisheries and Ocean Technolo 2014 수산해양기술연구 Vol.50 No.1

To compare the catches made using gillnets, trammel nets, and gillnets with supporting lines, several experiments were conducted with commercial vessels near Uljin and Pohang in Eastern Korea between July 2010 and May 2011. Two sets of 13 different nets were used, including 5 panels of gillnets and trammel nets each with stretched mesh sizes of 7.6, 9.1, 10.6, 12.1, and 13.6 cm and 3 panels of gillnets with a mesh size of 9.1 cm with supporting lines with different line spacing. The outer (stretched) mesh size of the trammel nets measured 51.5 cm. The target fishes of the fishing nets were various types of flounders. The catch rate of flounders was 50.7% of the total catch in weight. The total catch for all nets was 443.8 kg. The predominant species was pointhead flounder (Cleisthenes pinetorum). The total catch by trammel nets was 1.4 times that of the comparable gillnets. But more pointhead flounder were caught by gillnets than by trammel nets, though there was no significant difference. Fishermen catching the pointhead flounder in Korea said that there was no need to use trammel net to catch it; this was an unexpected finding compared to the findings of other flounder fisheries. The amounts of roughscale sole, brown sole, and blackfin flounder caught by trammel nets were greater than those caught by gillnets. The mean lengths (standard deviation) of blackfin flounder, pointhead flounder, brown sole, and roughscale sole were 21.0 (4.57), 22.9 (3.40), 24.7 (4.90), and 28.3 (5.43) cm, respectively; there were significant differences in mean length (p < 0.00001). Therefore, in order to catch flounder efficiently, the fishing nets and mesh size should be chosen according to the target species. One advantage of using supporting lines is that it prevents breakage by strengthening the material especially when utilized on a rough bottom. Catch by using gillnet with supporting lines was not greater than that by using trammel net for the conservation of fisheries resources.

Mooring loads analysis of submersible aquaculture cage system using finite element method

Kim, Tae-Ho The Korean Society of Fisheries and Ocean Technolo 2006 수산해양기술연구 Vol.42 No.1

The expansion of near shore aquaculture is feasibility of moving aquaculture facilities into the open ocean. Numerical modeling technique using finite element method was used to enable the optimum design and evaluation of submersible aquaculture cage system. The characteristics of mooring loads response in mooring lines under waves and current and their response amplitude operators were calculated for single and three point mooring configuration at the surface condition and submerged one. The static mooring loads without wave and current loading were similar for both the surface and submerged configuration. It was calculated that three point mooring was more adequate than single point mooring for the mooring configuration of submersible aquaculture cage system. The wave induced response amplitude operators for the single point mooring configuration with the influence of currents were identical to those without the influence of currents.

On the direction of fisheries subsidies programs in Korea under fortifying international regulations for fisheries subsidies

LEE, Cheol,CHOI, Sang Duk The Korean Society of Fisheries and Ocean Technolo 2017 수산해양기술연구 Vol.53 No.4

We propose some countermeasures needed to cope with fortifying international regulations for fisheries subsidies. The government should rigorously select the recipients of fisheries subsidies to ensure that they are not engaged in ineffective projects by resorting to subsidies. On the other hand, the government should make the individual applicant's application for the subsidies easier by exempting them from the submission of a burdensome feasibility report. As for the strengthening regulatory international movements against the fisheries subsidies, we can consider the following countermeasures. One is not to designate and provide prohibitive subsidies in such a way that violates international norms. The other one is to reform the domestic fisheries subsidies system in Korea with the following points considered. It should be considered that fisheries subsidies, which can be categorized as the actionable subsidies, should not be granted to the items that can be exported but to the items that can be used for domestic consumption or processing. In the case of non-actionable subsidies, the subsidies are mainly allowed for promotion of public-sector research and development, regional development, and adaptation to new environmental regulations. Thus, the non-actionable subsidies should be designated in the consideration of the allowances for these activities.

Development of a 250-W high-power modular LED fish-attracting lamp by evaluation of its thermal characteristics

Lee, Donggil,Lee, Kyounghoon,Pyeon, Yongbeom,Kim, Seonghun,Bae, Jaehyun The Korean Society of Fisheries and Ocean Technolo 2015 수산해양기술연구 Vol.51 No.2

Recently LED fish-attracting lamps have been more widely used in fisheries as low-cost and high-efficiency fishing gear, and development of long-life high-efficiency lamps is required through the design of LED packages to optimize heat resistance. This study developed an improved LED fish-attracting lamp with excellent heat performance, which was verified using a numerical model. Heat-resistance design factors such as the heat-radiation fin shape, PCB type, and LED chip count were investigated and optimized. Comparison with a commercial 180-W LED fishing lamp showed that the increase in initial temperature was 40% higher than that of the surrounding LED chip because of design errors in contact thermal resistance. The 250-W LED lamp developed in this study has a characteristic with thermal rising in linearly stable according to the heat source. In addition, luminance efficiency was improved by 20-65% by using flow-visualization simulation. A decrease of 45% in total power consumption with a fuel-cost reduction of over 55% can be expected when using these optimized heat release design factors.

Analytical study of house wall and air temperature transients under on-off and proportional control for different wall type

Han, Kyu-Il The Korean Society of Fisheries and Ocean Technolo 2010 수산해양기술연구 Vol.46 No.1

A mathematical model is formulated to study the effect of wall mass on the thermal performance of four different houses of different construction. This analytical study was motivated by the experimental work of Burch et al. An analytical solution of one -dimensional, linear, partial differential equation for wall temperature profiles and room air temperatures is obtained using the Laplace transform method. Typical Meteorological Year data are processed to yield hourly average monthly values. These discrete data are then converted to a continuous, time dependent form using a Fast Fourier Transform method. This study is conducted using weather data from four different locations in the United States: Albuquerque, New mexico; Miami, Florida; Santa Maria, California; and Washington D.C. for both winter and summer conditions. A computer code is developed to calculate the wall temperature profile, room air temperature, and energy consumption loads. Three sets of results are calculated one for no auxiliary energy and two for different control mechanism -- an on-off controller and a proportional controller. Comparisons are made for the cases of two controllers. Heavy weight houses with insulation in mild weather areas (such as August in Santa Maria, California) show a high comfort level. Houses using proportional control experience a higher comfort level in comparison to houses using on-off control. The result shows that there is an effect of mass on the thermal performance of a heavily constructed house in mild weather conditions.

Comparison of circle hook and J hook catch rate for target and bycatch species taken in the Korean tuna longline fishery

Kim, Soon-Song,Moon, Dae-Yeon,Boggs, Christofer,Koh, Jeong-Rack,An, Doo-Hae The Korean Society of Fisheries and Ocean Technolo 2006 수산해양기술연구 Vol.42 No.4

The circle hook experiments were conducted to compare the catch rates of target and bycatch species between J hook and circle hooks in the tuna longline fishery of the eastern Pacific Ocean between $1^{\circ}48'S-7^{\circ}00'S\;and\;142^{\circ}00'-149^{\circ}13'W$ from July 15 to August 12, 2005. In the target species group no significant differences among 3 types hook, between size 4.0 traditional tuna hooks(J-4) and size 15 circle hooks(C15), and between C15 and size 18 circle hooks(C18) were revealed, but significant differences were found between J-4 and C18. In the bycatch species group significant differences were found among 3 types hook, between J 4 and C15, and between J-4 and C18, but no significant differences were revealed between C15 and C18. Large circle hook(C18) had the lowest catch rate for tunas and for other fishes, and the small circle hook(C15) had lowest rate for billfishes and sharks. The length distributions for bigeye tuna are very similar for the 3 hook types. There were very slight differences in length size between hook types in the bycatch species.

Dissolved oxygen analysis of an abalone aquaculture cage system using computational fluid dynamics

Kim, Taeho The Korean Society of Fisheries and Ocean Technolo 2015 수산해양기술연구 Vol.51 No.2

Abalone (Haliotis discus hannai) is a shellfish that feeds on kelp and, as a product, it can often achieve a high market value. However, the dissolved oxygen (DO) levels in coastal waters in Korea have been negatively impacted by pollution from many anthropogenic sources. Herein, a computational fluid dynamics (CFD) software package was used to analyze the distribution of the DO concentration within an abalone containment structure. A finite volume approach was used to solve the Reynolds-averaged Navier-Stokes equations combined with a $k-{\varepsilon}$ turbulence model to describe the flow. The distribution of DO was determined within the control volume domain, and the transport equations of the pollutants were interpreted using a CFD model. The CFD analysis revealed that more than 60% and 30% of the relative oxygen concentration in one and two containers, respectively, was maintained when the flow acts along the six sheets of polyethylene plates. Therefore, it is clear that the abalone plate shelters should be placed parallel to the flow.