• 제목/요약/키워드: Stock assessment

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Seismic risk estimation of the Kirikkale province through street survey based rapid assessment method (SSRA)

  • Sonmezer, Yetis Bulent;Bas, Selcuk;Akbas, Sami Oguzhan
    • Earthquakes and Structures
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    • v.14 no.6
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    • pp.615-626
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    • 2018
  • The seismic vulnerability of Turkey is relatively high due to its active fault systems with potential to create destructive earthquakes. Thus, reducing the loss of life and property, the number of the earthquake-prone buildings and their retrofit requirements are considerably significant key issues under the scenario earthquakes. The street survey based rapid assessment (SSRA) method can be considered as a powerful tool to determine the seismic vulnerability of building stock of an earthquake-prone city/state. In this study, the seismic vulnerability of the building stock of the Kirikkale province in Turkey is aimed to be estimated adopting the street survey based rapid assessment method (SSRA). For this purpose, central 2074 existing reinforced concrete (R/C) buildings were structurally surveyed with rapid visual site screening and disadvantages such as, the existence of short-column, soft-story, heavy overhangs, pounding effect and local soil conditions were determined for obtaining the structural performance score of each. The results obtained from the study demonstrate that 11-25% of the surveyed buildings in the study region needs to be investigated through more advanced assessment methods. Besides, higher correlation between increasing story number and unsafe/safe building ratio is obtained for the buildings with soft-story parameter than that for those with heavy overhangs and short-column parameters. The conformity of the results of the current study with the previous documented cases of rapid assessment efforts in the recent earthquakes in Turkey shows that the SSRA method for the Kirikkale province performed well, and thus this methodology can be reliably used for similar settlement areas.

Importance of Considering Year-to-year Variability in Length-weight Relationship in a Size-based Fish Stock Assessment (체장기반 수산자원평가모델에 적용되는 체장-체중 관계의 연도별 변동성의 중요성)

  • Gim, Jinwoo;Hyun, Saang-Yoon
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.52 no.6
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    • pp.719-724
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    • 2019
  • This study is an extension of our previous model for a size-based fish stock assessment. In the previous model, we applied an allometric length-weight relationship (W=α·Lβ) to convert lengths of fish to weights, and estimated those parameters α and β, using data about lengths and weights aggregated over years. In this study, we focused on whether consideration of temporal (e.g., year-to-year) variability in those estimates (i.e., ${\hat{\alpha}}$ and ${\hat{\beta}}$) would contributive. After calculating year-specific estimates (i.e., year-specific pairs of ${\hat{\alpha}}$ and ${\hat{\beta}}$) by applying data about lengths and weights separated by year, we evaluated the contribution of those year-specific pairs of ${\hat{\alpha}}$ and ${\hat{\beta}}$ to the performance of the size-based stock assessment model. The model with such year-to-year variability being considered (lower AIC) outperformed that with the variability being ignored (higher AIC). We illustrated this study using data on Korean chub mackerel Scomber japonicus from 2005-2017.

Effectiveness Analysis on Comb Pen Shell Based on TAC System (키조개 TAC 제도의 효과 분석)

  • Jeong, Min-Ju;Nam, Jong-Oh
    • The Journal of Fisheries Business Administration
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    • v.47 no.3
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    • pp.15-33
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    • 2016
  • This study aims to analyze effectiveness of the resource use under the total allowable catch system (TACs) of Comb pen shell, a species among TAC targeting ones through its stock assessment based on the surplus production model such as the Clark Yoshimoto Pooley (CYP) model. Particularly, this study is separated into five analysis periods in order to understand changes in Comb pen shell resource and its efficient use after TAC system implemented in 2001. The results of this study are as follows. First, five sustainable yield curves (SYCs) and exponential growth functions (EGFs) produced by the surplus production model based on Gompertz growth function to compare before and after implementation of the Korean TAC system show that the TAC system has generated a positive stock rebuilding effect for Comb pen shell caught by the diver fishery since 2001. Secondly, five profits based on differences between the sustainable total revenue (STR) and the total cost (TC) with respect to fishing efforts present that the TAC system has increased efficiency of resource use of Comb pen shell caught by the diver fishery after implementation of the Korean TAC system. In conclusion, the Korean TAC system has increased efficiency of resource use as well as has led a positive stock rebuilding effect for Comb pen shell.

Comparative analysis of stock assessment models for analyzing potential yield of fishery resources in the West Sea, Korea (서해 어획대상 잠재생산량 추정을 위한 자원평가모델의 비교 분석)

  • CHOI, Min-Je;KIM, Do-Hoon;CHOI, Ji-Hoon
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.55 no.3
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    • pp.206-216
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    • 2019
  • This study is aimed to compare stock assessment models depending on how the models fit to observed data. Process-error model, Observation-error model, and Bayesian state-space model for the Korean Western coast fisheries were applied for comparison. Analytical results show that there is the least error between the estimated CPUE and the observed CPUE with the Bayesian state-space model; consequently, results of the Bayesian state-space model are the most reliable. According to the Bayesian State-space model, potential yield of fishery resources in the West Sea of Korea is estimated to be 231,949 tons per year. However, the results show that the fishery resources of West Sea have been decreasing since 1967. In addition, the amounts of stock in 2013 are assessed to be only 36% of the stock biomass at MSY level. Therefore, policy efforts are needed to recover the fishery resources of West Sea of Korea.

Management of small yellow croaker stock in Korean waters based on production value-per-recruit analysis (가입당 생산액 분석에 의한 한국 해역 참조기 Larimichthys polyactis 자원의 관리)

  • Zhang, Chang-Ik;Lee, Eun-Ji;Kang, Hee-Joong
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.50 no.4
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    • pp.467-475
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    • 2014
  • This study was performed to estimate optimum fishing mortality (F) and the age at first capture ($t_c$) for small yellow croaker in Korean waters. We first estimated optimum F and $t_c$ using traditional yield-per-recruit (YPR) analysis, and the results were 0.8/year and 2.5 years old, respectively. However, the individual fish price per unit weight of small yellow croaker in Korea increases dramatically by size. Thus, we developed an alternative method, which is called as production value-per-recruit (PPR) analysis. We developed two types of the PPR analysis, that is, the discrete function and the continuous function method. We estimated optimum F and $t_c$ using the two types of the PPR analysis and compared the results. The optimum F and $t_c$ from the discrete function method, were 0.3/year and 5.0 years old, respectively, while those from the continuous function method were 0.5/year and 3.5 years old, respectively. These PPR estimates were much more conservative for the stock management than the traditional YPR analysis, which can prevent the fish stock from the economic overfishing. As a result, the PPR analysis could be more proper approach for stock assessment in the case that the individual fish price per unit weight increases dramatically by size like small yellow croaker in Korea.

Treasury Stock Sales and Management Rights Protection: Conflicts of Interest between an Owner-manager and Small Shareholders

  • CHO, SUNG ICK
    • KDI Journal of Economic Policy
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    • v.39 no.3
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    • pp.63-98
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    • 2017
  • This paper investigates the sales process of treasury stocks, while most previous research studies treasury stock repurchases. The sales of treasury stocks are an important measure to protect management rights only in Korea, as Korea's laws and systems allow treasury stock sales according to the board's resolution and not by the decisions made at the general shareholders' meetings. The board's resolution, which considers the owner-manager's interest on management rights, can cause damages to small shareholders. Considering (i) the economic characteristics of treasury stocks, (ii) other countries' institutions and experiences, (iii) a theoretical assessment of the possibility of small shareholder losses, and (iv) lessons from Korea's actual instances, Korea's present system should be corrected at least in the mid and long term. Even in the short-term, rules pertaining to sales enacted by the board's resolution inducing small shareholder losses should be overhauled. The autonomous discipline by various stakeholders could be an ideal measure by which to monitor ownermanager's decisions. In addition, temporary intervention measures, such as government examinations, could be implemented to protect small shareholders.

Priority for Developing Emission Factors and Quantitative Assessment in the Forestry Sector (산림부문의 국가온실가스 배출·흡수계수 개발 필요 우선순위 및 정량평가 방법론)

  • Han, Seung Hyun;Lee, Sun Jeoung;Chang, Hanna;Kim, Seongjun;Kim, Raehyun;Jeon, Eui-Chan;Son, Yowhan
    • Journal of Climate Change Research
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    • v.8 no.3
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    • pp.239-245
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    • 2017
  • This study aimed to suggest priority for developing emission factor (EF) and to develop the methodology of quantitative assessment of EF in the forestry sector. Based on the stock-difference method, 17 kinds of EFs (27 EFs based on forest types) were required to calculate the carbon emission in the forestry sector. Priority for developing EFs followed the standards, which is a development plan by the government agency, importance of carbon stock for greenhouse gas, and EFs by the species. Currently, the most urgent development of EFs was carbon fraction in biomass and carbon stock in dead wood. Meanwhile, the quantitative assessment of EF consisted of 7 categories (5 categories of compulsory and 2 categories of quality evaluation) and 12 verification factors. Category in compulsory verification consisted of administrative document, determination methodology of emission factors, emission characteristic, accuracy of measurement and analysis, and data representative. Category in quality evaluation consisted of data management and uncertainty estimates. Based on the importance of factors in the verification process, each factor was scored separately, however, the score needs to be coordinated by the government agency. These results would help build a reliable and accurate greenhouse gas inventory report of Korea.

Stock assessment and management of blackthroat seaperch Doederleinia seaperch using Bayesian state-space model (베이지안 State-space 모델을 이용한 눈볼대 자원평가 및 관리방안)

  • CHOI, Ji Hoon;KIM, Do Hoon;CHOI, Min-Je;KANG, Hee Joong;SEO, Young Il;LEE, Jae Bong
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.55 no.2
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    • pp.95-104
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    • 2019
  • This study is aimed to take a stock assessment of blackthroat seaperch Doederleinia seaperch regarding the fishing effort of large-powered Danish Seine Fishery and Southwest Sea Danish Seine Fishery. For the assessment, the state-space model was implemented and the standardized catch per unit effort (CPUE) of large powered Danish Seine Fishery and Southwest Sea Danish Seine Fishery which is necessary for the model was estimated with generalized linear model (GLM). The model was adequate for stock assessment because its r-square value was 0.99 and root mean square error (RMSE) value was 0.003. According to the model with 95% confidence interval, maximum sustainable yield (MSY) of Blackthroat seaperch is from 2,634 to 6,765 ton and carrying capacity (K) is between 33,180 and 62,820. Also, the catchability coefficient (q) is between 2.14E-06 and 3.95E-06 and intrinsic growth rate (r) is between 0.31 and 0.72.

Digital mapping of soil carbon stock in Jeolla province using cubist model

  • Park, Seong-Jin;Lee, Chul-Woo;Kim, Seong-Heon;Oh, Taek-Keun
    • Korean Journal of Agricultural Science
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    • v.47 no.4
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    • pp.1097-1107
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    • 2020
  • Assessment of soil carbon stock is essential for climate change mitigation and soil fertility. The digital soil mapping (DSM) is well known as a general technique to estimate the soil carbon stocks and upgrade previous soil maps. The aim of this study is to calculate the soil carbon stock in the top soil layer (0 to 30 cm) in Jeolla Province of South Korea using the DSM technique. To predict spatial carbon stock, we used Cubist, which a data-mining algorithm model base on tree regression. Soil samples (130 in total) were collected from three depths (0 to 10 cm, 10 to 20 cm, 20 to 30 cm) considering spatial distribution in Jeolla Province. These data were randomly divided into two sets for model calibration (70%) and validation (30%). The results showed that clay content, topographic wetness index (TWI), and digital elevation model (DEM) were the most important environmental covariate predictors of soil carbon stock. The predicted average soil carbon density was 3.88 kg·m-2. The R2 value representing the model's performance was 0.6, which was relatively high compared to a previous study. The total soil carbon stocks at a depth of 0 to 30 cm in Jeolla Province were estimated to be about 81 megatons.

A Study on Stock Assessment of Japanese Flying Squid (Todarodes pacificus) in Korea·China·Japan Waters (한·중·일 해역의 살오징어(Todarodes pacificus) 자원평가 연구)

  • Sungsu Lim;Do-Hoon Kim;Jae-Beum Hong
    • Environmental and Resource Economics Review
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    • v.31 no.4
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    • pp.451-480
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    • 2022
  • The Japanese Flying Squid (Todarodes pacificus) is a commercially important species in South Korea and the most popular species among consumers. However commercial catches of Japanese Flying Squid have been declining since 2000. In this study, we conducted a stock assessment to identify stock status. This study differed from previous studies in two aspects: a greater amount of available fishing effort data was used, and data from China, Japan, and Korea were included. A CMSY (catch-maximum sustainable yield) model was used to estimate MSY, biomass and exploitation with Bayesian state-space implementation of the Schaefer (BSS) model for the method of stock assessment, and evaluated the species by dividing into two groups, 'Korea' and ' Korea·China·Japan'. In all cases, Japanese flying squid biomass showed a general decreasing trend. Additionally, the biomass estimated for 2020 was lower than the biomass necessary to achieve the maximum sustainable yield. To manage Japanese Flying Squid effectively, it is necessary to strengthen the resource management strategies of individual countries and prepare a cooperative plan among countries.