• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.6
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• pp.942-953
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• 2020

Achieving optimal sustainable yields (i.e., avoiding overfishing and maximizing fishery harvest at the same time) is one of the main objectives in fisheries management. Generally, management reference points (MRPs) such as fishing mortalities (Fmsy, F0.1, Fx%) have been suggested for the purpose. In this study, we intended to suggest MRPs for Korea chub mackerel Scomber japonicus stock, using a stochastic catch-at-age model (SCAA) and evaluate whether the current fishing intensity on the stock is appropriate. We used length frequency and catch-per-unit-effort data on the Korea chub mackerel stock collected from the large purse-seine fishery, and yields landed by all fisheries from years 2000 - 2019. We calculated yield per recruit and spawning potential ratio, and projected spawning stock biomass (SSB) under different fishing mortality, assuming annual recruitments were solely controlled by environmental effects (i.e., steepness of 1.0). Some of our major findings and suggestions were that the overfishing threshold would be F46%; i.e., the fishing mortality in the terminal year, 2019 was 0.257/year, which corresponded to F46%.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.57 no.3
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• pp.292-301
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• 2024

It is challenging to simultaneously estimate parameters in a stock-recruitment relationship, steepness, and natural mortality rate with the other parameters within an age-structured assessment model even in a data-rich situation. Such a problem leads to uncertainty in estimates of management references such as maximum sustainable yield (MSY), which are affected by those components. The objective of this study was to evaluate the effects of those parameters on MSY by analyzing the process of estimating the MSY. For illustration, we used two data sets: The chub mackerel Scomber japonicus in the Korean waters and the yellowtail flounder Limanda ferruginea in the Southern New England-Mid Atlantic. As a result, the natural mortality rate influenced spawning stock biomass per recruit, yield per recruit, and MSY, while steepness affected MSY. A sensitivity analysis enabled us to estimate the natural mortality rate and steepness. The optimal set of steepness and natural mortality was 1.0 and 0.37 per year for the chub mackerel, and 0.35, and 0.8 per year for the yellowtail flounder, respectively.

• The Journal of Fisheries Business Administration
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• v.49 no.1
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• pp.51-66
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• 2018

During the Joseon period, the East Sea would be called 'Gyeonghae' due to a large number of whales. In the Republic of Korea, whaling was locally permitted in 1946. However, the number drastically dropped because the hunting of the marine mammal had already been carried out in Russia, the U.S. and Japan since 1800s. Before a moratorium on commercial whaling was introduced by the International Whaling Commission(IWC) in 1986, whale populations in the East Sea had plunged. Furthermore, Korean gray whales and fin whales weren't found anymore in that area. With the suspension, whale hunting was banned in Korea as well. Even so, accidentally caught whales have been allowed to be distributed on the market with respect for local food culture. With the establishment of Whale Museum and hosting of the 57th Annual Meeting of the International Whaling Commission(IWC) at Jangsaengpo in 2005, whale tourism was facilitated in earnest. This whale tourism has been operated by Nam-gu Office and Nam-gu City Management Corporation in Ulsan. However, the popularity of whale tourism has increased a demand for whale meat. At the same time, there has been concern over decrease in whale populations because of illegal whaling. In addition, a conflict between the use and protection of whales has caused confusion in tourism identity. Actually, there is a serious doubt on the sustainability of whale tourism due to the decade-long deficit and excessive investments. This study attempts to define a concept of whale tourism and propose a future direction for the sustainable growth and development of Korea's whale tourism industry after developing such comprehensive assessment indicators as a basic research for the introduction of sustainable whale tourism. To achieve the aim of this study, AHP(Analytic Hierarchy Process) was chosen as a main research tool and the factors were ranked by a comprehensive analysis of principal factors and detail factors. The current study showed the following results. First, ecological environment(0.430) was indicated the most important factor of whale tourism assessment indicators. Moreover, Population(0.1302), Action for Cetacean protection(0.1031), Governance(0.0898) were critical factors. On the other hand, Accommodations(0.0085), Whale meat(0.0088) were unimportant factors than others.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.49 no.3
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• pp.367-375
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• 2016

Marbled flounder Pseudopleuronectes yokohamae is a commercially important flatfish in the coastal waters of the East Sea off Pohang, Korea. Maturity and spawning dynamics of P. yokohamae were investigated based on samples collected by gill net and long line in the coastal waters off Pohang from January 2013 to December 2014. We analyzed monthly changes in maturity stage, gonadosomatic index (GSI), egg diameter, fecundity, and total length at 50% group maturity. We found that the spawning period was December to February, wherein fecundity ranged from 55,760 eggs at 20.40 cm total length (TL) to 1,559,007 eggs at 46.6 cm TL. The relationship between TL and fecundity (F) was F = 0.0017 TL^3.5604 (R² = 0.6984), and F increased with increasing TL. We estimated the TL at 50% group maturity as 27.4 cm for female and 23.5 cm for male P. yokohamae, respectively. The results from this research will aid in the development of policies on season and minimum catch length for sustainable production of P. yokohamae. We propose that it is necessary to conduct long-term ecological monitoring for this species because biological properties such as spawning ecology and growth performance are being affected by climate change.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.46 no.4
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• pp.392-405
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• 2010

The population of small yellow croaker, Larimichthys polyactis, in the Yellow and East China Seas has decreased significantly since the mid 1970s. Several management measures have been introduced to conserve it, but population size remains low. To rebuild this population, it is now necessary to consider more effective management methods based on the stock assessment. To determine long-term population changes, fishery and biological data collected over 34 years (1969-2002) were analysed. Yearly fish length compositions were analysed for the time periods 1968 through 1970, 1978 through 1982, and 1993 through 2002; and catch data was available from 1969 to 2002. Annual population sizes were calculated based on length composition, the relationship between total length and body weight, and total landings. Analyses showed that since the 1970s, average size of harvested fish decreased; the proportion of less mature fish (smaller than the 50% maturity length, 19cm) in catches has increased and the estimated biomass has decreased significantly. Consequently, the main management recommendation is that juvenile fish need to be better protected to allow the rebuilding of resources to a more sustainable population level. This will require fish size limit, permissible mesh size, and closed area and season regulations.

• 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.

• The Journal of Fisheries Business Administration
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• v.41 no.2
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• pp.25-44
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• 2010

The laver has been cultivated long time ago in Korea. And traditional production system was changed to new system about 30 years ago. The new production system is understood the specialization of laver products, that is, originally individual fishery households made final laver products from raw cultured laver in sea working to dry working in land, but the new system was separated raw laver production in sea and dry laver production, which made final dry laver products by purchase the raw laver in land. This change has been increased laver production, 10 billion sheets in 2000's from 5 billion sheets in 1980's. And rapid production increase gave rise to some troubles on laver industry that is a serious drop in real laver prices, discord structure between raw laver producer and dry laver producer, stagnation of laver consumption, etc. Now Korea is the best laver production country together with Japan in world. Then we have to consider some schemes for the sustainable development of laver industry. One of such schemes is export enlargement of laver against world. The consumption of laver has been globally increased in recent. The other is the grading test problem of dry laver. Because the rapid increase of laver production caused to drop laver quality. Then we seriously have to consider the grading test of dry laver for high level quality production.

• Ocean and Polar Research
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• v.27 no.3
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• pp.311-322
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• 2005

Fisheries buyback programs in Korea have been implemented since 1994, and their scales are estimated to be the present value of 930 billion won for the last 9 yens since 1994. The paper attempts to identify the patterns of each fish species, of which their yields can be steadily increased or significant]y decreased, and to evaluate its effective level and the optimal level for buyback programs by means of fishing capacity analysis. The paper distinguishes fish species, that there is no need to reduce the fishing efforts, such as anchovies, mackerels, squids, Spanish mackerels, and herrings, because MSY exceeds yields, from fish species to control overfishing such as file fish, yellow corvenias, young pollack, hair tail, snow crab, and pollack. The paper also suggests that 65% of the fishing efforts (total tonnages) should be cut back at the national aggregate level in order to restore fish stocks.

• Fisheries and Aquatic Sciences
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• v.12 no.2
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• pp.118-129
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• 2009

To develop a sustainable management model for oyster farming in Pukman Bay, Korea, we estimated the carrying capacity for oyster farming using food availability data. Optimal culture densities were calculated to be 124-133 individuals per unit flux area ($m^2$) and 310-330 individuals per string. The present annual production is approximately 1,038 tons/year, which is 87% of the estimated maximum yield of 1,193 tons/year. Therefore, considering annual fluctuations and a critical buffer to reduce ecological impacts, the current level is within optimal conditions. During periods of increased water temperature, energy demand was largely met by high primary production. The food supply significantly decreased as the harvest season approached, and 10 out of 21 oyster farms had a deficient food supply for at least 1 month. Therefore, these farms (39% of the farms within the bay) exceeded optimal densities.

• Journal of Fisheries and Marine Sciences Education
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• v.27 no.1
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• pp.284-299
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• 2015

The purpose of this study is to look at the elementary school teachers' practical experiences of change and knowledges in promotion of Education for Sustainable Development(ESD) process with Community of Practice(CoP) of teachers and Biographical Approach. ESD project of 'S' elementary school was started by Principal's recognition of further and that was practiced with a common theme over the course through various experiences in educational field with teachers' involvement and finally came to the changes in teachers' personal life and lifelong cognition. Through Community of Practice teachers could look the concept of ESD to a wide field of view and tried various activities in the classroom with students and also, as a further, were able to equip new professional competency with skills. Through the process of learning and experience teachers accepted the ESD philosophy as the engine of life and experienced that their long-term recognition was extended to the whole personal life and the global community.