Yield per recruit model is the most popular method for fisheries stock assessment. However, stock assessment using yield per recruit model can lead to recruitment overfishing as this model only considers the maximum yield per recruit without spawning biomass for reproduction. For this reason, spawning biomass per recruit model which reveals variations of spawning stock biomass per fishing mortality (F) and age at first capture (tc) is considered as more proper method for stock assessment. There are mainly two methods for spawning biomass per recruit model known as age specific selectivity method and knife– edged selectivity method. In the knife–edged selectivity method, the spawning biomass per recruit has been often calculated using biomass per recruit value by multiplying the maturity ratio of the recruited age. But the maturity ratio in the previous method was not considered properly in previous studies. Therefore, a new method of the knife–edged selectivity model was suggested in this study using a weighted average of the maturity ratio for ages from the first capture to the lifespan. The optimum fishing mortality in terms of F35% which was obtained from the new method was compared to the old method for small yellow croaker stock in Korea. The value of F35% using the new knife–edged selectivity model was 0.302/year and the value using the old model was 0.349/year. However, the value of F35% using the age specific selectivity model was estimated as 0.320/year which was closer to the value from the new knife–edged selectivity model.
신체크기는 다양한 동물그룹에서 짝짓기의 성공을 결정짓는 중요한 요소로 알려져 있다. 그럼에도 불구하고, 한국산 유미양서류의 짝짓기 경쟁에 있어 수컷도롱뇽들의 신체크기가 어떻게 영향을 미치는 지는 연구가 잘 수행되어 있지 않다. 우리는 한국 고유종으로 짝짓기 행동이 알려져 있지 않은 고리도롱뇽(Hynobius yangi)을 이용하여, 큰 고리도롱 뇽 수컷이 작은 수컷에 비하여 짝짓기 경쟁에서 우세한지 여부를 연구하였다. 큰 수컷, 작은 수컷, 암컷 각 한 마리를 그룹으로 수행된 짝짓기 행동을 암컷에 대한 구애행동, 수컷간 경쟁행동, 알의 수정행동으로 구분하여 분석한 결과, 큰 수컷과 작은 수컷 사이의 구애, 경쟁, 수정행동 어느 것에서도 통계적으로 유의한 차이를 보이지 않았다. 이러한 결과는 아마도 고리도롱뇽 수컷들 간 크기 변이 정도가 작으며, 암컷이 알을 산란할 장소가 서식처 내에 풍부함에 기인한 것으로 판단된다. 이 연구는 고리도롱뇽의 짝짓기 행동에 관한 첫 번째 보고이다.
This study was performed to estimate biomass and to provide management plan through population ecological characteristics, including survival rate, instantaneous coefficient of natural and fishing mortalities, and age at first capture of Flathead grey mullet, Mugil cephalus, in the coastal waters of Yeosu. Survival rate (S) of the flathead grey mullet was 3.671. The instantaneous coefficients of natural mortality (M) and fishing mortality (F) was estimated to be 0.325 /year, 0.962 /year for flathead grey mullet. Also fist capure age of flathead grey mullet was 3.61year. The current biomass of the flathead grey mullet in the study area was estimated to be 19.6 M/T and F0.1 and F40% were estimated 0.340 /year, 0.225 /year. For the stock assessment result, flathead grey mullet was not overfished but overfishing.
Fishing trend and characteristics of Korean tuna purse seine fishery in the Pacific Ocean were investigated using logbook data compiled from captain onboard and the statistical data from 1980 to 2013. The historical catch of this fishery had sharply increased since mid–1980s, and it has shown fluctuations with about 2–3 hundred thousands, whereas the catch per number of vessel has steadily increased with fluctuations since commencing this fishery. As for the proportion of catch by set type, unassociated type had increased from the mid–1980s to the end of 1990s, and then has decreased up to 2010s. Associated type had decreased continually to the end of 1990s, however, it started to increase since the beginning of 2000s. As for the catch proportion of set type by main species, those of skipjack tuna and bigeye tuna showed higher in the associated type, whereas that of yellowfin tuna has the highest proportion in the unassociated type. Fishing distribution of Korean tuna purse seine fishery was concentrated on the area of 5°N~10°S and 140°E~180° through the decades. The monthly catch distribution by longitudinal zone of Korean tuna purse seine fishery expanded the most further to the eastward in September to October.
Korean distant water tuna longline fishery commenced in 1966 in the Atlantic Ocean. Since then, it has become one of the most important fisheries of Korea. By early of 1970s, total amount of tuna caught in the Atlantic Ocean was the highest among other Korean distant water tuna fisheries, but has become minor since 1990s. The annual catch of tuna and tuna-like species by Korean tuna longline fishery in the Atlantic Ocean was about 1,900 mt in 2013. Bigeye tuna was the predominant species in species composition followed by yellowfin tuna, Albacore tuna, Blue shark and Swordfish. Korean distant water tuna longline fishery have mainly operated in the tropical area of the Atlantic Ocean (20°N~20°S, 20°E~60°W), fishing ground was almost similar as in the previous years. The length frequency of major species (Bigeye tuna, Yellowfin tuna, Albacore tuna, Blue shark and Swordfish) were estimated. As the result of length (size) frequency data on main species caught by lonline fishery in the Atlantic Ocean, main length intervals of bigeye tuna caught in 2011, 2012 and 2013 were 120~125 cm, 160~165 cm and 130~135 cm, respectively. For yellowfin tuna, those were 125~130 cm, 150~155 cm, 145~150 cm and for albacore, 109 cm, 102 cm, 109 cm and 106 cm respectively. For swordfish caught in 2011, 2012 and 2013, main length intervals were 130~135 cm, 125~135 cm and 125~130 cm, respectively, and for blue shark, 195~200 cm in 2011 and 185~190 cm in 2012, 2013.
This study identified problems of the existing ecosystem-based fisheries assessment approach, and suggested new methods for scoring risk and for the estimation of fishery risk index. First, risk scores of zero to two for target and limit reference points for each indicator were replaced by those of zero to three, and the risk scores were calculated from new formulae which were developed in this study. Second, a new method for estimating fishery risk index (FRI) was developed in this study, considering the level of indicators. New method was applied to the Korean large purse seine fishery, large pair trawl fishery and drag net fishery. More precise and detailed risk scores were obtained from the new method, which can explain the risks by the wider range of both risk levels for 'better than target' and 'beyond limit'. The new method for estimating FRI could avoid the basic problem related with duplicated computations of fishery-level indicators, which improved the estimated FRI to be more accurate. Also, a method for estimating variance of FRI using the bootstrap was proposed in this study.
In the application of the ecosystem-based fisheries assessment Jeonnam marine ranching ecosystem, two fisheries, funnel fishery and trap fishery, were selected as target fisheries. Black seabream, Acanthopagru schlegelii, rock bream, Sebastes inermis, gray mullet, Mugil cephalus, were selected as target species for the funnel fishery, and conger eel, Conger myriaster, was target species for the trap fishery. For assessing indicators of four management objectives, that is the maintenance of sustainability, biodiversity, habitat quality and socio-economic benefits, indicators were selected considering the availability of data, which were 5 indicators for sustainability, 3 indicators for biodiversity, 4 indicators for habitat, 2 indicators for socio-economic benefit. The Objective risk indices for sustainability and biodiversity of two fisheries were estimated at yellow zone, medium risk level. The objective risk indices for habitat and socio-economic benefit were estimated at green zone, safe level. The species risk indices (SRI) were estimated at yellow zone. The fishery risk indices (FRIs) were estimated at 1.143 and 1.400 for funnel net fishery and trap fishery, respectively. Finally the ecosystem risk index estimated at 1.184.
본 연구는 고대 종법사회에서 시작된 효가 동서고금을 망라하여 현재까지 논의되고 있음으로부터 출발한다. 그간에 ‘효’의 연구는 주로 인문학 분야에서 이루어져왔으나, 근래에 들어 사회학, 의학, 법학 등의 대상으로 확대되고 있으며, 본 논문 역시 효에 대한 새로운 이해와 실천방법을 찾고자 ‘인문학’, ‘심리학’, 그리고 ‘코칭학’이라는 별개의 학문을 접목하는 새로운 시도를 하였다. 그 첫 번째 이유는 언론사에서 효의식과 효행에 관한 조사를 실시하였던 바, 효에 대한 의식은 높이 나타났지만, 효행 실천 항목에서는 잘하지 못한다는 결과를 얻었다는 내용 때문이다. 즉, 효는 알고 있어야 할 덕목이 아니라 실천해야하는 방법이 중요하다는 점을 깨달은 점이다. 두 번째 이유는 ‘효와 충이 상충’하는 문제와 ‘부모를 봉양한 자녀의 효행이 부모를 떠나 외지에서 성공하고 귀향한 자녀의 효행에 비하여 초라해지는’ 주관적 평가에 대한 모순을 해결해보고자 하였다. 다만, 본 연구에서는 효행의 실천을 목적으로 『소학』에 나타난 내면적 효의내용을 살펴보고 효행의 코칭 방법을 제안하는 범위로 제한하고자 한다. ‘효’의 내용을 분석하고 ‘효’를 실천해야하는 이유와 방법을 찾아보기 위해 먼저, 효의 전범으로서의 위상을 지닌 『소학』을 텍스트로 택하였고,『소학』에서 효와 관련된 내용만을 선별한 후, 인간발달과 관련하여 전근대, 근대, 탈근대 자료들이 제시하는 불후의 통찰들을 모두 받아들인 켄 윌버의 통합적 접근 방법으로 그 내용을 분석하였다. 분석 내용을 토대로 코칭 방법론을 도구로 하는 실천 프로그램을 제안하고자 한다.
The age and growth of flathead grey mullet, Mugil cephalus, were studied using samples collected from the coastal water of Yeosu from September 2009 to August 2010. Spawning season estimated from the gonadosometic index (GSI) was from November to January. A method for increasing the readability of the otolith was described and criteria for the interpretation of otolith was provided. The annual ring was formed in September once a year. Annual ring in otolith for flathead grey mullet is validated for fish aged 1-8 using the marginal increment analysis. Using the sectioned otolith, between reader precision was 84%. Also, Within-reader agreement for sectioned otolith age readings was higher (reader 1=84%, reader 2=87%). The relationship between fork length and total weight was TW=0.022FL2.818. The estimated von Bertalanffy growth parameters for the flathead grey mullet were L∞=67.97cm K=0.164/year and to=-0.81year.
Ecosystem-based fisheries management requires a holistic assessment of the status of fisheries by integrating fishery ecosystem indicators for management objectives. In this study four objectives were identified such as the maintenance of the sustainability, biodiversity and habitat quality and socio-economic benefits. The ecosystem-based fisheries assessment (EBFA) model to assess fisheries and their resources at the ecosystem level developed for Korean fisheries (Zhang et al., 2009) has a number of indicators for three management objectives. However, it was found that there were some overlapping components among indicators and that there were difficulties in assessing some indicators in the EBFA model. This study identified problems of the approach and suggested more pragmatic and simpler indicators. It also presented alternative reference points to assess indicators and discussed issues associated with the application of the EBFA model to a marine ranching ecosystem. In this study a total of 24 indicators were used for the assessment which included 4 socio-economic indicators. New indicators and reference points were demonstrated by applying it to the Uljin marine ranch.
A self-regulatory community fisheries management program in Korea is designed to enhance fisheries resources, to protect fishing grounds of self-regulatory communities, and to manage their fisheries resources by their own regulations and knowledge. This study explored an applicable ecosystem-based management plan based on the scientific investigation and analysis. This study suggested objectives, indicators and reference points of the ecosystem-based resource management system which are applicable to selfregulatory community fisheries. The objectives of the management system are to maintain sustainable fisheries production, to maintain optimum fishing intensity, to reduce by-catch, to conserve spawning ground and habitat, to maintain optimum habitat environment, to increase/maintain abundance of prey species, to increase/maintain stock biomass, and to conduct stock enhancement on the basis of scientific assessment. The improved methods for the assessment and management are introduced by demonstrating a self-regulatory fishery which targets on hen clam in Dong-li fishing village in Busan.
This study was performed to estimate biomass and to provide management plan through population ecological characteristics, including growth parameters, survival rate, instantaneous coefficient of natural and fishing mortalities, and age at first capture of hen clam, Mactra chinensis, in the Dong-li self-regulatory community of Busan. The von Bertalanffy growth parameters estimated from a non-linear regression were SH∞=86.24mm, K=0.12/year, and = -1.37year. Survival rate(s) of the hen clam was 0.515. The instantaneous coefficients of natural mortality(M) was estimated to be 0.232/year and fishing mortality(F) 0.432/year for hen clam. The current biomass of the hen clam in the study area was estimated to be 713mt and the acceptable biological catch(ABC) was estimated under various harvest strategies based on F0.1 and F40%.