• Journal of Ecology and Environment
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• 제37권4호
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• pp.209-216
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• 2014

This study was undertaken to suggest an effective fisheries resources management system by using stock assessment and potential yield analyses of crucian carp population in the mid-upper system of the Seomjin River. Fieldwork was conducted seasonally from 2008 to 2009 in the mid-upper system of the Seomjin River. The stock assessment was carried out by the swept area method and the potential yield was estimated by improved fisheries resource potential estimation system based on the Allowable Biological Catch. Also, the yield-per-recruit analysis was used to review the efficient management implication of the resource, Carassius auratus. As a result, the age at first capture ($t_c$) was estimated as 1.468 year, converted body length (BL) was 10.8 cm. Meaning the current fishing intensities, the instantaneous coefficient of fishing mortality (F) was $0.067year^{-1}$, and the yield-per-recruit analysis showed that the current yield per recruit was estimated to be 15.999 g with F and $t_c$. The instantaneous rate of fishing mortality that provides for Allowable Biological Catch ($F_{ABC}$) based on the current $t_c$ and F was estimated as $0.618year^{-1}$. Therefore, the optimum fishing intensities could be achieved at the higher fishing intensity for Carassius auratus. The calculated annual stock of C. auratus was estimated as 7,608 kg, and the potential yield was estimated as 343 kg with $t_c$ and F at the fixed current level. Using yield-per-recruit analysis, if F and $t_c$ were set at $0.618year^{-1}$ and 2 year, the yield per recruit and total allowable catch would be predicted to increase to 62 g and 2,531 kg by about 3.9 times and 7.3 times, respectively.

• 수산해양기술연구
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• 제36권3호
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• pp.234-243
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• 2000

This paper is to study population ecological characteristics, including growth parameters, survival rate, instantaneous coefficients of natural and fishing mortalities, and age at first capture of the soft-shelled clam, Mya japonioa in the intertidal zone of South Sea in Korea. For describing growth of the clam a von Bertalanffy growth model was adopted, The von Bertalanffy growth curve had an additive error structure and the growth parameters estimated from a non-linear regression were SH/sub ∞/=79.83mm, K=0.26, and t/sub 0/= -0.01. Survival rate (S) of the soft-shelled clam was 0.26 (SD=0.02). The instantaneous coefficients of natural mortality (M) was estimated to be 0.78/year and fishing mortality (F) 0.57/year for the soft-shelled clam. The age at first capture (t/sub c/) was estimated as 2.69 year. The mean densities of the soft-shelled clam by bottom type were 3.40 inds./m²(SE=0.18) in the sand, 63.4 inds./m²(SE= 0.53) in the muddy sand, and 0 inds./m2 (SE=0) in the gravelly sand. The mean densities of the soft-shelled clam by 3 different areas were 4.88 inds./m²(SE=0.09), 2.61 inds./m²(SE=0.13), 7.20 inds./m²(SE=0.18), respectively and the biomass of the clam were estimated as 131mt, 121mt, 665mt, respectively. An yield-per-recruit analysis showed that the current yield-per-recruit of about 8.30g with F=0.57/year and the age at first capture (t/sub c/) 2.69 year, was lower than the maximum possible yield-per-recruit of 9.60g. Fixing to at the current level and increased fishing intensity (F) could produce an increase in the predicted yield-per-recruit from 8.30g to about 9.40. However, estimated yield-per-recruit increased to 1.30g by decreasing to from the current age (2.69 year) to age two with F fixed at the current level. Yield-per-recruit was estimated under harvest strategies based on F/sub max/ and F/sub 0.1/.

• 한국수산과학회지
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• 제45권5호
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• pp.493-498
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• 2012

We derived biological reference points for Pacific cod Gadus macrocephalus in southeastern Korean waters by applying a yield-per-recruit analysis based on a daily simulation that adopted size-dependent fecundity, growth, and natural mortality functions. This showed that the yield per recruit of Pacific cod can be maximized at an instantaneous rate of fishing mortality (F)=0.37 $yr^{-1}$ under the current regulations, where the minimum catch size ($L_c$)=30 cm in total length (TL). The maximum economic yield was estimated to be attained at $L_c$=35-45 cm TL, if F>1 $yr^{-1}$ but at $L_c$=35-40 cm TL, if F<1 $yr^{-1}$. Despite great uncertainty in the stock assessment, to develop fisheries management plans for the sustainable exploitation of Pacific cod in southeastern Korean waters, it is necessary to estimate F using capture-recapture or other expedient methods.

• 한국수산과학회지
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• 제23권6호
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• pp.475-483
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• 1990

An assessment of Kuwait's commercial fish stocks: hamoor (Epinephelus tauvina), zobaidy (Pampus argenteus), nakroor (Pomadasys argenteus) and sheiry (Lethrinus nebulosus), was conducted using length-frequency data, mean growth and mortality estimates obtained during 1981$\~$1988. The length-cohort analysis indicated that increases in fishing effort would not lead to long-term gains in yield of the stocks at the current estimate of natural mortality rate (M). At high M which was assumed arbitrarily, some benefit in yield could be obtained, especially for hamoor and sheiry. At low M, the yield of all stocks decreased with increased fishing effort. Increases in fishing effort resulted in significant dec-line in spawning stock size for all the stocks. Yield-per-recruit analysis indicated that, un-der low M assumption, a higher yield can be obtained for zobaidy and nakroor by reducing fishing effort. At moderate M, decreases in fishing effort brought gains in yield per recruit of the stocks, but it was not substantial compared with the present level of M. At high M, most of the stocks reached the maximum yield-per-recruit. Overall, increased fishing effort either will not be associated with large long-term gains in yield or, in some stocks, might cause a decline from the present level.

• 수산해양기술연구
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• 제50권4호
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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.

• 수산해양기술연구
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• 제52권3호
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• pp.220-231
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• 2016

Yield-per-recruit (YPR) analysis is used to provide management guidance for the efficient use of a fish cohort. However, the individual fish price per unit weight of small yellow croaker (Larimichthys polyactis) or hairtail (Trichiurus lepturus) increases dramatically by size in Korea. Therefore, age-based production value-per-recruit (PPR) analysis has recently been developed (Zhang et al., 2014). Since age determination requires a substantial amount of money and time and it is even impossible for some fish species, it is difficult to obtain age information to apply the age-based PPR model. Thus, we attempted to develop an alternative method, which uses length data rather than age information, called the length-based PPR analysis. The results revealed that length-based PPR analysis was much more conservative for stock management than the YPR analysis. Furthermore, the PPR analysis was more economically beneficial than the YPR analysis, which can prevent the fish stock from the economic overfishing. In conclusion, the length-based PPR analysis could be a proper approach for stock assessment in the case that the individual fish price per unit weight increases dramatically by size, and this analysis is useful to obtain vital management parameters under data-deficient situation when traditional stock assessment methods are not applicable.

• 수산해양기술연구
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• 제51권4호
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• pp.535-544
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• 2015

본 연구에서는 가입에 따른 산란자원량의 변화를 나타내어 가입남획을 방지하는 가입당 산란자원량 모델(spawning biomass per recruit model)을 비교 분석하였다. 가입당 산란자원량 모델은 연령별 선택비를 고려하지 않는 (knife-edged selectivity) 방법과 연령별 선택비를 고려한 (age specific selectivity) 방법의 두 가지가 있으며 연령별 선택비를 고려하지 않는 방법의 경우 가입당 자원량의 식에 성숙비를 곱함으로써 가입당 산란자원량을 나타낼 수 있다. 하지만 기존의 가입당 산란자원량 추정 방법은 어구가입 이후의 모든 연령을 고려하지 않고 어구가입 연령의 성숙비만을 가입당 자원량에 곱함으로써 가입당 산란자원량을 계산하였다. 본 연구에서는 이를 수정하여 어구가입 이후의 모든 연령을 고려한, 즉, 연령별 자원량에 대해 가중평균된 성숙비를 가입당 자원량에 곱하여 가입당 산란자원량을 추정하였다. 한국 근해에서 유자망에 의해 어획되는 참조기자원을 대상으로 기존의 방법과 새로운 방법을 적용하여 추정된 가입당 산란자원량을 비교한 결과 어구가입연령의 성숙비가 1.00 이상에서는 가입당 산란자원량이 차이가 없었다. 그러나 성숙비가 1.00 미만인 연령에서는 어구가입연령이 낮을수록 오차가 크게 나타났으며 기존 방법에 의해 가입당 산란자원량이 과소 추정되었고 어구가입연령별로 가입당 산란자원량의 오차 값을 비교하였을 때, 적게는 4세 때의 0.25 g에서 많게는 1세 때의 130.69 g만큼의 오차가 나타났다. 또한 연령별 선택비를 고려하지 않는 방법과 연령별 선택비를 고려한 방법을 통해 $F_{35%}$를 비교한 결과 연령별 선택비를 고려하지 않는 방법 중 기존 방법에 의한 $F_{35%}$가 0.349/year로 나타났으며 새로운 방법에 의한 $F_{35%}$가 0.302/year로써 새로운 방법에 의한 값이 연령별 선택비를 고려한 방법에 의한 $F_{35%}$인 0.320/year와 유사하게 추정되었다. 따라서 본 연구에서 제시된 새로운 가입당 산란자원량 방법은 대부분의 어구가입연령이 2세 미만으로 낮게 나타나는 한국 연근해 어종을 대상으로 가입당 산란자원량 모델을 통해 자원평가를 실시할 경우 가입당 산란자원량과 그에 따른 적정어획수준의 오차 값을 줄여줄 것이며 기존의 방법을 통한 $F_{35%}$의 값은 과대 추정되어 남획의 위험이 있으므로 새로운 방법을 통해 적정어획수준을 추정하는 것이 옳다고 판단된다.

• 한국패류학회지
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• 제24권3호
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• pp.189-197
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• 2008

In order to develop the sustainable ecological management, short-necked clams, Ruditapes philippinarum, were collected from Yoengi coast in Tongyoeng, Korea. The growth of the clam was estimated as: $L_f=68.08{\cdot}(1-e^{-0.145(t+0.324)})$ from ring radius composition of shell. Instantaneous co-efficiency of total mortality and natural mortality were calculated as: 0.991/year and 0.494/year, respectively. The age of the clams from the first capture was estimated to be 3.28. The total biomass was estimated to be 212 MT in the fisheries area (6.4 ha). Applied by these parameters, the annual recruit biomass and the current yield per recruit were calculated to be 649.5 individual/$m^2$ and $0.7\;g/m^2$, respectively. The current fishing intensity was much lower for maximum sustainable yield and acceptable biological catch. Although higher yield per recruit could be achieved by increasing fishing intensity, it is favorable to retain the current fishing intensity because of the unique fishing attitude on Yeongi coast in Tongyoeng, Korea.

• 한국수산과학회지
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• 제50권4호
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• pp.437-446
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• 2017

To evaluate the consequences of possible fisheries regulations of anchovy Engraulis japonicus in the Korea Strait, we developed and applied a simulation-based yield-per-recruit (Y/R) model that considered temperature-dependent growth and size-dependent mortality, covering the egg to adult stages. We projected changes in commercial yield and egg production of anchovy with respect to varying biological reference points of 1) the instantaneous fishing mortality, 2) the minimum fork length of anchovy allowed to catch for protecting smaller anchovy ($L_{c,min}$), and 3) the maximum fork length allowed to catch for protecting bigger anchovy ($L_{c,max}$). Our Y/R model showed that the anchovy yield will be maximized at ca. $1.4{\times}10^6tons$ when $L_{c,min}$ ranges between 42-60 mm or at ca. $0.8{\times}10^6tons$ when $L_{c,max}$ ranges from 88-160 mm. At $L_{c,min}=30mm$, the present minimum length of catch, our simulations indicated that the anchovy yield can reach a maximum of $1.2{\times}10^6tons$ in the long-term when the present fishing effort, which annually yields ca. $0.2{\times}10^6tons$ of anchovy, can be increased by a factor of 28. We expect that our simulation-based Y/R model can be applied to other commercially-important small pelagic species in which the traditional Beverton-Holt Y/R model is difficult to apply.

• 생태와환경
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• 제44권2호
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• pp.172-177
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• 2011

본 연구는 최적화된 자원량을 기반으로 최대 생산성을 얻을 수 있는 잠재생산량 추정을 통한 어족자원(꺽지)의 효율적 관리방안을 모색하고자 하였다. 이를 위해 섬진강 중 상류 수계에서 2008년 8월부터 2009년 4월까지 계절별로 총 4회 조사를 실시하였다. 자원량 추정은 소해면 적법(Swept Area method)을 이용하였으며, 잠재생산량은 생물학적 허용어획량(Allowable Biological Catch, ABC)에 기초한 어족자원 잠재력 추정시스템을 수정 보완하여 사용하였다. 또한, 꺽지 자원의 효율적인 관리 방안을 검토하기 위해 가입당생산량모델(Beverton and Holt)을 사용하였다. 연구결과, 어획개시연령($t_c$)은 1.464 age로 나타났으며, 이를 체장으로 환산한 결과 7.8 cm(BL)로 확인되었다. 현재 어획강도를 나타내는 순간어획사망계수(F)는 0.061 $year^{-1}$이었으며, 이를 기준으로 한가입당 생산량(Y/R)은 4.124 g로 추정되었다. 어획개시연령($t_c$)과 순간어획사망계수(F)를 기준으로 한 적정어획사망계수($F_{ABC}$)는 0.401 $year^{-1}$로 추정되었는데 이는 현재 꺽지 자원에 대한 어획강도가 매우 낮은 상태임을 시사한다. 꺽지의 연간 자원량은 3,048 kg으로 나타났으며, 현재 어획개시연령과 적정어획사망계수를($F_{ABC}$)를 바탕으로 한 잠재생산량은 861 kg으로 추정되었다. 가입당 생산량 모델을 사용하여 어획개시연령을 3 age로 어획사망계수는 0.643 $year^{-1}$로 가정할 경우, 가입당 생산량은 현재의 4.12 g에서 13.84 g로 약 3.4배 증가될 것으로 예상되었다.