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장창익,김수암,윤성봉 한국수산학회 1992 한국수산과학회지 Vol.25 No.4
한국근해 참조기의 지난 20여년 동안의 어획자료를 사용하여 잉여생산량 모델에 의해 추정된 MSY를 비교하여 보면, Shaefer와 Fox 모델에 의하여 추정된 값들은 각각 37,000mt와 33,450mt였고, Zhang 모델에 의하여 자원량과 순간어획사망계수를 적용시킨 MSY는 45,328mt, 자원량과 어획량 자료를 이용하는 방법에서는 40,160mt로 각각 추정되었다 이 현상은 이 모델들이 각기 독립된 다른 자료를 이용하여 MSY를 추정하였으나, 추정된 값은 거의 비슷한 결과를 보였다. 참조기자원을 가입당생산량 모델에 적용시킨 결과를 사용하여 자원관리 방안을 모색해 보면, 가능한 최대 가입당 생산량이 43g임에 비하여 현재의 t_c=0.604, F=1.11에서의 가입당생산량은 약 20g 정도에 불과하다. 여기서 t_c를 현재 상태로 고정시킨후, 가입당생산량을 높이는 방안을 생각해 보면, F를 현재의 1.11에서 0.4 정도로 낮추어야 하나, 가입당생산량의 큰 증가는 없다. 즉, 현재의 20g에서 25g밖에 증가되지 않는다. 그러나, 현재의 어획강도 (F)를 고정시키는 경우에는 t_c를 현재의 0.604세에서 3세 부근으로 조정하면 최대의 가입당생산량 (43g)을 얻을 수 있고, 이 t_c 값은 역시 F_(0.1) 방법에서 추정된 적정어획체장을 연령으로 환산한 결과와 거의 일치함을 알 수 있다. Zhang모델을 이용한 자원의 회복 방안에서 참조기 자원의 최대생산가능 자원량(B^*_MSY)를 유지시키려면 F를 약 0.5 수준으로 낮추어야 하고. 이 수준에서 약 8년 뒤에는 자원량이 적정 수준에 거의 접근하게 된다. Based on surplus production models using fishery data for the last 20 years, a stock assessment was conducted for the small yellow croaker in Korean waters. The maximum sustainable yields (MSY) from the Schaefer and Fox models were estimated to be 37,000 metric tons (mt) and 33,450 mt. Zhang's model using time-series biomass with instantaneous coefficients of fishing mortality (F) and using time-series biomass and catch yielded MSY estimates of 45,328 mt and 40,160 mt, respectively. A yield-per-recruit analysis showed that the current yield per recruit of about 20g with F=1.11 yr^(-1), where the age at first capture (t_c) is 0.604, was much lower than the maximum possible yield per recruit of 43g. Fixing t_c at the current level and reducing fishing intensity (F) from 1.11 yr^(-1) to 0.4 yr^(-1) yielded only a small increase in predicted yield per recruit, from 20 to 25g. However, estimated yield per recruit increased to 43g by increasing t_c from the current age (0.604) to age three with F fixed at the current level. This age at first capture corresponded to the optimal length which was obtained from the F_(0.1) method. According to the analysis of stock recovery strategies employing the Zhang model, the optimum equilibrium biomass (B^*_MSY) which produces the maximum yield could be achieved after approximately five years at the lower fishing intensity (F=0.5).
장창익,이성일,김종만 한국수산자원학회 2003 한국수산자원학회지 Vol.6 No.-
An ecosystem-based approach is introduced to manage fisheries resources in marine ranching areas by considering ecological interactions of organisms in the ecosystem. The ecosystem structure model (ESM) analyses ecotrophic levels among functional groups in the ecosystem and the ecosystem dynamic model (EDM) conducts dynamic simulation of the ecosystem according to the fishing mortality intensity or environmental changes. Here, we developed two models : the fishery stock enhancement model which estimates parameters to enhance required fishery stocks by artificial releasing and the ABC(acceptable biological catch) estimation model for an effective fishery resource management. In addition, methods for estimating parameters required for the ecosystem models and population models were also investigated. Finally, a necessity for studying the ecosystem-based approach for the management of fisheries resources was stressed.
Changes in Fisheries Resources and Future Research Need for the Yellow Sea Ecosystem
Zhang,Chang-Ik,Sohn,Myoung-Ho,Yoo,sin-Jae 濟州大學校海洋硏究所 1993 해양과환경연구소 연구논문집 Vol.17 No.-
Korean annual catches from the Yellow Sea have been gradually increased until the mid 1980s, showing about 130,000 metric tons (mt) in the 1960s, 300,000 mt in the 1970s, and 450,000 mt in the 1980s. Three major fisheries, that is, the two-boat large bottom trawl fishery, the large staw net fishery and the medium-sized bottom trawl fishery, accounted for about 70% of the total catch from the sea. During the three decades the catch per unit of effort (CPUE) declined substantially, indicating that the relative abundance of the 1960s was reduced by about one tenth of that of the 1980s for all of the three fisheries, due possibly to overexploitations of the fish stocks. In addition species compositions in the catch revealed a remarkable change in species dominance for the same period. Nine species, which are anchovy, hairtail, small yellow croaker, filefish, mackerel, Jack mackerel, Spanish mackerel, skaterays and pomfret, were consistently dominant in the catches as well as commercially important. There was a general trend of species shifts in species compositions from large, high-valued fishes to small, low-valued fishes.
Abundance Estimation of the Chesapeake Bay Blue Crab, Callinectes sapidus
( Chang Ik Zhang ),( Jerald S. Ault ) 한국수산학회 1995 한국수산과학회지 Vol.28 No.6
This study is to estimate abundance of the Chesapeake Bay blue crab stock. Using 823 dredge tows which were conducted during the 1991 winter survey, blue crab abundance was estimated on the basis of newly developed methods which account for unequal dredge tow distances, size- and sex-specific heterogeneous overwintering spatial distributions, wintertime exploitation, the time period of quasi-hibernation, and dredge capture efficiency. The estimate of total abundance before correction by gear efficiency was 131.8 million crabs (95% C.I.=118.2 million crabs to 145.4 million crabs). Dredge capture efficiency was estimated to be 0.474. Thus, the estimate of total abundance was calculated as 278.1 million crabs after correction by the efficiency factor.