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한국 연근해 갈치의 자원평가 및 관리방안 연구 1. 한국 연근해 갈치의 자원생태학적 특성치 추정
장창익 ( Chang Ik ZHANG ) 한국수산과학회 1996 한국수산과학회지 Vol.29 No.5
This study is to estimate population ecological parameters, including growth parameters, survival rates, instantaneous coefficients of natural and fishing mortalities, and age at first capture, as well as growth rates at age of the hairtail, Trichiurus lepturus Linne in Korean waters. For describing the growth of the hairtail, three growth models were fitted, and the von Bertalanffy growth model was adopted for the purpose of the further stock assessment work. The von Bertalanffy growth parameters estimated from a nonlinear regression using EXCEL Solver were L_∞=46.01 ㎝, K=0.3868, and t_o=-0.3220. Annual survival rate (S) of the hairtail was estimated to be 0.277 (variance=0.00035) and the instantaneous coefficient of natural mortality (M) was estimated to be 0.441/year. Instantaneous coefficient of fishing mortality (F) for the recent years was calculated as 0.843/year, implying an impact from fishing about two times greater than that of natural mortality. The age at first capture (t_c) was estimated to be 0.787 years, which is much younger age than 50% mature age. Finally, the growth rates at age were estimated.
한국 연근해 갈치의 자원평가 및 관리방안 연구 2 . 한국 연근해 갈치의 자원량 변동
장창익(Chang Ik Zhang),손명호(Myoung Ho Sohn) 한국수산과학회 1997 한국수산과학회지 Vol.30 No.4
Annual biomasses of the hairtail, Trichiurus lepturus, were estimated from the biomass-based cohort analysis(Zhang, 1987), using data of annual catch in weight at age during 1970-1988 in Korean waters. Annual biomass of the hairtail was peaked at about 240,000 mt in 1975, and thereafter declined with a slight fluctuation. Adult biomass showed a peak in 1978 with about 55,000 mt. However, it has continuously decreased until 1980 to the level of 9,000 mt and remained at this level till 1988. Age compositions of the hairtail in the 1980s differed greatly from those in the 1970s. The proportions of older hairtail(>4 years) were very low in the 1980s and even the biomasses of young hairtail(1-3 years) were at a low level in the 1980s compared with the level in 1970s. The 1973 and 1974 year classes appeared to be relatively dominant. The mean value of instantaneous rate of fishing mortality(F) in the 1980s was significantly different from that of the 1970s(P<0.05). Recruitment of the hairtail exhibited a similar trend with stock biomass until 1974, indicating the density-dependent Ricker curve.
가입당 생산액 분석에 의한 한국 해역 참조기 Larimichthys polyactis 자원의 관리
장창익 ( Chang Ik Zhang ),이은지 ( Eun Ji Lee ),강희중 ( Hee Joong Kang ) 한국어업기술학회 2014 수산해양기술연구 Vol.50 No.4
This study was performed to estimate optimum fishing mortality (F) and the age at first capture (tc) for small yellow croaker in Korean waters. We first estimated optimum F and tc 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 tc using the two types of the PPR analysis and compared the results. The optimum F and tc 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.
연어, Oncorhynchus keta 전기자어의 난황흡수 및 초기성장
장창익 ( Chang Ik Zhang ),손명호 ( Myoung Ho Sohn ),성기백 ( Ki Baik Seong ),박인석 ( In Seok Park ) 한국수산학회 1995 한국수산과학회지 Vol.28 No.5
연어, Oncorhynchus keta 전기자어의 부화 직후부터 부상기 이전까지의 난황흡수과정 및 체성장의 형태가 조사되었다. 한국 동해안 남대천에서 채포된 암수 친어로부터 채취한 알과 정자를 사용하여 인공수정을 시켰다. 사육수온은 13℃로 조절되었다. 부화 직후와 부화 후 12일부터 부화 후 33일까지 3일 간격으로 매회 40마리의 난황자어가 임의로 표본되었다. 부화 직후 난황자어의 평균 전장 및 평균 전중은 각각 1.97cm, 1.85g이었으며 난황흡수는 부화 후 33일에 거의 이루어졌다. 전장, 전중 및 체세포 중량의 성장곡선은 Gompertz의 성장모텔에 잘 적합되었다. 그러나 난황장, 난황중, 난황고 및 난황부피는 난황흡수가 완전히 이루어지기까지 선형의 감소경향을 나타내었다. 아울러 전장과 전중 혹은 전중과 난황중 등의 상관관계를 나타내는 상대성장도 역시 조사되었다. The process of yolk absorption and the growth pattern of chum salmon, Oncorhynchus keta alevin were studied. Matured males and females of chum salmon were sampled from the Namdaechun River in the east coast of Korea, and then an artificial fertilization was carried out using their eggs and sperms. Fertilized eggs were incubated in controlled water temperature of 13℃ and samples of 40 alevins were randomly taken at just hatching and at every three days between 12 days after hatching and yolk absorption. The means of total length and total weight of hatched alevins were respectively 1.97cm and 1.85g, and the yolk absorption took about 33 days after hatching, based on the morphological measurement. Growth curves of total length, total weight and somatic weight were fitted well with the Gompertz growth model. However, the shrinking in yolk-sac length, yolk-sac weight, yolk-sac height and yolk-sac volume revealed a linear phenomenon until the absorption of yolk was completed. The relative growth of chum salmon alevin, such as the relationship between total length and total weight, or between total weight and yolk-sac weight, was also studied.
체장기반 가입당생산액 분석에 의한 한국 연근해 참조기 Larimichthys polyactis 자원과 갈치 Trichiurus lepturus 자원의 관리
장창익 ( Chang-ik Zhang ),김현아 ( Hyun-a Kim ),강희중 ( Hee-joong Kang ) 한국어업기술학회 2016 수산해양기술연구 Vol.52 No.3
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.