• 한국수산과학회지
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• 제42권5호
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• pp.487-493
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• 2009

Available ecological and fishery data of sailfin sandfish, Arctoscopus japonicus, was examined to ascertain its population dynamic parameters in Korean waters. The instantaneous coefficient of total mortality (Z) was estimated to be 1.361/yr, and annual survival rate (S) was 0.256. The estimated instantaneous coefficient of natural mortality (M) was 0.482/yr, and the instantaneous coefficient of fishing mortality (F) for recent years was calculated to be 0.879/yr from Z and M values. Age at first capture was estimated to be 1.958 years. These parameters, in conjunction with catch landings data between 1991 and 2008, were used to estimate annual biomass using a biomass-based cohort analysis. The biomass of A. japonicus was estimated at approximately 7,600 mt in 1991, but since 1994 decreased to below 4,000 mt by 2001. After 2002 they started to increase gradually, and showed the level of more than 5,000 mt in recent years.

• 한국수산과학회지
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• 제42권3호
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• pp.290-296
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• 2009

Acoustic technologies are commonly used to estimate biomass and distribution of fisheries resources in coastal areas and the open ocean. The pelagic species of Engraulis japonica, Scomber japonicus and Sardinops melanosticta spawn migrate to the southern part of the Sea of Korea and capture of these three species comprise 50% of the total abundance in Korean waters. Since 1970, anchovy landings have increased to 0.2 million tons in 1990, 0.27 million tons in 2001, and 0.25 million tons in 2003. Acoustic surveys were conducted on 24-26, May and 20-21, June 2005 around the Tongyeong, Geojae, and Namhae anchovy fishing ground using a dual beam echo sounder (DT-5000, 200 kHz Biosonics). Using this approach, information was obtained on the distribution (depth and position) of zooplankton, and adult and juvenile anchovy. We calculated and compared anchovy biomass using simple summation and geostatistic methods to assess the advantages and constraints of the two techniques.

• 한국수산과학회지
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• 제26권4호
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• pp.363-368
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• 1993

어획량의 단기 예측은 자원관리에 있어 중요한 항목이지만 전통적인 개체군 모델은 수산자원 관리에 있어 실제적으로 요구되는 예측력이 크게 부족하다. 다종 또는 생태계 모델도 요구되는 매개변수의 수가 많아 실제적 적용이 어렵다. 반면에 단변수 시계열 분석법은 시계열 자체에서 변동성에 관한 특성을 추정하여 이를 토대로 장래 변동성을 예측함으로 최소한의 자료를 가지고 비교적 정확한 단기예측이 가능하므로 유용성이 높다. 본 연구에서는 ARIMA 시계열 모델을 $1971{\sim}1988$년 간의 한국근해의 월별 갈치어획량 자료에 적용하였다. 여기서 나온 예측치와 분석에 포함되지 않았던 $1989{\sim}1990$년 간의 어획량과 비교하였다. 분석 결과 예측치와 실제어획량이 잘 일치하였으며(r=0.938) 평균상대오차는 $59.5\%$였다.

• 한국양식학회:학술대회논문집
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• 한국양식학회 2004년도 수산관련학회 공동학술대회 발표요지집
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• pp.513-513
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• 2004

Manila clam, Ruditapes philippinarum, is commercially and ecologically important marine bivalve in Korea and japan. However, clam landings in the two countries have dramatically declined since the 1980-1990's. In the present study, the protozoan parasite, Perkinsus sp., lectin (host's defense-related glycoprotein) and histopathological features were investigated in Manila clams collected from Gomso Bay in Korea and Ariake Bay in japan (one of the largest clam beds in each country) during summer and fall, 2002-2003. DNA sequences of non-transcribe spacer (NTS), internal transcribed space. (ITS) and 5.85 rRNA of Perkinsus sp. were identical to those of P. atlanticus that was reported in Europe and Korea. For diagnosis of Perkinsus, the fluid thioglycollate medium (FTM) and the 2 M NaOH lysis methods were used. Prevalence of the parasite varied from 92.5-98.7% in Gomso Bay and 35.5-37.9% in Ariake Bay. Infection intensity, in terms of the number of Perkinsuscells per gram tissue wet weight, in the clams of Gomso Bay in fall 2002 averaged 1,010,077-470,937 recording approximately100 times higher than that of Ariake Bay, and these were twice higher than those of summer samples in each location. Mean hemagglutination titer of the clams from Gomso Bay was approximately 60-folds higher than that of clams from Ariake Bay in 2002. In histological preparation of the clams from Gomso Bay in 2002, trophozoites of P. atlanticus were in groups and resulted in severe inflammatory response of host clam. Prevalence of the trematod, Cercaria tapes-like in the clams of Gomso Bay and Ariake Bay were 8.8 % and 10.5% respectively. In conclusion, the clams from Gomso Bay showed more severe pathologic symptoms and higher immune response than those of the clams from Ariake Bay.

• Fisheries and Aquatic Sciences
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• 제17권3호
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• pp.361-367
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• 2014

Cuttlefish Sepia esculenta are commercially important in Korea. Assessments of their biomass currently depend on fishery-landings data, which may be biased. Towards fishery-independent acoustic surveys of cuttlefish, target strength (TS) measurements at 70 and 120 kHz were made of 23 live cuttlefish, in early May 2010. The fish were caught by traps in the inshore waters around Geojedo, Korea. The TS were measured using split-beam echosounders (Simrad ES60 and EY500, respectively). The cuttlefish mantle lengths (L) ranged from 15.6 to 23.5 cm (mean L=17.8 cm) and their masses (W) ranged from 335 to 1020 g (mean W=556.1 g). Their mean TS values at 70 and 120 kHz were -33.01 dB (std=1.39 dB) and -31.76 dB (std=2.15 dB), respectively. The mean TS at 70 kHz was 0.17 dB higher than the TS-length relationship resulting from a least-squares fit to the data ($TS=24.67{\log}_{10}L(cm)-64.03$, $r^2$ = 0.52, N=23). The mean TS at 120 kHz was 0.45 dB higher than the fitted TS-length relationship ($TS=40.59{\log}_{10}L(cm)-82.96$, $r^2$ = 0.58, N=23). The differences between the mean TS values and an equation regressed from all of the TS measurements at both frequencies ($TS=24.92{\log}_{10}L(cm)-4.92{\log}_{10}{\lambda}(m)-22.82$, $r^2$ = 0.86, N=46) was 0.22 dB at 70 kHz and 0.31 dB at 120 kHz, respectively.

• 수산해양기술연구
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• 제46권4호
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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.

• 한국수산과학회지
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• 제41권2호
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• pp.94-101
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• 2008

In Korean waters, there are two color types (blue and purple) of the blue crab Portunus trituberculatus. The blue type is common, but the ratio of the purple type has increased in landings. To determine whether there were significant morphometric or genetic differences between the blue and purple types, crabs caught from the West Sea of Korea were examined. Based on covariance analysis, there were significant differences in 1 of 10 morphometric characteristics of males between the two types, in none of the ten characteristics for females. Using amplified fragment length polymorphism (AFLP) DNA fingerprinting, no specific AFLP marker was detected for each type. The heterozygosity and genetic diversity were very low. Analyses of pairwise distance, the Fst index, and genetic similarity revealed similar results, with very low genetic differentiation. Therefore, there is no significant difference between blue and purple types of the crab from the West Sea of Korea, and the two types in the West Sea can be managed as one stock.

• 한국전문물리치료학회지
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• 제12권1호
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• pp.28-35
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• 2005

The purpose of this study was to determine whether gender differences existed in knee valgus kinematics in college students when performing a vertical drop landing. The hypothesis of this study was that females would demonstrate greater knee valgus motion. These differences in knee valgus motion may be indicative of decreased dynamic knee joint control in females. This study compared the initial knee valgus angle and maximum knee valgus angle at the instant of impact on vertical drop landings between healthy men and women. In this study, 60 participants (30 males, 30 females) dropped from a height of 43 cm. A digital camera and two-dimensional video motion analysis software were used to analyze the kinematic data. There was significant difference in the mean knee valgus angle at initial contact landing between the two groups (Mean=$7.88^{\circ}$, SD=$4.24^{\circ}$ in males, Mean=$12.93^{\circ}$, SD=$2.89^{\circ}$ in females). The range of knee valgus angle on landing (Mean=$3.25^{\circ}$, SD=$5.72^{\circ}$ in males, Mean=$11.44^{\circ}$, SD=$6.39^{\circ}$ in females) was differed significantly (p<.05). The maximal angle of knee valgus on landing (Mean=$10.91^{\circ}$, SD=$6.89^{\circ}$ in males, Mean=$24.25^{\circ}$, SD=$6.38^{\circ}$ in females) was also differed significantly (p<.05). The females landed with a larger range of knee valgus motion than the males and this might have increased the likelihood of a knee injury. The absence of dynamic knee joint stability may be responsible for increased rates of knee injury in females. No method for accurate and practical screening and identification of athletes at increased risk of ACL injury is currently available to target those individuals that would benefit from neuromuscular training before sports participation.

• 수산경영론집
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• 제33권2호
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• pp.49-74
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• 2002

This study examines, from an economic perspective, the reasons for introducing a resource taxe system into the Korean off-shore fisheries and the type of charges that can be introduced. Following a review of the charging systems in other advanced fisheries, we consider the types of charging scheme and some implications for the Korean off-shore fishing industry. Charges could be used for recovering part of fisheries management cost from the industry(i.e. administration, enforcement, research, etc). This can be justified on the grounds that the fishing industry is the main beneficiary of management and that it should therefore bear at least part of the cost involved. It is arguable that publicly-funded management is in effect a subsidy to the industry. Using charges to raise revenue in excess of the cost of management would represent the extraction of a public rent from the fishery resource, but the short-run financial consqquences for the industry would be significant. Results from a qualtitative analysis suggest that while any new charge will have a significant financial impact on the industry in the short run, a landings tax would have a lesser impact on fleet structure in the long run. The study also considers the possibility of a capital gains tax on license sales in order to recover some rent from the industry. Despite any short run-financial consequences, making the fishing industry pay for at least some of the cost of management could benefit the industry as a whole if there were more cooperation between industry and managers as a result. It is acknowledged, however, that there could be disputes over the relative management costs of different sectors of the industry. Even though this study makes few specific recommendations about charging the Korean off-shore fishing industry, it does advise that the issue be reviewed on the basis of the entire Korea fisheries. Finally, the study notes that insufficient data are available on the economic performance of the Korean off-shore fishing vessels and it recommands that a comprehensive system for the collection of costs and earnings data be put in place. It also suggests that MOMAF pay much attention to the permit right market and its transactions.

• 한국운동역학회지
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• 제28권2호
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• pp.143-149
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• 2018

Objective: This study aimed to investigate the influence of landing foot orientations on biomechanics of knee joint in order to identify vulnerable positions to non-contact knee injuries during single-legged landing. Method: Seventeen men (age: $20.5{\pm}1.1 years$, height: $175.2{\pm}6.4cm$, weight: $68.8{\pm}5.8kg$) performed single-leg drop landings repeatedly with three different landing foot orientations. They were defined as toe-in (TI) $30^{\circ}$ adduction, neutral (N, neutral), and toe-out (TO) $30^{\circ}$ abduction positions. Results: The downward phase time of TI was significantly shorter than those of N and TO. The flexion and valgus angle of N was greater than those of TI and TO at the moment of foot contact. At the instance of maximum knee flexion, N showed the largest flexion angle, and TO position had the largest varus and external rotation angles. Regarding ground reaction force (GRF) at the moment of foot contact, TO showed the forward GRF, while others showed the backward GRF. TI indicated significantly larger mediolateral GRF than others. As for the maximum knee joint force and joint moment, the main effect of different foot positions was not significant. Conclusion: TI and TO might be vulnerable positions to knee injuries because both conditions might induce combined loadings to knee joint. TI had the highest mediolateral GRF with a shortest foot contact time, and TO had induced a large external rotation angle during downward phase and the peak forward GRF at the moment of foot contact. Conclusively, N is the preferred landing foot orientation to prevent non-contact knee injuries.