• 한국수산과학회지
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• 제46권4호
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• pp.351-358
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• 2013

A protease inhibitor from fish eggs was fractionated using chromatographic methods. The fractionation efficiency was evaluated in terms of specific inhibitory activity (SIA, U/mg), purity (fold), total inhibitory activity (TIA, U), and recovery (%). The protease inhibitor (PI) from egg extracts of skipjack tuna (ST Katsuwonus pelamis), yellowfin tuna (YT Thunnus albacares) and Alaska pollock (AP Theragra chalcogramma) was fractionated using Sephadex G-50 gel filtration and DEAE-Sepharose CL-6B anion exchange chromatography based on protein size exclusion and net charge, respectively. Fractions exhibiting strong inhibitory activity were contained in the 30-50 kDa fraction on gel filtration and in the range of 0.4-0.7 M NaCl gradient fraction on anion exchange chromatography. The respective TIA and percent recovery of the fraction obtained with gel filtration toward trypsin and $N{\alpha}$-benzoyl-L-arginine-p-nitroanilide (BAPNA) were 2,758.7 U and 29.6% for ST, 1,005.5 U and 25.6% for YT, and 1,267.5 U and 26.0% for AP. Gel filtration chromatography was more effective at fractionating PI than using ion exchange chromatography. These results suggest that fish eggs act as serine protease inhibitors and might be useful for protease inhibition in foodstuffs.

• 한국수산과학회지
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• 제46권4호
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• pp.445-453
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• 2013

Walleye pollock Theragra chalcogramma fisheries in Korean waters have changed dramatically during the last three decades: the highest catches occurred in 1981, followed by continuous decreases through the 1990s, ending with a complete collapse of the population in the 2000s. The major spawning ground of walleye pollock is located in North Korean waters, and some juveniles (called nogari in Korean, <300 mm) migrate to the south for feeding and growth. Since the 1960s, Korean fishermen have often caught juveniles, and the weight (metric tons) of juvenile catch was recorded from 1975-1997. However, because the walleye pollock were not aged, the population age structure was not delineated. We developed a model to estimate the number of walleye pollock of each size class based on catch statistics of adults and juveniles, the catch proportion of each size class, and length and weight information on specimens collected by Danish-seine and drift-gill-net fisheries. The model results demonstrated that the recruitment size of walleye pollock was consistently within the 200-250mm size class, and the highest number of this size class occurred in 1981, although values greatly fluctuated interannually. The number of juvenile pollock was 10.4 times higher than that of adult pollock during 1975-1997. The total yield of juvenile pollock was 0.95 million tons, which was equivalent to about 68.2% of total pollock production. The number of juvenile pollock caught during the same period, however, was 16 billion, comprising about 91.2% of the total number caught. Such high fishing pressure on juvenile pollock is considered one of the main factors causing the collapse of the pollock population.

• 한국수산과학회지
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• 제50권3호
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• pp.311-318
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• 2017

Four species of sea turtles (Chelonia mydas, Caretta caretta, Dermochelys coriacea, and Eretmochelys imbricata) have been recorded in Korean waters. However, nationwide surveys on the distribution and occurrence of each species have rarelybeen conducted in Korean waters. In this study, we comparatively analyzed the trends in occurrence of sea turtles and their morphological characteristics based on 148 reliable observations and stuffed specimen data and suggested Korean names for each species. Chelonia mydas (57 cases, 58.8%) and C. caretta (52 cases, 31.5%) were dominant species, and occupied > 90% of all observations. Most of observations of sea turtles in Korean waters were obtained through stranding (61 cases) and incidental catches (62 cases). A coastal set net was the main fishing gear for incidental catches (82%). Sea turtles were found mainly around Jeju-do and the Korea Strait from June to November. Most C. caretta found were adults, whereas most C. mydas were juveniles. Additionally, we provide detailed morphological characteristics of C. mydas (n=8) and C. caretta (n=4) using stuffed specimens. Finally, based on a literature search, we suggest appropriate Korean names, such as "Pureunbada-geobuk" for C. mydas, "Bulgeunbadageobuk" for C. caretta, "Jangsu-geobuk" for D. coriacea, and "Maeburibada-geobuk" for E. imbricate.

• 한국수산과학회지
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• 제41권5호
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• pp.353-362
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• 2008

The fish species composition and variation in the Youngil Bay, East Sea of Korea, were investigated every month from January, 2001, to December, 2002, using gill nets for sample collection. A total of 63 fish species belonging to 31 families under 10 orders, and a total of 40 species belonging to 26 families under 8 orders, were identified in 2001 and 2002, respectively. Of these, the families Pleuronectidae (9 species), Scorpaenidae (8 species) and Cottidae (5 species) were dominant in 2001, whereas Pleuronectidae (4 species), Cottidae (3 species) and Hexagrammidae (3 species) were dominant in 2002. The number of species recovered was the highest in August, 2001 (34 species) and January and September, 2002 (14 species each), and lowest in May, 2001 (6 species) and December, 2002 (5 species). The principal component analysis for each year showed that fish species composition differed over time even within the same sample area. In addition, the relationship between PC scores and temperature showed a positive relationship in 2001, but a negative relationship in 2002.

• 한국수산과학회지
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• 제7권4호
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• pp.187-194
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• 1974

순환여과장치에 의한 어류사육시 어병방제의 목적으로 약품을 사용하는 일이 많다. 이 때, 이들 약품이 여과 조중의 산화분해세균을 사멸시켜 여과기능을 마비시킬 우려가 있어 여과를 중단시키고 약품을 처리하므로, 큰 불편을 주고 있다. 이번에 뱀장어 양식시에 흔히 사용되는 formalin 33ppm+malachite green 0.15ppm 혼합처리, dipterex 0.25ppm 처리 및 furanace 0.1ppm 처리가 여과기능에 미치는 영향을 주로 DO 소비량 및 ammonia 처리능력에서 시험검토하여 본 결과 별다를 영향을 미치지 않는다는 것을 알았다. 따라서 이상의 약물을 사용할 경우에 여과를 중단시키지 않아도 상관이 없다고 인정된다.

• 한국수산과학회지
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• 제24권1호
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• pp.31-38
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• 1991

여수해만 광양만 입구의 조류 및 부유 퇴적물 함량 분석을 통하여 광양만 내의 부유 퇴적물 수지 균형을 조사하였다. 만 입구의 부유 퇴적물 함량은 바닥이 평균 약 17.80mg/l로 표층의 평균 약 4.75mg/l에 비해 상당히 높으며, 조류도 표층 부근에서는 썰물이 강하나 저층에서는 오히려 밀물이 강하여 유속의 비대칭 현상을 보이고 있다. 이러한 저층의 높은 부유 퇴적물 함량과 밀물우세 조류로 인하여 이 지역의 부유 퇴적물 이동은 저층을 통한 이동이 큰 중요성을 갖으며, 따라서 광양만의 내부 특히 서쪽 부분은 전체적으로 세립 퇴적물의 순수 퇴적이 이루어지고 있다. 이러한 조류에 의한 세립 퇴적물의 순수 유입량은 약 $5.66\times10^8g/day$로 계산되며, 이 순수 유입량이 만의 서부에 퇴적된다면 그 퇴적율은 약 1.15m/1,000years 정도가 될 것이다.

• 한국수산과학회지
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• 제49권3호
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• pp.367-375
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• 2016

Marbled flounder Pseudopleuronectes yokohamae is a commercially important flatfish in the coastal waters of the East Sea off Pohang, Korea. Maturity and spawning dynamics of P. yokohamae were investigated based on samples collected by gill net and long line in the coastal waters off Pohang from January 2013 to December 2014. We analyzed monthly changes in maturity stage, gonadosomatic index (GSI), egg diameter, fecundity, and total length at 50% group maturity. We found that the spawning period was December to February, wherein fecundity ranged from 55,760 eggs at 20.40 cm total length (TL) to 1,559,007 eggs at 46.6 cm TL. The relationship between TL and fecundity (F) was F = 0.0017 TL^3.5604 (R² = 0.6984), and F increased with increasing TL. We estimated the TL at 50% group maturity as 27.4 cm for female and 23.5 cm for male P. yokohamae, respectively. The results from this research will aid in the development of policies on season and minimum catch length for sustainable production of P. yokohamae. We propose that it is necessary to conduct long-term ecological monitoring for this species because biological properties such as spawning ecology and growth performance are being affected by climate change.

• Fisheries and Aquatic Sciences
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• 제10권2호
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• pp.74-85
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• 2007

Pacific anchovy (Engraulis japonicus) eggs were collected during the spawning season (2000-2003) using a revised ring net in the coastal waters adjacent to the Geum River Estuary in the West Sea of Korea (Yellow Sea). Anchovy eggs were present from May to September, showing a peak in spawning from June to July when the water temperature and salinity were $17-27^{\circ}C$ and above 30.00 psu, respectively. During the main spawning season, no clear diel cycle (regarding the 24-h sampling period of dusk, night, dawn, and daytime) was detected in the vertical distribution of anchovy eggs near Eocheong Island (50-60m depth). Judging from the developmental stages of the collected eggs, it appeared that anchovies spawned mostly at night and that the eggs hatched at dusk and during the night. The density of anchovy eggs was high in the southwest-northeast direction in June, and spawners appeared to move offshore in July. Mean egg density was higher in June 2002 than in June 2003 when water temperatures and salinities were lower. This study on the spatiotemporal distribution of eggs will contribute to developing management plans for the Pacific anchovy in Korea.

• 한국수산과학회지
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• 제45권4호
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• pp.379-386
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• 2012

The feeding habits of the Pacific cod Gadus macrocephalus were studied by analyzing the stomach contents of 423 specimens caught by coastal gill net in the coastal waters off Jumunjin, Gangwondo, Korea, from January to December, 2011. The size of Pacific cod ranged from 31.0 to 86.5cm in total length (TL). The proportion of empty stomachs was 25.1%. The main prey items were Macrura, Pisces, and Cephalopoda. In order of abundance, the most dominant species of Macrura, were Pandalus eous, Argis lar, and Neocrangon communis, and the most dominant species of Pisces, were Clupea pallasii, Actoscopus japonicus, and Glyptocephalus stelleri. Berryteuthis magister was the most dominant species of Cephalopoda. In terms of variation in feeding habits by growth, Macrura was the most important prey group for G. macrocephalus ranging in TL from 30- to 55 cm, but Pisces was the most important prey group for cod over 56 cm TL. Catch of G. macrocephalus was significantly positively correlated to catch of the three major Pisces prey species Clupea pallasii, Actoscopus japonicus and Glyptocephalus stelleri.

• 한국수산과학회지
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• 제47권2호
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• pp.160-167
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• 2014

The feeding habits of Tridentiger bifasciatus were studied using 733 individuals collected in the tidal creek at Sangnae-ri, Suncheon, Korea, using a push net, monthly, from April 2011 to March 2012. The standard length (SL) of the specimens ranged from 1.5 to 8.2 cm. The stomach content analysis indicated that T. bifasciatus consumed mainly amphipods, such as Corophium sp., while copepods, polychaetes, and shrimps were other important prey species. In addition T. bifasciatus ate small quantities of crab larvae, fish, gastropod larvae, and insects. T. bifasciatus is a generalist that feeds on various zoobenthos, including fish. T. bifasciatus underwent an ontogenetic dietary shift. Smaller individuals (1-2 cm SL) fed mainly on amphipods. The proportion of amphipods decreased as body size increased, whereas the consumption of polychaetes increased gradually. The seasonal variation in the diet composition of T. bifasciatus was significant. Insects were common prey during summer, while the amounts of other prey, including polychaetes, were similar during spring, autumn, and winter.