Lots of fishery stocks are overexploited and the overcapacity exists in Korean fishing fleets. One of the reasons is technological development, which increases the efficiency of the vessels continuously. The analysis was conducted to identify the change of fishing power index to develop the vessel and gear technology that may have improved the fishing efficiency of the offshore large powered purse seine fishery from 1960s to 2010s. Gross tonnage and horse power per fishing vessel was increased annually. Fishing gear material was changed to the knotless webbing to settle faster. Fishing equipments was modernized and supply rate was also increased. Therefore the relative fishing power index in the offshore large powered purse seine fishery increased from 0.4 in 1970 to 1.0 in 1980, to 1.5 in 2000 and to 1.6 in 2010, but the rate of increase slowed down gradually. The results are expected to contribute to reasonable fishery stock management.

Annual and monthly pollock catches, CPUE and fishing grounds in the high seas of Bering Sea between 1984 and 1992 were analyzed for centroid distribution and bivariate ellipses of trawlers of South Korea, Japan, Poland and China. The catch amount differed by country as 56.1%, 21.7%, 20.4% and 1.8% were caught by Japan, Korea, Poland and China respectively. Japan recorded the highest mean CPUE at 5.7 ton/hour while it was 4.3 ton/hour for Poland, 3.9 ton/hour for Korea and 2.4 ton/hour for China. Cumulative catch varied by month, with the minimum of 137,000 ton in March and the maximum of 848,000 ton in December. Monthly mean of CPUE was the lowest in February (2.0 ton/hour) and the highest in November (6.3 ton/hour). The centroid distribution of monthly fishing ground was located at a southern spot (56° 05'N, 178° 55'E) in January, and it moved anti-clockwise toward 56° 37'N, 178° 24'E in December. Fishing grounds were scattered more by the east-west direction than by the south-north direction. The fishing grounds were similar for Korean, Japanese and Polish trawlers, but Chinese trawlers that fished only from July to December showed distinctively different fishing grounds from the others.

This study aims to estimate the species, size and shape of fish using a non-contact 3 dimensional pattern laser so that this preliminary test was carried out to understand the structural feature and length of goldfish according to water turbidity and depth in the aquacultural tank. 3-D pattern laser could clearly detect its morphological shape except the caudal fin due to soft tissue. Since the sensing strength of line laser light according to depth has sufficient power, it is possible to measure its depth and structural feature in the detected range. The result showed that the measured error of individual’s fork length was less than ±1% in the water using 3-D pattern laser, when compared with the measured value in the air.

To obtain geographical range and growth–kinetics parameters of mottled sake (Beringraja pulchra) populations in the Yellow Sea, three mark–recapture experiments were carried out. Overall, 991 tagged individuals were released, and 4.1% of them were recaptured with the mean release period of 339 d (range, 8–1,420 d) and the mean growth rate of 1.4 cm mon–1 (female, 1.5 cm mon–1; male 1.3 cm mon–1). In the first experiment, 667 individuals were released at Heuksan Island from April to June, 2007–2009, and 30 individuals were recaptured mainly at the north and the north–east coasts of the island, indicating absence of migration to the south of the island. In the second experiment, 323 individuals were released at several fishing grounds scattered in the Yellow Sea in 2010–2013, and 11 individuals were recaptured at points deviated to all directions from the releasing points. As the last, one individual was released with pop–up satellite archival tag at a costal point (34°37.2’N, 124°59.3’E) off Hong Island on May 21, 2010. The tagged individual migrated to a north–east location (35°50.4’N, 126°03.6’E) of Eocheong Island by Aug. 25, 2010. The data archived for the three months in the tag indicated that the migration path had depths of 48–80 m and temperature of 12.6–14.4°C. The results indicated that mottled sake populations had a localized habitat ranges at the north of Heuksan Island and the west of Hong Island while growing at the rate of 1.4 cm mon–1.

Visual census and hydro-acoustic survey was carried out at Ulju small scale marine ranching area (MRA) to estimate demersal fish aggregations on September and November 2013. In this hydro-acoustic survey, the authors combined an image sonar with a scientific echo sounder to monitor an underwater situation and compare two acoustic data. Consequently, visual census survey was useful to estimate fish species composition for hydro-acoustic survey, because it is easy to identify aggregated fish species and overcome limits on a fishing depth and ability of an conventional fishing gear like a bottom gill-net or a fish trap at marine ranching area. Mean fish density was estimated as 0.757 g/m2 on September and 0.219 g/m2 on November and Fish abundance was finally calculated as 1.51ton (coefficient of variation, CV=13.1%) on September and 0.44ton (CV=47.7%) on November, respectively. Hydro-acoustic survey combined with the image sonar was useful to monitor fish aggregations and estimate fish stocks around artificial reefs at shallow coastal MRA. We were able to easily identify the underwater structures like an artificial reef and a fishing rope as well as fish aggregations from image sonar data. Therefore, the method was effective to separate unwanted echo signals in acoustic data of scientific echo sounder.

본 연구에서는 충남 연안에서 연안조망의 어획 특성을 파악하기 위하여, 2008년 3월부터 2009년 2월까지 매월 2∼4회 연안조망을 사용하여 어획조사를 실시하였다. 조사 해역은 동경 125도 50분∼126도 05분, 북위 36도 15분∼36도 25분의 해역이었고, 총 19목 63과 96종이 채집되었다. 그 중 어류가 54종, 갑각류가 27종, 복족류 및 이매패류가 9종, 그리고 두족류가 6종이었다. 생체량은 어류가 51.4 %로 가장 많았으며, 갑각류는 34.2 %를 차지하였다. 꽃새우는 7월~11월에 출현량이 많았고, 12월부터 5월까지는 적은 양이 출현하였다. 연안조망의 목표종인 꽃새우는 전체 어획물의 2.1 %로 낮은 채집 비율로 출현하였으며, 꽃새우 이외 어종의 부수적 어획물의 양적 비율이 높아, 꽃새우 어획이 부수어획으로 어획되는 종들의 수산자원에 미치는 영향이 클 것으로 판단된다.

Species composition and seasonal variation of aquatic organism in the marine ranchig ground of Taean, Korea were investigated using shrimp beam trawl from January to December 2010. A total of 99 species, 5,355,816ind./km2 and 84,697kg/km2 of aquatic organism were collected. Among them, fish include 9 orders 33 families 54 species, crustaceans include 2 orders 15 families 30 species, cephalopods consist of 3 orders 4 families 5 species, gastropods include 2 orders 3 families 4 species, echinoidea sp. include 1 order 2 families 2 species, bivalves were composed of 2 orders 2 families 2 species, and holothuroids include 1 family 1 order. According to the dominants by month, Palaemon gravieri was dominant in January, Cynoglossus joyneri was dominant in February, March, and June, and Hexagrammos otakii was dominant, in July. And Oratosquilla oratoria was dominant echinoidea sp. was dominant in April, May, and August and in September, October, November, and December. Cluster analysis based on species composition of the 38 most common species showed that the species were separated into 5 different groups. Group A was composed of species which were abundant in spring and summer, group B was composed of year-round residents, and group C was composed of species which were abundant in autumn.

Species composition and seasonal variation of aquatic organism in the coastal waters off Taean, Korea were investigated using catches by commercial fishing of the pot and gill net from April 2010 to January 2011. A total of 58 species, 10,602 individuals and 547,569g of aquatic organism were collected during the study. Aquatic organism were composed of 22 species of Pisces, 20 species of Crustacea, 8 species of Gastropoda, 3 species of Echinodea, 2 species of Cephalopoda and Bivalvia, and 1 species of Holothuroidea. 41 species in 9 orders and 22 families were collected by the pot, and 28 species in 15 orders and 22 families were collected by the gill net. Volutharpa ampullacea was the most dominant in the pot, while Okamejei kenojei was the most dominant in the gill net. These two species accounted for 73.9% in the number of individuals, and 64.4% in biomass. The number of species was high in spring in the pot, and autumn in the gill net. The number of individuals and biomass were highest in winter and summer respectively in the pot, and summer in the gill net. The number of species of the consignment quantity caught by commercial fishery of the pot and gill net in Mohang was 12 and 14 respectively. Cluster analysis based on species composition of the 18 most common species showed that the species were separated into 3 different group. Group A was composed of species which were abundant in spring, group B was composed of species which were abundant in summer and autumn, and group C was composed of year-round residents.

Catches, CPUE, fishing season, disc width composition and fishing ground were studied to rebuild skate ray, Raja pulchra resource by the offshore longline fishery in Heuksan-do, Korea. Annual catches and CPUE of skate ray were increased from 2003 to 2010 (CPUE: from 2007 to 2010) continuously. The main fishing season of the skate ray was from December to next May. Disc width at 50% maturity for Raja pulchra by sex were estimated to be 65.83cm, 57.01cm by female and male respectively. The range of disc width was 22.3-112.0cm and the average disc width was 66.9cm, 60.0cm by female and male of Raja pulchra respectively during 2007-2010. Annual average of disc width of female skate ray was decreased from 2007 to 2010. The fishing grounds were formed from the coastal water off Hong-do to the coastal water off Gyeogyeolbiyeol-do, Korea. The center of fishing ground in October was formed in the northwestern coastal water off Gyeogyeolbiyeol-do and separated from that of the other months.

The purpose of this paper is to provide useful information for fishermen in the manner of investigation a sinking speed of current type tuna longline gear at the North Pacific Ocean as a new developed tuna longline fishing ground. The sinking depth of mainline in connection with different basket was investigated. The experiments were also performed with different materials such as Supermansen (i.e., PE) and Hitech (i.e., PA) for the mainline to investigate the sinking depth of mainline and hooks. Furthermore, the relation between the sinking depth of hooks and catches are investigated also. The sinking depth of mainline at the first and the last shooting basket shows deeper than that of middle part of a basket due to reduced shortening ratio. The sinking depth of mainline and hook with Hitech material shows more shallow than that of Supermanse material, even the Hitech case was designed to sink deeper than that of Supermanse case. The highest catches arise at the middle part basket as the hook number 7 with around 248m sinking depth. From the results, longline with Hitech material is needed to increase the sinking force for reaching the relevant sinking depth. Moreover, the current strength at the North Pacific Ocean will be considered for further commercial fishing.

To investigate the catches of squid jigging fishery, a series of fishing experiments was conducted in the high seas of the Northwest Pacific(40˚-43˚N, 150˚-155˚E) during the period of 1 August to 22 October 2005 by commercial fishing vessel. The number of 142 test fishing was carried out in the Northwest Pacific during 83days. The total catch were 47,524kg as 4 squid species and CPUE was 8.9kg/line·day. CPUE showed high values in the frontal zone during the survey. Main squid species caught from the experimental fishing were the neon flying squid, Ommastrephes bartrami(96.8%) and the boreopacific gonate squid, Gonatopsis borealis(3.2%). Dorsal mantle length of the neon flying squid were increased by the time and increasing of the hook size. Loss rate of the neon flying squid in the water showed the highest values in 28.2% compare to the others. And the loss rate of the front roller and in the air were 1.1% and 1.0%, respectively.

The transmittance properties of fishing lamp of the squid jigging vessel was investigated during nighttime operations in the Northwest Pacific on 21 and 29 September 2005. The metal halide lamps of white color(2.0kW×168) in the air and metal halide lamp of white color(10.0kW×1) in the underwater were used as a fishing lamp for gathering squids. The relative irradiance of metal halide lamp in the air showed peak in 850nm of wave length. The relationship between underwater illuminance(Y) and water depth(X) of metal halide lamp light in the observation areas is represented, Y=84.137e-0.1105X, R2=0.9974. The distribution of underwater illuminance of measure points St. 1-5 showed low value of 0.11x in 80m depth.

To determine the relative efficiency and mesh selectivity of gill net for the Pacific saury, Cololabis saira, a series of fishing experiments was carried out in the Northwest Pacific Ocean from August 13 to October 13 in 2002, using gill nets of different mesh size(30, 33, 35, 37, 39 and 42mm) constructed from two kinds of twine material(monofilament, twisted multifilament nylon web). The relative efficiency of two material gears was expressed as the ratio obtained by dividing monofilament catch by multifilament catch in number. The master selection curve of each material gear was estimated by applying the extended Kitahara's method. The catch of experimental gears is mostly Pacific saury(98.6%), Cololabis saira. The kinds of bycatch are common squid(0.7%), Pacific mackerel(0.6%), etc. Catch comparisons in the two gears showed that monofilament nylon nets are 1.7 times more efficient. The optimum values in monofilament and multifilament gill net for Pacific saury are 8.28 and 8.23, respectively.

In order to investigate influence of moon light to the fishing of Pacific saury stick-held dip net fishery in the northwestern Pacific Ocean, casting number, catch and CPUE were analyzed between the full moon and the new moon phases. Based on analyses of data taken from 8 vessels during 1992~2002, casting numbers at the full moon phase and the new moon phase were 110.3 and 121.0 times, respectively, and the first was lower than the latter by 8.8%. Catches of the full moon phase were higher than the new moon phase by 12.5% and CPUE expressed in ton/day and ton/haul were also higher by 31.5%, 26.1% respectively.

북태평양에서 조업하는 우리나라 꽁치봉수망어업의 어획량과 시기별 어장 중심 및 어획적수온 등을 검토하고 조업시 소나 사용에 따른 어획 효과를 분석하였다. 조업 시기는 5~12월이었고 어획 비율과 CPUE 측면에서 볼 때, 한·일 어업협정 발효 이전인 1985~1998년의 주어기는 9~11월로, 발효 이후인 1999~2002년의 주어기는 8~10월로 추정되었다. 한·일 어업협정 이후 어장 중심은 일본 동쪽 연안 측으로부터 러시아 남쿠릴열도 동쪽인 43˚N 와 151˚E 부근으로 이동하였다. 꽁치의 어획적수온은 5월에는 12.5~14.4℃, 6월은 12.0~14.2℃, 7월은 11.4~13.9℃, 8월은 11.4~15.9℃, 9월은 12.9~16.9℃, 10월은 12.7~l7.3℃, 11월은 13.1~17.6℃ 그리고 12월에는 15.0~19.1℃이었다. 어획종은 총 13종으로서 목표종인 꽁치가 99.9% 어획되어 대부분을 차지하였다. 조업일수는 소나를 보유한 조업선과 소나를 보유 하지 않은 조업선 사이에 뚜렷한 차이를 나타내지 않았으나 투망횟수, 어획량 및 CPUE는 소나를 보유한 조업선이 각각 13%, 26%, 12% 높게 나타났다.

상호배타적인 공학적 투자사업들의 채택 또는 기각 결정을 할 때 현금흐름할인법(DCF법)을 사용할 수 있다. 비교대상이 되는 투자대안들의 초기투자금액이나 사업수명이 다른 경우에는 증분투자분석을 하는 것이 편리하다고 알려져 있다. 두 투자대안의 현금흐름 차이를 서로 비교하는 증분투자분석법은 투자안의 채택 또는 기각 결정에서 DCF법과 동일한 결정을 얻을 수 있다. 그러나 그 계산량이 많고 기각되는 투자대안에 대한 정보를 무시하는 단점이 있다. 이 논문에서는 투자대안별로 순현재가치나 순연간등가를 구하여 투자대안들의 순위를 매김으로써 투자대안들의 수익성 순위 외에도 수익성의 크기도 비교하여 의사결정에 활용할 수 있도록 한다.

꽁치봉수망 조업시 어선의 집어등에 의한 수중환경의 변화를 밝혀 광 환경이 꽁치의 어획에 미치는 영향을 분석하기 위한 기초 단계로 수중 조도를 측정하여 꽁치가 분포하는 어획 수층의 광 환경을 분석한 결과를 요약하면 다음과 같다. 공기중에서 홍색 백열등과 할로겐등의 방사조도는 둘 다 1,052nm의 파장에서 최대치를 보인 후 감소하는 경향을 나타내었고, 600nm이하의 파장에서는 할로겐등이 홍색 백열등에 비해 방사조도가 약간 높게 나타났다. 공기중 조도는 좌현 선미에서 가장 높았고 선수에서 가장 낮게 나타났다. 조사해역에서의 집어등 불빛의 수중투과 특성은 50m 수층에서 각각 0.31x, 0.61x 이하로 나타났으며 일반적인 꽁치어장의 특성을 가진 어장에서 볼 때 , 꽁치가 집어되는 수층의 조도는 0.51x 이상인 것으로 보인다.