Hyun-Su Jo

Transmittance properties of fishing lamp in distant-water squid jigging vessel

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() in the air and metal halide lamp of white color() 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,

Species composition and seasonal variation of the aquatic organism caught by commercial fishing of the pot and gill net in the coastal waters off Taean, Korea

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Fishing characters of skate ray, Raja pulchra by the offshore longline fishery in Heuksan-do, Korea

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.

Species composition and community structure caught by shrimp beam trawl in the marine ranching ground of Taean, Korea

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.

Relative efficiency and mesh selectivity of monofilament and twisted multifilament nylon gill net for Pacific saury, Cololabis saira, in the Northwest Pacific Ocean

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, and 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.

Spawning Characteristics and Artificial Hatching of Female Mottled Skate, Beringraja pulchra in the West Coast of Korea

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.

Transmittance Properties of Fishing Lamp in Stick-held Dip Net Fishing Vessel for Pacific Saury

The gonadsomatic index (GSI) of mottled skate was the highest in April, GSI and HSI showed a reverse phase for its reproductive cycle. The fish had one pair of egg capsules, having 1 to 7 fertilized eggs, and spawned all the year round. When surveying the reproductive characteristics of females over 63 ㎝ in disc width, we found the spawning peak was between April to June, and the appearance ratio of egg capsules was the highest in May (32.1%). The eggs were hatched at 8°C, 13°C, 18°C, water temperature (12.8 to 24.2°C), and the best hatching temperature was 18°C. The number of fish hatched was 4 to 5 fish/egg capsules, and the hatching rate was 100%. The sex ratios of hatching larvae were 45.5% female and 54.5% male. Therefore this study will provide fundamental data and information for artificial reproduction of the mottled skate.

Distribution of Demersal Fish Based on a Combined Acoustic and Trawl Survey during Day and Night in Costal of the South Sea, Korea

The transmittance properties of fishing lamp in stick-held dip net fishing vessel for Pacific saury was investigated during nighttime operations in the North Pacific on May 19 and 24, 2003. The incandescent lamps of red color (750W100) and halogen lamps (750W521) were used as a fishing lamp for gathering Pacific saury. The relative irradiance of red incandescent lamp and halogen lamp in the air showed peak in 1,052nm of wave length. However, the irradiance of halogen lamp below 600nm of wave length was higher than that of incandescent lamp. The relationship between underwater illuminance (Y) and water depth (X) of sunlight in the observation areas A (37 11`N, 178 46`W) and B (31 11`N, 178 01`E) is represented as follows;

Comparison of Species Composition and Seasonal Variation of Demersal Organisms Caught by Otter Trawl in the Coastal Waters off the Taean Peninsula, in the West Sea of Korea

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Sinking depth of tuna longlines related to mainline materials in the North Pacific Ocean

남해 연안은 연근해에 서식하거나 내유하는 다양한 어종의 서 식장 및 산란장으로 어족 자원의 관리를 위해 주요 어종에 대 한 생태와 회유 및 분포에 대한 다양한 과학적인 연구가 지속 적으로 이루어 지고 있다. 이러한 수산 자원의 시·공간 분포 및 자원량 파악을 위한 조사는 1960년 이후 주로 어구 어업을 이 용한 연구가 진행되고 있다(Choi, 1972; Huh, 1986; Cha et al., 2004). 어구를 이용한 자원 조사는 어류 자치어 및 성어에 대 해서 중층 및 저층 트롤과 같은 대형 어구로 어획 후 종조성 및 체장 특성을 파악하는 것이 일반적이다(Cha and Park, 1997; Huh and Kwak, 1998). 그 중 저서 어종의 특성에 관련 연구는 일반적으로 저층 트롤(bottom trawl) 기법이 널리 활용되고 있 다(Lee and Kim, 1992; Lee et al., 1993). 저층 트롤은 타 어구 에 비해서 어획성능이 뛰어나고 조업의 주 대상이 되는 어종은 물론 비대상 어종과 소형 어종들에 대해서 선택성 없이 어획되 는 장점 때문에 저층어종의 분포 및 자원량을 조사하는데 적합 한 기법이다. 어구를 이용한 조사는 정성적인 측면에서는 많은 장점이 있 지만, 어획 면적 및 어획 수층의 제한성과 작업시간에 대한 비 용 증가요인이 높기 때문에 효율성 측면에서 단점이 존재한다. 정성 분석에 치우친 기존 어획 방법의 문제점을 극복하기 위 한 방법 중 하나로 1980년 초부터 제시되어 최근에 생물의 분 포 및 자원량 조사에 활발히 적용하고 있는 생물 음향을 이용 하는 방법이 대두되고 있다(Abad et al., 1998; Simmonds and MacLennan, 2005). 생물 음향 기법의 특징은 연구자의 주관을 배제시키고 사전에 설정된 음향 조사 정선으로부터 연속적이며 전 수층에 대한 객관적인 자료를 얻을 수 있는 장점이 있고, 우 점 어종의 음향 반사강도(acoustic target strength, TS) 특성이 제공 된다면 조사 해역의 어류 밀도 및 현존량까지 산정이 가능 하다. 따라서 종 조성이나 다양도 조사 연구는 어구를 이용한 방 법이 효과적이며, 음향 조사기법은 수산자원의 시·공간 분포 특 성 파악 및 자원량 산정에 응용이 가능하므로 이들 두 가지 방 법들의 효과적인 결합을 통한 조사가 진행되고 있는 추세이다. 음향과 저층 트롤 기법을 이용한 남해 저층 어군의 주·야 밀도분포 조사 이형빈·서영일*·오택윤·최정화·조현수·최광호