• 수산해양기술연구
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• 제41권3호
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• pp.179-187
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• 2005

This study was conducted in order to the experiment of bottom trawl fisheries in the sea mount of central northern pacific($30^{\circ}-40^{\circ}N$, $170^{\circ}-175^{\circ}E$), during the period of July 1 to August 25, 2004 by commercial trawl ship. Fishing experiment was carried out by bottom trawl, with the codend of 110mm mesh size. The number of 101 test fishing was done in the sea mount of central northern pacific during 56 days and the total catches were 198,593kg as 18 fish species, and CPUE/day and catches/day were 8.3 hours towing time and 3,546kg. Catch ratio according to each fishing ground was higher with the order of B, C, and E, and catches for B was 7,171.0kg during the towing time of 13.2 hours. Main target species were Pseudopentaceros richardsoni and Beryx splendens, there was 14.9% of damage ratio for fishing gears on catching the target fishes inhabiting on the rough sea bottom. Catches by water depth was the order of 300m below, 301-350m, 451-500m and 351-400m. It is thought that there was no problem on the mesh size because most of fishes caught from the experimental fishing was 30cm over.

• Fisheries and Aquatic Sciences
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• 제16권2호
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• pp.101-108
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• 2013

An active stimulating device (ASD) consisting of a net panel or ropes fluttering in the turbulence inside the cod end was effective in driving fish near the cod end to reduce juvenile by-catch. The fluttering characteristics of the rope and net panel were examined by video observations and analyzed for fluttering amplitude and period in a water channel and in field experiments with a bottom trawl. The amplitude ratio of the fluttering ropes or nets in the tank test increased with the fluttering index as the diameter of the twine, mesh size, flexibility, and flow velocity changed, whereas the period decreased with the above factors. In bottom trawl experiments, the range of mean depth difference in the fluttering net panel was 12-17% of the length of the fluttering net, and the period of depth difference or three-dimensional (3D) tilt was revealed, with shorter ones ranging from 2 to 6 s. The amplitude as depth difference and period from field measurements were similar to those of nets in tank experiments and also to the period of 3D flow velocity inside the cod end. These results could be used to design an ASD that could be used for to the cod end of actual towed fishing gear to reduce juvenile by-catch.

• 수산해양기술연구
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• 제42권2호
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• pp.69-77
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• 2006

The aim of this study was to develope a fishing technology for fisheries management for improving the survival rate of young fishes escaped from trawl net. Sea experiments were carried out to investigate the survival rate of the fishes in off Geomun island and Korean southern sea. Cover-net fish cage was designed and manufactured to collect fishes escaped from COD(codend) and TED(trawl escapement device). Fish cage was installed in a shallow site where scuba diver can observe the surviving fishes after separating the cage from trawl net. Most of fishes except horse mackerel(Trachurus japonicus) and mackerel(Scomber japonicus) could escaped through TED(bar space 35mm) easier than COD(mesh size 54mm). Especially, escapement rate of redlip croaker(Pseudosciaena polyactis) escaped from TED was the highest as 73.9%. Survival rate of horse mackerel(Trachurus japonicus) escaped from TED was 85.5% at the point of 96 hours over, while the survival rate for COD showed a rapid decrease according to the time elapse as 85.0% at the point of 24 hours, 76.4% for 48 hours, 62.7% for 72 hours and 56.1% for 96 hours. Over 90% of red seabream(Pagrus major) and rock bream(Oplegnathus fasciatus) escaped from TED were survived 96 hours over and the survival rate of those fishes were excellent compared with the other fish species. All korean pomfret(Pampus echinogaster) escaped from both COD and TED were died within 48 hours. Most of redlip croaker(Pseudosciaena polyactis) were also died within 12 hours because of the weak physiological characteristics by water pressure change. Survival rate of fishes like as horse mackerel(Trachurus japonicus) having hard skin was high while it was low for the fishes like as squid(Todarodes pacificus) and hair-tail(Trichiurus lepturus) having soft skin. We could know that there were big differences in the survival rate offish species escaped from trawl net.

• 수산해양기술연구
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• 제52권1호
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• pp.72-77
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• 2016

We examined monthly changes in the rate of fishes by-caught by gape net with wings and their immature ratio in the coast of Yeosu and Jindo Island, Korea. A minus correlation between bycatch rate, the ratio of fishes except for anchovy, Engraulis japonicus, to all fishes collected by gape net with wings, and individuals of the collected anchovy was significantly observed, implying that as the anchovy catch decreased and the bycatch rate increased. Immature ratios by the dominant bycatch species during the study is the following; Leiognathus nuchalis was 72.7~99.0%, Sphyraena pinguis was 84.0%, Sardinella zunasi was 90.0%, others (Leptocephalus, Trichiurus lepturus, Ammodytes personatus, Sphyraena pinguis, Trachurus japonicas, Mugil cephalus and Erisphex pottii) were 100.0%. In order to decrease the high bycatch rates of immature fishes in spring and autumn, our study suggested increasing of codend mesh size and developing suitable bycatch reduction devices in a gape net with wings.

• 수산해양기술연구
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• 제34권3호
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• pp.241-258
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• 1998

우리나라 남해안에 대한 어업생물자원의 평가와 관리 및 유효이용방안 등을 모색하기 위한 기초연구로서, 남해안의 전해역에 설정한 생물학적 샘플링 정점을 대상으로 저층트롤에 의한 시험조업을 실시하고, 이들 정점에서 샘플링된 어획물의 생물학적 조성, 計量魚探調査와 관련한 漁獲選擇性의 영향 底棲漁業資源의 분포실태 등을 분석, 고찰한 결과를 요약하면 다음과 같다. 1. 1996년 10월과 1997년 1월, 3월, 7월~8월, 9월 ~ 10월에 우리나라 남해안에 설정한 64개의 조사정점을 대상으로 저층트롤에 의한 시험조업을 실시한 결과, 魚類 114종, 軟體類 8종, 甲殼類 7종(총 129종)에 총 9,9910.6 kg이 어획되었는 데, 이 중에서 어류의 점유비율은 전갱이 19.8%, 고등어 15.0%, 달강어 6.2%, 전어 6.1%, 병어 5.1%, 아귀 5.1%, 눈볼대 3.6%, 밴댕이 3.5%, 꼼치 3.4%, 꼬치고기 1.4% 등이었고, 甲殼類로서는 깨다시꽃게 0.34%, 보리새우 0.18% 등이었고, 頭足類로서는 창꼴두기 9.0%, 살오징어 5.8%, 참갑오징어 0.28% 등이 어획되었다.2. 1996년 ~ 1997년 사이에 우리나라 남해안에 설정한 트롤조사정점을 대상으로 실시한 저층트롤조업에 의해 어획된 어획량을 트롤예망층의 공간체적으로 나누어 산출한 단위체적당에 대한 어업생물자원의 분포밀도는 해역, 계절, 어획 어종의 조성, 조업시간 등에 따라 큰 차이를 나타내었으나, 그 값은 17.9 x 10$^{-6}$ ~ 1,440.9 x 10$^{-8}$kg/m$^{3}$의 범위였고, 그 평균적인 분포밀도는 153.8 x 10$^{-6}$kg/m$^{3}$이었다. 3.우리나라 남해안에 설정한 64개의 조사정점에서 어구의 파망사고 및 조업장애가 없었던 50개의 트롤정점을 대상으로 끝자루와 커버 네트에 의한 어획비율을 조사한 결과, 커버 네트에 의한 어획비율은 0.7 ~ 91.9%의 범위로서, 그 평균적인 어획비율은 44.4%였다. 이처럼 우리나라 남해안에서는 어족자원의 감소 등에 기인하여 소형어의 어획비율이 매우 높은 실정이기 때문에 향후, TAC제도가 도입되는 경우, 조업어선에서는 상품 가치가 적은 이들 소형어를 바다에 그대로 폐기할 우려가 있으므로 소형어의 어획방지와 서식환경의 보호를 위한 대책의 수립이 절실히 요구된다.