Hybrid surveys using hydroacoustic and fish sampling gears such as trammel net, trap were conducted to investigate total biomass, distribution and dominant fish species of the demersal fishes in the marine ranching area (MRA) of Jeju. Four surveys were carried out in June, August, October and November using 38kHz quantitative echo sounder. Catch data using trammel net and trap were used to calculate biomass and to examine dominant fish species. Fish schools were mainly detected in the waters of 20 meters below and around Chagwido waters. By the result of fishing experiments, fish species living in MRA of Jeju were about 40 species, dominant fish species of a detectable fish such as Family Sparidae and Family Monacanthidae etc. were identified 59.4~68.8% of total biomass. Based on the hydroacoustic data, fish length-weight function and target strength information, mean density of the demersal fish estimated were as follows; 0.88g/m2 on June, 1.12g/m2 on August, 1.35g/m2 on October and 1.18g/m2 on November. An estimated average biomass in MRA of Jeju was founded 20.5 tons in 2007, 20.6 tons in 2008, 23.0 tons in 2009, 25.9 tons in 2010. The results showed that biomass of MRA is getting increased slowly. Therefore the hybrid survey method using hydroacoustic and fish sampling gears is assured an effective biomass survey in the waters of mixed species.

The purpose of this study was to identify the state of demersal fish resource catch by small trawlers, which live in the southern waters off Goheung. We investigated the results of catch of sample fishing vessels, and performed fishing experiments using the actual fishing operation vessels from early November in 2002 till end of October in 2003. The daily amount of catch per vessel of the 35 small trawlers selected as sample vessels was the highest in summer seasons(June and July) as 70kg and the lowest in winter seasons(January and February) as 45kg and Octopus minor occupied as 17 to 30kg nearly 30% of the total catch. Additionally the catch of Octopus minor per vessel, per dragging hour ranges 3 to 6kg, which is the highest in March and June and the low in January to February, April to May and September. In the fishing experiments using small trawler, during the study period, a total of 75 fish species were collected. The number of individuals by species consisted 58.2% in Shrimps, 17.8% in Fish, 2.3% in Cephalopod. Of these, Parapenaeopsis tenella was the highest in 29.2%, Squilla oratoria and Crangon hakodatel was 14.6% respectively and Octopus minor was 0.2% of the total number of individuals. As far as the appearance number of individuals by month was concerned, February was the highest and then May, April and June followed in order, and October showed the lowest. Additionally the monthly catch per dragging was the lowest in December to January as 20kg and the highest in July as 160kg. Specially, Octopus minor was caught throughout the year regardless of season and the catch was the highest at the period from March to June. When looking into the body mean length of dominant fishes caught, we could observe the followings; Trachurus japonicus 8.9cm, Cynoglossus robustus 10.8cm, Muraenesox cinereus 15.3cm, Setipinna taty 10.3cm, Amblchaeturichfhys hexanema 9.3 cm and Collichthys niveatus 8.9cm, most of which were in their immaturity when they were caught.

한국 거문도 연안에서 시설된 세라믹 어초의 시설 효과를 구명하기 위하여 2001년부터 2003년까지 어초 시설구, 자연초구 및 비시설구 어장에서 삼중자망에 의한 어획량과 어획종을 조사하였다. 어초 시설구에서의 폭당 어획량은 1,621.9g으로 자연초구와 비시설구에 비해 각각 67.9%, 333.3%많았는데, 이를 Tukey test로 검정한 결과, 어초 시설구와 자연초구에서는 유의차가 없었으며, 어초 시설구와 비시설구와는 유의차가 인정되었다.(p<0.05). 어초 시설구에서 어획된 월 평균 종수는 7.2종으로 자연초구에 비해 7.1% 적었던 반면 비시설구보다 97% 많았는데, ANOVA 분석결과 유의차가 없었다. 어초 시설구의 어획률은 11월에 최대, 5월에 최소치를 보였으며, 이러한 현상은 자연초구, 비시설구에서도 나타났다. 어초 시설구의 우점종은 참동, 말쥐치, 쥐치, 도다리, 거북복 등 암초성이 강한 저서어종이었고, 자연구와 비시설구에서는 저서성 및 회유성 어종이 혼재하였다.

선망어법의 어회과정에 있어서 어군행동에 관한 기초적인 연구를 목적으로 제주 근해에서 사용하고 있는 고등어 선망어구인 파워불록용 선망(Powetblock seine)과 앞으로 예상되는 단선조작에서의고등어 선망어구인 트리플레스용 선망(Triplex seine)의 두 가지 모형망을 1/180로 제작 하고 선망에 의해 포위된 어군의 망내행동과 양쪽 선단의 개구부를 통하여 도피하는 어군의 행동을 관찰 분석함과 동시에 망단의 개구부의 면적 및 장력변화 등을 해석하였으며, 그 결과는 다음과 같다. 1. 죔줄죄기 소요시간 20분일 때, 개구부로 도피하는 아군의 평균 유영속도는 Powerblcok seine에서 9.71cm/sec, Triplex seine에서 9.97cm/sec였다. 2.죔줄죄기 소요시간 20분중 좀줄을 50% 정도 감아들었을 때, 선망내의 어군은 Powerblock seine의 경우 I section 10%, II section방향으로 10% 유영하는 행동을 보였다. 3.죔줄죄기 소요시간 20분중 10분 경과했을 때, 전면 망단 개구부의 면적 감소율은 Powerblock seine이 63.5%, Triplex seine이 어군도피에 대한 수평적 서단능력이 높았따. 그리고, 좀줄에 걸리는 최대장력은 Powerblock seine이 약 8.1톤, Triplex seine이 8.3톤으로 나타 났는데, 양자의 차이는 그다지 크지 않았다.

The authors analyzed the daily catch data which were obtained from two different regions at the Southern Sea in Korea, Neungpo, Geoje island and Yangwhagum, Namhae island, during three or four years in 1978, 1981-1985, in order to know the fishing characteristics of the set net fisheries. The favorable fishing season was summer in the southern sea. The total catches during one year were greatly affected by those several day when the dominant species of fish were caught in large quantities. The dominant species of fish at Neungpo were little horse mackerel, sand lance, sardine, hair tail, spanish mackerel and common mackerel, and those at Yangwhagun were anchovy, little horse mackerel, sardine, spanish mackerel and gizzard shad, in order of catch. Especially, the little horse mackerel and the sardine appeared to make up very big schools at both Neungpo and Yangwhagum. The occurrence seasons of the dominant species were different by the region, but generally those were earlier at western part than at eastern part of the Southern Sea in Korea.

재래식 권현망의 천장망을 제거하고 옆판 위 언저리에 뜸을 장치한 어구에 의하여 활멸치의 어획을 시험하고, 동시에 이렇게 어획한 멸치를 버팀대를 써서 축양조를 예인하는 방법으로 축양 시험을 실시한 결과 대략 다음과 같은 결론을 얻었다. 축양개시 15일후의 생잔률은 최고 약 71%여서 다른 어구. 어법에 의한 생잔률 보다는 낮지마는, 권현먕 어구 자체가 한국의 멸치 어업에서는 가장 보편화된 어구이므로, 2차적으로 활멸치를 어획하는데는 충분한 실용성이 있다고 보아진다.