Anchovy (Engraulis japonicus) is one of the most important species in the South Sea of South Korea. In order to estimate the biomass of anchovy, acoustic surveys, concurrently with trawling, were conducted in April, July, and September of 2013 and February of 2014 off the coast of Tongyeong and Yeosu. However, anchovies were found only during spring (April) and winter (February) surveys. To display only anchovy species confirmed by trawls on empty spaced echograms, virtual echograms were created. Three target strength (TS) values of anchovy were used: TS_z = 20 log L – (20/3) log (1+z/10) – 67.6 (Zhao et al.), TS_y =20 log L – 72.9 (Yoon et al.), TS_f = 20 log L – 71.9 (Foote). For anchovy schools combined with other species e.g., hairtail, squid, and Korean pomfret, their TS values were used to calculate an average TS. As a result, the anchovy biomass in the winter survey was approximately 75,000 tons (TS_z), 90,000 tons (TS_f), 114,000 tons (TS_y), respectively. The biomass in spring was 9,000 tons (TS_z), 9,200 tons (TS_f), 10,000 tons (TS_y). The sampling variance of spring was 70% and of winter was 30%. In order to manage anchovy resource sustainably, larvae and adult anchovy should be separately surveyed, the optimal area, date, and time for acoustic survey should be investigated, and the biomass survey should be done for relatively long and regular base.

본 연구는 남부지역 맹종죽 및 솜대림의 죽령에 따른 현존량 추정 및 비교를 위해 당년생과 2년생 이상의 죽림을 대상으로 10m × 10m 크기의 조사구 3개를 각각 설치하여 경급에 따라 선발하고 벌채하였다. 부위별 건중량은 맹종죽과 솜대 모두 줄기>가지>잎, 죽령별로 2년생 이상>당년생 순으로 나타났으며, 건중량비는 맹종죽 2년생 이상 0.62, 당년생 0.55, 솜대 2년생 이상 0.60, 당년생 0.57로 나타났다. 줄기 건중량비를 이용한 절단 위치 선정 군집분석 결과 두 죽종 모두 수고의 75% 위치에서 상단부와 하단부 두 집단으로 구분 후 절단하여 분석하면 현존량 조사가 효율적이라고 판단된다. 추정식 W=aD+bD2을 이용하여 추정된 지상부의 ha당 현존량은 맹종죽 2년생 이상 106.4ton/ha, 1년생 5.5ton/ha, 전체연령 113.3ton/ha, 솜대 2년생 이상 109.2ton/ha, 1년생 6.4ton/ha, 전체연령 106.0ton/ha로 나타났다. 지하부의 ha당 현존량은 맹종죽 지하경이 32.85ton/ha, 원뿌리 10.56ton/ha로 지하경>원뿌리 순이였으며 지상부 현존량의 35.8%였다. 솜대는 지하경 16.89ton/ha, 원뿌리 21.06ton/ha로 원뿌리>지하경 순이였으며 지상부 현존량의 38.3%로 나타났다.

Hydro-acoustic surveys with scientific echo sounder were carried out to estimate the total density and distribution of the juvenile cod in Jinhae bay, Korea. The surveys were conducted 4 times from May to June using 2 frequency method (38kHz and 120kHz) and beam trawl were used to investigate the species composition. Also the catch amounts of juvenile cod were compared with the cod density estimated by the hydro-acoustic method. It was confirmed that the juvenile cod was stayed in Jinhae bay in early June and There was the relationship between catch of juvenile cod and the estimated density by hydro-acoustic survey. The number of juvenile cod was consequently about 365,000 fish (CV 12.9%) in May and 113,000 fish (CV 9.2%) in May based on the hydro-acoustic data.

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.

Planktonic crustaceans were collected monthly around Hamduck, northern part of Cheju Island from April 1989 to March 1990. Occurrence of mean individuals (244 rods. m^(-3)) from inner~ay stations was 2.4 times higher than that (102 rods. m^(-3)) in outer-bay stations. Mean biomass (wet weight, 18.6 mgm^(-3)) from inner-bay stations was 3.6 times higher than that(5.2 mgm^(-3)) in outer-bay ones. The estimated mean values (251.5 ㎍Cm^(-3)d^(-1)) of daily production from inner-bay, having 141.1 ㎍Cm^(-3)d^(-1) of annual mean, was 2.8 times higher than that (90 ㎍Cm^(-3)d^(-1)) in outer-bay. The ratio of daily production of biomass with average value 0.17 suggested a high turnover rate to maintain a temperate costal ecosystems, in spite of a low biomass around Cheju Island.