• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2006년도 PARALLEL CFD 2006
• /
• pp.393-394
• /
• 2006

• 수산해양기술연구
• /
• 제51권1호
• /
• pp.120-127
• /
• 2015

Morphological properties of dark banded rockfish (Sebastes inermis) were analysed to investigate its acoustic scattering characteristics. Total of 18 live samples was prepared for X-ray photos and collected morphological coordinates of their body and swim bladder shapes. Kirchhoff-ray mode model was used to calculate acoustic scattering pattern for broad-band frequency range. Inclination of swim bladder ranged from 17 to 30 and the averaged value was about $25.2^{\circ}$ (S.D.(standard deviation)=3.15). There were no any tendency of increase or decrease in volume and area ratio of swim bladder to fish body and ranged from 2.2 % to 4.43 % and 14.85 % to 21.31 %, respectively. The averaged value of volume and area ratio was 3.13 % (S.D.=0.52) and 17.6 % (S.D.=1.5). $b_{20}$ values were -69.01 for 38 kHz, -69.83 for 70 kHz, -70.17 for 120 kHz and -70.93 for 200 kHz, recpectively. Broadband acoustic patterns of dark banded rockfish for 20 ~ 200 kHz were similar among samples and they reflected size and morphological properties of fish species.

• 수산해양기술연구
• /
• 제48권4호
• /
• pp.487-494
• /
• 2012

Acoustical backscattering characteristics of Japanese anchovy can be estimated by Kirchhoffray mode model (KRM model) due to estimate exact body and swim-bladder shape of the fish, the samples were rapidly frozen by dry-ice and alcohol. X-ray photos for ventral and lateral direction for 6 samples were taken and the 3D coordinates of the body swim-bladder were estimated by digitizing from the photos. The angles between the axis of body and swim-bladder were about $9^{\circ}$ at 38kHz and $7^{\circ}$ at 120kHz, 200kHz. General formula of TS and BL estimated were < $TS_{38kHz}$ >=20logBL-67.3, < $TS_{120kHz}$ >=20logBL-66.6, < $TS_{200kHz}$ >=20logBL-67.0. As a result, we confirmed KRM model is very useful to estimate TS (Target Strength) for design of experiment and it also can be applied to estimate the abundance of Japanese anchovy distributed by 2 frequency difference method in the survey area.

• 한국어류학회지
• /
• 제33권1호
• /
• pp.8-14
• /
• 2021

멸종위기 담수어류 모래주사의 산란행동을 조사하기 위해 산란시기인 2012년 4월부터 5월까지 전북 임실군의 섬진강 일대에서 연구를 실시하였다. 모래주사의 산란은 무리산란 (group spawning)하는 어류와 달리 암수 한 쌍에 의해 이루어졌으며, 수중으로 대량의 생식세포를 방출하여 산란하는 원시적인 생식모드 (broadcast spawner)로 확인되었다. 자연에서 모래주사의 산란행동은 휴식(resting), 유혹(male chase), 자극(body beating), 평행유영(parallel swim), 암컷의 산란회피(female withdrawal), 경쟁(male competition), 산란(spawning), 산란 후 난을 보호하는 행동은 보이지 않아(not guard) 총 8가지 행동을 보인 반면 수조 내에서는 휴식, 유혹, 자극, 평행유영, 산란, 산란 후 난을 보호하지 않은 6가지 행동이 관찰되었다. 특히 산란전 행동은 수조 내에서 보다 자연상태에서 더 빈번하게 일어났다. 이와 같은 행동적 차이는 작고 좁은 수조에서의 행동적 제약에 의한 결과로 추정된다.

• 수산해양기술연구
• /
• 제50권4호
• /
• pp.427-434
• /
• 2014

Although ex situ target strength (TS) measurements using dual- and split-beam systems have become the primary approach of estimating fish abundance, theoretical model estimation is a powerful tool for verifying the measurements, as well as for providing values when making direct measurements is difficult. TS values for 20 samples of live bambooleaf wrasse (Pseudolabrus japonicus) whose target length (TL) ranged between 13.7 and 21.3 cm were estimated theoretically using the Kirchhoff-ray mode model, and the TS values for 18 live fish samples were additionally measured at ${\sim}0^{\circ}$ tilt angle to the swimming aspect using a tethered method at a frequency of 120 kHz to verify the theoretical values. The digitizing intervals used to extract the fish body and swim bladder morphology in the X-ray photographs significantly affected the calculated TS patterns, but variations based on the speed of sound and density ratio values for the general range of fish flesh were relatively small (within 1 dB). Close agreement was observed between the measured and theoretical TS values, and the correlation between the average TS and body length of the fish could be calculated accurately as <$TS_{120kHz}$>= 20logTL (cm) -71.6 using the theoretical method.

• 수산해양기술연구
• /
• 제59권2호
• /
• pp.125-134
• /
• 2023

The swimming behavior of pacific bluefin tuna (Thunnus orientalis) in the offshore sea cage of the brass fishing net was observed and analyzed by imaging sonar techniques. The cultured fish spent most of the time swimming a circular path along the circular cage wall and continued to swim only clockwise direction without completely changing the swimming direction during the 23-hour observation time. In addition, changed swimming behaviors were divided into four categories: (a) the behavior of a large group temporarily swimming in the opposite (counter clockwise) direction, (b) the behavior of a small group temporarily swimming in a small circular path, (c) the behavior swimming small circular path in the center of the cage, and (d) the behavior of a large group swimming across the center of the cage. The maximum swimming speed of the cultured fish was from 3.5 to 3.8 TL/s, the mode was from 1.2 to 1.4 TL/s and the swimming speed during the day time was faster than at night time. It was confirmed the cultured fish swam not only on the surface but also near the bottom net of the cage during the day, but swam mainly at the upper part of the cage at night.