Fishing Gear Shape Measuring Equipment

To efficiently collect biological samples, it is important to know the depth of the net and the opening of the net mouth during the tow. By attaching underwater sensors with acoustic communication to the trawl net, the depth and shape of the net during operation can be monitored in real time (Figure 9). The sensor readings are converted into acoustic signals, which are received by an underwater microphone (hydrophone) located on the bottom of the ship. The received data is processed by the onboard controller and displayed on a monitor (Figure 10).

Figure 9 Underwater sensors and measurement items of the fishing gear shape measuring device

オッターボード深度: Otterboard depth ヘッドロープ深度: Headrope depth ヘッドロープ水温・傾斜: Headrope water temperature and inclination 網口高さ: Net mouth height ヘッドロープ- 海底間距離: Headrope to seabed distance

オッターボード間隔: Otterboard interval 網口縦断方向流速: Longitudinal current velocity at the net mouth 網口横断方向流速: Crossing current velocity at the net mouth 袖網感覚: Sleeve net sense

 Oshoro-Maru is equipped with the following underwater sensors

【Combined depth, water temperature, and inclination sensor】

Attached to the headrope, it measures depth, inclination, and water temperature.

【Trawl speed sensor】

Attached to the headrope, it measures depth, attitude, and water temperature.

【Trawl Eye Sensor】

　Attached to the headrope, this sensor acquires fish-finding images above and below the net. It also measures the distance from the headrope to the seafloor and to the groundrope.

Sleeve net interval sensor

 A spacing sensor and transponder are attached to each side of the sleeve net to measure the distance between them (how open the sleeve net is).

【Otterboard interval sensor with depth recorder】

An interval sensor and transponder are attached to the left and right otterboards, respectively, to measure the distance between them (how open the otterboards are).　The interval sensor and transponder also have a depth sensor built in to measure the depth of the otterboard as well.

Figure 10 Configuration of fishing gear shape measuring equipment

データ表示モニタ: Data display monitor 受信装置: Receiver 受波器: Transducer 水中センサ: Underwater sensor

Figure 11 Sonar dome

 The transducer of the acoustic measurement equipment are located in a structure on the bottom of the ship called a sonar dome. The hydrophone of the fishing gear shape measuring equipment is located at the very back of the sonardome (circled area) to facilitate reception of sound wave signals from behind.