Acoustic Target Strength measurements of a single fish: A case study of Crucian Carp

Research of fish Target Strength (TS) measurements is the foundation work of the acoustic assessment of fishery resources. An auxiliary experimental device with patent right is presented in this paper, which can be used for measuring the target strength of a single fish sample under controllable parameters by using the BioSonics DT-X echosounder. Taking 14 samples of breeding Crucian Carp as experimental subjects, we measured the target strength of all the samples one by one at different tilt angles. The results show that: (1)The fork length of Crucian Carp ranged from 17.1 to 23.2 cm and the corresponding range of average target strength was -51.9 ~ -45.8dB. (2) Relationship between fork length and the target strength of Crucian Carp are as follows: TS=20lgL-74.2. (3) Changes in the tilt angle can cause the target strength of the same experimental fish values vary more than 20dB at the same measurement depth. (4) This device can be seen as a kind of effective and feasible measurement experimental device, which solved the controllable problem of different parameters in the measurement of target strength of the single fish.