The rush and jerk motions in relation to hooking were analyzed hydrodynamically with fish behaviour restricted by a snood, in order to gain a mechanical understanding of the hooking pro-cess.
The rush was similar to a rapid starting performance and its kinematic stages are divisible into two. At the first stage, the fish changes its form from a stretched straight to an L-(or C-) shape by moving its tail and anterior parts laterally. The second was the propulsive stage where the fish moved its tail laterally at a high speed. During this stage, the calculated mean of practical thrust was 8.1 N. If it were not for the snood, the speed and distance that would have been covered at the end of this stage would be 5.6m/s and 37cm, respectively.
The first stage of the jerk motion was similar to the first stage of the rush. However at the sec-ond stage, the fish changed its form either by straightening out or reversing to a C-shape by moving mainly the anterior part. The length of this stroke was approximately 1/3 times the body length.
The distance covered and the stroke are very important factors in understanding the hooking process which includes a complicated interaction between the gear and the fish. This process must be considered at the gear designing stage.