ウバガイ桁網の漁獲による破損貝について

抄録

Dredges used in catching the Japanese surf clam Pseudocardium sybillae are known to cause damage to the shells during the dredging process. This is an important problem because clams resources are considerably affected.
In this paper, various factors causing damage to shells during dredging are analyzed. Also, considering the fact that the shell is damaged by collision with the teeth of the dredge while the dredge is being towed. The collision probability of the Japanese surf clams with teeth of the dredge was calculated using such variables as the shell shape, size, distance between dredge teeth, width of teeth and relative position between shells and teeth. Various sized surf clams caught by the dredge were collected and examined for data.
The probability of a shell colliding with the teeth of the dredge can be expressed as a function of distance between the teeth and the shell length. The damaged shell caught by the dredge can be considered to be in proportion to this collision probability.
It was found that 10 percent of the shells are damaged when the clams collide with the teeth of the dredge while the dredge is being towed.