Abstract
Lobsters are commonly caught by bottom-set gillnets in Japan, and the height of the net is rather low compared with other bottom-set gillnets.
Let N denote the number of lobsters caught by a certain mesh of a gillnet which is h in height above the sea bottom. Here the value of h is determined by h=l(n-1/2)√2s-s2, l being the mesh size of the gillnet used, h the number of mesh counted from the foot rope towards the head rope and s the coefficient of hanging given to the net.
The relationships between h and N obtained from the experiment were as follows:
The maximum catch of lobsters was obtained at the 3rd mesh which is about 19 cm high above the sea bottom and the relationships between h and N were LogN(%)=??.88+0.09 h and either Log N(%)=2.60-0.045 h or Log N(%)=2.78-0.055 h in accordance with changes in the value of h and the month experimented.
The maximum catch of top-shells was observed at the height of about 58 cm.
Although the catch of the lobster was strongly affected by the phase of moon, that of the top-shell was not influenced by the moon at all.
