The yield of octopus in Hyogo Prefecture decreased gradually till about 1929, so some spawners was protected in the districts of Akashi, Tsuna and others since 1929, as shown in Table 1. The protection was performed as follows: (1) she-octopus was protected in a crawl and feeded during the spawing season. (2) she-octopus was given a pot for spawning-bed.
We studied if the increase of yield since 1930 was based on the protection, and we got the following result: one spawner was protected in case forty pots were prepared, and the yield of about 200 kan was resulted by the protection of one spawner.