抄録
It is not rarely the case that fishing boats of Shiirazuke fishery catch dolphins taking advantage of natural flotages in the sea other than their original “Tsukegi” (a bamboo raft set afloat to attract dolphins). In this paper the author intended to report how fishing boats are utilizing flotages and how is the fishing condition of dolphins there.
1) Flotages utilized by Shiirazuke fishing boats off Shimane Prefecture are composed of following three kinds, that is, a) drifting “Tsukegi” (50% of total flotages utilized): They had been set in more western sea areas but were drifted into the fishing ground off Shimane Prefecture as their anchor lines were broken by some causes. b) drifting sea-weeds (40%), c) drifting timber (10%).
They are utilized mainly from early summer to midsummer (Table 1).
2) Although flotages are distributed abundantly in the coastal region, those which are utilized by fishing boats are flotages drifting in the sea areas more than 10 miles offshore. There is an indication that more dolphins tend to accompany a single flotage in the offshore area close to the center of the warm Tsushima current than the coastal area (Fig. 1).
3) No direct relation between the number of dolphines under a flotage and the kind or size of the flotage is recognizable (Figs. 2, 3).
4) Dolphins gather around drifting dead bodies of large animals likewise as other flotages (Table 2).
