The anadromous Ugui-minnows, Tribolodon hakonensis hakonensis (Günther), one of the cyprinid fishes attained about 59 cm in total length, are distributed in the brackish waters and the estuaries along the shore from the Hakata Bay to the Karatsu Bay in the northern Kyushu, and they migrate mainly into Matsuura River to spawn. The authors have ovserved their spawning habits with reference to fishery in the spawning area of Matsuura River. The results obtained are as follows: (1) The spawning season of these fishes extends from February to April at 9-17℃ in water temperature. They ascend to the middle reaches of this river in January to March, ranging 16-25 km from the river mouth, where the artificial spawning beds are prepared for fishing by the fishermen. (2) Prior to spawning season the fishermen build the artificial spawning beds to attract the fish and to capture by the cast net (Plate 16, D, E, F, Fig. 5). It is a mound piled by gravel in the middle reaches to a cone-like form, 1.0-1.5 m in diameter and 0.5-0.7 m in height, with the several stones for control the water current in upper side and for the cast net in lower side (Plate 16, D, Fig. 5, Table 1). (3) The possible effects of some environmental factors upon the spawning of these fishes in this river are of close concern to rise in water level and turbidity (Fig. 3). Consequently the spawnings are usually carried out shortly after the rainfall, and are observed in several times during this season. In earlier spawning season the larger fishes are dominant, and the smaller ones become to abound gradually with the process of the spawning season. The male fishes are exceeding the female throughout the season, especially in the earlier (Fig. 4). (4) Before the spawning, the fishes are splashing at the surface of the deeps near the artificial spawning bed at intervals of 2 or 3 minutes, and it continues for about 30 minutes. Then two or more males followed one female pass harriedly over the bed, and the bed is often hidden by the many passing groups. In a little while, one female attended by three to seven males swims towards the bed. Arriving at the bed, they immediately thrust their head among the gravels and sometimes they spawn in that posture with slow quivering. Soon the female and males raise up their bodies and creep over the bed, and release the eggs and sperms among the gravels, pressing against the vent of female with the males and quivering all over. After this spawning act, females immediately leave from the bed as a rule, but most of males remain and join in the other spawning groups. It is observed that the spawning acts are not limited to two or three groups; as many as five groups at one time, and these spawning above mentioned last for about 30 minutes. (5) The spawning area of Matsuura River is divided into 19 fishing-grounds, which are granted to the fishermen by means of a bid (Imari area) or payment of a fixed price (Ochi area) (Fig. 7, Table 2). In all grounds the beds counted some 20 sets and the total catch in the be seems to have amounted approximately 750 kg in 1959.