The tide dam is composed of a dam and pipes, and inhibits the development of oxygen-deficient water mass in a bay by the use of tidal potential energy. For applications of the tide dam, there are a lot of problems to be solved. In this paper, the following problems became clear.
(1) The relation between the dimension of pipes and the water flux of jet flow.
(2) Vertical mixing and despersion in a bay due to the jet flow of the tide dam.
The investigation by the bottom long-1ine at the six artificial reefs was carried out in the coastal waters of Iwate Prefecture in June and July from 1980 to 1982. The brown hakeling, Physiculus maximowiczi, was the most abundant species in these reefs and appeared at all of them. This paper examined the relationship between the catch of this fish and the artificial reef density.
The number of effective lines, fish individuals which were caught and the total hooking rate (number of fish /number of total hooks) were the highest at the reef of which density is 0.037m3/m2, and low at the other reefs of which density is smaller or larger than this reef. But the effective hooking rate (number of fish/number of effective hooks) was constant at the reefs of which density is larger than this reef. These results suggest that the reef density is very important for the fishing ground constructed by the artificial reef, and these value should be supported by the investigation of the fish behavior to the artificial reef and the characteristics of fishing gear used and the way of its operation.
After contending against adverse conditions, successful wild spat collection of the Japanese scallop, Patinopecten yessoensis, kept being accomplished by the HOTAC (Hotate-Aid-Conglomerate) methods under a new strategy in Nemuro Waters particularly during seven years ruming of 1982-88. The combinative strategy is elaborated with both results from the network survey and the expIorative one. HOTAC methods are constructed by the technoIogical skills of an imovative knowhow on the base of a mandala concept for the scallop mariculture. All rights of intellectual roperty on both of the scallop mariculture mandala concept and the HOTAC technological methods are reserved for the author and Hotac Co.
Estimation of the depth of sunlight penetration and upward irradiance from the depth in the ocean and the coastal water were made. Although chlorophyll-a contentc can be calculated by sea surface radiant spectrum, the effective depth of light Penetration is different by water quality itself. Optical information from secchi disk depth seemed to be very low. The 90 percent of surface upward irradiance come from the slightly shallower than the secchi disk depth and the 70 percent of it come from the half of scchi disk depth. So, the optical information depth has different value by
each areas and seasons.
The man-made structure for upwelling was set in the eastem part of the Bungo Channel, Seto Inland Sea, in October 1987. Much fish gathered in the surface layer at night and in the middle layer in the daytime, respectively, just above the structure in August 1989. Much fish also gathered in the middle layer just above the structure only in the daytime in October 1989.