For realization of the marine ranching, the most important subject is barrier formation technology. The purpose of the study is the development of a method of the electrical screen formation for the marine ranching. This paper, first of all, describes the results of experimental analysis on the adaptive control method of fish behavior with the electric exciting. Secondly, it discusses a theoretical consideration on a formation technique of the electrical screen that has linear electric field, and introduces the original electrical screen. Furthermore, the paper discribes the outline of the electrical screen for prototype marine ranching, and considers a few points about barrier effect on this marine ranching from the results of pasturage experiments using the electrical screen. This screen is named the '3 poles-2 potential way', and has remarkable chracteristics as followings; (1) It is based on the way of shielding electric field in the screen. (2〉The electric field in the screen:is composed of several intensity levels to barricade with soft exciting. (3) This technology is applied not only to sea fishes but also to shellfishes, sea urchin, sterfishes, and river fishes.

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Artificial fishing reefs which are precasted on the parmanent or temporary fabrication yard are often installed in the coastal fishing ground in order to recover decreased living resources. The installation of these artificial fishing reefs are generally just putting on the sea bed around the fishing ground situating at the neighbouring of surf zone. It is seldom to install the reef with foundation treatment and to fix it on the treated foundation. Then, the safety considerations against the sliding and the tuming over of its arise as an important problem to be forecasted. The resistance factor C_D and the added mass coefficient C_MOf the reef play an important role in the stability estimation of installed artificial fishing reef. As far as simple shaped column or submerged object, values of C_D and C_M are derived analytically with the theories of hydrodynamics. But for the complicated structures like these artificial fishing reefs with various members, it is impossible to determine C_D and C_M theoretically, it is necessary to do it with hydraulic model test. Authors made it for Sumi-reef and for Tetra-reef, and got the values of them which were considered to be relatively reasonable.

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MK-type artificial fishing reef is developed with the view point of being out of net catch, generating upwelling flow, stable free settling at the instalation. Hydraulic model test was carried out in order to confirm such characteristics as above mentioned. Since the net catch ofthe artificial reefis depeds mainly on the smoothness of its surface, not on its shape, net catch test was not executed, and the other hydraulic characteristics were tested. Upwelling capacity was not so large, large scaled upwelling such as oceanographical sense was not recognized. Others were approximately satisfying.

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Occurrence, abundance, recruitment, settlement and mortality of Japanese flounder larvae and juveniles were investigated in Shijiki Bay, Hirado Island, during the period of 1982 through 1986, as a biological basis for farming fisheries. The pelagic larvae were found to be widely dispersed over the entire offshore area examined, but metamorphosed demersal juveniles were found to be restricted to shallow near-shore sandy areas. Recruitment from offshore to inshore area, which mainly occurs at metamorphosing stages, exhibits a semi-lunar rhythm related to spring tides. The tidal phase-synchronized vertical migration of metamorphosing larvae suggests that selective tidal transport is primarily important for inshore migration of Japanese flounder. High mortality was supposed to occur immediately after settlement as inferred from the length composition of settled juveniles; number of individuals sampled decreased between 11 mm and 14mm SL, corresponding to about one week growth. The factors causing high mortality were discussed in relation to food deficiency, predation (including cannibalism), and so on. The 'settling mortality' seems to be primarily by food deficiency and secondarily by starvation-induced predation in the nursery ground examined, in which over-populated juveniles recruit in a rather restricted space.

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ウバガイ人工種苗の放流,中間育成試験を実施して,次の結果を得た。 〈1)昭和58年5月及び7月に,鹿島港南海浜埋立地沖潜堤周辺海域(7m水深域)及び鹿島港北海浜(8 m水深域)へ,前者は平均殻長10mm以上の種苗を1.4万個体,後者には平均殻長2mmの種苗を190万個 体放流したが,継続的再捕資料は得られず放流後の動態は明らかにされなかった。 (2)昭和61年7月から昭和62年2月にかけて平均殻長4mm台及び7mm台の種苗を用い,昭和62年6月 から10月にかけては平均殻長2mm台の種苗を用いて平磯漁港内の2-3 m水深域において延縄垂下方式に よる中間育成試験を行った結果,育成期間中の成長は概ね順調で生残率は大型種苗ほど高かったものの, 2mm台の種苗についても約85%と良好な値を示した。

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