The investigations by the bottom long-line were carried out at the artificial fish reefs in the coastal waters of Iwate Prefecture. It was found that Physiculus maximowiczi and Alcichthys alcicornis were abundant at the artificial reefs off Osaki, Kamaishi, especially the fomer was the most of all catches in every month. There were, however, the conspicuous seasonal changes in the catches of these species, which decreased in autumn and increased in winter and spring. Also, P. maximowiczi was most abundant and occupied more than 40% in number at the other nine artificial reefs which were investigated in June or July from 1980 to 1982. In A. alcicorniss, on the other hand, there was large variation in catch at each reef. The ratios of the species to all varied from o% to 56%. Judging from these facts, it was estimated that P. maximowiczi is dominant species at the artificial fish reefs in the coastal waters of Iwate Prefecture.

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The floating cages made of galvanized steel wire netting provided with cathodic protection treatment using aluminum alloy anode, were installed at the inner bay and open sea respectively. The results ; the floating cage installed at the inner bay could maintain its effective life of wire netting for over 48 months, and that installed at the open sea up to 27 months. Simultaneously, any meohanical wear or damage could scarcely be observed at the linked wire crossing sections of the wire netting provided with cathodic protection treatment. It was also found that the wear observed at the linked wire crossing sections without corrosion-proof treatment resulted simply corrosion. In addition, the wire gauge corrosion rate of 0.2φmm/yr was observed above the water line of the wire netting of inner bay cage. In case of wire netting of open sea cage, however, the wear and corrosion could scarcely be observed above the water line, as the wire netting frequently makes contact with wave. And the anode service life of the open sea cage was approximate 1/2 that of inner bay cage, as it is additionally applied with other open sea factors. However, it was confimed that the wire netting can be successively provided with another cathodic protection treatment if new anodes are supplemented.

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