Seaweed beds have recently declined and changed into barren ground in some Japanese coastal areas. On the other hand, the seaweed beds are important for production of fishery resources and conservation of marine environment. Experimental study to form a seaweed bed by preventing invading herbivores was arranged at the western part of Wakasa Bay, Sea of Japan. By using a net over the artificial constructions where Sargassum patens had not previously grown, young S. patens were able to survive. The effect of the covering net on the substrate crevasses where some herbivores may inhabit. To form a submarine forest effectively in this area. it was suggested that it is necessary to prevent herbivores from hiding in the substrate crevasses as habitats.

View full abstract

The effective function as anchoring materials of pebbles (mean diameter 30mm) or oyster shells (mean diameter 30mm) for enhancing the adhering strength of Zostera marina plants was clarified. The Z. marina plants collected at Mitsukuchi Bay, Hiroshima Prefecture, Seto Inland Sea, Japan were set for our experiments on the bottom of an outdoor 20ton capacity concrete water tank, by using commercial pebbles (mean diameter 30mm) or coarsely ground oyster shells (mean diameter 30mm) as anchoring material at a volume ratio 10%, 20%, 50% and 100% with sand or mud as the substrate. Test of the adhering strength by pulling out the rhizome of Z. marina plants was examined after the tank cultivation during periods of 3 months and 1.5 years. Maximum values of adhering strength in Z. marina plants were observed in the cases of mixing rate 20% of pebbles or oyster shells. On the other hand, the minimum values were confirmed for the cases of 100% pebbles or 100% oyster shells. These quantitative results on effective anchoring materials for artificial sandy bottoms for Zostera beds, indicate that improved design of actual sandy shallow bottom restoration for artificial sea coasts would be useful to enhance Z. marina beds.

View full abstract

In the coastal areas of the Seto Inland Sea of Hyogo prefecture, seaweed beds have been declined in their density because of reclaiming due to drastic urbanization and industrialization after the high economic growth period in the 1950's in Japan. In order to estimate the area of seaweed beds in the 1950's, the following methods were adopted. Questionnaire survey was carried out in 23 fisheries departments and 72 fisheries cooperatives and then set the objected area from this result, and the range of present seaweed bed areas was obtained by using the topographical maps, charts, side scanning sonar, underwater video camera and transparency. As the results of our survey, total seaweed bed area in the 1950's was about 2300ha but about 920ha was disappeared by the reclaiming (430ha), bank protection work (140ha) and others (280ha). Good grasp for the transition of seaweed bed area in the past is very important issue to carried out the natural reproduction plan of seaweed bed area in future.

View full abstract

Vertical movement of the moon jelly Aurelia aurita was investigated in the southwestern area (5.8〜9.4m deep) of Omura Bay, Nagasaki. We examined the influence of attaching micro data loggers on the behavior of six moon jellies in an aquarium. No significant difference was observed in mean bell pulse frequencies in experimental animals vs. controls (p>;0.05). In addition, micro data loggers remained attached to the bells for at least 5h. From June to July and October to November, 2009, the vertical movements of 10 moon jellies were recorded in the field. Moon jellies that were tracked remained within the 2m-depth layer during the daytime in June, but were closely associated with the seabed in October to November. Eight out of 10 individuals exhibited the initial descending behavior when released, which might be a reaction of the moon jellies to handling and/or micro data logger attachment.

View full abstract

Fishery in Fukui Prefecture, the decline in catches and production value, increased operating costs, an aging workforce and the decline of fisheries, producer prices drop, reducing the consumption of seafood has become the issues. The county has developed the following five basic measures to resolve the issues. 1. Promote increased consumption of marine products to provide of local seafood and fresh produce to consumers, 2. Promote the activation of fishing utilizing local resources to increase the number of tourists, 3. Promote context-sensitive resource management for stable catches, 4. Promote a shift to lowcost, high profitable fisheries in order to improve and increase the income of fishermen, 5. Advance the development of core fishers to revitalize the fishing village

View full abstract

Various environmental changes including the increase of large-sized jellyfish and the expansion of muddy area have recently been occurring in Wakasa Bay and simultaneously fish catches and production values have been reducing. Towards these environmental changes, various technologies have been developed to maintain and restore the fishing ground environment Applying the respective technology in simple manner is not sufficient for effective expansion of these techniques but it is necessary to fully consider the restoration goals and methods from the perspectives of fishery production, proper nutrient concentrations, securing shallow bottom (tidal flats and seaweed beds) and the amount of bottom dissolved oxygen. This paper illustrates the cases of ocean fertilization technologies for the purpose of increasing the fishery production, biological habitat improvement technologies, and improvement technologies to improve the bottom mud quality. These were cited from ones have been so far studied and conducted regarding restoration technology of the fishery environment Furthermore examples of creating mechanisms to promote restoration of the fishing ground environment at regional scale were introduced and the possibilities and problems in the case of applying them to Wakasa Bay were summarized.

View full abstract

It is very important to understand environment factors of the fishing grounds. In this paper, the author presents the factors of Wakasa Bay in recent years. 1. The surface sea water temperature around Japan is showing a tendency to rise, and a phenomenon was similar in Wakasa Bay. 2. The relationships between the surface sea water temperature in Wakasa Bay and the catching fluctuations of two-year-old and over yellowtail were investigated. As a result, a correlation of both items was suggested. 3. Since 1999, the catch of scomberomorus inhabit in warm waters is increasing rapidly in Japan Sea, and the fish is becoming the important species in Fukui Prefecture. 4. After 2002, a large amount of appearance of giant jellyfish was often observed in Japan sea. It was suggested that a current in Wakasa Bay effected a large accumulation and the long term remaining period of the species.

View full abstract

In order to protect the snow crab population, a crab sanctuary was established. An untethered remotely operated vehicle was used to gauge crab population numbers in the protected area and an unprotected area between the years 1996-1999. UROV results conclude higher crab densities in the protected area each.

View full abstract