Along the Kansai International Airport islands, which are two artificial contiguous islands in the eastern area of Osaka Bay, a large-scale sloped seawall suited for seaweed bed development was constructed for the first time in Japan. The degree of coverage and areas of seaweed vegetation were monitored from 1989 to 2010. However, the change in standing stock of seaweed was not followed in the monitoring program. We conducted a new survey to convert the seaweed coverage data to standing stock for evaluation of the ecological functions of seaweed beds formed on the seawalls of the airport islands. The result showed that the total surface coverage of the airport island seawalls in 2010 was approximately 2.5 times higher than in 1999 but the total standing stock in 2010 was only approximately 1.4 times higher than in 1998. This is thought to be attributed to the significant decrease of Ecklonia that had been growing thickly near the first airport island, caused by reduced current speed and wave flows due to the second island. The annual production from the surface area of seawalls in 2010 is estimated at 44,680 kgC/y, 2,992 kgN/y, and 181 kgP/y, respectively. We estimate that 18% of the annual carbon absorption of seaweed beds that was lost in Osaka Bay in the past is absorbed by the sloped seawall area near the airport islands. The annual production from the slightly sloped seawalls (per unit area) in terms of carbon, nitrogen, and phosphorus is approximately 9, 7, and 8 times higher than that of vertical seawalls, respectively. In terms of the cost of constructing a sewage treatment facility, we estimate that converting vertical seawalls to sloped seawalls for a distance of 1 km would yield benefits of 8.2 million yen per annum in terms of nitrogen treatment amount and 4.5 million yen in terms of phosphorus treatment amount.
The mammoth earthquake and tsunami that resulted in the death of tens of thousands and wiped out coastal cities in northeast Japan left the region to deal with 22 million tons of rubble, perhaps the biggest recycling challenge ever. It examined a way of manufacturing the concrete block as substrata for seaweed, which used concrete rubble. The postpacked and prepacked concrete using recycled coarse aggregate, concrete rubble were experimented. As the result, the postpacked method was easy for the blocks as seaweed breeding reef to be composed. At the earthquake-stricken district, concrete blocks as seaweed breeding reef were manufactured using the concrete rubble in March, 2012. Seaweed on the block which were mounted in Otsuchi area in Iwate pref. were observed in April, 2013. Seaweed on the block was observed to 13 months after mounting. Cover of the seaweed on the block was 100 %. On the natural rock, it was 80%.
This paper introduces a case study of an underwater acoustic and optical surrey method for quantitatively monitoring the biodiversity and marine ecosystem, especially the prey (zooplankton) - predator (fish) relationship in an artificial mound reef. The acoustic and optical survey was conducted from 2009 to 2011 in the eastern Tsushima off, Nagasaki prefecture. In that area, an artificial mound reef had been built with width of about 70 m and a height of about 14 m, which were measured by a multibeam echosounder (70-100 kHz). Acoustic transects were run to investigate the zooplankton and fish school spatial temporal distributions around the artificial mound reef, by the multi-frequency scientific echosounder (18, 38, 70, 120, 200 kHz) calibrated using the standard reference spheres. In addition, an ADCP (75 kHz) simultaneously measured the speed and direction of the ocean currents at multiple depths around the artificial mound reef. Therefore, we used the Sonar Synchronizing Unit (SSU) to eliminate any acoustic interference between the acoustic equipment. Also, we examined whether the multi-frequency technique, the difference between the mean volume-backscattering strength at two frequencies, the so-called Sv difference method, could be used to classify between the zooplankton and fish in the artificial mound reef area. An optical observation and sampling survey by a ROV and a Mocness plankton net were then conducted to verify the validity of the acoustic classification result.
The present status and on-going concerns of fisheries in western Sea of Japan waters are analysed. Major fisheries for pelgic fish stocks, conducted by purse seiners, have primarily targeted sardine, round herring, ancovy, horse mackerel and mackerel species. Japanese sardin stocks, which have undergone large fluctuations over the last 50 years, have been at a low level in recent years, whereas Japanese anchovy stocks are currently stabilized at a high level. However, the unit price of the latter is low and the stock not highly utilised. Japanese horse mackerel is now the most important pelagic fishery in the western Sea of Japan, with the highest catch amount and value levels. Although high fishing pressure, particularly of age 0 individuals, may be a serious concern. The stock amount and catch of yellow-tail have increased marckedly in recent years, but unit price have decreased. The status and problems for benthic fish stocks taken by paired trawlers in the western Sea of Japan are also described. Although yellow sea bream stocks are stable at high levels, decreasing prices are serious concern. By comparison, the high prices commanded by red sea bass have resulted in significant targeting of this species, although increasing over-fishing, particularly of young specimens, remains a concern. Willowy flounder and yellow angler fish stocks, which increased markedly in the late 1990's, are presently stable at high levels. Factors responsible for stock increases may be strong year classes by the effect of gloval warmning.
In the "Fishery Resources in the western part of the Sea of Japan: Conservation of the Biodiversity and Direction of Future Fisheries" symposium held by the Japanese Society of Fisheries Engineering at the National Fisheries University in Shimonoseki, Japan, on November 10^<th> 2012, we exchanged very useful information between the participants and talked about the future of the resources in this sea. The main items discussed were showed as follows: 1. Background and definition of the biodiversity, 2. National strategies on preservation the biodiversity, 3. International conference of COP 10, 4. Basic action plans of the Ocean Policy of Japan, 5. Ocean policy in overseas countries, 6. Research on biodiversity conducted by the authors and 7. Future subjects. On April 26^<th> 2013, the Japanese Government established a new Basic Plan of Ocean Policy and we need to preserve and promote the biodiversity based on that plan. Particularly, it is necessary to establish a comprehensive research project between the conservation of biodiversity and the management of fisheries in the western part of the Sea of Japan, which faces other countries such as Korea and China. For resolving these problems, the authors recommended the use of the new advanced technologies available to establish a comprehensive research project on this matter, being bio-logging science one of the most useful tools for this kind of research.
The fish catch of snow crab Chionoecetes opilio in the Sea of Japan peaked in 1970 at approximately 16,000 tons. Since then the catch has been in decline and efforts to recover these marine resources are performed. One such effort (a project subsidized by Fisheries Agency since 1982) involves the installation of artificial nursery reefs on the sea beds inhabited by snow crabs to serve as MPA (Marine Protected Area) to protect the crabs. Currently, these sanctuaries have been established in 29 places which cover a total area of 32,900ha. Furthermore, Fisheries Agency started the frontier project in 2007. In this project, installation of the artificial nursery reefs of 21 places which cover a total area of 8400ha are planned from 2007 to 2014, and installation of 10 places, 4000ha was completed now. In this research, we sought to clarify the effects of these artificial nursery reefs on the protection of snow crabs.project on this matter, being bio-logging science one of the most useful tools for this kind of research.
For a sustainable use of the fisheries resources, it is important not only to investigate the dynamics of the fish stocks but also the ecological integrity and health of the habitat from the point of view of the biodiversity. Here, we introduced an example of conservation and management of fish stocks in natural reefs conducted in the Hachri-ga-se reefs, a good fishing ground off Mi-shima Isand in Hagi, Japan. The reefs here are located on the continental shelf, where they contribute significantly to the productivity of the coastal ecosystem enhancing the supply of prey and providing resting grounds for several fish populations. The mayor of Hagi City initiated the project for the management of the resources in the reefs in 1999 with fishermen, scientists and local governments. This project was a succeeded example of the bottom-up control of resource management in offshore reefs by a citizens' leadership. It demonstrates that the key of success is a strong communication and collaboration among policy makers, scientists, fishermen and the general public that fosters mutual understanding and recognition of shared interests.
In recent years, the biodiversity gets to be paid more attention to in the field installed artificial fish reefs. Therefore we present some examples to study in the followings; (1) change of the organism species community by artificial fish reefs installation, (2) differences in the composition by the difference of fish catch thing between reef s structures, and (3) a practical use experiment in breakwater caisson.
Effects of fishing on marine ecosystems are concern throughout the world. Bottom fishing, especially employing towed fishing gear such as shrimp trawl, is considered as major sources of discards and habitat disturbances. Many kinds of by-catch reduction device (BRD) has been tested in the world as a possible counter measure for mitigating discard issues. In order to develop BRDs, we consider that verification of separation function of BRDs is important which suits specific objectives of fisheries management. Quantitative assessment methods such as the contact probability modelshould be employed for this purpose. Regarding measures aimed at reducing the physical impact of towed fishing gear on the seabed environment. We also introduce studies on the environment-benigntowed fishing gear in Japan. These gears are still in the developing stage because considerable degree of catch reduction was reported while they reduced physical impacts on seafloors. Future research will focus on optimizing these gears to reduce catch reduction while minimizing the damaging effect of towed fishing gear on the seafloor environment.