The aim of this study was to investigate the effect of the shape and open area ratio of traps on the downstream flow speed distribution. The box and cylinder traps were made of an iron frame (5 mm diameter) and had dimensions of L : 0.40×W : 0.40×H : 0.22 m and D : 0.40×H : 0.22 m, respectively. In addition, two types of sidewalls were employed in this study: wooden rods and netting. For each type, five different designs were constructed by changing the interval of the wooden rods and the bar length of the netting. Each trap was set on the bottom of a flume tank. The flow speed in the rear of the trap was measured with an electromagnetic current meter. Measurements were taken at points located in the rear area of the trap, which had dimensions of 4L length×2L breadth, where L denotes the length of the trap. A total of 81 measurement points were located at the intersections of a grid that was formed by nine lines running downstream and nine lines running across the flow. The flow speeds in the flume tank were set as 0.15 and 0.30 m/s. The flow speeds measured during these experiments were converted to the ratio of the flow speed to that of a blank condition at the same point (R_v). The low flow speed (R_v<0.6) region appeared downstream from both lateral sides closest to the trap. The low flow speed region of the box traps was higher than that of the cylinder traps in the same open area ratio. However, the low downstream flow speed of box traps was not observed when the open area ratio was above 80%. In the cylinder trap, the low flow speed region was disappeared over 70% of the open area ratio. Consequently, the downstream flow speed distribution formed as a result of the shape and open area ratio of the traps affects their capture process.
New cleaning system for cooling water line in outboard engine was developed, and the trial equipment was produced. For this system, cleaning fluid which mixed the scallop powder and the compressed air into the water was used. The experiments for cleaning the acrylic resin tubes which simplified cooling water line of the outboard engine and the actual outboard engine were conducted, in order to evaluate the removal effect of the fouling. The results show that the removal effect was the best in scallop concentration 5% in the experiment using the acrylic resin tubes; The removal of the fouling was confirmed, when cleaning fluid of the flow rate 30 L/min, the concentration of the scallop powder 10%, running time 20 min, and the pressure of compressed air 0.08 MPa was used, in the experiment using actual outboard engine.
We examined effective utilization of herbivores (e.g., sea urchins and herbivorous fish) distributed in barren grounds. It was confirmed that sea urchins and the herbivorous fish species can be utilized as fertilizer and fish paste, respectively. However, some steps toward the practical use of these species remain to be elucidated.
After the Isoyake Taisaku guideline was published, sea urchin removal has been carried out in various places ever. In this article, I reported the effective removal method and problem of the sea urchin from those examples. Sea urchin removal is most effective at barren ground measures. The author explained important point of sea urchin removal and also introduced a sea urchin fence and some tool for sea urchin removal. In order to seaweed restoration, it is important to maintain a low density of sea urchin.
It is important to monitor the seafloor habitat on a regular basis for early detection of "Isoyake", which means sea desertification, and identifying the reason. Because traditional monitoring techniques, diving survey, take much time and energy to obtain spacious and periodical information of the seafloor habitat, new monitoring methods are necessary for the continuous management of macrophyte benthos bed. Recently, high-performance monitoring devices are sold at low price and used to examine distribution of marine bottom material and vegetation and behavior of herbivorous fishes. This report introduces three monitoring devices, inexpensive side-scan sonar, radio-controlled multicopter and interval camera.
Lack of seed of seaweeds is considered to be one of the significant factors that continue barren ground called Isoyake in Japan. "Spore bag method" using a net bag filled with mature seaweed was most commonly-used method of seeding. As the freshness of seaweed was faded soon, so the duration of seeding became shorter. Then a seeding method called "Submerged mid-layer nets" was thought up. The new method intended to extend the freshness of seaweed has developed into "Open spore bag method" widely-used for seaweed restoration in various regions in Japan. In this paper, three seeding methods designed in the same light are introduced. The first one is "U-bolts method" for Sargassaceae growing on intertidal zine. The second one is "Plastic net method" for Lessoniaceae growing on upper sublittoral zone. The last one is "Small net method" for both species above-mentioned growing on sublittoral calm zone. The habitats of seaweed are mainly determined by the condition of light and wave action. Therefore, the basic of seeding is transplanting the seaweed to a similar environment inhabiting before.
With the support of government, fishermen and local residents are now actively engaged in efforts to conserve seaweed beds in the coastal areas of Japan. Among such efforts, 184 groups have taken part in the Environment and Ecosystem Protection Project (EEPP) between 2009 and 2012, and 275 groups implemented the Fisheries Multiple function Demonstration Project (FMDP) in 2013. Many groups are working to remove sea urchins from seaweed beds, transplant matured seaweeds that supply spores, plant seaweed seedlings, and clean bedrock. The two main challenges in the coming years are to enhance technical support to groups including the ones mentioned above and to evaluate the effects of the conservation efforts in a quantitative manner.
Restoration of perennial beds of large macroalgae, e.g. kelp or Sargassum bed, with year-round vegetation is usually difficult under high grazing or browsing pressure by herbivorous fishes. Some species of small-sized macroalgae that have not yet been recognized as target species for restoration are known to contribute to the diet and the shelter of juvenile lobsters and turban shells on their nursery grounds, and to abalone and sea urchins as primary foods. Therefore, using small macroalgae would be significant for bed restoration in de-vegetated area. The unintentional restoration of beds of small macroalgae that we observed near Nagasaki city suggests that their reconstruction would be easier and more realistic than restoring beds of large macroalgae. If small macroalgae were included as target species for algal bed construction, it would contribute to more flexible and realistic algal bed restoration.
To promote the growth of seaweed using fertilization is one of the Isoyake recovery techniques. However, the nutrient concentration in sea water which is necessary for the recovery of the seaweed bed was indefinite. Therefore, it was difficult to judge the appropriate provision of the fertilizer. The author has illustrated about the problem on the fertilization as the Isoyake recovery technique. Also, to make the nutrient concentration rise in the coastal region which is under the influence of the advection and diffusion phenomena, a great deal of fertilizer would be necessary. Therefore, the use of fertilizer to a vast area is not practical. In Japan, the small-scale seaweed community to supply withering seaweed beds with the seed is sometimes developed. If nutrient salt is supplied to such small-scale community, the effect may be expected.
Reduction of seaweed beds called Isoyake has become a serious problem in coastal prefectures in Japan. Isoyake Recovery Guideline was published in 2007. This report was reviewed about various effects and problems for grazing control techniques of herbivorous fishes which have been conducted in many places after publishing this guideline. And then, it was discussed about the present status of each element techniques and the problems which it should solve in the future. As a result, as grazing control techniques of herbivorous fish, we found that active "removal" for lowering the density of herbivorous fish is more important than "defense" or "dispersion". As the specific case about active removal, it was shown about gill net catch tests of Kyphosus bigibbus we have carried out in 2014 in Iki, Nagasaki prefecture.
As seven years have passed since the publication of 'Isoyake Taisaku guideline' (Fisheries Agency 2007), it is now under revision. The guideline introduced the adaptive management (AM) and collaboration among fishermen, administrative, researcher and citizen, and strongly recommended flexible soft techniques to restore seaweed beds on deforested areas; component techniques were categorized into 25 groups for convenience and commented with illustration. The guideline has been a core of the subsequent national restoration projects (2007-2009, 2010-2014) and practical supporting programs (2009-2012, 2013-2015), in which many improvements and the subsequent success of restoration were brought. In spite of rapid environmental deterioration and decrease of fishermen, former status (i.e., misunderstanding of deforestation, abuse of hard techniques, short of knowledge for planning and practicing, inadequate support system, utilization of nasty herbivores) has been highly improved. All of these progresses as well as the current status should be included in the revised version, while the useless techniques should be reconsidered. Furthermore, the ways to decide initial target and enlarge and monitor restored beds should be also shown. Finally, importance of base data, man, skill and flow in the restoration should be emphasized to achieve the goal and the AM cycle should be coupled with daily monitoring of seaweed beds.
The various technologies to remove the factors which disturb forming of seaweed beds were mentioned on 'Isoyake Recovery guideline' (Fisheries Agency 2007). The cases and the problems which used artificial substrata to eight elemental technologies shown in the guideline were introduced in this report. After settling these substrata as the measure to restore seaweed beds, periodic monitoring to observe the effect should be implemented. Moreover, after settlement of the artificial substratum, the "softer" measure must be implemented (i.e., removal of sea urchins and herbivorous fishes). In these processes, new products which correspond to latest problems will be developed.