Codend opening/closing MOHT （COC-MOHT） was developed by installing the codend frame with
five codend nets on the base of the MOHT （Matuda-Oozeki-Hu Trawl）. To investigate the diel vertical
migration and net avoidance of lantern fish, three oblique tows from 250 m and 450 m depths to the
surface and one horizontal tow at different towing speed of 4, 3 and 2 knots for each codend were
conducted using COC-MOHT in Sagami Bay on 16 October 2014 by training vessel Umitaka-Maru
belonging to Tokyo University of Marine Science and Technology. Samples were sorted into
Myctophidae, Cephalopoda, Euphausiidae, Sergestidae, and other fishes. Lantern fish was measured in
standard body length and classified into 5mm intervals. It was found from the result of three oblique
tows that lantern fish distributed in the two major depth zones: shallower than 150 m and deeper than
250 m at daytime, depending on the myctophid species. And after sunset, lantern fish migrated from the
deeper zone to the shallower zone. In the horizontal tow, Diaphius spp. with SL › 30 mm were less
caught at lower towing speed. A possible explanation is that net avoidance of the larger fish occurred
because they can generally swim faster.
We tracked ten threeline grunts （Parapristipoma trilineatum）, using biotelemetry for 179 days
around an artificial mound reef off the coast of Akune, Kagoshima Prefecture, Japan. Three resided
around the artificial mound reef for about six months. Their swimming depth changed diurnally, being
shallower during the day time and deeper the night time. However, during spawning periods, the cycle
reversed: they swam deeper during the day time and shallower （30 - 35 meters deep） the night time.
This appears to be a spawning behavior characteristic of threeline grunts.
In the present study, we developed an estimation model for the production values of kelp products
with the aim of revitalizing the kelp-farming business. Production values of two primary products, Long
and Round, are calculated from expected unit price and the number of kelp units to be harvested.
Production values of three secondary products, Offcut, Edge, and Root, are calculated from estimated
values of the two primary products.
In terms of product quality, grade evaluation system has been applied to every primary product in
Fukushima-cho, Hokkaido. This model has a matrix that represents the occurrence rate of each grade.
The matrix values are based on the analysis of hundreds of samples. Expected mean unit price and
coefficients of variation can be calculated from production value of each grade in the past 8 years.
The production simulation based on the proposed model will optimize expenditure and increase the
profits of kelp-farming fishermen.
Conservation and restoration of seaweed beds and tidal flats are becoming important activities in the
coastal management of Japan not only because seaweed beds and tidal flats have seriously decreased and
deteriorated historically but also ecosystem-based management and conservation of biodiversity are
gaining ground recently. Accordingly, legal and administrative systems which support conservation and
restoration of these are gradually prepared. Fisheries Agency of Japan publicized “Future vision of
seaweed beds and tidal flats” in 2016. In order to realize the vision, varieties of activities such as intersectoral
cooperation and collaboration of various stakeholders are necessary. In this article, established
legal and administrative system to assist the conservation are introduced as well as case studies of local
activities to restore the damaged seaweed beds and tidal flats. Finally, desirable conservation of seaweed
beds and tidal flats in future are discussed from the view point of integrated and holistic coastal
The sudden decrease in “seaweed beds and tidal flats“ are serious problems in the coastal areas of
Japan. Fisheries Agency is promoting conservation and restoration of “seaweed beds and tidal flats” to
restore fisheries resources. However, there are many problems in expansion of the area and recovery of
the function. And therefore, Fisheries Agency publicized a new policy, “Future vision of seaweed beds
and tidal flats“ in 2016 for the promotion efficient conservation and restoration of “seaweed beds and tidal
flats“. In this article, the current status and issues of conservation and restoration of “seaweed beds and
tidal flats“ in Japan had been summarized, in addition, the overview of several visions and specific
examples had been introduced.
We studied the factors affecting decline of seaweed beds by unmanned aerial vehicle （ UAV） survey,
diving-survey and past findings along south-west coast of Hokkaido, Japan. It was considered that the
feeding damage by sea urchin, the lack of seaweed seed such as zoospore, germ and the shortage of
stable substrate were main factors of decline of seaweed beds, in addition to the increase in water
temperature and the lack of nutrient. In order to restore the seaweed beds, it is necessary to act not only
artificial formation of seaweed beds with stones and concrete blocks but also density management of sea
urchin, and transplantation of mother seaweed and seaweed seed. In addition, it is very important to
reduce the management cost of seaweed beds, define the enforcement standard and update the
techniques against environmental changes.
The hearing survey was conducted to clarify the present status and the changes in the last 10 years
on seaweed beds and fishery organisms related to seaweed on the coast of Japan Sea, Aomori Prefecture,
Japan. We interviewed the 29 fishermen at 21 coastal areas about the extents of sargassum beds,
ISOYAKE caused by feeding of sea urchins, and the resources of sea urchin, top shell, abalone, edible
algae, rockfish and sailfin sandfish in April and May 2017.
As the result, it became clear that the extents of the ISOYAKE and the amount of sea urchin
Mesocentrotus nudus remarkably decreased, while the extents of sargassum beds turned to increase on
the Japan Sea coast of Aomori Prefecture. The amount of red/black rock fish which lives in sargassum
beds, and of sailfin sandfish that spawn on sargassum also increased. Top shell and abalone which feed on
seaweed increased especially on the southern coast. On the survey coast from 2010 to 2014, the highest
water temperature exceeded 26℃ as the lethal temperature of sea urchin, and in the same period its fish
catch declined. The feeding behavior of Mesocentrotus nudus prevents the growth of seaweeds and is
known as the main sustained factor of ISOYAKE along the coast of Aomori Prefecture.
From these results, it was considered that the high seawater temperature in the summer that
continued for several years would have contributed to the reduction of ISOYAKE and the expansion of
the sargassum beds.
We report a concept for “Seaweed Bed and Tidal Flat Vision” of Fukuoka prefecture. Fukuoka
prefecture is formulating the concept in response to a new “long-term plan for development of fishing
ports and fishing grounds” created by the Japanese government. Because three water areas in our
prefecture, the Chikuzen Sea, the Ariake Sea, and the Buzen Sea have own characteristics, the visions for
each water areas are under consideration.
We introduce the visions for the Chikuzen Sea and the Ariake Sea in this paper. In the Chikuzen Sea
facing open water area, the substrates such as rocks and concrete blocks are installed for creation of
seaweed beds. In addition, we perform transplantation of mature seaweeds and eradication of algae-eating
pests. On the other side, tidal flat is well developed in the Ariake Sea. We install various substrates to
improve sea beds environments for creation of rich sandy ecosystem. We also set about preparing
conservation and management of clam stocks in the Ariake Sea.
In addition to hardware elements for development of a new fishing grounds, we need software
elements such as management of fishing grounds using monitoring by local government, activities for the
conservation and the management by fishers. It is important of the conservation and the creation of
seaweed beds and tidal flat that combine the software elements and the hardware elements.
The fishery is the main industry in Nagasaki Prefecture. Therefore, the various policies are implemented
because of the promotion of the fisheries industry. Seaweed beds are very important as the field of the
inhabiting by the various marine organisms. However, because the decrease of seaweed beds continues in
recent years, the effect to the fisheries industry is worried about. Therefore, the restoration vision of
seaweed beds was worked out in 2016 by such a background. This vision was introduced in this paper.