Fukuoka Institute of Technology transports sand accumulated in Kumamoto Prefecture's Midorikawa Dam to cover tidal flats, leading to an increase in the population of clams and other shellfish!
Hello, I am Tasuki.
I don't remember it myself, but my maternal uncle apparently took me and my family clam digging.
Covered in mud, I tried my best to collect shells as a child. I probably haven't been clam digging since I became an adult, so that might have been the only time.
Nowadays, for various reasons, shellfish catches are poor. The Ariake Sea, which is adjacent to Fukuoka Prefecture where I live, is one such place.
The catch in the Ariake Sea, which used to be a treasure trove of bivalves like hamaguri clams and asari clams, has decreased. One of the causes feared is that the environment has deteriorated because the tidal flats, which are their habitat, have become covered in mud.
A research group led by Professor Akira Tai of the Fukuoka Institute of Technology is working on a "two birds with one stone" project that is useful for disaster prevention in addition to restoring the habitat for hamaguri and asari clams.
The mud-like state of the Ariake Sea's tidal flats is partly due to a decrease in the supply of sand and pebbles from rivers.They collected sand accumulated on the lake bed from the Midorikawa Dam, located upstream of the Midorikawa River that flows into the Ariake Sea in Misato Town, Kumamoto Prefecture. They moved it to the tidal flats off the coast of Kumamoto City, and are focusing their analysis on whether the habitat for hamaguri and asari clams will recover.
This time, I will share a realization plan for a dream where Fukuoka Institute of Technology's research results might make it possible to harvest hamaguri clams and asari clams in the future.
What is the project, supported by Kumamoto Prefecture, that is entrusted with the fate of not only hamaguri and asari clams but also farmed seaweed?
Professor Tai expressed a growing sense of crisis, stating, "Sediment that flows down from the mountains upstream and continues to accumulate in the dam can reduce water storage capacity and potentially increase the risk of flooding."
Through this research progress, there are high hopes for both a means of disaster prevention and the reconstruction of the hamaguri and asari clam fisheries. In March 2024, 200 tons of pebbles and sand accumulated in the Midorikawa Dam were moved to the center of the tidal flats spreading at the river mouth. Kumamoto Prefecture supported the transport of the sand and pebbles as part of commissioned research from the prefecture. The Prefectural University is also participating in the research.
They covered the tidal flats in circular areas with diameters of 5 to 20 meters, classified into 5 locations, and confirmed the difference in effects based on scale.After 4 months had passed, it was confirmed that the population of asari clams had increased.
The growth of the asari clams was also good, and there were areas where they were about twice as long compared to other locations.The sand covering was found to be effective even on a small scale.
For the autumn of 2025, it was assumed that there would be an impact from the heavy rains in August. It was suggested that large amounts of driftwood and mud had flowed in and it was becoming muddy again, but Professor Tai was also pleased with the unexpected effect, saying, "Because it is raised higher than the surroundings due to the sand covering, it seems it was difficult for it to be covered in mud." The growth of the asari clams is going well. He is contemplating continuing the research in the near future and linking it to the revival of shellfish.
There is a nationwide trend of declining harvests of hamaguri and asari clams. With the increase in weirs and dams, and the progress of bank protection work, the flow of sand from rivers has weakened or been stopped, and the decline of sandy beaches is also being observed across Japan.
Professor Tai entrusts his hopes, saying, "If hamaguri and asari clams revive, the phytoplankton they feed on will be consumed, reducing red tides, which might also have a positive impact on farmed seaweed."
Reference site
I want to eat them again
I have liked shellfish since I was a child. When I went to my maternal grandmother's house, sometimes turban shells were served with sashimi, and I often enjoyed eating them.
My uncle also seemed to like turban shells, and if I ate them, there wouldn't be any for him, so if I was slow to notice, my uncle would eat them first, and it was a tug-of-war every time.
I also love clams, and in the past, I used to eat them in miso soup or sautéed in butter. I really loved them.
However, a few years ago, a certain issue arose regarding clams, Japanese-produced ones stopped being available on the market, and I became unable to eat clams.
Clams that I love, but now I cannot eat them. How sad...
If the research results from the Fukuoka Institute of Technology progress, will I be able to eat Japanese clams again?
I hope that one day I will be able to eat clams again. Yes, that is my wish.
