One Habitat, Designated by the State in 1961
Okichimozuku Habitat in the Toguro River (土黒川のオキチモズク発生地, Hijikurogawa no Okichimozuku Hasseichi) lies in Unzen City, Nagasaki Prefecture, and was designated by the state on 1 May 1961. Its category is that of natural monuments.
The field for a managing body stands empty.
The Agency records that okichimozuku is a freshwater red alga found only in Japan, that the places where it grows are very few, and that this site is valuable as one of them. The commentary runs to those two sentences alone.
Neither a Building Nor a Shape of Ground
What is protected here is a living thing that grows in the place.
The designation names a habitat: the place where the organism arises.
At Futatsuzuka Kofun, what was designated was a mound and its chambers, shaped in earth and stone. With a building, posts and roof are the matter.
Here it is a stretch of river, designated for the alga that grows in it.
Okichimozuku is a freshwater red alga. Most red algae grow in the sea; this one grows in rivers.
The record adds that it is found only in Japan.
Three Habitats of One Organism, Designated Separately
One species has brought several places under designation.
A habitat at Yoshihisa in Toon City, Ehime Prefecture, was designated on 26 June 1944, recorded as the first place in Japan where the alga was found and as the northern limit of its range.
A habitat on the Shizugawa in Minamioguni, Aso District, Kumamoto Prefecture, was designated on 1 July 1959.
This site followed on 1 May 1961, the third of them: 3 designations across 17 years.
With buildings, the halls of one temple go on the register together. The 7 at Kannonshoji share a day, as do the 6 at Shotokukan.
Here places where one organism grows are designated separately, in prefectures far apart. What gathers them is of another kind.
Valued Because the Places Are So Few
The reason given turns on scarcity.
The Agency closes that the places where it grows are very few, and that this site is valuable as one of them.
Not the making of a thing nor the craft in it, but how few there are, carries the assessment.
The former Takahashi main house was called one of the surviving examples of farmhouse building in its district: one among what remains.
At Otonashi Shrine, the assessment was qualified by region, in an area where cultural properties are few.
Here it is the places of growth themselves that are very few. As a way of stating value this is the seventeenth met.
Visiting
The site lies in Unzen City, Nagasaki Prefecture. The field for a managing body stands empty in the record.
Of the Kumamoto habitat, the record says the alga grows attached to stones on the river bed.
For this site nothing is said of where or when it grows. The record runs to two sentences.
The Ehime habitat is where the alga was first found and marks the northern limit of its range. This site lies in Kyushu, to the south.
This is a living thing in a river, and whether and how it may be seen follows the arrangements of the local authority. Check before travelling.
Q&A
- When was the habitat designated?
- On 1 May 1961, by the state. Its category is that of natural monuments.
- What is okichimozuku?
- A freshwater red alga found only in Japan. Most red algae grow in the sea; this one grows in rivers.
- Why was it designated?
- The Agency closes that the places where it grows are very few, and that this site is valuable as one of them.
- Are there other habitats?
- Yes. One in Ehime Prefecture was designated in 1944 and one in Kumamoto Prefecture in 1959. This is the third.
- Where does it grow?
- Of the Kumamoto habitat the record says it grows attached to stones on the river bed. For this site nothing of the kind is recorded.
Basic Information
| Name | Okichimozuku Habitat in the Toguro River (土黒川のオキチモズク発生地, Hijikurogawa no Okichimozuku Hasseichi) |
|---|---|
| Location | Unzen City, Nagasaki Prefecture |
| Designation | Natural monument; designated as the habitat of an organism rather than as a building or a work of art |
| Year Designated | 1961 (1 May), designated |
| Quantity | 1 habitat; okichimozuku is a freshwater red alga |
| Dimensions | No measurements are recorded. The commentary runs to two sentences: that okichimozuku is a freshwater red alga found only in Japan, that the places where it grows are very few, and that this site is valuable as one of them |
| Owner | The field for a managing body stands empty in the record |
| Public Access | A living thing in a river; viewing follows the arrangements of the local authority |
References
- Cultural Heritage Online: the habitat in the Toguro River
- https://bunka.nii.ac.jp/heritages/detail/202966
- Cultural Heritage Online: the habitat on the Shizugawa
- https://bunka.nii.ac.jp/heritages/detail/139684
- Cultural Heritage Online: the habitat in Ehime Prefecture
- https://bunka.nii.ac.jp/heritages/detail/139434
- Agency for Cultural Affairs, National Cultural Properties Database
- https://kunishitei.bunka.go.jp/
Last verified: 2026.09.16