A dome-shaped shell and a sharp tail. The horseshoe crab is a representative creature of Kasaoka City, Okayama.
Horseshoe crabs require beautiful waters and tidal flats, and due to the advancements in development in modern times, their numbers have rapidly decreased and they have been designated as a threatened species.
We do not want to let the horseshoe crab go extinct. We want to continue walking together with the horseshoe crab.
People who love horseshoe crabs have risen up to increase their population.
The target participants are those who have a heart that loves horseshoe crabs.
We will report on the rare nationwide event of releasing horseshoe crab larvae into the tidal flats.
The information provided is based on data from the article published in August 2024. Please note that it may differ from current information.
What is a horseshoe crab?
The horseshoe crab is one of the organisms called a "living fossil," as its appearance has hardly changed since the time of the dinosaurs.
It inhabits tidal flats and lives by eating marine worms and shellfish.
Once, it is said that there were 100,000 horseshoe crabs in Kasaoka City. Due to land reclamation and water pollution from development, the ecosystem of the tidal flats, which are their breeding grounds, has collapsed, and they have been disliked by fishermen because they break nets with their sharp claws. As a result, the number of horseshoe crabs began to decrease rapidly around 1985.
Currently, horseshoe crabs are designated as a Class I threatened species on the Red List of the Ministry of the Environment and Okayama Prefecture, and they are considered to be at a high risk of extinction in the near future.
What is the release of horseshoe crab larvae?
To address the declining numbers of horseshoe crabs, Kasaoka City has taken action. In 1990, the Kasaoka Municipal Horseshoe Crab Museum was established for the purpose of protecting and breeding horseshoe crabs. The Kasaoka Municipal Horseshoe Crab Museum is the only museum in the world themed around horseshoe crabs.
Since July 1995, artificial breeding has started at the museum to increase the number of horseshoe crabs. Activities to hatch eggs and release larvae in July of the following year also began.
It takes one year from spawning to release for horseshoe crabs. We want the local people to know about the horseshoe crab, which is also a symbol of Kasaoka City. We want to protect the beautiful tidal flats that nurture horseshoe crabs. The release of larvae is conducted to widely promote awareness of horseshoe crabs.
In 2022, there were no eggs laid because we could not secure parent horseshoe crabs, and the release in 2023 did not take place.
The year 2024 will mark the first release of larvae in two years.
When the announcement for participant recruitment was made, there was an overwhelming response, and the 100 available spots were filled in just five days.
It seems that many people were eagerly awaiting the release of horseshoe crab larvae. Some even traveled all the way from Tokyo to participate. This indicates that there was significant attention on this rare event nationwide.
Participants were advised to bring rubber boots, clothes that could get dirty, and a heart that loves horseshoe crabs.
People who love horseshoe crabs from all over the country gathered in Kasaoka City, Okayama.
Research at the Kasaoka Municipal Horseshoe Crab Museum has shown that there are differences in size and shape between horseshoe crabs that grow in tidal flats and those that are artificially bred.
The breeding environment of horseshoe crabs remains largely unexplained. To increase the wild horseshoe crab population, the Kasaoka Municipal Horseshoe Crab Museum avoids long-term breeding and conducts early release of larvae.
The horseshoe crabs to be released in 2024 are those that hatched in September 2023. The baby horseshoe crabs have been carefully raised in the breeding room for about 10 months.
The attempt to increase the rare horseshoe crab and connect it to the future is the release of horseshoe crab larvae.
The process of releasing horseshoe crab larvae
Participants first complete registration in front of the Kasaoka Municipal Horseshoe Crab Museum. Behind the registration area, there are buckets lined up containing baby horseshoe crabs. The children’s eyes sparkled at the sight of the small horseshoe crabs.
As they floated in the water, exclamations of "So small!" and "So cute!" arose. To prevent the horseshoe crabs from weakening, touching them is strictly prohibited.
Each bucket contains about three horseshoe crabs, each about 1 cm long.
These are second-stage larvae of horseshoe crabs that have molted once since birth and third-stage larvae that have molted twice. Horseshoe crabs increase in size by about 1.3 times with each molt. Even horseshoe crabs born in the same month can vary in size depending on the number of molts.
Participants who received the buckets from the museum staff gazed intently at the horseshoe crabs. Here too, to avoid weakening the horseshoe crabs, they move carefully without shaking the buckets.
The participants slowly walk the five-minute path to the nearby tidal flats without shaking the buckets.
They pass through the woods and descend the stairs to arrive at the tidal flats.
Participants walk slowly along the rocky coast to avoid the tidal flats.
At the call of the museum staff, they simultaneously release the contents of the buckets into the tidal flats.
If you try to gently pour only the horseshoe crabs, sometimes they remain in the bucket. To avoid putting unnecessary strain on the horseshoe crabs, they pour the water and horseshoe crabs into the tidal flats vigorously.
Warm voices from participants were directed at the horseshoe crabs: "Come back big!"
Some horseshoe crabs were unable to land properly and ended up upside down. Participants watched anxiously as they observed the horseshoe crabs.
The horseshoe crabs released into the tidal flats quickly burrowed into the mud after adjusting their positions.
After seeing off the horseshoe crabs, they walk back along the rocky coast to avoid stepping on the creatures in the tidal flats.
They return the buckets, and the release of horseshoe crab larvae concludes.
Voices of participants in the larvae release
We spoke with the members of the Okayama Prefectural Kasaoka Commercial High School Kasa SHOP Research Group who participated in the release of juvenile horseshoe crabs.
“Horseshoe crabs are not often seen in Kasaoka City. Especially, there are few opportunities to interact with small horseshoe crabs, so I thought this was a very valuable event. Since there were many small children among the participants, I believe awareness of environmental conservation can be fostered between parents and children.”
In schools within Kasaoka City, it seems that investigations and larval breeding of horseshoe crabs are conducted during integrated learning time. Even students who are usually involved with horseshoe crabs were very interested in this rare event of release.
“This was my first time participating in the release of horseshoe crab larvae. The tiny horseshoe crabs are so cute, and I thought it was amazing that they grow to such a large size from this small stage.”
“I was able to have fun conversations with other participants, and I think the larvae release is a good activity that allows communication through horseshoe crabs.”
I was also surprised that horseshoe crabs, which can grow over 50 cm as adults, are only about 1 cm in their first year.
We also asked the director of the Kasaoka Municipal Horseshoe Crab Museum, Morinobu Satoshi, for his thoughts on this release of horseshoe crab larvae.
“I am very happy to be able to do the release of horseshoe crab larvae with everyone after it could not be done last year (2023). Especially, seeing the children’s faces light up with joy saying that horseshoe crabs are cute makes me feel that it was worth doing.”
“This year, we were able to secure parent horseshoe crabs and confirm spawning. If all goes well, we should be able to hold the larvae release again next year.”
Sowing seeds for the future with the release of horseshoe crab larvae
The tidal flats were cleaned by local residents before the larvae release. However, many pieces of trash were seen again during the release.
It takes over 10 years for horseshoe crabs to grow and be able to spawn. Until then, it may be our mission to create a beautiful environment where horseshoe crabs can grow safely.
The Kasaoka Municipal Horseshoe Crab Museum is holding a special exhibition titled "True Horseshoe Crab" from July 20, 2024 (Saturday) to September 29, 2024 (Sunday), exploring the secrets of horseshoe crabs.
You can observe the mysteries of horseshoe crabs, from the siblings of the released horseshoe crabs to their fascinating ecology. While direct contact with horseshoe crabs was not possible during the larvae release, here you can also touch taxidermy specimens.
How about immersing yourself in the unknown world of horseshoe crabs this summer of 2024?
Release of Horseshoe Crab Larvae Information
| Name | Release of Horseshoe Crab Larvae |
|---|---|
| Date | July 20, 2024 (Saturday) 3:00 PM - 3:30 PM |
| Location | 1946-2 Yokoshima, Kasaoka City, Okayama Prefecture |
| Participation Fee (including tax) | Free participation Pre-registration required |
| Homepage | Kasaoka Municipal Horseshoe Crab Museum |
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