"From Ogasawara to Sumida: The 1,000km Journey of Fish"

Since its opening in 2012, Sumida Aquarium has partnered with Ogasawara Village in Tokyo, undertaking various initiatives with the aim of "letting people know about the nature of the Ogasawara, a World Natural Heritage site."

The "Ogasawara Sea Life" is an exhibit created as part of this project, incorporating advice on underwater scenery and other aspects from various locations in Ogasawara Village.

With approximately 45 species and 450 individual animals on display, a water volume of about 300 tons, and a maximum depth of 6 meters, it is one of the most representative tanks at Sumida Aquarium.

In January 2026, we conducted a collection of fish in Ogasawara Village, located 1,000 km away, to welcome new fish into the Ogasawara Sea Life .

This time, we'll show you what happens from collecting the specimens to welcoming them into your home.

(Author: Matsuda, Exhibition and Animal Care Team)

Towards collecting

The Ogasawara Islands are a group of islands located about 1,000 km south of central Tokyo. They enjoy a warm climate throughout the year, and if you look into the sea, you'll see a deep, rich, and crystal-clear blue color known as "Bonin Blue."

The Ogasawara Sea Life at Sumida Aquarium recreates that underwater landscape.

For example, the shape of the rock formations or the blue color of Bonin Blue.

The animals that live there include the sand tiger shark, which has only been confirmed to inhabit the waters around the Ogasawara in Japan, as well as fish that are commonly found in the waters around the Ogasawara.

These fish were actually animals in the Ogasawara Islands.

While some fish, such as the sand tiger shark and the spotted eagle ray, have lived here since the aquarium opened, the numbers of other species have decreased due to lifespan and other factors.

Therefore, at Sumida Aquarium, approximately once every three years, animal care staff travel to the site and collect specimens in cooperation with the Ogasawara Island Fisheries Cooperative and local fishermen.

This time, we planned and prepared to collect schooling fish, including species such as the yellowtail snapper, sawtooth snapper, red grouper, and four-striped snapper.

Off to Ogasawara!

The only way to get to Chichijima in the Ogasawara is basically by ferry called the "Ogasawara Maru." The journey takes 24 hours.

Having previously traveled to the Ogasawara for other business purposes, I was quite familiar with how to spend my time at sea.

Since there was hardly any cell phone reception, I spent my time relaxing, reading books, watching videos, and enjoying the scenery.

In particular, gazing at the sunset over the vast ocean or the sunrise is a special experience that can only be enjoyed on a cruise.

After sunset, once I had done most of what I wanted to do, I slept so soundly I lost count of how many times, and arrived in the Ogasawara Islands the next morning (lol).

Delicate and busy fishing and collecting

After arriving, we checked into our accommodation, greeted the members of the Ogasawara Island Fisheries Cooperative and confirmed the itinerary, and then started fishing and collecting the next day.

The fish are collected by hand using a fishing rod, carefully catching them one by one.

People sometimes ask me, "Why don't you collect them using nets or by diving?" But collecting them with nets can easily injure the fish's bodies, and it's difficult to collect a large number at once.

On the other hand, fishing allows you to target and collect fish if you know the right spots, resulting in less injury, and it allows you to approach fish in deeper waters or wary fish that cannot be reached by diving.

However, there are also difficulties in collecting by fishing.

When I usually go fishing, my goal is to eat the fish, so I only think about "how to catch them?" But with fishing and collecting, I have to think not only about how to catch them, but also "how to bring them home in a healthy condition so that they can be welcomed as new members of my large aquarium?"

Specifically, first, remove the hook without touching the fish as much as possible to avoid harming it.

Additionally, for fish whose swim bladders or other organs expand due to changes in water depth, a procedure called "air release" is performed, which involves inserting a hypodermic needle to release the air.

Performing these tasks on a rocking ship is far more difficult than you might imagine.

"Bleeding the air" was a task I don't usually do when fishing, so I struggled with it.

Inserting the needle in the wrong place can damage internal organs, so careful and swift work is required.

Furthermore, the fish are sensitive to tidal changes, and if you miss the active time, you'll have a slow period with little to no catch. However, once they start biting, you'll be extremely busy as you need to perform these tasks quickly.

At first, collecting fish was unfamiliar territory, but with guidance from senior staff and fishermen, I managed to gather some fish.

Afterward, a second round of care is performed using water with dissolved medication to prevent illness from developing in the mouth or body wounds.

This time, we spent six days out at sea, departing at 8:30 every morning and returning to port in the evening. The fish we collected each day were placed in a large, round fish tank that we borrowed from the fishing cooperative.

The next day, I started giving them krill and other food, and I was surprised to see that some of them quickly let their guard down and started eating.

Conversely, cautious cats are often reluctant to eat, so you need to observe them carefully while feeding them.

When I actually took care of the fish that I had collected myself, I was reminded even more that I was a member of the animal care staff.

These are the fish we collect. A few days before they depart for the aquarium, we ask them to refrain from eating a little to prevent them from regurgitating or defecating during the long journey (fish can also experience symptoms similar to seasickness), as they prepare for their grand 1000km adventure.

Let's head to the aquarium!

The fish that were collected will travel back together on the "Ogasawara Maru" ship.

On the day of departure, starting early in the morning, with the cooperation of the fisheries cooperative, we carefully move the fish, along with the water they are in, from the holding tanks to live fish transport containers, checking their condition as we go.

Then, the containers were loaded onto the Ogasawara Maru, and we set off with great excitement.

With a warm farewell from the islanders, we'll spend the entire day returning to Sumida Aquarium.

Unlike the trip there, we're carrying the fish we've collected, so we can't afford to be complacent.

Every 1-2 hours, we check the condition of the fish in the container, the water temperature, and whether the aeration is working.

Incidentally, the sea conditions that day were so rough—the kind that only happen a few times a year—that there were rumors that the departure might be moved up.

Checking the containers on a rocking ship, where anything could happen, required constant vigilance.

The ship finally docked at 5pm the following day, two hours behind schedule. We met up with the animal care staff who had been waiting at the port and transferred the fish to live fish trucks and containers.

After that, without a moment's rest, they return to Sumida Aquarium by land, a one-hour journey, and upon arrival, the animal care staff works together to carefully and quickly move the fish.

To ensure they would remain calm in their new environment, we initially placed them in cages to allow them to acclimate to the water before releasing them all at once.

The large aquarium became vibrant once again, and as I looked around, wondering things like, "Where will each fish go?" and "How will they get along with the other fish?", I reflected on this collecting trip in my mind and finished with a sigh of relief.

Ultimately, as originally planned, we were able to welcome approximately 200 new members to the Ogasawara Sea Life, including yellowfin snapper, sawfish, fusiliers, and red grouper.

Finally

Although it was my first time collecting fish by fishing, and I was unfamiliar with the process, with the help of senior staff and fishermen, I managed to collect some fish.

On the other hand, I was constantly thrilled by the vibrant colors of the fish from Ogasawara and the large size of the ones that were caught, and I looked forward to welcoming them into the large aquarium from start to finish.

The fish that we thought were huge when we collected them suddenly seem quite small when we release them into a large aquarium.

This was proof that the children who had been living here for a while had grown up, and it was a moment to feel the history of their growth.

For example, the yellow-striped snapper school consists of older and newer fish, each of varying sizes.

Comparing them side-by-side should make the difference in growth more apparent.

Going forward, we will continue to watch over the newly arrived animals so that they grow to the point where they are indistinguishable from the older ones.