This page is adapted from the original transcript of NHK’s TOMORROW, broadcast on October 12, 2015
“A tsunami is coming! Please evacuate to a higher place!”
That day, the Sanriku Coast was hit by a major tsunami. It not only took many people’s lives and destroyed many buildings, it also had a tremendous affect on the ocean environment.
Four years on, the sea looks calm, but in fact it still bears scars of the disaster.
Around Shizugawa Bay in Miyagi Prefecture, a surprising phenomenon has been occurring to sea urchins.
Large numbers of spongy sea urchins have been developing.
A variety of additional problems have piled up, including the fact that many fishermen who lost their fishing gear have given up fishing.
Those who are now trying to find solutions to these matters are scientists who have long been conducting ocean research.
Since the disaster, they have been using their research results to help the Sanriku fisheries to recover.
“I feel it’s important to use an approach that can only be provided by science.”
(Kiyoshi Tanaka: Associate Professor,
The University of Tokyo)
How can the challenge being faced by scientists change the sea off the Sanriku Coast? Russell Goodall reports on a new form of fishing which has adopted the power of science.
“The fishing industry in Tohoku seems to be recovering from the earthquake, but four years after the disaster it is facing a new crisis. Now, marine scientists have come on the scene to help. Let’s take a look at this new relationship between fishermen and scientists.”
(Russell Goodall: Reporter)
Minamisanriku-cho in Miyagi Prefecture is a prominent fishing port in the Tohoku region.
Russell has heard that an unexpected phenomenon has been occurring to its specialty, sea urchins.
A fisherman shows him the inside of a sea urchin that has just been caught.
“So, usually they’re packed with roe…”
(Tadashi Kudo: Fisherman)
“How’s the taste compared with one full of roe?”
“Totally different. Not good.”
Regular sea urchins have five yellowish gonads inside the shell, generally referred to as ‘roe’.
Sea urchin roe is very popular as a sushi ingredient because of its unique texture and sweetness.
Today, however, many spongy sea urchins are being found in Shizugawa Bay, which do not carry much of the precious roe.
“Hello. May I come in?”
(Yukio Agatsuma: Professor, Tohoku University)
“Nice to meet you. I’m Russell.”
“Nice to meet you, too.”
Professor Yukio Agatsuma at Tohoku University is a leading sea urchin expert who has been studying them for the last 34 years.
He has been going out into Shizugawa Bay to do research since before the disaster.
“We’ve identified a massive outbreak of sea urchins. It’s been a while since I started coming here, but this is the first time I’ve ever experienced this kind of phenomenon.”
Agatsuma carries out his underwater investigations by diving.
This is a perfect point to dive because it provides a habitat for many sea urchins.
Immediately after diving into the sea, a rich forest of seaweed appears. This is Arame kelp. Known as ‘sea oak’ in English, it grows in colonies.
Called a “seaweed bed”, it nurtures tasty sea urchins filled with roe.
However, about five meters offshore, the seaweed bed suddenly disappears. Beyond is a desert on the sea bottom. This is called “rocky-shore denudation”. There are almost no fish or crustaceans.
But a large number of sea urchins can be seen here.
“You can see quite a lot of sea urchins. A considerable number, in fact.”
Why are there so many of them? The team measures their size…
“There are many around the same size. They all hatched in 2011. All those around 43 millimeters hatched in 2011.”
It has been discovered that an explosive outbreak of sea urchins occurred after the disaster.
This is Agatsuma’s idea of the relationship between the disaster and the sea urchin phenomenon. Before the disaster, a variety of marine creatures were living in Shizugawa Bay.
Among them were natural enemies of sea urchins such as starfish and crabs which eat their young. This maintained the sea urchin population at a constant level.
However, most of those creatures disappeared as a result of the tsunami. In that kind of environment, the few sea urchins that survived produced a large number of eggs.
In fact one sea urchin of the type found in this bay produces up to 20 million eggs at one time. Because the urchins’ predators had gone, they could develop safely.
As they grew, the large number of sea urchins started eating seaweed, their favorite food.
Their appetite was so strong that they rapidly consumed the whole seaweed bed.
“Locusts sometimes appear in huge numbers on land and eat up all the vegetation. I think what’s happening here is a similar phenomenon.”
On the desert-like sea bottom where all the seaweed has been consumed, sea urchins have managed to survive in huge numbers because their life force is so strong. In fact, they can survive for around six months without consuming anything. In areas where the seaweed bed remains, sea urchins of good quality filled with roe can still be caught. However, it’s just a matter of time before those seaweed beds will disappear.
What on earth can be done to solve this issue?
The local fishermen’s association has been trying to reduce the number of unsalable sea urchins without roe.
One idea was to recycle them by removing them from the sea bottom and selling them as fertilizer, but that was not cost-effective.
Then Agatsuma came up with an unexpected suggestion… It was to try the “catch and culture” method. The idea is to provide nutrient-rich kelp to the spongy sea urchins in wire cages, hang them in the sea and let the urchins grow.
This was a counter-intuitive idea to cultivate the urchins properly instead of getting rid of the unsalable urchins.
This technique was developed in Hokkaido 25 years ago. Agatsuma was a member of the research team and he thought he could apply it to Shizugawa Bay.
Tadashi Kudo, a local fisherman, is helping Agatsuma. Wanting to revive the sea urchins in Shizugawa Bay, Kudo, along with his young colleagues, started supporting Agatsuma.
“It’s an excellent cycle for turning the troublemakers into at least some cash. Otherwise, you feel rather sorry for the sea urchins, who appear to have become nothing but a burden to us. Turning them into fertilizer? Rather than doing that, I think the important thing is to think about eating them.”
(Tadashi Kudo: Local fisherman)
Agatsuma and Kudo have been working hard on practical implementation of the catching and culturing of the sea urchins. The first focus is the feed, which will be the key to the sea urchin revival.
“This kelp is the precious feed. It naturally attaches itself to ropes, so this is a kind of natural farming. Sea urchins love it and it allows them to produce good roe.”
They are using kelp attached to fishing gear that would normally be thrown back into the sea.
“When the kelp gets stuck on fishing gear, we have to get rid of it completely. Now it can be recycled instead of discarding it.”
To put the sea urchins to practical use, they try to reduce costs as much as possible.
“You can, of course, spend money or use subsidies to protect the seaweed beds, or consider a counterplan for rocky-shore denudation. But the important thing for us is that we rely on fishing to make a living, so if we can use a method that earns us some money, I think everyone’s life will improve.”
Kudo makes suggestions to Agatsuma to improve the technique based on the knowhow that only experienced fishermen possess.
“If the cages keep moving because of wave action, the sea urchins also move. They can’t feed and roll to death. To avoid that, we have to adjust the number of buoys so that the cages won’t be too buoyant. We have to make sure they are not affected by the waves.”
“It’s important to hear the ideas of culturists, like ‘Wouldn’t it work better if we did it this way?’ They have experience of many things we don’t know about.”
During the three months of “catch and culture”, the sea urchins are fed kelp once every 10 days without fail. By doing this, the sea urchins are expected to become filled with roe…
So, what are they like after “catch and culture”?
“As we expected, there’s roe.”
“It’s full of roe.
“Yes, it looks fine.”
“How about the size?”
“It’s small, but it’s filled with the right amount of roe for its size.”
“For its size, it’s filled with…”
“Yes, a lot of roe.”
“Yes. It tastes sweet. Sweet!”
“It’s salty, but the after-taste is sweet.”
“I might be turning into a sea urchin fan! Hmm, I can taste a umami.”
Agatsuma continued experimental “catch and culture” for more than a year.
He held a briefing for the fishermen for the first time this summer. He even had a scientific analysis of the taste of the sea urchins he had cultured.
“The red items show the amino acid that indicates sweetness, and the blue items show the amino acid that indicates bitterness.”
The analysis shows that the constituents including serine and alanine that determine the tastiness of sea urchins have doubled compared with before “catch and culture” was launched. They are now the same level as those in natural sea urchins. There are signs that good business could return to the sea urchin fishermen.
“I think it’s good. Their efforts are proving to be very useful to us, the fishermen. We never had such a thing before the tsunami. If we can help in some way, like going out on our boats or something, that’s possible. We can do that!”
“When they’re cropped, how much can they be sold for? That’s the biggest issue. We want to develop sea urchins that will sell for a reasonable price. I’m going to study further with that purpose in mind.”
Around Shizugawa Bay, a scientist and the fishermen have started working hand in hand. And a new attempt to revive the local fishing industry is about to begin.
“I saw a really interesting example of scientists working together with the fishermen, and it feels like there’s a new potential here for the fishing industry that is unique to this region.”
Another attempt to revive fisheries with the cooperation of a scientist is underway. Otsuchi-cho is a coastal town in Iwate Prefecture.
A research institute of the University of Tokyo is located here on the coast. Russell pays a visit, hoping to meet a scientist that he has heard is working here…
“These must be traces of the tsunami.”
The room is empty and still shows evidence of the 2011 disaster.
“Remains of the damage can be seen here, too.”
This is how the second floor looks now. Four years ago, this building was hit by a 12-meter-high tsunami and was flooded up to the 2nd floor.
Today, the researchers’ worksite is on the third floor, which suffered less damage.
Russell finally gets to meet the scientist he has been hoping to talk to.
“Hello. I’m Russell.”
“Nice to meet you. I’m Tanaka.”
(Kiyoshi Tanaka: Assosiate Professor,
The University of Tokyo)
Kiyoshi Tanaka is an associate professor at the University of Tokyo.
He specializes in physical oceanography, which studies the movements of ocean currents.
Immediately after the disaster, Tanaka voluntarily came here to Otsuchi Bay wanting to help the fisheries. And he started an initiative for the sake of the local seafood culturists.
“There’s a nursery over there, but what is that yellow device?”
“It’s a water temperature gauge that our university team set up to monitor the water temperature.”
“Ah, a temperature gauge?”
“Yes. The gauge hangs down from the buoy.”
The water temperature gauge can take the temperature every five meters, down to a depth of 25 meters deep.
Some culturists particularly need this data.
They are the culturists of scallops, a specialty of Otsuchi-cho. Scallops feature a thick adductor ligament that is full of umami.
Scallops are popular around the world, and in Japan they are used not only as sushi ingredients but often for home cooking as well.
They are cultured by stringing up small scallops and hanging them in the sea for about one year. That is all.
This looks simple at a glance, but in fact there is one very tough problem. Scallops are very sensitive to changes in the seawater temperature.
The optimal temperature for scallop growth is 17℃ and below.
If the temperature rises too high, they stop growing and sometimes die.
Up to now, the scallop culturists could only guess the temperature of the seawater based on experience and intuition accumulated over many generations.
The temperature data has always been approximate. The accurate data provided by Tanaka is really helping scallop culture.
“Our research results provide part of the knowledge that could previously only be obtained by experience accumulated over the years. It’s useful data that is easy to understand even without long-term experience.”
However, scallop culture in Otsuchi-cho is now standing at a crossroads. The scallop catch which fell after the disaster has nowhere near recovered.
Before the disaster, the total catch amounted to 244 tons per year. Today, four years on, it has only recovered to 60% of that figure. The reason behind this is the drastic decrease in the number of scallop culturists. There were 53 before the disaster, but only about one quarter of them remain today.
“Some culturists have gradually stopped working because of their age. Some fishermen lost their lives in the disaster. And nearly all the fishing boats were wrecked by the tsunami.”
(Eiki Hirano: President, Shin-Otsuchi Fishermen’s Cooperative Association)
The town was already suffering the serious issue of a lack of successors because of aging, and the disaster provided an additional blow. The entry of new culturists is essential to revive the local scallop culture.
“We’re hoping there’ll be an increase in the number of people who work for aquaculture, a new form of fishery. We’d be very grateful if that happens. But I think it may be difficult.”
Against that background, Tanaka’s data is producing results.
Two men arrive at the University of Tokyo Institute.Seiju Abe and Yasuhiro Kurosawa are both newcomers who only began scallop culture after the disaster. They have started using Tanaka’s data. They are here today to find out more about the temperature changes in Otsuchi Bay.
“Hello. Nice to meet you.”
It is the first time that Tanaka has been visited by scallop culturists. They do not waste time on greetings but start asking questions immediately about use of the temperature data.
“We had no idea until last year. We were just hanging the scallops at random, thinking they would grow as long as we hung them. But they didn’t grow at all. ‘What’s wrong?’ we thought. When we heard that the sea temperature this year was high, we suddenly realized that the temperature was very important. And we started wondering how we could measure it.”
“Actually, the temperatures at two meters and at 10 meters are different. What you’re looking at now is one meter and five meters. They’re different.”
“This is exactly what we want to know. So if this data is fully available, it will really help us.”
The two men listen intently to Tanaka’s words because they set up in this business with a fervent desire to succeed despite the risks involved.
“We tell each other that our failures can also be useful experience. However, we can’t fail because we’re already grown-ups. Suppose we failed the first year, then we could do it the same way the second year, and fail again. But we couldn’t go on like that for the third and fourth years, because we’re no longer young, and there’s a limit to how much we can force ourselves!”
For the sake of newcomers who jump into the new world of scallop culture without much knowhow, Tanaka has figured out a good way to disclose the data on water temperature.
He now distributes it real time via the Internet. It can be accessed by mobile phones so that the culturists can grasp the seawater temperature at any time.
“Please come this way.”
“Oh, this is the data. And this is photo of the buoy.”
Using your PC or smart phone, it is possible to get more detailed information, such as graphs showing temperature changes.
Newcomer Abe checks out the temperature every day.
“I really need as much of this kind of information as possible.”
Abe says the water temperature data is essential for his work. Referring to Tanaka’s data, he checks out the best temperature for the growth of scallops and uses the information to improve his new culture business.
“I’m also experimenting personally on how many of them survive at what temperature. All our seniors have knowhow, but I’m just a beginner, so I have to experience everything firsthand.”
“We don’t want to destroy traditional scallop culture.” That is how these newcomers are thinking. And Tanaka’s data is providing them with a supportive push.
“Without the data, I’d probably have one failure after another. In a way, it’s providing me with hints. With this information, I feel more secure.”
“Ah, it makes you feel secure?”
“The rest is up to me. That’s what I think.”
Tanaka is now taking his research one step further. Using a special measuring instrument, he is investigating the detailed speed and direction of the water currents that flow into Otsuchi Bay.
When the obtained data is analyzed in detail, it will help to predict future seawater temperature changes just like a weather forecast, and this will surely help to increase the efficiency of the scallop culture.
Tanaka started his research in Otsuchi Bay. He is now thinking of spreading the results of his research to the whole Tohoku region in the near future.
“I feel that the usefulness of my physical oceanography is being tested right now. So for that reason I’m working very earnestly on that!”
“Since the 2011 disaster, new methods of fishery have been suggested through the teamwork of fishermen and scientists. These could become breakthroughs in the Japanese fishing industry. Let’s hope that their combined knowledge brings about a new future.”