The secret of the unknown "sea of Kansai" March 3 at 31:11
Kansai Airport in Osaka Bay.
As the gateway to the skies of Kansai, it is a huge artificial island used by about 3000 million people a year.
When I dived into the sea around it, I found a surprising world full of life, from small fish that nurture life without anyone knowing it to schools of "giant monster fish" that are over 1 meter long.
We approached the richness of the "sea of Kansai", which does not seem to be the sea of a big city, and the secret of its formation.
(Wakayama Broadcasting Station Cameraman Yusuke Ogishima, Osaka Broadcasting Station Director Akari Kobayashi)
The sea around Kansai Airport where fishing is prohibited
Kansai Airport is located 5 kilometers off the coast of Osaka Bay.
The total area is a huge artificial island of 1055 hectares.
Fishing is prohibited in the waters around the airport so as not to interfere with the operation of airplanes, and is heavily guarded for security reasons.
What kind of world is there in this sea? We obtained special permission to photograph the creatures, mainly around the seawall.
Spreading "Seaweed Forest"
In the midst of the sunlight, a seaweed forest or seaweed bed spread out in a shallow area at a depth of about 3 meters.
More than 100 species of seaweed, including hondawara and wakame seaweed, cover the seawall.
The total area of seaweed beds is about 50 hectares. It will be about the size of 13 Koshien Stadiums.
Seaweed beds are also called "cradles of life" because they serve as spawning places and hideouts for fish.
I was able to meet various creatures here.
Diverse creatures gathering, including extra-large abalone
In the bushes, there were children of hagfish about 3 cm long.
In the sea, it is no wonder that you can be attacked by big fish at any time.
Seaweed beds are a "hideout" for hagfish children where they can protect themselves from enemies.
Hagfish children born in early spring spend time in seaweed beds and then move to deeper habitats as they grow.
We also saw many sazae and abalone, which are familiar to us.
These shellfish move crawling on the seabed and grow while feeding on seaweed.
Since it is a no-fishing zone, it will not go to the market, but we also saw extra-large abalone over 15 cm.
A flock of Narutobi rays circumnavigating the coast of the Japan in search of shellfish, which is their favorite food, swam to spread their cloaks.
It has been sighted in Osaka Bay for about 10 years.
If you come to this sea, you will find food.
For living creatures, Osaka Bay is truly a paradise.
Osaka Bay was decreasing due to water pollution
Why is there such a rich ocean around Kansai Airport?
One of the reasons behind this was the environmental problems that Osaka Bay faced in the past.
The Osaka Expo was held in the 1970s. Japan was in a period of high economic growth, and industrial development and land reclamation were progressing in the Kansai region.
On the other hand, the natural environment of the sea has gradually changed, and the decrease in seaweed beds and water pollution have become problems in Osaka Bay as well. The environment in which living things could live was lost.
It was against this backdrop that the construction of the airport began.
An airport with a structure in harmony with nature
At Kansai Airport, aiming to be an airport that coexists and co-prospers with the local community, we have constructed an airport with a structure in harmony with nature, including the creation of seaweed beds.
A typical landfill has a seawall perpendicular to the surface of the water.
On the other hand, the seawall of Kansai Airport uses what is called a "gently sloping stone revetment" with a gentle slope, and 24~8% of the total length of 9 km is this shape.
The slope increases the number of shallow areas exposed to light, making it an environment that is easy for seaweed that grows by photosynthesis to thrive.
Over the course of about 30 years, the total area of seaweed beds around Kansai Airport has reached 50 hectares, and the sea has become a rich place where diverse creatures gather.
Even now, seaweed seeding continues on the seawall, and the seaweed beds continue to expand.
A symbol of the richness of the sea, the giant monster fish "Kobdai"
In the course of my research, I found a huge fish that symbolizes the richness of this sea.
It is a fish characterized by a large developed hump and jaw, Kobdai.
Japan inhabits the nearshore waters, and in large ones reach a body length of 1 meter.
Even in the water, where the "rumbling"
sound is difficult to reach, you can clearly hear the sound of chewing the sazae vigorously.
Kobdai loves shellfish.
In fact, Kobdai has "another tooth" in the back of the throat, a "pharyngeal tooth". It develops as it grows and can be crushed like grinding even hard shells.
The daily meal is about 2 kg. On the seabed, fragments of shells that the kobfish would have eaten were falling here and there.
"It's rare to look all over the country."
Around Kansai Airport, at least 10 or more kobfish lived in close proximity.
Kobdai is a fish that has a strong territorial consciousness and usually acts alone.
Hiromitsu Takashima, who has been observing the sea of Sado Island in Niigata for more than 30 years, which is known worldwide as a place to observe kobdai, says that he was surprised to see photos of the dense kobdai around Kansai Airport.
Hiromitsu Takashima:
"I think it's rare to find a sea with such a high concentration of kobdai even if you look in the whole country. I think the area around Kansai Airport has become a sanctuary for Kobdai."
Creating seaweed beds that spread throughout Osaka Bay
The seaweed beds at Kansai Airport are about to spread throughout Osaka Bay.
In preparation for the Osaka-Kansai Expo in two years, the airport management company has launched a project to transplant seaweed around the airport to the coast of the bay.
By increasing the area of seaweed beds, we aim to make Osaka Bay a richer sea.
Osaka Bay, which has been regenerated from water pollution, may be recognized around the world as a model case where cities and nature coexist.
Wakayama Broadcasting Station cameraman
Yusuke
OgishimaStarted shooting news for his arrival in
2015 and also takes underwater photography. He is struggling to chase the creatures of the sea and rivers of Kansai.
Osaka Broadcasting Station Director
Akari Kobayashi
joined the station
in 2019 and belongs to the news program. He is interested in the relationship between human society and wildlife and produces programs. When he was a student, he studied raccoons.