IPCC = The report of the Intergovernmental Panel on Climate Change states that "rapid changes are occurring in a wide area such as the atmosphere and oceans" and that food production such as fisheries is also adversely affected, and Japan points out that the effects of global warming are one of the causes of poor fishing of saury, which is familiar to the table.
Dr. Sakana Kun, Honorary Doctor of Tokyo University of Marine Science and Technology, explained the "feelings of fish" regarding the effects of rising seawater temperatures on fish.
Q.Why is the number of saury landings decreasing in Japan?
A. We've always been familiar with saury.
First of all, it looks like a very slender fish, and it has a streamlined shape like a fish, which means that it is a migratory fish that always travels.
We humans are homeothermic animals and our bodies always stay warm, but fish are cold-blooded animals, and the optimum water temperature is said to be about 10 to 15 degrees Celsius.
In the waters around Japan, from winter to spring, the water temperature is relatively southern.
As it gradually gets warmer, the water temperature off the coast of Sanriku or the coast of Hokkaido rises, and you think, "Oh, the water temperature is just right! Off the coast of Hokkaido! I'm going to go further north," and we will travel according to the appropriate water temperature.
Food is very abundant off the coast of Sanriku and Hokkaido.
If you eat a lot, the saury's body will become plump and fat, and the fat will come on it.
However, due to the recent rise in water temperature in various places, it is thought that they are gradually moving to the back of the coast to "the water temperature of the coast has risen!
Since the fish has the right water temperature, "The water temperature in this area where I used to swim is hot! It's hot!" If you think about it, I think that the migration route may change further offshore.
Q.What is the effect of rising seawater temperature on fish?
A.It has been reported that in the last 100 years, it has risen by 2 to 3 degrees depending on the sea area.
I think that a 1 degree increase in water temperature for fish is the same as a 1 degree increase in normal heat for us.
If the water temperature changes drastically by 0 points or 1 degree or 2 degrees, "Wow! I think it's the same feeling as having a fever.
Therefore, very powerful migratory fish like saury can change their swimming route depending on the situation, which can lead to changing the migration route they have been using so far.
Q.Are the saury caught in Japan these days thin and small?
A.Of course, if saury eats the same as us, it will be able to grow healthier and bigger.
When it comes to "the coast where food is abundant, it's getting hotter, let's go offshore!", it is actually said that the further you go offshore, the less food you have.
In particular, the area around the open ocean off the coast is also called the "desert of the sea."
i.e. less food.
The coast close to our land is very rich in food, and the reason is that nutrients are transported to the sea from many rivers.
By nutrition and light, it is rich in phytoplankton and zooplankton.
For saury, the coast is very easy to live in, food is plentiful and easy to grow.
However, by gradually changing the migration route, it is good to come offshore, but there is little food! If there is little food, it will be difficult for a large and plump saury to grow.
Q.If you go fishing offshore, won't the landings increase?
A. If a fisherman says, "Wow, I'm in trouble, I can't get saury unless I go offshore," it takes fuel and utilities to go offshore, so there is nothing good about it.
Moreover, if the saury is small and skinny, even if it reaches our table, it will say, "Oh, she's thinner than the usual saury! It's small."
This is quite a difficult problem, and the person concerned, Saury, may be the most troubled.
I'm sure you're thinking, "I don't have much food, I wish I could swim more along the coast."
Q. Once I go offshore, will I not return to the coast of Japan?
A.I don't think so.
For example, if the water temperature returns to the past, I think that saury will surely live a life of walking along the coast as before.
However, since the water temperature in various places is rising remarkably, how to restore it is a global issue, and it is a difficult problem to "scare".
Not only saury, but also many fish have changed their migration routes due to fluctuations in water temperature, fishing grounds have changed, and fish that were in the south are moving north more and more, and fish that should not have been caught are often landed in various places.
Q.Yellowtail instead of saury in Kushiro. Is this happening everywhere?
A.Salmon are not in the set nets for catching salmon in each sea area at all, and fishermen often say, "It's not salmon, but yellowtail, sunfish, and sheila!
On the Boso Peninsula, where I live, around Tateyama in Chiba Prefecture, in set net fishing for horse mackerel and sardines, for some reason, in recent years, there have been more and more members of the hawkfish called "gurukun", which is a prefectural fish in Okinawa Prefecture.
An important prefectural fish for the people of Okinawa, Gurukun-chan, has come this far.
There were times when they came in small quantities on the warm current of the Kuroshio Current, but in recent years they have come together quite often.
Q.Is the taste of autumn saury different times?
A.On the Boso Peninsula, the water temperature usually drops from winter to early spring, and should drop to about 15 degrees Celsius, but even in winter, it is in the 20 degree range.
The water temperature drops so slowly that you are surprised that it is still this warm.
Saury is also a fish that migrates due to changes in water temperature, so if it is not the same as before, the seasons will gradually change.
Instead of autumn, you may end up with an image of a "winter sword fish".
Not only fish like saury, which tell us the season, but also vegetables and fruits may gradually change in season.
Originally, Japan was "scary" and clear about the changes in nature and the changing of the seasons, but if the changes of the seasons gradually become difficult to understand or shift, our lives may change.
Q.Will the poor catch of saury continue?
A.Actually, in our Japan, we are gradually moving away from fish, and the slump in fish eating is becoming more and more serious, but on the contrary, fish is becoming more and more popular in other countries.
In the past, saury was a fish that Japan and Russia caught a lot.
However, since 1980, the number of countries that take saury has gradually increased, especially in the high seas, which are quite offshore, and it is thought that this has led to a decrease in the amount of saury's resources.
For saury, the original enemies of the natural world are birds from the sky, large fish in the water, dolphins, whales, and many other large mammals.
We humans are also big enemies, and I think that the fact that many foreign countries have landed fish has increased the number of enemies tremendously.
For that reason, in order to keep our species alive, we may have to lay eggs as soon as possible, or we may have to keep them alive even when they are small.
When I think about the saury, until now she has been migrating from north to south in a regular manner and prefers to live along the coast where food is abundant, but I think it has been greatly affected in combination with the influence of water temperature, food, and the fact that we humans take a lot.
Q.What should we do and what can we do?
A.When you think about it, you are really grateful that you can eat delicious food in that season, so when you realize how grateful you are, you want to know more about it and think about why it is decreasing now.
Fish are also creatures that faithfully change the way of life in response to changes in nature, so it may be a message from saury, "Think carefully about why we are decreasing now."
I think it is necessary for us to think carefully about the environment from what fish tell us.
There are many fish in the wilderness surrounding Japan, and it is said that there are about 4000,<> species.
Depending on the season, there are many fish species such as horse mackerel, sardines, yellowtail, and bonito, so I think it is important to look closely at the fish unique to the sea area and place at that time of year and eat a wide range of fish.
I think that saury-chan and other fish, this is the excitement that I encountered at that time, "one fish and one fish".
I would like to thank you for the encounters of each fish.