Do Japanese fishermen put sharks in their tanks to keep fish fresh?

Question

I saw the following story on Quora and when I Googled it, I got a lot of inspirational websites like Patheos.org that were hosting this same story without any citations. I would like to know if the story is true.

The Japanese have always loved fresh fish. But the water close to Japan has not held many fish for decades. So to feed the Japanese population, fishing boats got bigger and went further than ever. The further the fishermen went, the longer it took to bring the fish. If the return trip took more time, the fish were not fresh. To solve this problem, fish companies installed freezers on their boats. They would catch the fish and freeze them at sea. Freezers allowed the boats to go further and stay longer. However, the Japanese could taste the difference between fresh and frozen fish. And they did not like the taste of frozen fish. The frozen fish brought a lower price. So, fishing companies installed fish tanks. They would catch the fish and stuff them in the tanks, fin to fin. After a little thrashing around, they were tired, dull, and lost their fresh-fish taste. The fishing industry faced an impending crisis! But today, they get fresh-tasting fish to Japan .

How did they manage? To keep the fish tasting fresh, the Japanese fishing companies still put the fish in the tanks but with a small shark. The fish are challenged and hence are constantly on the move. The challenge they face keeps them alive and fresh!

Have you realized that some of us are also living in a pond but most of the time tired and dull ? Basically in our lives, sharks are new challenges to keep us active. If you are steadily conquering challenges, you are happy. Your challenges keep you energized. Don’t create success and revel in it in a state of inertia. You have the resources, skills and abilities to make a difference. Put a shark in your tank and see how far you can really go!

Answer 1

The way most Japanese fishing companies actually do this is a process called Ikejime. There are a few different ways to do this but they are all basically the same cause brain death and/or paralysis in the fish in a specific way, in order to keep the fish fresh.

Kaimin Katsugyo which uses acupuncture to keep fish alive but docile, this seems to be much more of a speciality thing though which does make the fish caught this way rather valuable. Fish caught this way are usually sold to higher end sushi restaurants. Although with this method I can't find any documents produced by actual fisheries that use this method.

One actual Ikejime method recommended by the Asia-Pacific Economic Cooperation (APEC) Fisheries Working Group for air transport is:

a cut is made toward the front of the flatfish severing the major artery and the spinal cord. Placement of the cut is made to preserve the greatest amount of flatfish flesh. This paralyzes the flatfish. A second cut is made in the tail to hasten the removal of blood. Flatfish are then chilled slowly to maintain circulation and facilitate the bleeding process. After the flatfish have been bled, they are transferred to a salt/ice water slurry and chilled to 12 °C.

Here is another link that explains this process for use by amateur fishermen.

Also, there isn't really a issue that Japanese fisherman have to travel great lengths to find fresh fish, as Japan itself has, arguably, some of the most extensive artificial reefs in the world to combat this. I've just posted the Wikipedia article on this portion, as the references there are good and this wasn't what was asked.