Put in another catfish, and most of them come to life. This is called the catfish effect: (Norwegians like to eat sardines, especially live ones.) The price of live fish on the market is much higher than dead fish. So the fishermen always try to get the sardines back to the harbor alive. But despite all the efforts, most of the sardines die in the middle of the journey due to suffocation. But there was one fishing boat that always managed to bring most of the sardines back to the harbor alive. The captain of the boat kept it a secret. It was not until the captain died that the mystery was revealed. It turned out that the captain had put a catfish, whose main food was fish, into the fish trough filled with sardines. When the catfish entered the tank, it swam around because of the unfamiliar environment. The sardines were very nervous at the sight of the catfish and swam left and right, dodging around and speeding up. In this way the problem of lack of oxygen for the sardines is solved and the sardines will not die. In this way, a sardine returned to the fishing harbor alive and well.)