Catfish saves sardines. Briefly talk about the main content of this short article.

There is a very rare sardine in Norway, which tastes extremely delicious. However, due to the long time at sea, many sardines died on the way. Only one old fisherman could bring back a lot of delicious sardines every time. Later, people finally got his trick-----put a catfish in the sardines. Due to the arrival of the catfish, a foreign species, the sardines became very nervous and kept swimming, but finally maintained their vitality and saved their lives.