For a long time, people who fish have had to rely on luck to catch fish. Even big fishing ships, fitted out with radar and modern equipment, have their share of bad days. Wouldn't it be nice if fish could be trained to come at the call of a whistle the way some days are trained?   Well, the days of "fish whistle" may be just  _ . Japanese companies are working on methods that will train fish to return to harvest areas at the sound of an underwater whistle.   The method works like this: First, fish eggs are hatched in a laboratory. Whenever feeding time arrives, a whistle sounds. The young fish learn to return to their feeding areas at the sound of the whistle.    Later, the fish are set free at sea, near special-made under water "barns". There, the whistle-plus-feeding program continues. Being well fed and sheltered, the fish continue to live around the barn. So when fishing time arrives, all the harvesters need to do is to sound the whistle, drop their nets, and draw in a lot of fish.   Many countries have closed their offshore fishing waters to ships from other countries. With fish whistle and barns, Japan hopes to become less dependent on importing fish from other countries. From the passage we learn that   _  .
bad days have no effect on big fishing ships Japan hopes to supply more fish to other countries the harvesters can catch as many fish as possible now many countries have taken measures to protect their fishing waters from foreign ships