Why did the fish land in the field?

One day, Alan, a friend of mine, who likes country life, was fishing in a river, when he caught a trout. He tried to put fish in but it slipped off the hook, flew over his head and landed in a field behind him.
Alan put down his rod, went through the gate and started searching for his trout. Some people, obviously from the city were having a picnic in the field. One of the men shouted. ‘What on earth are you doing? Thinking that it was a silly question because they could see how hews dressed, Alan replied ‘Fishing’.
‘Don’t be silly, the fish are down in the river’, answered the man, ‘Fish don’t live fields! He turned to his friends, laughing, thinking that he had made a good joke.
Oh, but they do, ‘said Alan, They jump out of the river to look for flies and I catch them with my hands. At that moment he found his trout in the grass and picked it up and showed it to the picnickers. He put it in his basket and bent down, as if he was hunting for another one. The picnickers, no longer laughing, spent the rest of the day searching the field.