On the French equivalent of April Fool’s Day – Poisson d'Avril – on 1st April, people play tricks on each other and shout 'Poisson d'Avril!' to show that it’s a joke. Some people insist that fish or at least a vague reference to fish should be included with the pranks.
The Poisson d'Avril tradition in France possibly dates back to 1564, when King Charles IX decided that the year should start on 1st January to mark the lengthening of days, rather than on 1st April, when it previously started to mark the beginning of spring. The many people who didn’t accept the change and continued to celebrate on 1st April were mocked and sent joke gifts.
Where the fish connections came from is a bit of a mystery. It might be a reference to Pieces (Poissons), the last sign of the Zodiac in winter. Or it might be related to the period of Lent, when the only flesh people were allowed to eat was fish. Another possibility is that it originates in the ‘fish trick’, which involves sending someone to a market to buy fish that are not in season – all French people know when things are in season.
At the beginning to the 20th century there was a tradition in France of sending richly decorated postcards featuring Poissons d'Avril.
One popular prank is to call someone on the phone then to ask them to hold during the conversation. When you come back you ask if there have been any bites. Another popular joke involves tricking people into phoning fish shops or aquariums. Children attach paper fish to the backs of their friends and to those of any adults they can catch, and run away yelling 'Poisson d'Avril!' when the victims discover that they’ve been tricked.
There are also Poisson d'Avril spoof articles and reports in the newspapers, on TV, on the radio and on the internet.
Poissons d'Avril are not just jokes and pranks but also chocolate fish, which are on sale from 1st April and enjoyed during the whole of the Easter season. When people order fish dishes in restaurants on 1st April they are sometimes served chocolate fish instead.