The fight near a tent camp between migrants from Afghanistan and Eritrea left one with a broken leg. Others suffered superficial wounds, police union official Gilles Debove said.
Calais is the destination of choice for migrants trying to sneak by truck or ferry across the English Channel. Many reached Europe via Italy.
The clash grew out of a dispute that erupted during the evening meal serving after someone cut the food line.
Tensions were high because of tough, winter living conditions and slow truck traffic that diminished chances to sneak to Britain, said Christian Salome of the Auberge des Migrants association, which distributes meals.