WHY AMERICANS EAT SO MUCH TUNA. “The tuna revolution really took off, however, during World War I. European countries, and eventually the American government, bought the inexpensive canned fish to feed the troops. (Uncle Sam was so desperate for protein during the Great War that the government even tried to push whale as a beef substitute.) Returning soldiers continued eating tuna, which displaced salmon as America‚Äôs fish of choice by the 1940s, and fishing boats had to venture further and further from shore to satisfy demand.”