They started it!
On Jan 6th, 1973, during a 5-2 Cornell win over the then #1 ranked Crimson in Cambridge, a Harvard fan walked up to the glass at Watson Rink and threw a dead chicken at Cornell netminder Dave Elenbaas.
When Harvard came to Lynah 5 weeks later on Feb 18th, 1973, the Faithful responded to the insult to our Ag school by pelting the Crimson players with fish. Even more fanatical members of the Faithful managed to sneak a *live* chicken onto the ice, which they then tied to Harvard's net during intermission. Cornell won the game 9-4 and went on to finish 4th at the NCAA tournament that season.
Although the tradition has changed over the years as to when the fish are thrown and the lack of the chicken, the throwing of the fish remains a cherished tradition to this day.