SAN FRANCISCO — StarKist Co. agreed to plead guilty to a felony price fixing charge as part of a broad collusion investigation of the canned tuna industry, the U.S. Department of Justice announced Thursday. The DOJ said StarKist faces up to a $100 million fine when it is sentenced. Prosecutors allege that the industry’s top three companies conspired between 2010 and 2013 to keep prices artificially high. “We have cooperated with the DOJ during the course of its investigation and accept responsibility,” said StarKist chief executive Andrew Choe.