Killer Whale (image) Aarhus University Share Print E-Mail Caption In some areas, killer whales feed primarily on sea mammals and big fish like tuna and sharks and are then threatened by PCBs. In areas where the killer whales primarily feed on small fish like herring, they are less threatened. Credit Audun Rikardsen Usage Restrictions May be used in relation to this press release. Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.