Header (IMAGE) Aarhus University Caption Harbor porpoises need to eat 2000 fish a day to meet their energy needs. Not because it's demanding to swim, dive and hunt as they are streamlined and very energy efficient. They simply need vast amounts of energy to keep warm in the cold water. Credit Solvin Zankl Usage Restrictions May only be used for this story. License Original content 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.