The Continuous Plankton Recorder (CPR) (IMAGE) University of Plymouth Caption The Continuous Plankton Recorder device is towed in surface waters and occupies a similar space to a marine mammal. It has been used to monitor the oceans since 1931 Credit Marine Biological Association Usage Restrictions None 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.