This report reviews, describes and evaluates the different monitoring options that are available for obtaining counts of the number of cetacean bycatches that occur in European fisheries. Three methods were adjudged able to obtain these data: self-reporting by fishers, at-sea observers, and remote electronic monitoring (REM) systems with CCTV. Of these, only the data collected by at-sea observers or REM can be collected independently of the fishers and only REM allows later verification of the bycatch events as often as required. Therefore, in this report these two methods are more fully