SEACAMS has been engaged on a collaborative project with Tidal Energy Limited (TEL) and Marine Current Turbines (MCT) with technical advice from NRW Marine Advisory Team to review existing marine mammal monitoring guidelines for marine renewable energy (MRE) industry, with particular reference to wave and tidal energy developments in Wales. The rationale for the project arose from the Natural Resources Wales (NRW) Marine Advisory Team and various developers’ request to develop a user friendly, practical set of guidelines to cetacean monitoring at wave and tidal developments in order to reduce discrepancies in survey design and data collection methods in particular. This report is a first step in developing such guidelines for the developers, by reviewing existing information and standard methodologies used in Wales. The aim was to compile available information and summarising current understanding on issues related to cetacean monitoring at tidal sites in order to assist developers with survey design, methodologies used and data analysis and interpretation. Please note this report is not intended to be an exhaustive account of all types of survey and analytical methods appropriate for marine renewable energy sites. Additional information on designing surveys to monitor seals will be published in a follow up report. The project was divided into several discrete tasks: identifying existing marine mammal and specifically cetacean surveying guidelines, reviewing the identified guidelines and reports; approaching and interviewing stakeholders (developers, consultants and marine mammal observers) for their opinions on current guidelines and practices and finally compiling these into one coherent report.