There are different phases in the life of an Offshore Wind Farm (OWF) that need to be considered in terms of how it interacts with the coastal ecosystem: the survey and construction, operation and decommissioning. Taking these phases and identifying the associated effectors and whether they have an effect on coastal organisms is an important step before going on to determine whether actual impact may occur. Hence, we have developed studies focussing first on assessing the effects on species individuals at an appropriate scale and, subsequently looking at the effect across multiple individuals which could then be used to assess effects at the level of the population, thereby providing evidence for an impact (either positive or negative). To obtain ecologically relevant results at a scale appropriate for OWFs, we have taken the experimental approach, incorporating a treatment and control, into the coastal environment using large underwater netted structures (mesocosms) to provide a more realistic setting. To date, our studies have used the mesocosm approach to increase understanding of two relatively unknown effectors on fish: underwater pile-driving noise (Construction Phase) and Electromagnetic Fields (EMF), associated with the production of the electricity by OWFs (Operational Phase). The approach presented here clearly demonstrates that specific effects of OWFs on fish (and potentially other marine organisms) can be determined at a scale that is ecologically relevant. Furthermore, it that provides an important step in assessing what effectors need to be considered in terms of their possible impacts, thereby moving the research agenda forward whilst also meeting the needs of the stake holders involved with OWF.