Confidence: It's likely to be this, but I can't be certain.
Notes: It was thought until recently that the only species of Ischnura in the Canary Islands was I. saharensis. Old records of I. senegalensis were thought to have been mis-IDd as this species. Recent DNA work on a specimen from Tenerife has proved to be senegalensis - so the odd one may occur. But it seems most likely that this photograph is saharensis.