Fishing activities have the potential to alter the behaviour of cetaceans and pose a threat through bycatch. We present observations concerning the influence of inshore trawling on group size and behaviour of Hector's dolphins ( Cephalorhynchus hectori ) at Banks Peninsula, New Zealand, made during photo‐ID surveys from 2003 to 2007. Aggregations of dolphins, typically involved in what we assumed to be foraging behaviour, were...