Hector's and Māui dolphin deaths occur as a direct result of commercial and recreational fishing due to entanglement or capture in gillnets or trawls. Death is ultimately caused by suffocation, although injury and sub-lethal effects can also result from the mechanical abrasion of fins resulting from entanglement. Since the 1970s, gillnets have been made from lightweight monofilament, which is difficult for dolphins to detect. Hector's dolphins are actively attracted to trawling vessels and can frequently be seen following trawlers and diving down to the net, which could result in the unwanted bycatch.