These petrels were caught on the hooks of longliners – commercial fishing vessels trailing spools of fishing line which stretch for kilometres. Attracted to fishing vessels as a source of food, the birds had dived under the water and become caught up on the baited hooks of the longlines. By-catch, the term for species killed accidentally, is one of the most serious issues facing the fishing industry. Attempts are being made to develop devices that scare away seabirds or reduce their chances of being caught.