The Sea Shepherd vessel Sam Simon is making a direct line for the last known location of toothfish poachers in the Southern Ocean.
The activist group is using new information from Interpol in its bid to catch three ships illegally fishing.
At New Zealand's request, Interpol has issued formal alerts against the vessels.
The Sam Simon's captain, Sid Chakravarty, said the notices make the poachers' vessels wanted across 190 countries.
He said while that would make it extremely hard for them to offload their catch, they need to be stopped from fishing in the first instance.
Mr Chakravarty said he was still prepared to use direct action against the poachers.