The Federal Government's Southern Ocean patrol boat, Australian Defence Vessel (ADV) Ocean Shield, has docked in Hobart amid speculation it may soon start pursuing illegal fishers.

ADV Ocean Shield is one of two ships used for patrolling the Southern Ocean for illegal fishing boats.

Tasmanian Greens senator Peter Whish-Wilson said he hoped it had come to Hobart to start patrols.

"My expectation is that the boat will now head south and patrol the Southern Ocean," he said.

"It is long overdue so this is a case of better late than never."

The Federal Government has faced criticism in recent weeks from New Zealand authorities and Sea Shepherd activists over its lack of surveillance, as both chase boats illegally fishing for Patagonian toothfish.

Senator Whish-Wilson was also critical of the Government's delay in carrying out two patrols it had previously promised using ADV Ocean Shield.

"We've been waiting for this boat to appear on the horizon all summer after the Government promised that they would do two 40 day patrols in the Southern Ocean," he said.

"The ice-rated $150 million ACV Ocean Shield was purpose-built to patrol in environments like the Southern Ocean.

"We hope it is on the way to the Southern Ocean to provide the patrols it was promised to do."

A spokeswoman for the Border Protection Minister Peter Dutton said the Government can not disclose the location of its assets or operational activity.