An unmanned boat has been found in the search for a fisherman who is missing in waters off Victoria’s south-west coast.

The 65-year-old professional fisherman has not been seen since he left Port Fairy to fish for gummy shark about 1.30pm on Wednesday.

Family members raised the alarm early on Thursday morning when the Warrnambool man failed to return to port.

The man's boat was spotted by a helicopter on Thursday evening in waters about 32 kilometres off Warrnambool, and was towed to Port Fairy overnight, a police spokeswoman said.

A massive air and sea search for the man, who has more than 40 years of fishing experience, resumed at first light on Friday.

Police search boats, coastguard vessels, a volunteer marine rescue boat, helicopters and a fixed-wing aircraft were involved in the search operation on Thursday.