Gary Roberts, from Heamoor, had returned from the sea on March 12 to celebrate his 56th birthday at the Swordfish pub.
He left the premises around midnight to take a taxi home but it is believed that instead he had decided to head towards the harbour.
Penzance sergeant Marc Sayers said: "A friend of his reported him missing after he missed a fishing trip he normally goes on. We have done a CCTV search but failed to find any record of him since that day.
"We had a police dive team down there and have talked to friends and family but so far we have found nothing."
Boscastle-born Mr Roberts is well known in Newlyn and has been a member of The Britannia IV crew for four years.
Skipper Andy Stephens has described him as a very good and reliable team member. "I wasn't concerned until he failed to pick his money up which was three days after our fishing trip. I thought that was a bit odd.
"Gary kept himself to himself and worked for several boats in Newlyn before he joined me about four years ago. He never questioned me or never worried about the weather. He was a loyal crew member and a very good fisherman who will be greatly missed."
Anyone with any information is asked to contact Penzance police quoting log number 399/22/3.
article copyright THE CORNISHMAN