Whether the weather has contributed to an abundance of fish being caught in the area is not clear.
However, the weather has resulted in large numbers of people bringing their boats out.
Hunting & Fishing Dunedin owner Scott Kunac said for the second successive year bluefin tuna had turned up in January, in large numbers, and people fishing for them in the area were being rewarded.
"Usually they turn up later in the season, but the water is a lot warmer than it has been in the past, and the weather’s been tremendous, so you get the warm sea, the good weather and the holidays, and the place has just gone off," Mr Kunac said.
"You’re seeing bigger schools and bigger numbers of fish. They’re just everywhere, really.
"It’s pretty difficult not to catch one if you’re going out after them."
The West Coast had now had "two great summers" and there were a lot more people in the area fishing and they were catching a lot more fish, he said.
It was important to remember the daily limit was one bluefin per person, he said.
Marine heatwave researchers late last week warned Fiordland area sea surface temperatures could be up to 6degC warmer than average this week.
The MetService-led Moana Project issued a statement on Friday warning of an extreme marine heatwave, in part because of warming in the eastern Tasman Sea, which was more than 2degC warmer than normal at depths of 100m to 400m.
MetService oceanographer Joao de Souza said observations collected in partnership with the fishing industry showed waters in Fiordland had been a lot warmer than usual for the last few days, even at depth.
The trend would worsen over this week, Dr de Souza said.
Craig Jones, a commercial fishing operator off the West Coast who works with the marine heatwave researchers, said the patterns in fish were changing, including the number of snapper and kingfish trending up.
A long-time Fiordland fisherman, who asked not to be named, said reports of increased fish, such as reports of more bluefin tuna in Fiordland waters earlier than normal, were not necessarily reliable.
There were "certainly a few tuna around", but the fish had not arrived in the area particularly early this year.
"There are many factors involved.
"You’ve got a lot more people who’ve got boats now, that’s one of the major reasons there’s a lot more people going out and catching them.
"But there’s been bluefin coming down here for decades.
"This isn’t a new phenomenon."
