Gaze returned from a five-week training stint in South Africa while Cooper spent the last month training in the Central Otago mountain trails.
They broke away from the field on the first of five 4km laps before Gaze pushed hard to open a gap on the second lap, gaining a one-minute advantage. That gap stretched to three minutes after Cooper suffered a slow puncture and was forced to change the front wheel.
"I can't remember hitting anything but got the puncture and took the precaution to change my front wheel, which cost me over a minute," said Cooper. "But for sure the race was probably done for me by then anyway. Sam attacked hard on the second lap and I couldn't go with that. It was my first race for six months so I will now regroup and look forward to next week."
Gaze was able to settle into a strong pace, and was the fastest rider on each lap as he pushed to his second national championship title in 1hr 19.53mins. Cooper was second more than three minutes back with a further 90 seconds to Ben Oliver.
"I really wanted a result today that reflected the training I've done and I am really happy to do that today," said Gaze. "I was nervous coming into this first big goal of the season. It's unfortunate Anton did not have the best legs today because I really wanted a big battle with both of us at our best but I will take the win how it comes.
"I felt great today but now I have to put it behind me and focus on the Oceania championships next weekend, which is the next selection race. I am honoured to be able to wear the national championship colours when I race around the world this year."
Fluker made life challenging when she punctured on the first lap when she mistimed a jump, and was forced to make a wheel change. She trailled Samara Sheppard and Kim Hurst by two-and-a-half minutes after the first lap, but went on to win in 1:22.59, nearly two minutes ahead of Hurst with Sheppard a further three minutes back.
The Queenstown rider, setting herself for potential selection to the Rio Olympics, said she drew inspiration from close friend and prominent mountainbiker Kelly McGarry, who died recently.
"Kelly was my motivation for the day. I actually enjoyed the pain of fighting back because I feel very lucky to be able to do this sport. It was all for him," Fluker said.
The downhill competition is on tomorrow.