"Today was a huge relief. It's an amazing feeling - and getting under 1min 18s. In Beijing it was a mission to get under 1:20. To get a '17' and the win is a great stepping stone towards the Commonwealth Games next year."
Pascoe's buildup earlier in the year was patchy, but she put in a strong block of training in Flagstaff, Arizona leading up to Montreal.
"It's all paying off, which is great."
Pascoe has three more events to race - the 100m butterfly and backstroke, and 50m freestyle - after a day off tomorrow.
Wellingtonian Fisher, who also snared golds in her first two events in Montreal, the 100m backstroke and 50m freestyle, had to settle for silver, in the S11 400m freestyle.
German Daniela Schulte won well in 5min 25.24s, but Fisher, who has a genetic eye condition, surged home strongly, touching in 5:28.06s.
Northland's Cameron Leslie bagged a bronze medal in his S5 50m backstroke final - only just.
Leslie clocked 43.78s in touching behind Brazilian Daniel Dias in 35.97s and Britain's Andrew Mullen, 39.21s and a bare .07s ahead of Turkey's Beytullah Eroglu.
Nikita Howarth of Cambridge, the country's youngest Paralympian, was eighth in her S7 category 50m freestyle final, in 37.47s.