After a long flight from Johannesburg on Monday, Fisher only managed nine holes of practice at El Prat on Tuesday before walking the rest of the course during the pre-tournament pro-am.
However, that did not prevent the world number 172 from carding eight birdies and just one bogey in an opening 65 which left him one shot ahead of local favourite Eduardo de la Riva and England’s Tommy Fleetwood.
Fisher, who won his maiden European Tour title in the Africa Open in March, told Sky Sports 4: “I hit one or two loose shots but felt I kept the momentum going, which is key to any good round of golf.
“I sank one or two good putts for par and overall putted really well today, which helped.
“It’s nice to be out here. I can play a full schedule now which is good. It’s nice to play with some of the best players in the world. Hopefully we can put a few more good rounds together.”
Fleetwood had two eagles and three birdies in a round of 66 as he looks to remain inside the world’s top 60 after next week’s BMW PGA Championship in order to qualify for next month’s US Open.
“I was gutted to miss out on the Masters but at the moment my golf is in a good place so I’ve just got to keep my head down and keep going,” said world number 54 Fleetwood, who lost to compatriot Danny Willett in the quarter-finals of the WGC-Cadillac Match Play earlier this month.
“I did not play well in the pro-am on Wednesday then did some good work on the range and came out this morning and hit it really good. I did not miss many fairways and it was just a case of holing a few putts.
“The greens are tricky and we had to make the most of them this morning. Yesterday was firm, fast and tough and this morning was softer and the greens were a bit slower.
“Having the conditions like we did you had to go out and try to make a score.”
De la Riva is attached to the tournament venue of El Prat and features, along with his father and grandfather, on the honours board for winners of the Barcelona Championship in the clubhouse.
Starting on the back nine, the qualifying school graduate eagled the par-five 10th and birdied the 11th and 12th, before picking up shots on the second and fourth in a flawless round.
Defending champion Miguel Angel Jimenez, whose victory 12 months ago extended his record as the oldest winner in European Tour history, had been two under after five holes but eventually had to settle for a level-par 72.
Tournament favourite Sergio Garcia, who lost in a play-off for the Players Championship on Sunday, was among the afternoon starters as he looked to claim a sixth win on home soil and a second Spanish Open title.