Peter Senior posted a 66 and is alone in second place, while Chez Reavie carded a 5-under-par 67 at Clearwater Resort for third after round one.
Howison was hot early on. He birdied the par-5 second and made it two in a row with a birdie on three. Howison followed that with a birdie on the par-3 fourth.
The three-time winner made it four straight as he also birdied the par-5 fifth. Howison settled down with four straight pars.
Howison birdied the 10th and 12th get to minus-6. He stumbled to a bogey at the 14th, but quickly atoned for that mistake. Howison birdied 15 and 16 to move to seven-under. He closed with two pars to hold the first-round lead.
'You would have to say it is a surprise because I haven't posted some good rounds, but I've been playing well,' Howison commented. 'I haven't been holing the putts I've needed to and I think that has caused me to press a little bit.'
Senior started on the back nine at Clearwater Resort. He tripped to a bogey on the 13th, but got that stroke right back with a birdie on 14. He got into red figures with a birdie at 17.
The 47-year-old caught fire around the turn. Senior birdied three of the first four holes to fly up the leaderboard. Senior then collected back-to-back birdies from the sixth to jump to 6 under.
'The back nine is a bit harder than the front nine to start off and I've been first or second off that back nine the last six years and it's a hard start,' said Senior, who was in the second group off the 10th tee. 'There are a couple longish holes before you get to the par-5 14th. If you can weather the storm the first three or fours holes, you should be able to put a score together like I did today.'
Senior, who tied for fifth last week at the Jacob's Creek Open Championship, is still shaking off the rust from a month-long vacation he took with his family in December. He said it was the longest break he's ever taken without hitting a golf ball in his 30-year career.
Jason Caron had a chance to grab a share of the opening-round lead, but a double-bogey on his final hole left him at 4-under-par 68. He shares fourth place with Won Joon Lee, Jim McGovern, David Hearn and Matthew Jones. Twelve players are one stroke further back at minus-3.