Senden took advantage of benign morning conditions to shoot a six-under-par 66 that featured eight birdies.
The highest-ranked player in the field, Englishman Justin Rose, leads the chasing pack in a five-way share of second after carding an opening 68.
His feat was matched by Kim Felton, Gareth Paddison and Richard Green who also signed for 68s early in the day and Brendan Jones, the pick of the afternoon players in windy conditions.
Stephen Allan, Nick Flanagan and Marcus Fraser are a further shot back after posting solid 69s.
Fraser also earned shot-of-the-day honours with a hole-in-one at the par-three 15th.
Veterans Peter O'Malley and Stuart Appleby are among a cluster of players at minus two, alongside Marc Leishman and Josh Geary who posted impressive 70s after teeing off late in the day.
Defending champion Greg Chalmers carded a respectable 71 to be one shot clear of pre-tournament favourite Adam Scott who battled to an even-par 72.
Eight-time major winner Tom Watson carded an opening 78 that included six bogeys and two double bogeys.
At the other end of the age spectrum, 14-year-old Chinese star Guan Tianlang, who qualified for the US Masters by winning the Asia-Pacific amateur title last month, also found the going tough on the way to a 10-over 82.