Herne took the chequered flag 2.5270s clear of Joey Mawson to take his fourth win in the Tasman Series from four starts, with Cooper Webster completing the final step of the podium.
The Garry Rogers Motorsport driver started well to take the lead from pole-sitter Aaron Cameron, as a move from Mawson saw him displace Webster for third.
Herne and Cameron drove away from Mawson, with the gap 1.2s to the latter in third place.
While bettering the Adelaide Parklands Circuit lap record in qualifying, Herne officially broke the circuit lap record on Lap 4 with a 1:17.6929s effort, with his team-mate Cameron bettering the mark on Lap 5 with a 1:17.5364s.
Herne responded with a 1:17.2720s on Lap 6, as he led the way by 0.5886s ahead of Cameron.
After setting the fastest run through Sector 2 at the time with a 0:19.1479s, Cameron ran wide at Turn 11, with the right rear of the #18 collecting the tyre bundle at that corner, with Mawson moving up into second and Webster third.
While running in fourth, Fisichella displayed solid pace in the #56 Team BRM entry, setting the then-fastest first sector of the race on Lap 8 with a 0:26.6185s.
On Lap 11, Mawson set the new lap record, breaking into the 1:16s with a 1:16.8155s.
Herne sealed victory the following lap from the lap record holder, with Webster in third.
Fisichella was fourth, from Jordan Boys, while Ben Bargwanna finished sixth.
Blake Purdie, Tim Macrow, Noah Sands, and Jude Bargwanna rounded out the top 10.
S5000 will next take to the track tomorrow for Race 2 at 13:20 local time/13:50 AEDT.