Gregory A. Haran, 26, was booked into the Sonoma County jail after the 2 a.m. fight. Police said he punched a victim with brass knuckles. The victim was not located, Lt. Tim Lyons said.
Police were called to Gayle's Central Club Bar in the 100 block of Petaluma Boulevard North regarding a fight involving someone possibly armed with a knife, Lyons said.
Haran discarded the brass knuckles and fled but was arrested on Kentucky Street, Lyons said. The knife was not found but police recovered the brass knuckles, Lyons said.
Police responded to five other fights near downtown bars during the weekend, Lyons said.